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Puttock R, Manzin A, Neu V, Garcia-Sanchez F, Fernandez Scarioni A, Schumacher HW, Kazakova O. Modal Frustration and Periodicity Breaking in Artificial Spin Ice. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2003141. [PMID: 32985104 DOI: 10.1002/smll.202003141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Here, an artificial spin ice lattice is introduced that exhibits unique Ising and non-Ising behavior under specific field switching protocols because of the inclusion of coupled nanomagnets into the unit cell. In the Ising regime, a magnetic switching mechanism that generates a uni- or bimodal distribution of states dependent on the alignment of the field is demonstrated with respect to the lattice unit cell. In addition, a method for generating a plethora of randomly distributed energy states across the lattice, consisting of Ising and Landau states, is investigated through magnetic force microscopy and micromagnetic modeling. It is demonstrated that the dispersed energy distribution across the lattice is a result of the intrinsic design and can be finely tuned through control of the incident angle of a critical field. The present manuscript explores a complex frustrated environment beyond the 16-vertex Ising model for the development of novel logic-based technologies.
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Affiliation(s)
- Robert Puttock
- National Physical Laboratory, Teddington, TW11 0LW, UK
- Department of Physics, Royal Holloway University of London, Egham Hill, Egham, TW20 0EX, UK
| | | | - Volker Neu
- Leibniz Institute for Solid State and Materials Research Dresden, Dresden, 01069, Germany
| | - Felipe Garcia-Sanchez
- Istituto Nazionale di Ricerca Metrologica, Torino, 10135, Italy
- Departamento de Física Aplicada, University of Salamanca, Pza de la Merced s/n, Salamanca, 37008, Spain
| | | | | | - Olga Kazakova
- National Physical Laboratory, Teddington, TW11 0LW, UK
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Abstract
Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and (ii) rectangular stripes with long axes perpendicular to the chain axis. A variable magnetic field is applied parallel to the long axes. Micromagnetic simulations are compared with the corresponding discrete spin models (Stoner-Wohlfarth model, S-W). An antiferromagnetic configuration is the ground state for all the systems at vanishing field but a ferromagnetic configuration occurs when the field is strong enough. The switching of the infinite chains to the reversed ferromagnetic configuration proceeds directly for the ellipsoids and by an intermediate configuration, in which the magnetization within the particle is non-uniform, in the case of the stripes. The non-uniform configurations are well represented by tilted states in S-W model. Important differences are found in the finite analogs: the switching of ellipsoids becomes multistage and starts from the innermost particles relatively well reproduced with S-W model, whereas the reversal of the stripes, starts from the outermost particles and has no analog in S-W model. Practical consequences of the findings are discussed.
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53
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Bhat VS, Watanabe S, Baumgaertl K, Kleibert A, Schoen MAW, Vaz CAF, Grundler D. Magnon Modes of Microstates and Microwave-Induced Avalanche in Kagome Artificial Spin Ice with Topological Defects. PHYSICAL REVIEW LETTERS 2020; 125:117208. [PMID: 32975965 DOI: 10.1103/physrevlett.125.117208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 06/16/2020] [Accepted: 08/11/2020] [Indexed: 05/12/2023]
Abstract
We investigate spin dynamics of microstates in artificial spin ice (ASI) in Ni_{81}Fe_{19} nanomagnets arranged in an interconnected kagome lattice using microfocus Brillouin light scattering, broadband ferromagnetic resonance, magnetic force microscopy, x-ray photoemission electron microscopy, and simulations. We experimentally reconfigure microstates in ASI using a 2D vector field protocol and apply microwave-assisted switching to intentionally trigger reversal. Our work is key for the creation of avalanches inside the kagome ASI and reprogrammable magnonics based on ASIs.
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Affiliation(s)
- V S Bhat
- Institute of Materials, Laboratory of Nanoscale Magnetic Materials and Magnonics, School of Engineering, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
- International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, PL-02668 Warsaw, Poland
| | - S Watanabe
- Institute of Materials, Laboratory of Nanoscale Magnetic Materials and Magnonics, School of Engineering, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
| | - K Baumgaertl
- Institute of Materials, Laboratory of Nanoscale Magnetic Materials and Magnonics, School of Engineering, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
| | - A Kleibert
- Swiss Light Source, Paul Scherrer Institute, 5232 PSI Villigen, Switzerland
| | - M A W Schoen
- Swiss Light Source, Paul Scherrer Institute, 5232 PSI Villigen, Switzerland
| | - C A F Vaz
- Swiss Light Source, Paul Scherrer Institute, 5232 PSI Villigen, Switzerland
| | - D Grundler
- Institute of Materials, Laboratory of Nanoscale Magnetic Materials and Magnonics, School of Engineering, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
- Institute of Microengineering, Laboratory of Nanoscale Magnetic Materials and Magnonics, School of Engineering, École Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland
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54
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Wang D, Wei S, Yuan A, Tian F, Cao K, Zhao Q, Zhang Y, Zhou C, Song X, Xue D, Yang S. Machine Learning Magnetic Parameters from Spin Configurations. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2000566. [PMID: 32832350 PMCID: PMC7435232 DOI: 10.1002/advs.202000566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 05/29/2020] [Indexed: 05/27/2023]
Abstract
Hamiltonian parameters estimation is crucial in condensed matter physics, but is time- and cost-consuming. High-resolution images provide detailed information of underlying physics, but extracting Hamiltonian parameters from them is difficult due to the huge Hilbert space. Here, a protocol for Hamiltonian parameters estimation from images based on a machine learning (ML) architecture is provided. It consists in learning a mapping between spin configurations and Hamiltonian parameters from a small amount of simulated images, applying the trained ML model to a single unexplored experimental image to estimate its key parameters, and predicting the corresponding materials properties by a physical model. The efficiency of the approach is demonstrated by reproducing the same spin configuration as the experimental one and predicting the coercive field, the saturation field, and even the volume of the experiment specimen accurately. The proposed approach paves a way to achieve a stable and efficient parameters estimation.
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Affiliation(s)
- Dingchen Wang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Songrui Wei
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong ProvinceCollege of Optoelectronic EngineeringShenzhen UniversityShenzhen518060China
| | - Anran Yuan
- Key Laboratory of Intelligent Perception and Image Understanding of Ministry of EducationInternational Research Center for Intelligent Perception and ComputationJoint International Research Laboratory of Intelligent Perception and ComputationSchool of Artificial IntelligenceXidian UniversityXi'an710071China
| | - Fanghua Tian
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Kaiyan Cao
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Qizhong Zhao
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Yin Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Chao Zhou
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Xiaoping Song
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Dezhen Xue
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
| | - Sen Yang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceState Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong UniversityXi'an710049China
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Schánilec V, Canals B, Uhlíř V, Flajšman L, Sadílek J, Šikola T, Rougemaille N. Bypassing Dynamical Freezing in Artificial Kagome Ice. PHYSICAL REVIEW LETTERS 2020; 125:057203. [PMID: 32794868 DOI: 10.1103/physrevlett.125.057203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/01/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
Spin liquids are correlated, disordered states of matter that fluctuate even at low temperatures. Experimentally, the extensive degeneracy characterizing their low-energy manifold is expected to be lifted, for example, because of dipolar interactions, leading to an ordered ground state at absolute zero. However, this is not what is usually observed, and many systems, whether they are chemically synthesized or nanofabricated, dynamically freeze before magnetic ordering sets in. In artificial realizations of highly frustrated magnets, ground state configurations, and even low-energy manifolds, thus remain out of reach for practical reasons. Here, we show how dynamical freezing can be bypassed in an artificial kagome ice. We illustrate the efficiency of our method by demonstrating that the a priori dynamically inaccessible ordered ground state and fragmented spin liquid configurations can be obtained reproducibly, imaged in real space at room temperature, and studied conveniently. We then identify the mechanism by which dynamical freezing occurs in the dipolar kagome ice.
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Affiliation(s)
- V Schánilec
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
- Central European Institute of Technology, CEITEC BUT, Brno University of Technology, Purkyňova 123, Brno 612 00, Czech Republic
| | - B Canals
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - V Uhlíř
- Central European Institute of Technology, CEITEC BUT, Brno University of Technology, Purkyňova 123, Brno 612 00, Czech Republic
| | - L Flajšman
- Central European Institute of Technology, CEITEC BUT, Brno University of Technology, Purkyňova 123, Brno 612 00, Czech Republic
| | - J Sadílek
- Central European Institute of Technology, CEITEC BUT, Brno University of Technology, Purkyňova 123, Brno 612 00, Czech Republic
| | - T Šikola
- Central European Institute of Technology, CEITEC BUT, Brno University of Technology, Purkyňova 123, Brno 612 00, Czech Republic
- Institute of Physical Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2, Brno, 616 69, Czech Republic
| | - N Rougemaille
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
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Di Pietro Martínez M, Buceta RC. Energetic analysis of disorder effects in an artificial spin ice with dipolar interactions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:285801. [PMID: 32155604 DOI: 10.1088/1361-648x/ab7e58] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We study the effect of quenched disorder in square artificial spin ice by means of numerical simulations. We introduce disorder in the length of magnetic islands using two kinds of distributions: Gaussian and uniform. As the system behavior depends on its geometrical parameters, we focus on studying it in the proximity of the ice regime which is quite difficult to thermalize both in experiments and simulations. We show how length disorder affect the antiferromagnetic and (locally) ferromagnetic ordering, by inducing the system, in the case of weak disorder, to intermediate or mix states. Moreover, in the case of strong disorder, ferromagnetic plaquettes prevail regardless of whether the mean length of the islands corresponds to an antiferromagnetic ordering.
