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Vlaic S, Mousadakos D, Ouazi S, Rusponi S, Brune H. Increasing Magnetic Anisotropy in Bimetallic Nanoislands Grown on fcc(111) Metal Surfaces. NANOMATERIALS 2022; 12:nano12030518. [PMID: 35159863 PMCID: PMC8840744 DOI: 10.3390/nano12030518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/27/2022] [Accepted: 01/29/2022] [Indexed: 11/23/2022]
Abstract
The magnetic properties and the atomic scale morphology of bimetallic two-dimensional nanoislands, epitaxially grown on fcc(111) metal surfaces, have been studied by means of Magneto-Optical Kerr Effect and Scanning Tunneling Microscopy. We investigate the effect on blocking temperature of one-dimensional interlines appearing in core-shell structures, of two-dimensional interfaces created by capping, and of random alloying. The islands are grown on Pt(111) and contain a Co-core, surrounded by Ag, Rh, and Pd shells, or capped by Pd. The largest effect is obtained by Pd capping, increasing the blocking temperature by a factor of three compared to pure Co islands. In addition, for Co-core Fe-shell and Co-core FexCo1−x-shell islands, self-assembled into well ordered superlattices on Au(11,12,12) vicinal surfaces, we find a strong enhancement of the blocking temperature compared to pure Co islands of the same size. These ultra-high-density (15 Tdots/in2) superlattices of CoFe nanodots, only 500 atoms in size, have blocking temperature exceeding 100 K. Our findings open new possibilities to tailor the magnetic properties of nanoislands.
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Affiliation(s)
- Sergio Vlaic
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; (S.V.); (D.M.); (S.O.); (S.R.)
- Laboratoire de Physique et d’Étude des Matériaux (LPEM), ESPCI Paris-PSL Universtity, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
| | - Dimitris Mousadakos
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; (S.V.); (D.M.); (S.O.); (S.R.)
| | - Safia Ouazi
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; (S.V.); (D.M.); (S.O.); (S.R.)
| | - Stefano Rusponi
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; (S.V.); (D.M.); (S.O.); (S.R.)
| | - Harald Brune
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; (S.V.); (D.M.); (S.O.); (S.R.)
- Correspondence:
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Rousseau O, Beaujouan D, Petit-Watelot S, Thibaudeau P, Rohart S, Viret M. Giant rectified voltages from magnetization dynamics of an atomically sharp domain wall. NANOTECHNOLOGY 2019; 30:285201. [PMID: 30925492 DOI: 10.1088/1361-6528/ab1498] [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
Magnetization dynamics is of great interest in the aim of using spins in nanoscale information technology, which ultimately should reach the atomic size. In the present work, we explore magnetization and spin dynamics in atomic ferromagnetic contacts both experimentally and theoretically. We demonstrate that domain walls induce a giant rectification effect as the DC voltages measured across the contacts are greatly enhanced by the presence of a domain wall. This effect is understood using multiscale dynamic simulations showing that the atomic sized walls oscillate, both in position and size, when submitted to the radio-frequency excitation. This leads to an increase by three orders of magnitude due to the large atomic scale spin excursion at resonance in the presence of an atomic sized domain wall. Beside the interesting amplified rectification, this could also be used as a unique tool to measure dynamical properties at the atomic scale.
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Affiliation(s)
- O Rousseau
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, F-91191 Gif sur Yvette, France
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Mishra P, Qi ZK, Oka H, Nakamura K, Komeda T. Spatially Resolved Magnetic Anisotropy of Cobalt Nanostructures on the Au(111) Surface. NANO LETTERS 2017; 17:5843-5847. [PMID: 28806089 DOI: 10.1021/acs.nanolett.7b03114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the origin of perpendicular magnetic anisotropy in surface-supported nanoclusters is crucial for fundamental research as well as data storage applications. Here, we investigate the perpendicular magnetic anisotropy energy (MAE) of bilayer cobalt islands on Au(111) substrate using spin-polarized scanning tunneling microscopy at 4.6 K and first-principles theoretical calculations. Au(111) substrate serves as an excellent model system to study the effect of nucleation site and stacking sequence on MAE. Our measurements reveal that the MAE of bilayer islands depends strongly on the crystallographic stacking of the two Co layers and nucleation of the third layer. Moreover, the MAE of Co atoms on Au(111) is enhanced by a factor of 1.75 as compared to that reported on Cu(111). Our first-principles calculations attribute this enhancement to the large spin-orbit coupling of the Au atoms. Our results highlight the strong impact of nanometer-scale structural changes in Co islands on MAE and emphasize the importance of spatially resolved measurements for the magnetic characterization of surface-supported nanostructures.
