1
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Wortmann M, Viertel K, Westphal M, Graulich D, Yang Y, Gärner M, Schmalhorst J, Frese N, Kuschel T. Sub-Nanometer Depth Profiling of Native Metal Oxide Layers Within Single Fixed-Angle X-Ray Photoelectron Spectra. SMALL METHODS 2024; 8:e2300944. [PMID: 38009726 DOI: 10.1002/smtd.202300944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/31/2023] [Indexed: 11/29/2023]
Abstract
Many metals form nanometer-thin self-passivating oxide layers upon exposure to the atmosphere, which affects a wide range of interfacial properties and shapes the way how metals interact with their environment. Such native oxide layers are commonly analyzed by X-ray photoelectron spectroscopy (XPS), which provides a depth-resolved chemical state and compositional analysis either by ion etching or modeling of the electron escape depths. The latter is commonly used to calculate the average thickness of a native oxide layer. However, the measurement of concentration profiles at the oxide-metal interface remains challenging. Here, a simple and accessible approach for the depth profiling of ultrathin oxide layers within single fixed-angle XPS spectra is proposed. Instead of using only one peak in the spectrum, as is usually the case, all peaks within the energy range of a standard lab device are utilized, thus resembling energy-resolved XPS without the need for a synchrotron. New models that allow the calculation of depth-resolved concentration profiles at the oxide-metal interface are derived and tested, which are also valid for angular- and energy-resolved XPS. The proposed method not only improves the accuracy of earlier approaches but also paves the way for a more holistic understanding of the XPS spectrum.
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Affiliation(s)
- Martin Wortmann
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Klaus Viertel
- Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences and Arts, Interaktion 1, 33619, Bielefeld, Germany
| | - Michael Westphal
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Dominik Graulich
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Yang Yang
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Maik Gärner
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Jan Schmalhorst
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Natalie Frese
- Department of Physics and Astronomy, Watanabe Hall, University of Hawaii, 2505 Correa Road, Honolulu, HI, 96822, USA
| | - Timo Kuschel
- Faculty of Physics, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
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2
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Ilse SE, Schütz G, Goering E. Voltage X-Ray Reflectometry: A Method to Study Electric-Field-Induced Changes in Interfacial Electronic Structures. PHYSICAL REVIEW LETTERS 2023; 131:036201. [PMID: 37540862 DOI: 10.1103/physrevlett.131.036201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 04/26/2023] [Accepted: 06/07/2023] [Indexed: 08/06/2023]
Abstract
Magnetic multilayers with a separating insulating layer are used in a multitude of functional devices. Controlling the magnetic properties of such devices with an electric field has the potential to vastly enhance their performance. Nevertheless, experimental methods to study the origin of electric-field-induced effects on buried interfaces remain elusive. By using element selective x-ray resonant magnetic reflectometry we are able to gain access to changes in the electronic structure of interfacial atoms caused by an electric field. With this method it is possible to probe interfacial states at the Fermi energy. In a multilayer stack with a Ni/SiO_{2} interface, we find that the electric field slightly shifts the Ni L_{3}-edge in energy, which indicates a change of the oxidation state of interfacial Ni atoms. Further analysis of the strength of the effect reveals that only about 30% of the electrons moved by the electric field end up in interfacial Ni states.