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57
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Effects of magnetic monopoles charge on the cracking reversal processes in artificial square ices. Sci Rep 2020; 10:9959. [PMID: 32561787 PMCID: PMC7305124 DOI: 10.1038/s41598-020-66794-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 05/12/2020] [Indexed: 11/24/2022] Open
Abstract
In this paper we perform nanofabrication of square artificial spin ices with different lattice parameters, in order to investigate the roles of vertex excitation on the features of the system. In particular, the character of magnetic charge distribution asymmetry on the vertices are observed under magnetic hysteresis loop experiments. We then compare our results with simulation using an emergent Hamiltonian containing objects such as magnetic monopoles and dipoles in the vertices of the array (instead of the usual Hamiltonian based on the dipolar interactions among the magnetic nanoislands). All possible interactions between these objects are considered (monopole-monopole, monopole-dipole and dipole-dipole). Using realistic parameters we observe very good match between experiments and theory, which allow us to better understand the system dynamics in function of monopole charge intensity.
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58
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Bramwell ST, Harris MJ. The history of spin ice. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:374010. [PMID: 32554893 DOI: 10.1088/1361-648x/ab8423] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 03/27/2020] [Indexed: 06/11/2023]
Abstract
This review is a study of how the idea of spin ice has evolved over the years, with a focus on the scientific questions that have come to define the subject. Since our initial discovery of spin ice in 1997, there have been well over five thousand papers that discuss it, and in the face of such detail, it must be difficult for the curious observer to 'see the wood for the trees'. To help in this task, we go in search of the biggest insight to have emerged from the study of spin ice. On the way, we identify highlights and outstanding puzzles, and celebrate the inspirational role that Roger Cowley played in the early years.
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Affiliation(s)
- Steven T Bramwell
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1H 0AH, United Kingdom
| | - Mark J Harris
- School of Divinity, University of Edinburgh, New College, Edinburgh, EH1 2LX, United Kingdom
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59
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Oğuz EC, Ortiz-Ambriz A, Shem-Tov H, Babià-Soler E, Tierno P, Shokef Y. Topology Restricts Quasidegeneracy in Sheared Square Colloidal Ice. PHYSICAL REVIEW LETTERS 2020; 124:238003. [PMID: 32603179 DOI: 10.1103/physrevlett.124.238003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 05/26/2020] [Indexed: 06/11/2023]
Abstract
Recovery of ground-state degeneracy in two-dimensional square ice is a significant challenge in the field of geometric frustration with far-reaching fundamental implications, such as realization of vertex models and understanding the effect of dimensionality reduction. We combine experiments, theory, and numerical simulations to demonstrate that sheared square colloidal ice partially recovers the ground-state degeneracy for a wide range of field strengths and lattice shear angles. Our method could inspire engineering a novel class of frustrated microstructures and nanostructures based on sheared magnetic lattices in a wide range of soft- and condensed-matter systems.
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Affiliation(s)
- Erdal C Oğuz
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978, Israel
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
- Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Antonio Ortiz-Ambriz
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona 08028, Spain
| | - Hadas Shem-Tov
- School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
| | - Eric Babià-Soler
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
| | - Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona 08028, Spain
- Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona 08028, Spain
- Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona 08028, Spain
| | - Yair Shokef
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978, Israel
- Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978, Israel
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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60
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Wang B, Rong K, Maguid E, Kleiner V, Hasman E. Probing nanoscale fluctuation of ferromagnetic meta-atoms with a stochastic photonic spin Hall effect. NATURE NANOTECHNOLOGY 2020; 15:450-456. [PMID: 32341504 DOI: 10.1038/s41565-020-0670-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
The photonic spin Hall effect, a deep subdiffraction-limited shift between the opposite spin components of light, emerges when light undergoes an evolution of polarization or trajectory that induces the geometric phase. Here, we study a stochastic photonic spin Hall effect arising from space-variant Berry-Zak phases, which are generated by disordered magneto-optical effects. This spin shift is observed from a spatially bounded lattice of ferromagnetic meta-atoms displaying nanoscale disorders. A random variation of the radii of the meta-atoms induces the nanoscale fluctuation. The standard deviation of the probability distribution of the spin shifts is proportional to the fluctuation of the meta-atoms. This enables us to detect a five-nanometre fluctuation by measuring the probability distribution of the spin shifts via weak measurements. Our approach may be used for sensing deep-subwavelength disorders by actively breaking the photonic spin symmetry and may enable investigations of fluctuation effects in magnetic nanosystems.
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Affiliation(s)
- Bo Wang
- Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell Berrie Nanotechnology Institute, Technion, Israel Institute of Technology, Haifa, Israel
| | - Kexiu Rong
- Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell Berrie Nanotechnology Institute, Technion, Israel Institute of Technology, Haifa, Israel
| | - Elhanan Maguid
- Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell Berrie Nanotechnology Institute, Technion, Israel Institute of Technology, Haifa, Israel
| | - Vladimir Kleiner
- Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell Berrie Nanotechnology Institute, Technion, Israel Institute of Technology, Haifa, Israel
| | - Erez Hasman
- Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering and Russell Berrie Nanotechnology Institute, Technion, Israel Institute of Technology, Haifa, Israel.
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61
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Zhao K, Deng H, Chen H, Ross KA, Petříček V, Günther G, Russina M, Hutanu V, Gegenwart P. Realization of the kagome spin ice state in a frustrated intermetallic compound. Science 2020; 367:1218-1223. [PMID: 32165582 DOI: 10.1126/science.aaw1666] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 02/13/2020] [Indexed: 11/02/2022]
Abstract
Spin ices are exotic phases of matter characterized by frustrated spins obeying local "ice rules," in analogy with the electric dipoles in water ice. In two dimensions, one can similarly define ice rules for in-plane Ising-like spins arranged on a kagome lattice. These ice rules require each triangle plaquette to have a single monopole and can lead to different types of orders and excitations. Using experimental and theoretical approaches including magnetometry, thermodynamic measurements, neutron scattering, and Monte Carlo simulations, we establish HoAgGe as a crystalline (i.e., nonartificial) system that realizes the kagome spin ice state. The system features a variety of partially and fully ordered states and a sequence of field-induced phases at low temperatures, all consistent with the kagome ice rule.
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Affiliation(s)
- Kan Zhao
- Experimentalphysik VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
| | - Hao Deng
- Institute of Crystallography, RWTH Aachen University and Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), D-85747 Garching, Germany
| | - Hua Chen
- Department of Physics, Colorado State University, Fort Collins, CO 80523, USA
| | - Kate A Ross
- Department of Physics, Colorado State University, Fort Collins, CO 80523, USA
| | - Vaclav Petříček
- Institute of Physics, Academy of Sciences of the Czech Republic, 18221 Prague, Czech Republic
| | - Gerrit Günther
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - Margarita Russina
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - Vladimir Hutanu
- Institute of Crystallography, RWTH Aachen University and Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), D-85747 Garching, Germany
| | - Philipp Gegenwart
- Experimentalphysik VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
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Two-dimensional magnetic monopole gas in an oxide heterostructure. Nat Commun 2020; 11:1341. [PMID: 32165628 PMCID: PMC7067881 DOI: 10.1038/s41467-020-15213-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 02/18/2020] [Indexed: 11/19/2022] Open
Abstract
Magnetic monopoles have been proposed as emergent quasiparticles in pyrochlore spin ice compounds. However, unlike semiconductors and two-dimensional electron gases where the charge degree of freedom can be actively controlled by chemical doping, interface modulation, and electrostatic gating, there is as of yet no analogue of these effects for emergent magnetic monopoles. To date, all experimental investigations have been limited to large ensembles comprised of equal numbers of monopoles and antimonopoles in bulk crystals. To address these issues, we propose the formation of a two-dimensional magnetic monopole gas (2DMG) with a net magnetic charge, confined at the interface between a spin ice and an isostructural antiferromagnetic pyrochlore iridate and whose monopole density can be controlled by an external field. Our proposal is based on Monte Carlo simulations of the thermodynamic and transport properties. This proposed 2DMG should enable experiments and devices which can be performed on magnetic monopoles, akin to two-dimensional electron gases in semiconductor heterostructures. Heterostructure interfaces have physical properties distinct from bulk materials, providing the basis for many electronic devices. Miao et al. propose a spin ice heterostructure that can host a two-dimensional gas of emergent magnetic monopoles with a net magnetic charge.
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63
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Archimedean lattices emerge in template-directed eutectic solidification. Nature 2020; 577:355-358. [PMID: 31942052 DOI: 10.1038/s41586-019-1893-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 10/11/2019] [Indexed: 11/08/2022]
Abstract
Template-directed assembly has been shown to yield a broad diversity of highly ordered mesostructures1,2, which in a few cases exhibit symmetries not present in the native material3-5. However, this technique has not yet been applied to eutectic materials, which underpin many modern technologies ranging from high-performance turbine blades to solder alloys. Here we use directional solidification of a simple AgCl-KCl lamellar eutectic material within a pillar template to show that interactions of the material with the template lead to the emergence of a set of microstructures that are distinct from the eutectic's native lamellar structure and the template's hexagonal lattice structure. By modifying the solidification rate of this material-template system, trefoil, quatrefoil, cinquefoil and hexafoil mesostructures with submicrometre-size features are realized. Phase-field simulations suggest that these mesostructures appear owing to constraints imposed on diffusion by the hexagonally arrayed pillar template. We note that the trefoil and hexafoil patterns resemble Archimedean honeycomb and square-hexagonal-dodecagonal lattices6, respectively. We also find that by using monolayer colloidal crystals as templates, a variety of eutectic mesostructures including trefoil and hexafoil are observed, the former resembling the Archimedean kagome lattice. Potential emerging applications for the structures provided by templated eutectics include non-reciprocal metasurfaces7, magnetic spin-ice systems8,9, and micro- and nano-lattices with enhanced mechanical properties10,11.