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Affiliation(s)
- Puneet Mishra
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Zhi Kun Qi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Hirofumi Oka
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
| | - Kohji Nakamura
- Department of Physics Engineering, Mie University , Tsu, Mie 514-8507, Japan
| | - Tadahiro Komeda
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan
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Barla A, Bellini V, Rusponi S, Ferriani P, Pivetta M, Donati F, Patthey F, Persichetti L, Mahatha SK, Papagno M, Piamonteze C, Fichtner S, Heinze S, Gambardella P, Brune H, Carbone C. Complex Magnetic Exchange Coupling between Co Nanostructures and Ni(111) across Epitaxial Graphene. ACS NANO 2016; 10:1101-1107. [PMID: 26588469 DOI: 10.1021/acsnano.5b06410] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report on the magnetic coupling between isolated Co atoms as well as small Co islands and Ni(111) mediated by an epitaxial graphene layer. X-ray magnetic circular dichroism and scanning tunneling microscopy combined with density functional theory calculations reveal that Co atoms occupy two distinct adsorption sites, with different magnetic coupling to the underlying Ni(111) surface. We further report a transition from an antiferromagnetic to a ferromagnetic coupling with increasing Co cluster size. Our results highlight the extreme sensitivity of the exchange interaction mediated by graphene to the adsorption site and to the in-plane coordination of the magnetic atoms.
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Affiliation(s)
- Alessandro Barla
- Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy
| | - Valerio Bellini
- S3-Istituto di Nanoscienze-CNR , Via Campi 213/A, I-41125 Modena, Italy
| | - Stefano Rusponi
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland
| | - Paolo Ferriani
- Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany
| | - Marina Pivetta
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland
| | - Fabio Donati
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland
| | - François Patthey
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland
| | - Luca Persichetti
- Department of Materials, ETH Zurich , CH-8093 Zurich, Switzerland
| | - Sanjoy K Mahatha
- Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy
| | - Marco Papagno
- Dipartimento di Fisica, Università della Calabria , I-87036 Arcavacata di Rende (Cs), Italy
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland
| | - Simon Fichtner
- Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany
| | - Stefan Heinze
- Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany
| | | | - Harald Brune
- Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland
| | - Carlo Carbone
- Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy
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Spinelli A, Bryant B, Delgado F, Fernández-Rossier J, Otte AF. Imaging of spin waves in atomically designed nanomagnets. NATURE MATERIALS 2014; 13:782-785. [PMID: 24997736 DOI: 10.1038/nmat4018] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 05/28/2014] [Indexed: 06/03/2023]
Abstract
The spin dynamics of all ferromagnetic materials are governed by two types of collective phenomenon: spin waves and domain walls. The fundamental processes underlying these collective modes, such as exchange interactions and magnetic anisotropy, all originate at the atomic scale. However, conventional probing techniques based on neutron and photon scattering provide high resolution in reciprocal space, and thereby poor spatial resolution. Here we present direct imaging of standing spin waves in individual chains of ferromagnetically coupled S = 2 Fe atoms, assembled one by one on a Cu(2)N surface using a scanning tunnelling microscope. We are able to map the spin dynamics of these designer nanomagnets with atomic resolution in two complementary ways. First, atom-to-atom variations of the amplitude of the quantized spin-wave excitations are probed using inelastic electron tunnelling spectroscopy. Second, we observe slow stochastic switching between two opposite magnetization states, whose rate varies strongly depending on the location of the tip along the chain. Our observations, combined with model calculations, reveal that switches of the chain are initiated by a spin-wave excited state that has its antinodes at the edges of the chain, followed by a domain wall shifting through the chain from one end to the other. This approach opens the way towards atomic-scale imaging of other types of spin excitation, such as spinon pairs and fractional end-states, in engineered spin chains.