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Affiliation(s)
- Sven Erik Ilse
- Max-Planck-Institute for Solid State Research, D-70569 Stuttgart, Germany
| | - Gisela Schütz
- Max-Planck-Institute for Intelligent Systems, D-70569 Stuttgart, Germany
| | - Eberhard Goering
- Max-Planck-Institute for Solid State Research, D-70569 Stuttgart, Germany
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3
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Soltan S, Macke S, Ilse SE, Pennycook T, Zhang ZL, Christiani G, Benckiser E, Schütz G, Goering E. Ferromagnetic order controlled by the magnetic interface of LaNiO 3/La 2/3Ca 1/3MnO 3 superlattices. Sci Rep 2023; 13:3847. [PMID: 36890187 PMCID: PMC9995495 DOI: 10.1038/s41598-023-30814-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 03/01/2023] [Indexed: 03/10/2023] Open
Abstract
Interface engineering in complex oxide superlattices is a growing field, enabling manipulation of the exceptional properties of these materials, and also providing access to new phases and emergent physical phenomena. Here we demonstrate how interfacial interactions can induce a complex charge and spin structure in a bulk paramagnetic material. We investigate a superlattice (SLs) consisting of paramagnetic LaNiO3 (LNO) and highly spin-polarized ferromagnetic La2/3Ca1/3MnO3 (LCMO), grown on SrTiO3 (001) substrate. We observed emerging magnetism in LNO through an exchange bias mechanism at the interfaces in X-ray resonant magnetic reflectivity. We find non-symmetric interface induced magnetization profiles in LNO and LCMO which we relate to a periodic complex charge and spin superstructure. High resolution scanning transmission electron microscopy images reveal that the upper and lower interfaces exhibit no significant structural variations. The different long range magnetic order emerging in LNO layers demonstrates the enormous potential of interfacial reconstruction as a tool for tailored electronic properties.
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Affiliation(s)
- S Soltan
- Physics Department, Faculty of Science, Helwan University, Helwan, Cairo, 11798, Egypt. .,Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany. .,Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - S Macke
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
| | - S E Ilse
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany
| | - T Pennycook
- EMAT, University of Antwerp Campus Groenenborger, 2020, Antwerp, Belgium.,Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090, Vienna, Austria
| | - Z L Zhang
- Erich-Schmid-Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, 8700, Leoben, Austria
| | - G Christiani
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
| | - E Benckiser
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
| | - G Schütz
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany
| | - E Goering
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany.
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4
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Verna A, Alippi P, Offi F, Barucca G, Varvaro G, Agostinelli E, Albrecht M, Rutkowski B, Ruocco A, Paoloni D, Valvidares M, Laureti S. Disclosing the Nature of Asymmetric Interface Magnetism in Co/Pt Multilayers. ACS APPLIED MATERIALS & INTERFACES 2022; 14:12766-12776. [PMID: 35254812 DOI: 10.1021/acsami.1c22341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Nowadays, a wide number of applications based on magnetic materials rely on the properties arising at the interface between different layers in complex heterostructures engineered at the nanoscale. In ferromagnetic/heavy metal multilayers, such as the [Co/Pt]N and [Co/Pd]N systems, the magnetic proximity effect was demonstrated to be asymmetric, thus inducing a magnetic moment on the Pt (Pd) layer that is typically higher at the top Co/Pt(Pd) interface. In this work, advanced spectroscopic and imaging techniques were combined with theoretical approaches to clarify the origin of this asymmetry both in Co/Pt trilayers and, for the first time, in multilayer systems that are more relevant for practical applications. The different magnetic moment induced at the Co/Pt interfaces was correlated to the microstructural features that are in turn affected by the growth processes that induce a different intermixing during the film deposition, thus influencing the interface magnetic profile.
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Affiliation(s)
- Adriano Verna
- Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, Roma I-00146, Italy
- ENEA-FSN-Fiss-SNI, Casaccia R. C., Via Anguillarese 301, Roma 00123, Italy
| | - Paola Alippi
- Istituto di Struttura della Materia, CNR, Monterotondo Scalo, Roma 00015, Italy
| | - Francesco Offi
- Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, Roma I-00146, Italy
| | - Gianni Barucca
- Dipartimento SIMAU, Università Politecnica Delle Marche, Via Brecce Bianche, Ancona 60121, Italy
| | - Gaspare Varvaro
- Istituto di Struttura della Materia, CNR, nM2-Lab, Monterotondo Scalo, Roma 00015, Italy
| | - Elisabetta Agostinelli
- Istituto di Struttura della Materia, CNR, nM2-Lab, Monterotondo Scalo, Roma 00015, Italy
| | - Manfred Albrecht
- Institute of Physics, University of Augsburg, Universitätsstraße 1 Nord, Augsburg D-86159, Germany
| | - Bogdan Rutkowski
- Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. A. Mickiewicza 30, Kraków 30-059, Poland
| | - Alessandro Ruocco
- Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, Roma I-00146, Italy
| | - Daniele Paoloni
- Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, Roma I-00146, Italy
| | - Manuel Valvidares
- ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona E-08290, Spain
| | - Sara Laureti
- Istituto di Struttura della Materia, CNR, nM2-Lab, Monterotondo Scalo, Roma 00015, Italy
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5
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Ghosh M, Bhat SG, Pal A, Kumar PSA. Tuning the semimetallic charge transport in the Weyl semimetal candidate Eu 2Ir 2O 7(111) epitaxial thin film with an all-in-all-out spin structure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:165701. [PMID: 35105826 DOI: 10.1088/1361-648x/ac50da] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
We report the stoichiometric epitaxial growth of the Eu2Ir2O7(111) thin film on YSZ substrate by a two-step solid phase epitaxy (SPE) method. An optimized post-annealing environment of the SPE was superior over the conventional air annealing procedure to get rid of the typical impurity phase, Eu2O3. The thickness-dependent structural study on Eu2Ir2O7(111) thin films suggests a systematic control of Ir/Eu stoichiometry in our films, which is otherwise difficult to achieve. In addition, the low-temperature electrical resistivity studies strongly support the claim. The power-law dependence analysis of the resistivity data exhibits a power exponent of 0.52 in 50 nm sample suggesting possible disorder-driven semimetallic charge transport in the 3D Weyl semimetallic (WSM) candidate Eu2Ir2O7. In addition, the all-in-all-out/all-out-all-in antiferromagnetic domains of Ir4+sublattice is verified using the field cooled magnetoresistance measurements at 2 K. Hall resistivity analysis indicate semimetallic hole carrier type dominance near the Fermi level up to the measured temperature range of 2-120 K. Altogether, our study reveals the ground state of stoichiometric Eu2Ir2O7(111) thin film, with an indirect tuning of the off-stoichiometry using thickness of the samples, which is of interest in the search of the predicted 3D WSM phase.
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Affiliation(s)
- Mithun Ghosh
- Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - Shwetha G Bhat
- Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka, India
| | - Anand Pal
- Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka, India
- Department of Physics, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal-576104, Karnataka, India
| | - P S Anil Kumar
- Department of Physics, Indian Institute of Science, Bangalore 560012, Karnataka, India
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6
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Suzuki-Sakamaki M, Amemiya K. Three-dimensional chemical-state imaging with reflection-mode soft x-ray absorption spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:123702. [PMID: 34972431 DOI: 10.1063/5.0069096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 11/19/2021] [Indexed: 06/14/2023]
Abstract
In this study, a method for reflection-mode soft x-ray absorption spectroscopy was developed to realize three-dimensional chemical-state imaging. Soft x rays from a pinhole were reflected by the sample, and the magnified image was observed with a two-dimensional detector. This technique was applied to a Co film with an Au-island-covered surface to obtain the surface chemical state images with a spatial resolution of several tens of micrometers. Furthermore, the soft x-ray reflection spectra within and outside the Au layer were extracted from the images by changing the photon energy. Distinct differences were observed at the Co absorption edge. By considering anomalous x-ray scattering around the Co L-edges in the simulation, the reflection spectrum near the absorption edge in the nm depth resolution was reproduced. In the region without the Au layer, the results were well reproduced, assuming that 4 nm CoO was formed at the surface. These results demonstrate the feasibility of three-dimensional imaging of the chemical states in multilayer films.
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Affiliation(s)
- M Suzuki-Sakamaki
- Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan
| | - K Amemiya
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
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7
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Resonant Soft X-ray Reflectivity in the Study of Magnetic Properties of Low-Dimensional Systems. MAGNETOCHEMISTRY 2021. [DOI: 10.3390/magnetochemistry7100136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this review, the technique of resonant soft X-ray reflectivity in the study of magnetic low-dimensional systems is discussed. This technique is particularly appealing in the study of magnetization at buried interfaces and to discriminate single elemental contributions to magnetism, even when this is ascribed to few atoms. The major fields of application are described, including magnetic proximity effects, thin films of transition metals and related oxides, and exchange-bias systems. The fundamental theoretical background leading to dichroism effects in reflectivity is also briefly outlined.