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Ghosh A, Ma F, Lourembam J, Jin X, Maddu R, Yap QJ, Ter Lim S. Emergent Dynamics of Artificial Spin-Ice Lattice Based on an Ultrathin Ferromagnet. NANO LETTERS 2020; 20:109-115. [PMID: 31692358 DOI: 10.1021/acs.nanolett.9b03352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present high-frequency dynamics of magnetic nanostructure lattices, fabricated in the form of "artificial spin-ice", that possess magnetically frustrated states. Dynamics of such structures feature multiple resonance excitation that reveals rich and intriguing microwave characteristics, which are highly dependent on field-cycle history. Geometrical parameters such as dimensions and ferromagnetic layer thickness, which control the interplay of different demagnetizing factors, are found to play a pivotal role in governing the dynamics. Our findings are highlighted by the evolution of unique excitations pertaining to magnetic frustration, which are well supported by static magnetometry studies and micromagnetic simulations.
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Affiliation(s)
- Abhijit Ghosh
- Data Storage Institute, Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-01 Innovis , Singapore 138634
- Institute of Materials Research and Engineering , Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis , Singapore 138634
| | - Fusheng Ma
- Jangsu Key Laboratory of Optoelectronic Technology, Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology , Nanjing Normal University , Nanjing 210023 , China
| | - James Lourembam
- Data Storage Institute, Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-01 Innovis , Singapore 138634
- Institute of Materials Research and Engineering , Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis , Singapore 138634
| | - Xiangjun Jin
- Jangsu Key Laboratory of Optoelectronic Technology, Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology , Nanjing Normal University , Nanjing 210023 , China
| | - Ramu Maddu
- Data Storage Institute, Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-01 Innovis , Singapore 138634
- Institute of Materials Research and Engineering , Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis , Singapore 138634
| | - Qi Jia Yap
- Data Storage Institute, Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-01 Innovis , Singapore 138634
- Institute of Materials Research and Engineering , Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis , Singapore 138634
| | - Sze Ter Lim
- Data Storage Institute, Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-01 Innovis , Singapore 138634
- Institute of Materials Research and Engineering , Agency for Science Technology and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis , Singapore 138634
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Lendinez S, Jungfleisch MB. Magnetization dynamics in artificial spin ice. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:013001. [PMID: 31600143 DOI: 10.1088/1361-648x/ab3e78] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In this topical review, we present key results of studies on magnetization dynamics in artificial spin ice (ASI), which are arrays of magnetically interacting nanostructures. Recent experimental and theoretical progress in this emerging area, which is at the boundary between research on frustrated magnetism and high-frequency studies of artificially created nanomagnets, is reviewed. The exploration of ASI structures has revealed fascinating discoveries in correlated spin systems. Artificially created spin ice lattices offer unique advantages as they allow for a control of the interactions between the elements by their geometric properties and arrangement. Magnonics, on the other hand, is a field that explores spin dynamics in the gigahertz frequency range in magnetic micro- and nanostructures. In this context, magnonic crystals are particularly important as they allow the modification of spin-wave properties and the observation of band gaps in the resonance spectra. Very recently, there has been considerable progress, experimentally and theoretically, in combining aspects of both fields-artificial spin ice and magnonics-enabling new functionalities in magnonic and spintronic applications using ASI, as well as providing a deeper understanding of geometrical frustration in the gigahertz range. Different approaches for the realization of ASI structures and their experimental characterization in the high-frequency range are described and the appropriate theoretical models and simulations are reviewed. Special attention is devoted to linking these findings to the quasi-static behavior of ASI and dynamic investigations in magnonics in an effort to bridge the gap between both areas further and to stimulate new research endeavors.
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Affiliation(s)
- S Lendinez
- Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, United States of America
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66
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Magnetization dynamics of weakly interacting sub-100 nm square artificial spin ices. Sci Rep 2019; 9:19967. [PMID: 31882867 PMCID: PMC6934880 DOI: 10.1038/s41598-019-56219-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 12/06/2019] [Indexed: 12/02/2022] Open
Abstract
Artificial Spin Ice (ASI), consisting of a two dimensional array of nanoscale magnetic elements, provides a fascinating opportunity to observe the physics of out-of-equilibrium systems. Initial studies concentrated on the static, frozen state, whilst more recent studies have accessed the out-of-equilibrium dynamic, fluctuating state. This opens up exciting possibilities such as the observation of systems exploring their energy landscape through monopole quasiparticle creation, potentially leading to ASI magnetricity, and to directly observe unconventional phase transitions. In this work we have measured and analysed the magnetic relaxation of thermally active ASI systems by means of SQUID magnetometry. We have investigated the effect of the interaction strength on the magnetization dynamics at different temperatures in the range where the nanomagnets are thermally active. We have observed that they follow an Arrhenius-type Néel-Brown behaviour. An unexpected negative correlation of the average blocking temperature with the interaction strength is also observed, which is supported by Monte Carlo simulations. The magnetization relaxation measurements show faster relaxation for more strongly coupled nanoelements with similar dimensions. The analysis of the stretching exponents obtained from the measurements suggest 1-D chain-like magnetization dynamics. This indicates that the nature of the interactions between nanoelements lowers the dimensionality of the ASI from 2-D to 1-D. Finally, we present a way to quantify the effective interaction energy of a square ASI system, and compare it to the interaction energy computed with micromagnetic simulations.
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67
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Wyss M, Gliga S, Vasyukov D, Ceccarelli L, Romagnoli G, Cui J, Kleibert A, Stamps RL, Poggio M. Stray-Field Imaging of a Chiral Artificial Spin Ice during Magnetization Reversal. ACS NANO 2019; 13:13910-13916. [PMID: 31820931 DOI: 10.1021/acsnano.9b05428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Artificial spin ices are a class of metamaterials consisting of magnetostatically coupled nanomagnets. Their interactions give rise to emergent behavior, which has the potential to be harnessed for the creation of functional materials. Consequently, the ability to map the stray field of such systems can be decisive for gaining an understanding of their properties. Here, we use a scanning nanometer-scale superconducting quantum interference device (SQUID) to image the magnetic stray field distribution of an artificial spin ice system exhibiting structural chirality as a function of applied magnetic fields at 4.2 K. The images reveal that the magnetostatic interaction gives rise to a measurable bending of the magnetization at the edges of the nanomagnets. Micromagnetic simulations predict that, owing to the structural chirality of the system, this edge bending is asymmetric in the presence of an external field and gives rise to a preferred direction for the reversal of the magnetization. This effect is not captured by models assuming a uniform magnetization. Our technique thus provides a promising means for understanding the collective response of artificial spin ices and their interactions.
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Affiliation(s)
- Marcus Wyss
- Department of Physics , University of Basel , 4056 Basel , Switzerland
| | - Sebastian Gliga
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow , G12 8QQ , United Kingdom
- Paul Scherrer Institute , Villigen 5232 , Switzerland
| | - Denis Vasyukov
- Department of Physics , University of Basel , 4056 Basel , Switzerland
| | | | - Giulio Romagnoli
- Department of Physics , University of Basel , 4056 Basel , Switzerland
| | - Jizhai Cui
- Paul Scherrer Institute , Villigen 5232 , Switzerland
- Laboratory for Mesoscopic Systems, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland
| | | | - Robert L Stamps
- Department of Physics and Astronomy , University of Manitoba , Winnipeg , R3T 2N2 , Canada
| | - Martino Poggio
- Department of Physics , University of Basel , 4056 Basel , Switzerland
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68
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Salaheldeen M, Vega V, Caballero-Flores R, Prida VM, Fernández A. Influence of nanoholes array geometrical parameters on magnetic properties of Dy-Fe antidot thin films. NANOTECHNOLOGY 2019; 30:455703. [PMID: 31362273 DOI: 10.1088/1361-6528/ab36cc] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanoscale artificially engineered spintronic materials could be used to enlarge the storage density of magnetic recording media. For this purpose, magnetic nanostructures such as antidot arrays exhibiting high uniaxial magnetic anisotropy are new contestants in the field of ultrahigh density magnetic data storage devices. In this context, we focus on the synthesis of nanostructured magnetic materials consisting of Dy-Fe alloyed antidot thin films, deposited onto the surface of nanoporous alumina membranes served as patterned templates. Noticeable variations of in the in-plane magnetic anisotropy have been observed by modifying the layer thickness at both microscopic and macroscopic scales. The microscopic magnetic properties have been locally studied by Nano-MOKE magnetometry. For thinner antidot samples with 15, 20 and 25 nm in thickness, a tri-axial in-plane magnetic anisotropy has been detected. Meanwhile, for thicker antidot samples (40-60 nm of layer thickness), an in-plane uniaxial magnetic anisotropy has been noted. We attribute these changes in the magnetic anisotropy to the strong correlation between the edge-to-edge distance among adjacent nanoholes, W, and the local magnetic anisotropy of antidot samples. The effective magnetic anisotropy exhibits an unexpected crossover from the in-plane to out-of-plane direction due to the increasing of the effective perpendicular magnetic anisotropy with varying the layer thickness of antidot thin films. Therefore, we detected a critical layer thickness, t = 25 nm for the Dy-Fe alloy antidot arrays, at which the appearance of the perpendicular magnetization is observed. Furthermore, an enhancement in the Curie temperature of the antidot arrays compared to the continuous thin films has been obtained. We attribute these effects to the complex magnetization reversal processes and the high thermal stability of the hexagonal structure of antidot arrays. These findings can be of high interest for the development of novel magnetic sensors and for thermo-magnetic recording patterned media based on template-assisted deposition techniques.