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Affiliation(s)
- A Spinelli
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - B Bryant
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - F Delgado
- International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - J Fernández-Rossier
- International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, 4715-310 Braga, Portugal
| | - A F Otte
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Leblanc MD, Whitehead JP, Plumer ML. Monte Carlo simulations of intragrain spin effects in a quasi-2D Heisenberg model with uniaxial anisotropy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:196004. [PMID: 23603318 DOI: 10.1088/0953-8984/25/19/196004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A combination of Metropolis and modified Wolff cluster algorithms is used to examine the impact of uniaxial single-ion anisotropy on the phase transition to ferromagnetic order of Heisenberg macrospins on a 2D square lattice. This forms the basis of a model for granular perpendicular recording media where macrospins represent the magnetic moment of grains. The focus of this work is on the interplay between anisotropy D, intragrain exchange J' and intergrain exchange J on the ordering temperature T(C) and extends our previous reported analysis of the granular Ising model. The role of intragrain degrees of freedom in heat assisted magnetic recording is discussed.
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Affiliation(s)
- M D Leblanc
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St John's, NF, Canada
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Battaglini N, Qin Z, Campiglio P, Repain V, Chacon C, Rousset S, Lang P. Directed growth of mixed self-assembled monolayers on a nanostructured template: a step toward the patterning of functional molecular domains. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15095-15105. [PMID: 23016599 DOI: 10.1021/la302943t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on the elaboration of networks of SAM domains. More precisely, we show the feasibility in making arrays of functionalized alkylthiol nanodomains bordered with an alkylthiol matrix. The several step process relies on the replication of a self-organized cobalt array grown on Au(111). The SAM process takes place in solution. The chemical affinity of thiol for gold leads to the selective grafting of molecules on the surface. After having removed the inorganic array, alkylthiol functionalized with a terthiophene unit is grafted in free gold areas. The efficiency of the replication of the initial template depends on the stability of the first SAM. We also investigate electronic tunnel transport through oligothiophene islands with the STM. The variation of the molecular contrast with bias voltage between the two molecular species indicates a potential resonant tunneling mechanism through the orbitals of the aromatic compound.
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Affiliation(s)
- N Battaglini
- University Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, Paris, France.
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He W, Osmulski ME, Lin J, Koktysh DS, McBride JR, Park JH, Dickerson JH. Remarkable optical and magnetic properties of ultra-thin europium oxysulfide nanorods. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm31779f] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Bauer DSG, Mavropoulos P, Lounis S, Blügel S. Thermally activated magnetization reversal in monatomic magnetic chains on surfaces studied by classical atomistic spin-dynamics simulations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:394204. [PMID: 21921308 DOI: 10.1088/0953-8984/23/39/394204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We analyse the spontaneous magnetization reversal of supported monatomic chains of finite length due to thermal fluctuations via atomistic spin-dynamics simulations. Our approach is based on the integration of the Landau-Lifshitz equation of motion of a classical spin Hamiltonian in the presence of stochastic forces. The associated magnetization lifetime is found to obey an Arrhenius law with an activation barrier equal to the domain wall energy in the chain. For chains longer than one domain wall width, the reversal is initiated by nucleation of a reversed magnetization domain primarily at the chain edge followed by a subsequent propagation of the domain wall to the other edge in a random-walk fashion. This results in a linear dependence of the lifetime on the chain length, if the magnetization correlation length is not exceeded. We studied chains of uniaxial and triaxial anisotropy and found that a triaxial anisotropy leads to a reduction of the magnetization lifetime due to a higher reversal attempt rate, even though the activation barrier is not changed.
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Affiliation(s)
- David S G Bauer
- Institut für Festkörperforschung, Institute for Advanced Simulation, and JARA, Forschungszentrum Jülich, D-52425 Jülich, Germany
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Magnan H, Bezencenet O, Stanescu D, Belkhou R, Barbier A. Beyond the magnetic domain matching in magnetic exchange coupling. PHYSICAL REVIEW LETTERS 2010; 105:097204. [PMID: 20868191 DOI: 10.1103/physrevlett.105.097204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Indexed: 05/29/2023]
Abstract
We report a new macroscopic first-field-induced magnetic anisotropy for Co/α-Fe2O3(0001) layers, a prototypical ferromagnetic-antiferromagnetic interface for which the antiferromagnetic film has small in-plane magnetic anisotropy as compared to the interface coupling. We demonstrate that the effect is due to a first-field-induced irreversible magnetic domain motion in the antiferromagnetic layer, dragged by the ferromagnetic Co one. Whereas the initial domain matching is lost, the macroscopic manifestations of the exchange coupling remain stable. Therefore, the initial domain matching probably has only a marginal role in the explanation of the magnetic exchange coupling.
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Affiliation(s)
- H Magnan
- CEA Saclay, DSM/IRAMIS/SPCSI, F-91191 Gif-sur-Yvette Cedex, France
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