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8
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Chardonnet V, Hennes M, Jarrier R, Delaunay R, Jaouen N, Kuhlmann M, Ekanayake N, Léveillé C, von Korff Schmising C, Schick D, Yao K, Liu X, Chiuzbăian GS, Lüning J, Vodungbo B, Jal E. Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:034305. [PMID: 34235231 PMCID: PMC8225393 DOI: 10.1063/4.0000109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
During the last two decades, a variety of models have been developed to explain the ultrafast quenching of magnetization following femtosecond optical excitation. These models can be classified into two broad categories, relying either on a local or a non-local transfer of angular momentum. The acquisition of the magnetic depth profiles with femtosecond resolution, using time-resolved x-ray resonant magnetic reflectivity, can distinguish local and non-local effects. Here, we demonstrate the feasibility of this technique in a pump-probe geometry using a custom-built reflectometer at the FLASH2 free-electron laser (FEL). Although FLASH2 is limited to the production of photons with a fundamental wavelength of 4 nm ( ≃ 310 eV ), we were able to probe close to the Fe L 3 edge ( 706.8 eV ) of a magnetic thin film employing the third harmonic of the FEL. Our approach allows us to extract structural and magnetic asymmetry signals revealing two dynamics on different time scales which underpin a non-homogeneous loss of magnetization and a significant dilation of 2 Å of the layer thickness followed by oscillations. Future analysis of the data will pave the way to a full quantitative description of the transient magnetic depth profile combining femtosecond with nanometer resolution, which will provide further insight into the microscopic mechanisms underlying ultrafast demagnetization.
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Affiliation(s)
- Valentin Chardonnet
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Marcel Hennes
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Romain Jarrier
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Renaud Delaunay
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Nicolas Jaouen
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | | | - Cyril Léveillé
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | - Daniel Schick
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Kelvin Yao
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Xuan Liu
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | - Gheorghe S. Chiuzbăian
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Jan Lüning
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Boris Vodungbo
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Emmanuelle Jal
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
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9
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Golias E, Kumberg I, Gelen I, Thakur S, Gördes J, Hosseinifar R, Guillet Q, Dewhurst JK, Sharma S, Schüßler-Langeheine C, Pontius N, Kuch W. Ultrafast Optically Induced Ferromagnetic State in an Elemental Antiferromagnet. PHYSICAL REVIEW LETTERS 2021; 126:107202. [PMID: 33784145 DOI: 10.1103/physrevlett.126.107202] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 01/15/2021] [Accepted: 01/25/2021] [Indexed: 06/12/2023]
Abstract
We present evidence for an ultrafast optically induced ferromagnetic alignment of antiferromagnetic Mn in Co/Mn multilayers. We observe the transient ferromagnetic signal at the arrival of the pump pulse at the Mn L_{3} resonance using x-ray magnetic circular dichroism in reflectivity. The timescale of the effect is comparable to the duration of the excitation and occurs before the magnetization in Co is quenched. Theoretical calculations point to the imbalanced population of Mn unoccupied states caused by the Co interface for the emergence of this transient ferromagnetic state.
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Affiliation(s)
- E Golias
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - I Kumberg
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - I Gelen
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - S Thakur
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - J Gördes
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - R Hosseinifar
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Q Guillet
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - J K Dewhurst
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - S Sharma
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - C Schüßler-Langeheine
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein Straße 15, 12489 Berlin, Germany
| | - N Pontius
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein Straße 15, 12489 Berlin, Germany
| | - W Kuch
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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10
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Burn DM, Zhang SL, Yu GQ, Guang Y, Chen HJ, Qiu XP, van der Laan G, Hesjedal T. Depth-Resolved Magnetization Dynamics Revealed by X-Ray Reflectometry Ferromagnetic Resonance. PHYSICAL REVIEW LETTERS 2020; 125:137201. [PMID: 33034462 DOI: 10.1103/physrevlett.125.137201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/29/2020] [Accepted: 08/13/2020] [Indexed: 06/11/2023]
Abstract
Magnetic multilayers offer diverse opportunities for the development of ultrafast functional devices through advanced interface and layer engineering. Nevertheless, a method for determining their dynamic properties as a function of depth throughout such stacks has remained elusive. By probing the ferromagnetic resonance modes with element-selective soft x-ray resonant reflectivity, we gain access to the magnetization dynamics as a function of depth. Most notably, using reflectometry ferromagnetic resonance, we find a phase lag between the coupled ferromagnetic layers in [CoFeB/MgO/Ta]_{4} multilayers that is invisible to other techniques. The use of reflectometry ferromagnetic resonance enables the time-resolved and depth-resolved probing of the complex magnetization dynamics of a wide range of functional magnetic heterostructures with absorption edges in the soft x-ray wavelength regime.