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Affiliation(s)
- M Salaheldeen
- Physics Department, Faculty of Science, Sohag University, 82524 Sohag, Egypt. Depto. Física, Universidad de Oviedo, C/Federico García Lorca 18, E-33007 Oviedo, Asturias, Spain
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69
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Thermally and field-driven mobility of emergent magnetic charges in square artificial spin ice. Sci Rep 2019; 9:15989. [PMID: 31690773 PMCID: PMC6831649 DOI: 10.1038/s41598-019-52460-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 10/14/2019] [Indexed: 12/03/2022] Open
Abstract
Designing and constructing model systems that embody the statistical mechanics of frustration is now possible using nanotechnology. We have arranged nanomagnets on a two-dimensional square lattice to form an artificial spin ice, and studied its fractional excitations, emergent magnetic monopoles, and how they respond to a driving field using X-ray magnetic microscopy. We observe a regime in which the monopole drift velocity is linear in field above a critical field for the onset of motion. The temperature dependence of the critical field can be described by introducing an interaction term into the Bean-Livingston model of field-assisted barrier hopping. By analogy with electrical charge drift motion, we define and measure a monopole mobility that is larger both for higher temperatures and stronger interactions between nanomagnets. The mobility in this linear regime is described by a creep model of zero-dimensional charges moving within a network of quasi-one-dimensional objects.
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70
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Gu H, Boehler Q, Ahmed D, Nelson BJ. Magnetic quadrupole assemblies with arbitrary shapes and magnetizations. Sci Robot 2019; 4:4/35/eaax8977. [PMID: 33137733 DOI: 10.1126/scirobotics.aax8977] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 10/09/2019] [Indexed: 12/21/2022]
Abstract
Magnetic dipole-dipole interactions govern the behavior of magnetic matter across scales from micrometer colloidal particles to centimeter magnetic soft robots. This pairwise long-range interaction creates rich emergent phenomena under both static and dynamic magnetic fields. However, magnetic dipole particles, from either ferromagnetic or paramagnetic materials, tend to form chain-like structures as low-energy configurations due to dipole symmetry. The repulsion force between two magnetic dipoles raises challenges for creating stable magnetic assemblies with complex two-dimensional (2D) shapes. In this work, we propose a magnetic quadrupole module that is able to form stable and frustration-free magnetic assemblies with arbitrary 2D shapes. The quadrupole structure changes the magnetic particle-particle interaction in terms of both symmetry and strength. Each module has a tunable dipole moment that allows the magnetization of overall assemblies to be programmed at the single module level. We provide a simple combinatorial design method to reach both arbitrary shapes and arbitrary magnetizations concurrently. Last, by combining modules with soft segments, we demonstrate programmable actuation of magnetic metamaterials that could be used in applications for soft robots and electromagnetic metasurfaces.
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Affiliation(s)
- Hongri Gu
- Institute of Robotics and Intelligent Systems, ETH Zürich, Zürich CH-8092, Switzerland
| | - Quentin Boehler
- Institute of Robotics and Intelligent Systems, ETH Zürich, Zürich CH-8092, Switzerland
| | - Daniel Ahmed
- Institute of Robotics and Intelligent Systems, ETH Zürich, Zürich CH-8092, Switzerland
| | - Bradley J Nelson
- Institute of Robotics and Intelligent Systems, ETH Zürich, Zürich CH-8092, Switzerland.
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71
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Rollano V, Muñoz-Noval A, Gomez A, Valdes-Bango F, Martin JI, Velez M, Osorio MR, Granados D, Gonzalez EM, Vicent JL. Topologically protected superconducting ratchet effect generated by spin-ice nanomagnets. NANOTECHNOLOGY 2019; 30:244003. [PMID: 30790770 DOI: 10.1088/1361-6528/ab0923] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We have designed, fabricated and tested a robust superconducting ratchet device based on topologically frustrated spin ice nanomagnets. The device is made of a magnetic Co honeycomb array embedded in a superconducting Nb film. This device is based on three simple mechanisms: (i) the topology of the Co honeycomb array frustrates in-plane magnetic configurations in the array yielding a distribution of magnetic charges which can be ordered or disordered with in-plane magnetic fields, following spin ice rules; (ii) the local vertex magnetization, which consists of a magnetic half vortex with two charged magnetic Néel walls; (iii) the interaction between superconducting vortices and the asymmetric potentials provided by the Néel walls. The combination of these elements leads to a superconducting ratchet effect. Thus, superconducting vortices driven by alternating forces and moving on magnetic half vortices generate a unidirectional net vortex flow. This ratchet effect is independent of the distribution of magnetic charges in the array.
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Affiliation(s)
- V Rollano
- IMDEA-Nanociencia, Cantoblanco, E-28049 Madrid, Spain
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72
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Pancaldi M, Leo N, Vavassori P. Selective and fast plasmon-assisted photo-heating of nanomagnets. NANOSCALE 2019; 11:7656-7666. [PMID: 30951080 DOI: 10.1039/c9nr01628g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Thermal relaxation of nanoscale magnetic islands, mimicking Ising macrospins, is indispensable for studies of geometrically frustrated artificial spin systems and low-energy nanomagnetic computation. Currently-used heating schemes based on contact to a thermal reservoir, however, lack the speed and spatial selectivity required for the implementation in technological applications. Applying a hybrid approach by combining a plasmonic nanoheater with a magnetic element, in this work we establish the robust and reliable control of local temperatures in nanomagnetic arrays by contactless optical means. Plasmon-assisted photo-heating allows for temperature increases of up to several hundred kelvins, which lead to thermally-activated moment reversals and a pronounced reduction of the magnetic coercive field. Furthermore, the polarization-dependent absorption cross section of elongated plasmonic elements enables sublattice-specific heating on sub-nanosecond time scales. Using optical degrees of freedom, i.e. focal position, polarization, power, and pulse length, thermoplasmonic heating of nanomagnets offers itself for the use in flexible, fast, spatially-, and element-selective thermalization for functional magnetic metamaterials.
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73
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Luo Z, Dao TP, Hrabec A, Vijayakumar J, Kleibert A, Baumgartner M, Kirk E, Cui J, Savchenko T, Krishnaswamy G, Heyderman LJ, Gambardella P. Chirally coupled nanomagnets. Science 2019; 363:1435-1439. [DOI: 10.1126/science.aau7913] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 02/26/2019] [Indexed: 11/02/2022]
Abstract
Magnetically coupled nanomagnets have multiple applications in nonvolatile memories, logic gates, and sensors. The most effective couplings have been found to occur between the magnetic layers in a vertical stack. We achieved strong coupling of laterally adjacent nanomagnets using the interfacial Dzyaloshinskii-Moriya interaction. This coupling is mediated by chiral domain walls between out-of-plane and in-plane magnetic regions and dominates the behavior of nanomagnets below a critical size. We used this concept to realize lateral exchange bias, field-free current-induced switching between multistate magnetic configurations as well as synthetic antiferromagnets, skyrmions, and artificial spin ices covering a broad range of length scales and topologies. Our work provides a platform to design arrays of correlated nanomagnets and to achieve all-electric control of planar logic gates and memory devices.
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Affiliation(s)
- Zhaochu Luo
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Trong Phuong Dao
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Laboratory for Magnetism and Interface Physics, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
| | - Aleš Hrabec
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Laboratory for Magnetism and Interface Physics, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
| | | | | | - Manuel Baumgartner
- Laboratory for Magnetism and Interface Physics, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
| | - Eugenie Kirk
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Jizhai Cui
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | | | - Gunasheel Krishnaswamy
- Laboratory for Magnetism and Interface Physics, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
| | - Laura J. Heyderman
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Pietro Gambardella
- Laboratory for Magnetism and Interface Physics, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
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74
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Abstract
Vertex models are an important class of statistical mechanical system that admit exact solutions and exotic physics. Applications include water ice, ferro- and antiferro-electrics, spin ice and artificial spin ice. Here we show that it is possible to engineer spin ice films with atomic-layer precision down to the monolayer limit. Specific heat measurements show that these films, which have a fundamentally different symmetry to bulk spin ice, realise systems close to the two-dimensional F-model, with exotic phase transitions on topologically-constrained configurational manifolds. Our results show how spin ice thin films can release the celebrated Pauling entropy of spin ice without an anomaly in the specific heat. They also significantly expand the class of vertex models available to experiment.
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75
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Li Y, Paterson GW, Macauley GM, Nascimento FS, Ferguson C, Morley SA, Rosamond MC, Linfield EH, MacLaren DA, Macêdo R, Marrows CH, McVitie S, Stamps RL. Superferromagnetism and Domain-Wall Topologies in Artificial "Pinwheel" Spin Ice. ACS NANO 2019; 13:2213-2222. [PMID: 30588800 DOI: 10.1021/acsnano.8b08884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
For over ten years, arrays of interacting single-domain nanomagnets, referred to as artificial spin ices, have been engineered with the aim to study frustration in model spin systems. Here, we use Fresnel imaging to study the reversal process in "pinwheel" artificial spin ice, a modified square ASI structure obtained by rotating each island by some angle about its midpoint. Our results demonstrate that a simple 45° rotation changes the magnetic ordering from antiferromagnetic to ferromagnetic, creating a superferromagnet which exhibits mesoscopic domain growth mediated by domain wall nucleation and coherent domain propagation. We observe several domain-wall configurations, most of which are direct analogues to those seen in continuous ferromagnetic films. However, charged walls also appear due to the geometric constraints of the system. Changing the orientation of the external magnetic field allows control of the nature of the spin reversal with the emergence of either one- or two-dimensional avalanches. This property of pinwheel ASI could be employed to tune devices based on magnetotransport phenomena such as Hall circuits.
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Affiliation(s)
- Yue Li
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Gary W Paterson
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Gavin M Macauley
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Fabio S Nascimento
- Departamento de Física , Universidade Federal de Viçosa , Viçosa 36570-900 , Minas Gerais , Brazil
| | - Ciaran Ferguson
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Sophie A Morley
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
- Department of Physics , University of California , Santa Cruz , California 95064 , United States
| | - Mark C Rosamond
- School of Electronic and Electrical Engineering , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Edmund H Linfield
- School of Electronic and Electrical Engineering , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Donald A MacLaren
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Rair Macêdo
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Christopher H Marrows
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Stephen McVitie
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
| | - Robert L Stamps
- SUPA, School of Physics and Astronomy , University of Glasgow , Glasgow G12 8QQ , United Kingdom
- Department of Physics and Astronomy , University of Manitoba , Manitoba R3T 2N2 , Canada
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76
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Farhan A, Saccone M, Petersen CF, Dhuey S, Chopdekar RV, Huang YL, Kent N, Chen Z, Alava MJ, Lippert T, Scholl A, van Dijken S. Emergent magnetic monopole dynamics in macroscopically degenerate artificial spin ice. SCIENCE ADVANCES 2019; 5:eaav6380. [PMID: 30783629 PMCID: PMC6368442 DOI: 10.1126/sciadv.aav6380] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 12/21/2018] [Indexed: 05/26/2023]
Abstract
Magnetic monopoles, proposed as elementary particles that act as isolated magnetic south and north poles, have long attracted research interest as magnetic analogs to electric charge. In solid-state physics, a classical analog to these elusive particles has emerged as topological excitations within pyrochlore spin ice systems. We present the first real-time imaging of emergent magnetic monopole motion in a macroscopically degenerate artificial spin ice system consisting of thermally activated Ising-type nanomagnets lithographically arranged onto a pre-etched silicon substrate. A real-space characterization of emergent magnetic monopoles within the framework of Debye-Hückel theory is performed, providing visual evidence that these topological defects act like a plasma of Coulomb-type magnetic charges. In contrast to vertex defects in a purely two-dimensional artificial square ice, magnetic monopoles are free to evolve within a divergence-free vacuum, a magnetic Coulomb phase, for which features in the form of pinch-point singularities in magnetic structure factors are observed.
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Affiliation(s)
- Alan Farhan
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Michael Saccone
- Physics Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Charlotte F. Petersen
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria
| | - Scott Dhuey
- Molecular Foundry, LBNL, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Rajesh V. Chopdekar
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Yen-Lin Huang
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Noah Kent
- Physics Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
- Materials Sciences Division, LBNL, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Zuhuang Chen
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, Guangdong 518055, China
| | - Mikko J. Alava
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland
| | - Thomas Lippert
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute, 5232 Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, Laboratory of Inorganic Chemistry, ETH Zurich, Switzerland
| | - Andreas Scholl
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Sebastiaan van Dijken
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
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77
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Loreto RP, Nascimento FS, Gonçalves RS, Borme J, Cezar JC, Nisoli C, Pereira AR, de Araujo CIL. Experimental and theoretical evidences for the ice regime in planar artificial spin ices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:025301. [PMID: 30521491 DOI: 10.1088/1361-648x/aaeeef] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this work, we explore a kind of geometrical effect in the thermodynamics of artificial spin ices (ASI). In general, such artificial materials are athermal. Here, We demonstrate that geometrically driven dynamics in ASI can open up the panorama of exploring distinct ground states and thermally magnetic monopole excitations. It is shown that a particular ASI lattice will provide a richer thermodynamics with nanomagnet spins experiencing less restriction to flip precisely in a kind of rhombic lattice. This can be observed by analysis of only three types of rectangular artificial spin ices (RASI). Denoting the horizontal and vertical lattice spacings by [Formula: see text] and [Formula: see text], respectively, then, a RASI material can be described by its aspect ratio [Formula: see text]. The rhombic lattice emerges when [Formula: see text]. So, by comparing the impact of thermal effects on the spin flips in these three appropriate different RASI arrays, it is possible to find a system very close to the ice regime.
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Affiliation(s)
- R P Loreto
- Laboratory of Spintronics and Nanomagnetism (LabSpiN), Departamento de Física, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
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78
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Streubel R, Kent N, Dhuey S, Scholl A, Kevan S, Fischer P. Spatial and Temporal Correlations of XY Macro Spins. NANO LETTERS 2018; 18:7428-7434. [PMID: 30248262 DOI: 10.1021/acs.nanolett.8b01789] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We use nano disk arrays with square and honeycomb symmetry to investigate magnetic phases and spin correlations of XY dipolar systems at the micro scale. Utilizing magnetization sensitive X-ray photoemission electron microscopy, we probe magnetic ground states and the "order-by-disorder" phenomenon predicted 30 years ago. We observe the antiferromagnetic striped ground state in square lattices, and 6-fold symmetric structures, including trigonal vortex lattices and disordered floating vortices, in the honeycomb lattice. The spin frustration in the honeycomb lattice causes a phase transition from a long-range ordered locked phase over a floating phase with quasi long-range order and indications of a Berezinskii-Thouless-Kosterlitz-like character, to the thermally excited paramagnetic state. Absent spatial correlation and quasi periodic switching of isolated vortices in the quasi long-range ordered phase suggest a degeneracy of the vortex circulation.
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Affiliation(s)
- Robert Streubel
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
| | - Noah Kent
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
- Physics Department , UC Santa Cruz , Santa Cruz California 95064 , United States
| | - Scott Dhuey
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
| | - Andreas Scholl
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
| | - Steve Kevan
- Advanced Light Source , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
- Department of Physics , University of Oregon , Eugene , Oregon 97401 , United States
| | - Peter Fischer
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley California 94720 , United States
- Physics Department , UC Santa Cruz , Santa Cruz California 95064 , United States
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79
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Louis D, Lacour D, Hehn M, Lomakin V, Hauet T, Montaigne F. A tunable magnetic metamaterial based on the dipolar four-state Potts model. NATURE MATERIALS 2018; 17:1076-1080. [PMID: 30374201 DOI: 10.1038/s41563-018-0199-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 09/18/2018] [Indexed: 06/08/2023]
Abstract
Metamaterials, tunable artificial materials, are useful playgrounds to investigate magnetic systems. So far, artificial Ising spin systems have revealed features such as emergent magnetic monopoles1,2 and charge fragmentation3. Here we present a metasystem composed of a lattice of dipolarly coupled nanomagnets. The magnetic spin of each nanomagnet is constrained to lie along a body diagonal, which yields four possible spin states. We show that the magnetic ordering of this metasystem (antiferromagnetic, ferromagnetic or spin ice like) is determined by the spin states orientation relative to the underlying lattice. The dipolar four-state Potts model explains our experimental observations and sheds light on the role of symmetry, as well as short- and long-range dipolar magnetic interactions, in such non-Ising spin systems.
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Affiliation(s)
- D Louis
- Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France
| | - D Lacour
- Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France
| | - M Hehn
- Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France
| | - V Lomakin
- University of California San Diego, Department of Electrical and Computer Engineering, La Jolla, CA, USA
| | - T Hauet
- Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France
| | - F Montaigne
- Institut Jean Lamour, CNRS-Université de Lorraine, Nancy, France.
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80
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Libál A, Lee DY, Ortiz-Ambriz A, Reichhardt C, Reichhardt CJO, Tierno P, Nisoli C. Ice rule fragility via topological charge transfer in artificial colloidal ice. Nat Commun 2018; 9:4146. [PMID: 30297820 PMCID: PMC6175946 DOI: 10.1038/s41467-018-06631-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 09/05/2018] [Indexed: 11/09/2022] Open
Abstract
Artificial particle ices are model systems of constrained, interacting particles. They have been introduced theoretically to study ice-manifolds emergent from frustration, along with domain wall and grain boundary dynamics, doping, pinning-depinning, controlled transport of topological defects, avalanches, and memory effects. Recently such particle-based ices have been experimentally realized with vortices in nano-patterned superconductors or gravitationally trapped colloids. Here we demonstrate that, although these ices are generally considered equivalent to magnetic spin ices, they can access a novel spectrum of phenomenologies that are inaccessible to the latter. With experiments, theory and simulations we demonstrate that in mixed coordination geometries, entropy-driven negative monopoles spontaneously appear at a density determined by the vertex-mixture ratio. Unlike its spin-based analogue, the colloidal system displays a "fragile ice" manifold, where local energetics oppose the ice rule, which is instead enforced through conservation of the global topological charge. The fragile colloidal ice, stabilized by topology, can be spontaneously broken by topological charge transfer.
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Affiliation(s)
- András Libál
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.,Mathematics and Computer Science Department, Babeş-Bolyai University, Cluj, 400084, Romania
| | - Dong Yun Lee
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona, 08028, España
| | - Antonio Ortiz-Ambriz
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona, 08028, España.,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona, 08028, Spain
| | - Charles Reichhardt
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | | | - Pietro Tierno
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, Barcelona, 08028, España.,Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona, 08028, Spain.,Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Barcelona, 08028, Spain
| | - Cristiano Nisoli
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA. .,Institute for Materials Science, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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81
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Karl RM, Mancini GF, Knobloch JL, Frazer TD, Hernandez-Charpak JN, Abad B, Gardner DF, Shanblatt ER, Tanksalvala M, Porter CL, Bevis CS, Adams DE, Kapteyn HC, Murnane MM. Full-field imaging of thermal and acoustic dynamics in an individual nanostructure using tabletop high harmonic beams. SCIENCE ADVANCES 2018; 4:eaau4295. [PMID: 30345364 PMCID: PMC6195334 DOI: 10.1126/sciadv.aau4295] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 09/12/2018] [Indexed: 05/11/2023]
Abstract
Imaging charge, spin, and energy flow in materials is a current grand challenge that is relevant to a host of nanoenhanced systems, including thermoelectric, photovoltaic, electronic, and spin devices. Ultrafast coherent x-ray sources enable functional imaging on nanometer length and femtosecond timescales particularly when combined with advances in coherent imaging techniques. Here, we combine ptychographic coherent diffractive imaging with an extreme ultraviolet high harmonic light source to directly visualize the complex thermal and acoustic response of an individual nanoscale antenna after impulsive heating by a femtosecond laser. We directly image the deformations induced in both the nickel tapered nanoantenna and the silicon substrate and see the lowest-order generalized Lamb wave that is partially confined to a uniform nanoantenna. The resolution achieved-sub-100 nm transverse and 0.5-Å axial spatial resolution, combined with ≈10-fs temporal resolution-represents a significant advance in full-field dynamic imaging capabilities. The tapered nanoantenna is sufficiently complex that a full simulation of the dynamic response would require enormous computational power. We therefore use our data to benchmark approximate models and achieve excellent agreement between theory and experiment. In the future, this work will enable three-dimensional functional imaging of opaque materials and nanostructures that are sufficiently complex that their functional properties cannot be predicted.
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82
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Östman E, Arnalds UB, Kapaklis V, Taroni A, Hjörvarsson B. Ising-like behaviour of mesoscopic magnetic chains. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:365301. [PMID: 29968584 DOI: 10.1088/1361-648x/aad0c1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate an experimental realization of the short range magnetic order in a one-dimensional Ising chain using fabricated mesospins. We confirm an excellent agreement between the experimental findings and simulations obtained using the original Ising model. In particular, we are able to show that the thermal behaviour of the mesoscopic Ising chain dominates over the thermal behaviour of the individual mesospins themselves, confirming that fabricated mesospins can be viewed as artificial magnetic atoms.
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Affiliation(s)
- Erik Östman
- Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden
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83
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Leo N, Holenstein S, Schildknecht D, Sendetskyi O, Luetkens H, Derlet PM, Scagnoli V, Lançon D, Mardegan JRL, Prokscha T, Suter A, Salman Z, Lee S, Heyderman LJ. Collective magnetism in an artificial 2D XY spin system. Nat Commun 2018; 9:2850. [PMID: 30030427 PMCID: PMC6054668 DOI: 10.1038/s41467-018-05216-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/12/2018] [Indexed: 11/09/2022] Open
Abstract
Two-dimensional magnetic systems with continuous spin degrees of freedom exhibit a rich spectrum of thermal behaviour due to the strong competition between fluctuations and correlations. When such systems incorporate coupling via the anisotropic dipolar interaction, a discrete symmetry emerges, which can be spontaneously broken leading to a low-temperature ordered phase. However, the experimental realisation of such two-dimensional spin systems in crystalline materials is difficult since the dipolar coupling is usually much weaker than the exchange interaction. Here we realise two-dimensional magnetostatically coupled XY spin systems with nanoscale thermally active magnetic discs placed on square lattices. Using low-energy muon-spin relaxation and soft X-ray scattering, we observe correlated dynamics at the critical temperature and the emergence of static long-range order at low temperatures, which is compatible with theoretical predictions for dipolar-coupled XY spin systems. Furthermore, by modifying the sample design, we demonstrate the possibility to tune the collective magnetic behaviour in thermally active artificial spin systems with continuous degrees of freedom.
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Affiliation(s)
- Naëmi Leo
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland.
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
| | - Stefan Holenstein
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Physik-Institut der Universität Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Dominik Schildknecht
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Condensed Matter Theory Group, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Oles Sendetskyi
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Hubertus Luetkens
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Peter M Derlet
- Condensed Matter Theory Group, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Valerio Scagnoli
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Diane Lançon
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - José R L Mardegan
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen, Switzerland
| | - Thomas Prokscha
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Andreas Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Zaher Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
| | - Stephen Lee
- School of Physics and Astronomy, SUPA, University of St. Andrews, St Andrews, KY16 9SS, UK
| | - Laura J Heyderman
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093, Zurich, Switzerland
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
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84
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Sung D, Jung C, Cho BG, Jo W, Han HS, Lee KS, Bhat V, Farmer B, De Long LE, Lee KB, Keavney DJ, Lee DR, Song C. Imaging the magnetic structures of artificial quasicrystal magnets using resonant coherent diffraction of circularly polarized X-rays. NANOSCALE 2018; 10:13159-13164. [PMID: 29963676 DOI: 10.1039/c8nr03733g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Unraveling nanoscale spin structures has long been an important activity addressing various scientific interests, that are also readily adaptable to technological applications. This has invigorated the development of versatile nanoprobes suitable for imaging specimens under native conditions. Here we have demonstrated the resonant coherent diffraction of an artificial quasicrystal magnet with circularly polarized X-rays. The nanoscale magnetic structure was revealed from X-ray speckle patterns by comparing with micromagnetic simulations, as a step toward understanding the intricate relationship between the chemical and spin structures in an aperiodic quasicrystal lattice. Femtosecond X-ray pulses from free electron lasers are expected to immediately extend the current work to nanoscale structure investigations of ultrafast spin dynamics, surpassing the present spatio-temporal resolution.
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Affiliation(s)
- Daeho Sung
- Department of Physics, POSTECH, Pohang 37673, Korea.
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85
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Tunable and switchable magnetic dipole patterns in nanostructured superconductors. Nat Commun 2018; 9:2576. [PMID: 29968732 PMCID: PMC6030140 DOI: 10.1038/s41467-018-05045-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 06/08/2018] [Indexed: 11/08/2022] Open
Abstract
Design and manipulation of magnetic moment arrays have been at the focus of studying the interesting cooperative physical phenomena in various magnetic systems. However, long-range ordered magnetic moments are rather difficult to achieve due to the excited states arising from the relatively weak exchange interactions between the localized moments. Here, using a nanostructured superconductor, we investigate a perfectly ordered magnetic dipole pattern with the magnetic poles having the same distribution as the magnetic charges in an artificial spin ice. The magnetic states can simply be switched on/off by applying a current flowing through nanopatterned area. Moreover, by coupling magnetic dipoles with the pinned vortex lattice, we are able to erase the positive/negative poles, resulting in a magnetic dipole pattern of only one polarity, analogous to the recently predicted vortex ice. These switchable and tunable magnetic dipole patterns open pathways for the study of exotic ordering phenomena in magnetic systems.
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86
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Wang YL, Ma X, Xu J, Xiao ZL, Snezhko A, Divan R, Ocola LE, Pearson JE, Janko B, Kwok WK. Switchable geometric frustration in an artificial-spin-ice-superconductor heterosystem. NATURE NANOTECHNOLOGY 2018; 13:560-565. [PMID: 29892018 DOI: 10.1038/s41565-018-0162-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 05/03/2018] [Indexed: 06/08/2023]
Abstract
Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics1, such as data storage, memory and logic2. However, it is difficult to achieve very high degeneracy, especially in a two-dimensional system3,4. Here, we showcase in situ controllable geometric frustration with high degeneracy in a two-dimensional flux-quantum system. We create this in a superconducting thin film placed underneath a reconfigurable artificial-spin-ice structure5. The tunable magnetic charges in the artificial-spin-ice strongly interact with the flux quanta in the superconductor, enabling switching between frustrated and crystallized flux quanta states. The different states have measurable effects on the superconducting critical current profile, which can be reconfigured by precise selection of the spin-ice magnetic state through the application of an external magnetic field. We demonstrate the applicability of these effects by realizing a reprogrammable flux quanta diode. The tailoring of the energy landscape of interacting 'particles' using artificial-spin-ices provides a new paradigm for the design of geometric frustration, which could illuminate a path to control new functionalities in other material systems, such as magnetic skyrmions6, electrons and holes in two-dimensional materials7,8, and topological insulators9, as well as colloids in soft materials10-13.
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Affiliation(s)
- Yong-Lei Wang
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA.
- Department of Physics, University of Notre Dame, Notre Dame, IN, USA.
- Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, Nanjing University, Nanjing, China.
| | - Xiaoyu Ma
- Department of Physics, University of Notre Dame, Notre Dame, IN, USA
| | - Jing Xu
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA
- Department of Physics, Northern Illinois University, DeKalb, IL, USA
| | - Zhi-Li Xiao
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA.
- Department of Physics, Northern Illinois University, DeKalb, IL, USA.
| | - Alexey Snezhko
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA
| | - Ralu Divan
- Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA
| | - Leonidas E Ocola
- Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - John E Pearson
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA
| | - Boldizsar Janko
- Department of Physics, University of Notre Dame, Notre Dame, IN, USA.
| | - Wai-Kwong Kwok
- Materials Science Division, Argonne National Laboratory, Argonne, IL, USA
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87
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Taberlet N, Ferrand J, Plihon N. Stability Analysis of an Array of Magnets: When Will It Jump? PHYSICAL REVIEW LETTERS 2018; 120:264301. [PMID: 30004779 DOI: 10.1103/physrevlett.120.264301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Indexed: 06/08/2023]
Abstract
A bidimensional array of magnets whose magnetic moments share the same vertical orientation, and lying on a planar surface, can be gradually compacted. As the density reaches a threshold, the assembly becomes unstable, and the magnets violently pop out of plane. In this Letter, we investigate experimentally and theoretically the maximum packing fraction (or density) of a bidimensional planar assembly of identical cylindrical magnets. We show that the instability can be attributed to local fluctuations of the altitude of the magnets on the planar surface. The maximum density is theoretically predicted assuming dipolar interactions between the magnets and is in excellent agreement with experimental results using a variety of cylindrical magnets.
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Affiliation(s)
- Nicolas Taberlet
- Univ Lyon, Ens de Lyon, Univ Claude Bernard Lyon 1, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| | - Jérémy Ferrand
- Univ Lyon, Ens de Lyon, Univ Claude Bernard Lyon 1, CNRS, Laboratoire de Physique, F-69342 Lyon, France
| | - Nicolas Plihon
- Univ Lyon, Ens de Lyon, Univ Claude Bernard Lyon 1, CNRS, Laboratoire de Physique, F-69342 Lyon, France
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88
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Nisoli C. Unexpected Phenomenology in Particle-Based Ice Absent in Magnetic Spin Ice. PHYSICAL REVIEW LETTERS 2018; 120:167205. [PMID: 29756919 DOI: 10.1103/physrevlett.120.167205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Indexed: 06/08/2023]
Abstract
While particle-based ices are often considered essentially equivalent to magnet-based spin ices, the two differ essentially in frustration and energetics. We show that at equilibrium particle-based ices correspond exactly to spin ices coupled to a background field. In trivial geometries, such a field has no effect, and the two systems are indeed thermodynamically equivalent. In other cases, however, the field controls a richer phenomenology, absent in magnetic ices, and still largely unexplored: ice rule fragility, topological charge transfer, radial polarization, decimation induced disorder, and glassiness.
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Affiliation(s)
- Cristiano Nisoli
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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89
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Direct-write of free-form building blocks for artificial magnetic 3D lattices. Sci Rep 2018; 8:6160. [PMID: 29670129 PMCID: PMC5906635 DOI: 10.1038/s41598-018-24431-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 03/29/2018] [Indexed: 11/30/2022] Open
Abstract
By the fabrication of periodically arranged nanomagnetic systems it is possible to engineer novel physical properties by realizing artificial lattice geometries that are not accessible via natural crystallization or chemical synthesis. This has been accomplished with great success in two dimensions in the fields of artificial spin ice and magnetic logic devices, to name just two. Although first proposals have been made to advance into three dimensions (3D), established nanofabrication pathways based on electron beam lithography have not been adapted to obtain free-form 3D nanostructures. Here we demonstrate the direct-write fabrication of freestanding ferromagnetic 3D nano-architectures. By employing micro-Hall sensing, we have determined the magnetic stray field generated by our free-form structures in an externally applied magnetic field and we have performed micromagnetic and macro-spin simulations to deduce the spatial magnetization profiles in the structures and analyze their switching behavior. Furthermore we show that the magnetic 3D elements can be combined with other 3D elements of different chemical composition and intrinsic material properties.
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90
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Kockum AF, Johansson G, Nori F. Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics. PHYSICAL REVIEW LETTERS 2018; 120:140404. [PMID: 29694115 DOI: 10.1103/physrevlett.120.140404] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Indexed: 06/08/2023]
Abstract
In quantum-optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation with which they interact. However, superconducting qubits coupled to a meandering transmission line, or to surface acoustic waves, can realize "giant artificial atoms" that couple to a bosonic field at several points which are wavelengths apart. Here, we study setups with multiple giant atoms coupled at multiple points to a one-dimensional (1D) waveguide. We show that the giant atoms can be protected from decohering through the waveguide, but still have exchange interactions mediated by the waveguide. Unlike in decoherence-free subspaces, here the entire multiatom Hilbert space (2^{N} states for N atoms) is protected from decoherence. This is not possible with "small" atoms. We further show how this decoherence-free interaction can be designed in setups with multiple atoms to implement, e.g., a 1D chain of atoms with nearest-neighbor couplings or a collection of atoms with all-to-all connectivity. This may have important applications in quantum simulation and quantum computing.
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Affiliation(s)
| | - Göran Johansson
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
| | - Franco Nori
- Theoretical Quantum Physics Laboratory, RIKEN, Saitama 351-0198, Japan
- Physics Department, The University of Michigan, Ann Arbor, Michigan 48109-1040, USA
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91
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Attraction Controls the Entropy of Fluctuations in Isosceles Triangular Networks. ENTROPY 2018; 20:e20020122. [PMID: 33265213 PMCID: PMC7512615 DOI: 10.3390/e20020122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 02/08/2018] [Accepted: 02/10/2018] [Indexed: 11/16/2022]
Abstract
We study two-dimensional triangular-network models, which have degenerate ground states composed of straight or randomly-zigzagging stripes and thus sub-extensive residual entropy. We show that attraction is responsible for the inversion of the stable phase by changing the entropy of fluctuations around the ground-state configurations. By using a real-space shell-expansion method, we compute the exact expression of the entropy for harmonic interactions, while for repulsive harmonic interactions we obtain the entropy arising from a limited subset of the system by numerical integration. We compare these results with a three-dimensional triangular-network model, which shows the same attraction-mediated selection mechanism of the stable phase, and conclude that this effect is general with respect to the dimensionality of the system.
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92
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Al Mamoori MKI, Keller L, Pieper J, Barth S, Winkler R, Plank H, Müller J, Huth M. Magnetic Characterization of Direct-Write Free-Form Building Blocks for Artificial Magnetic 3D Lattices. MATERIALS (BASEL, SWITZERLAND) 2018; 11:E289. [PMID: 29439553 PMCID: PMC5848986 DOI: 10.3390/ma11020289] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/07/2018] [Accepted: 02/07/2018] [Indexed: 11/16/2022]
Abstract
Three-dimensional (3D) nanomagnetism, where spin configurations extend into the vertical direction of a substrate plane allow for more complex, hierarchical systems and the design of novel magnetic effects. As an important step towards this goal, we have recently demonstrated the direct-write fabrication of freestanding ferromagnetic 3D nano-architectures of ferromagnetic CoFe in shapes of nano-tree and nano-cube structures by means of focused electron beam induced deposition. Here, we present a comprehensive characterization of the magnetic properties of these structures by local stray-field measurements using a high-resolution micro-Hall magnetometer. Measurements in a wide range of temperatures and different angles of the externally applied magnetic field with respect to the surface plane of the sensor are supported by corresponding micromagnetic simulations, which explain the overall switching behavior of in part rather complex magnetization configurations remarkably well. In particular, the simulations yield coercive and switching fields that are in good quantitative correspondence with the measured coercive and switching fields assuming a bulk metal content of 100 at % consisting of bcc Co 3 Fe. We show that thermally-unstable magnetization states can be repetitively prepared and their lifetime controlled at will, a prerequisite to realizing dynamic and thermally-active magnetic configurations if the building blocks are to be used in lattice structures.
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Affiliation(s)
| | - Lukas Keller
- Institute of Physics, Goethe University, 60438 (M) Frankfurt, Germany.
| | - Jonathan Pieper
- Institute of Physics, Goethe University, 60438 (M) Frankfurt, Germany.
| | - Sven Barth
- Institute of Materials Chemistry, Vienna University of Technology, 1060 Vienna, Austria.
| | - Robert Winkler
- Graz Centre for Electron Microscopy, 8010 Graz, Austria.
| | - Harald Plank
- Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, 8010 Graz, Austria.
| | - Jens Müller
- Institute of Physics, Goethe University, 60438 (M) Frankfurt, Germany.
| | - Michael Huth
- Institute of Physics, Goethe University, 60438 (M) Frankfurt, Germany.
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93
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Libál A, Nisoli C, Reichhardt CJO, Reichhardt C. Inner Phases of Colloidal Hexagonal Spin Ice. PHYSICAL REVIEW LETTERS 2018; 120:027204. [PMID: 29376707 DOI: 10.1103/physrevlett.120.027204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Indexed: 06/07/2023]
Abstract
Using numerical simulations that mimic recent experiments on hexagonal colloidal ice, we show that colloidal hexagonal artificial spin ice exhibits an inner phase within its ice state that has not been observed previously. Under increasing colloid-colloid repulsion, the initially paramagnetic system crosses into a disordered ice regime, then forms a topologically charge ordered state with disordered colloids, and finally reaches a threefold degenerate, ordered ferromagnetic state. This is reminiscent of, yet distinct from, the inner phases of the magnetic kagome spin ice analog. The difference in the inner phases of the two systems is explained by their difference in energetics and frustration.
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Affiliation(s)
- A Libál
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
- Mathematics and Computer Science Department, Babeş-Bolyai University, Cluj 400084, Romania
| | - C Nisoli
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C J O Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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94
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Liu Y, Kempinger S, He R, Day TD, Moradifar P, Yu SY, Russell JL, Torres VM, Xu P, Mallouk TE, Mohney SE, Alem N, Samarth N, Badding JV. Confined Chemical Fluid Deposition of Ferromagnetic Metalattices. NANO LETTERS 2018; 18:546-552. [PMID: 29236505 DOI: 10.1021/acs.nanolett.7b04633] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A magnetic, metallic inverse opal fabricated by infiltration into a silica nanosphere template assembled from spheres with diameters less than 100 nm is an archetypal example of a "metalattice". In traditional quantum confined structures such as dots, wires, and thin films, the physical dynamics in the free dimensions is typically largely decoupled from the behavior in the confining directions. In a metalattice, the confined and extended degrees of freedom cannot be separated. Modeling predicts that magnetic metalattices should exhibit multiple topologically distinct magnetic phases separated by sharp transitions in their hysteresis curves as their spatial dimensions become comparable to and smaller than the magnetic exchange length, potentially enabling an interesting class of "spin-engineered" magnetic materials. The challenge to synthesizing magnetic inverse opal metalattices from templates assembled from sub-100 nm spheres is in infiltrating the nanoscale, tortuous voids between the nanospheres void-free with a suitable magnetic material. Chemical fluid deposition from supercritical carbon dioxide could be a viable approach to void-free infiltration of magnetic metals in view of the ability of supercritical fluids to penetrate small void spaces. However, we find that conventional chemical fluid deposition of the magnetic late transition metal nickel into sub-100 nm silica sphere templates in conventional macroscale reactors produces a film on top of the template that appears to largely block infiltration. Other deposition approaches also face difficulties in void-free infiltration into such small nanoscale templates or require conducting substrates that may interfere with properties measurements. Here we report that introduction of "spatial confinement" into the chemical fluid reactor allows for fabrication of nearly void-free nickel metalattices by infiltration into templates with sphere sizes from 14 to 100 nm. Magnetic measurements suggest that these nickel metalattices behave as interconnected systems rather than as isolated superparamagnetic systems coupled solely by dipolar interactions.
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Affiliation(s)
- Yunzhi Liu
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Susan Kempinger
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Rongrui He
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Todd D Day
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Parivash Moradifar
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Shih-Ying Yu
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Jennifer L Russell
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Vincent M Torres
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Pengtao Xu
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Thomas E Mallouk
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Suzanne E Mohney
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Nasim Alem
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - Nitin Samarth
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
| | - John V Badding
- Department of Chemistry, ‡Department of Physics, §Department of Materials Science and Engineering, ∥Department of Biochemistry and Molecular Biology, and ⊥Materials Research Institute, Penn State University , University Park, Pennsylvania 16802, United States
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95
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Abstract
A novel approach to investigate geometrical frustration is introduced using two-dimensional magnonic vortex crystals. The frustration of the crystal can be manipulated and turned on and off dynamically on the timescale of milliseconds. The vortices are studied using scanning transmission x-ray microscopy and ferromagnetic resonance spectroscopy. They are arranged analogous to the nanomagnets in artificial spin-ice systems. The polarization state of the vortices is tuned in a way that geometrical frustration arises. We demonstrate that frustrated polarization states and non-frustrated states can be tuned to the crystal by changing the frequency of the state formation process.
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96
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Gartside JC, Arroo DM, Burn DM, Bemmer VL, Moskalenko A, Cohen LF, Branford WR. Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing. NATURE NANOTECHNOLOGY 2018; 13:53-58. [PMID: 29158603 DOI: 10.1038/s41565-017-0002-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 09/14/2017] [Indexed: 06/07/2023]
Abstract
Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing-a scanning probe technique-provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy 'monopole-chain' states that exhibit negative effective temperatures.
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Affiliation(s)
- Jack C Gartside
- Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK.
| | - Daan M Arroo
- Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
| | | | - Victoria L Bemmer
- Department of Materials, Imperial College London, London, SW7 2AZ, UK
| | - Andy Moskalenko
- Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
| | - Lesley F Cohen
- Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
| | - Will R Branford
- Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK
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97
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Summers B, Chen Y, Dahal A, Singh DK. New Description of Evolution of Magnetic Phases in Artificial Honeycomb Lattice. Sci Rep 2017; 7:16080. [PMID: 29167461 PMCID: PMC5700068 DOI: 10.1038/s41598-017-15786-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 11/01/2017] [Indexed: 11/08/2022] Open
Abstract
Artificial magnetic honeycomb lattice provides a two-dimensional archetypal system to explore novel phenomena of geometrically frustrated magnets. According to theoretical reports, an artificial magnetic honeycomb lattice is expected to exhibit several phase transitions to unique magnetic states as a function of reducing temperature. Experimental investigations of permalloy artificial honeycomb lattice of connected ultra-small elements, [Formula: see text] 12 nm, reveal a more complicated behavior. First, upon cooling the sample to intermediate temperature, [Formula: see text] 175 K, the system manifests a non-unique state where the long range order co-exists with short-range magnetic charge order and weak spin ice state. Second, at much lower temperature, [Formula: see text] 6 K, the long-range spin solid state exhibits a re-entrant behavior. Both observations are in direct contrast to the present understanding of this system. New theoretical approaches are needed to develop a comprehensive formulation of this two dimensional magnet.
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Affiliation(s)
- B Summers
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - Y Chen
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - A Dahal
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
| | - D K Singh
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA.
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98
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Gliga S, Hrkac G, Donnelly C, Büchi J, Kleibert A, Cui J, Farhan A, Kirk E, Chopdekar RV, Masaki Y, Bingham NS, Scholl A, Stamps RL, Heyderman LJ. Emergent dynamic chirality in a thermally driven artificial spin ratchet. NATURE MATERIALS 2017; 16:1106-1111. [PMID: 29058727 DOI: 10.1038/nmat5007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 09/12/2017] [Indexed: 05/22/2023]
Abstract
Modern nanofabrication techniques have opened the possibility to create novel functional materials, whose properties transcend those of their constituent elements. In particular, tuning the magnetostatic interactions in geometrically frustrated arrangements of nanoelements called artificial spin ice can lead to specific collective behaviour, including emergent magnetic monopoles, charge screening and transport, as well as magnonic response. Here, we demonstrate a spin-ice-based active material in which energy is converted into unidirectional dynamics. Using X-ray photoemission electron microscopy we show that the collective rotation of the average magnetization proceeds in a unique sense during thermal relaxation. Our simulations demonstrate that this emergent chiral behaviour is driven by the topology of the magnetostatic field at the edges of the nanomagnet array, resulting in an asymmetric energy landscape. In addition, a bias field can be used to modify the sense of rotation of the average magnetization. This opens the possibility of implementing a magnetic Brownian ratchet, which may find applications in novel nanoscale devices, such as magnetic nanomotors, actuators, sensors or memory cells.
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Affiliation(s)
- Sebastian Gliga
- SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Gino Hrkac
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - Claire Donnelly
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Jonathan Büchi
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
| | | | - Jizhai Cui
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Alan Farhan
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, California 94720, USA
| | - Eugenie Kirk
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - Rajesh V Chopdekar
- Department of Materials Science and Engineering, University of California, Davis, Davis, California 95616, USA
| | - Yusuke Masaki
- Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
| | - Nicholas S Bingham
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- National Research Council Research Associate at the US Naval Research Laboratory, 4555 Overlook Avenue, SW Washington DC 20375, USA
| | - Andreas Scholl
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, California 94720, USA
| | - Robert L Stamps
- SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
| | - Laura J Heyderman
- Laboratory for Mesoscopic Systems, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
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99
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Realization of Rectangular Artificial Spin Ice and Direct Observation of High Energy Topology. Sci Rep 2017; 7:13982. [PMID: 29070908 PMCID: PMC5656638 DOI: 10.1038/s41598-017-14421-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 10/10/2017] [Indexed: 11/29/2022] Open
Abstract
In this work, we have constructed and experimentally investigated frustrated arrays of dipoles forming two-dimensional artificial spin ices with different lattice parameters (rectangular arrays with horizontal and vertical lattice spacings denoted by a and b respectively). Arrays with three different aspect ratios γ = a/b = \documentclass[12pt]{minimal}
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\begin{document}$$\sqrt{{\bf{4}}}$$\end{document}4 are studied. Theoretical calculations of low-energy demagnetized configurations for these same parameters are also presented. Experimental data for demagnetized samples confirm most of the theoretical results. However, the highest energy topology (doubly-charged monopoles) does not emerge in our theoretical model, while they are seen in experiments for large enough γ. Our results also insinuate that the string tension connecting two magnetic monopoles in a pair vanishes in rectangular lattices with a critical ratio γ = γc = \documentclass[12pt]{minimal}
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\begin{document}$$\sqrt{{\bf{3}}}$$\end{document}3, supporting previous theoretical predictions.
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100
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Farhan A, Petersen CF, Dhuey S, Anghinolfi L, Qin QH, Saccone M, Velten S, Wuth C, Gliga S, Mellado P, Alava MJ, Scholl A, van Dijken S. Nanoscale control of competing interactions and geometrical frustration in a dipolar trident lattice. Nat Commun 2017; 8:995. [PMID: 29042556 PMCID: PMC5727135 DOI: 10.1038/s41467-017-01238-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 08/31/2017] [Indexed: 11/30/2022] Open
Abstract
Geometrical frustration occurs when entities in a system, subject to given lattice constraints, are hindered to simultaneously minimize their local interactions. In magnetism, systems incorporating geometrical frustration are fascinating, as their behavior is not only hard to predict, but also leads to the emergence of exotic states of matter. Here, we provide a first look into an artificial frustrated system, the dipolar trident lattice, where the balance of competing interactions between nearest-neighbor magnetic moments can be directly controlled, thus allowing versatile tuning of geometrical frustration and manipulation of ground state configurations. Our findings not only provide the basis for future studies on the low-temperature physics of the dipolar trident lattice, but also demonstrate how this frustration-by-design concept can deliver magnetically frustrated metamaterials. Artificial magnetic nanostructures enable the study of competing frustrated interactions with more control over the system parameters than is possible in magnetic materials. Farhan et al. present a two-dimensional lattice geometry where the frustration can be controlled by tuning the unit cell parameters.
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Affiliation(s)
- Alan Farhan
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA, 94720, USA.
| | - Charlotte F Petersen
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Espoo, FI-00076, Aalto, Finland
| | - Scott Dhuey
- Molecular Foundry, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Luca Anghinolfi
- Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, I-16146, Genova, Italy
| | - Qi Hang Qin
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076, Aalto, Finland
| | - Michael Saccone
- Department of Physics, University of California, Santa Cruz, CA, 95064, USA
| | - Sven Velten
- Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA.,Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Jungiusstrasse 11, 20355, Hamburg, Germany
| | - Clemens Wuth
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA.,Daegu Gyeongbuk Institute of Science and Technology (DGIST), 50-1 Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 42988, Republic of Korea
| | - Sebastian Gliga
- SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Paula Mellado
- School of Engineering and Sciences, Adolfo Ibáñez University, Diagonal Las Torres, 2640, Peñalolén, Santiago, Chile
| | - Mikko J Alava
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Espoo, FI-00076, Aalto, Finland
| | - Andreas Scholl
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Sebastiaan van Dijken
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076, Aalto, Finland
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