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Affiliation(s)
- D M Burn
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - S L Zhang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China
- ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University, Shanghai 200031, China
| | - G Q Yu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Y Guang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - H J Chen
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - X P Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - G van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - T Hesjedal
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
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11
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Belloeil M, Proietti MG, Renevier H, Daudin B. Nanoscale x-ray investigation of composition fluctuations in AlGaN nanowires. NANOTECHNOLOGY 2020; 31:375709. [PMID: 32434176 DOI: 10.1088/1361-6528/ab94e1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the present study we combined, in the same synchrotron x-ray experiment, reciprocal space mapping, multiwavelength anomalous diffraction and diffraction anomalous fine structure, to determine the strain, crystallographic polarity, alloy composition and ordering at the atomic scale in [0001]-oriented AlGaN nanowires grown by molecular beam epitaxy on GaN nanowire bases. The information that we obtained was averaged over a macroscopic ensemble of NWs. We found from the diffraction anomalous fine structure that there were an isotropic increased number of Ga-Ga pairs in the Ga next nearest coordination shell (cation sublattice) with respect to what is expected for the AlGaN alloy composition determined by anomalous diffraction. This significant deviation from random alloy atomic distribution is present whatever the AlN molar fraction and growth conditions. Our results are consistent with nanoscale composition fluctuations expected from both alloy disorder or kinematically driven spontaneous ordering, both effects being suspected to account for the physical properties of AlGaN ternary alloys.
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Affiliation(s)
- M Belloeil
- Univ. Grenoble Alpes, CEA, IRIG-PHELIQS-NPSC, 38000 Grenoble, France
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12
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Gorkov D, Toperverg BP, Zabel H. Artificial Magnetic Pattern Arrays Probed by Polarized Neutron Reflectivity. NANOMATERIALS 2020; 10:nano10050851. [PMID: 32354026 PMCID: PMC7711518 DOI: 10.3390/nano10050851] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/03/2020] [Accepted: 04/05/2020] [Indexed: 11/16/2022]
Abstract
Traditionally, neutron scattering is an essential method for the analysis of spin structures and spin excitations in bulk materials. Over the last 30 years, polarized neutron scattering in terms of reflectometry has also contributed largely to the analysis of magnetic thin films and magnetic multilayers. More recently it has been shown that polarized neutron reflectivity is, in addition, a suitable tool for the study of thin films laterally patterned with magnetic stripes or islands. We provide a brief overview of the fundamental properties of polarized neutron reflectivity, considering different domain states, domain fluctuations, and different domain sizes with respect to the neutron coherence volume. The discussion is exemplified by a set of simulated reflectivities assuming either complete polarization and polarization analysis, or a reduced form of polarized neutron reflectivity without polarization analysis. Furthermore, we emphasize the importance of the neutron coherence volume for the interpretation of specular and off-specular intensity maps, in particular when studying laterally non-homogeneous magnetic films. Finally, experimental results, fits, and simulations are shown for specular and off-specular scattering from a magnetic film that has been lithographically patterned into a periodic stripe array. These experiments demonstrate the different and mutually complementary information that can be gained when orienting the stripe array parallel or perpendicular to the scattering plane.
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Affiliation(s)
- Dmitry Gorkov
- II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
- Festkörperphysik/Experimentalphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
- Correspondence:
| | - Boris P. Toperverg
- Festkörperphysik/Experimentalphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
- Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, 188300 Gatchina, Russia
| | - Hartmut Zabel
- Festkörperphysik/Experimentalphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
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13
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Rogge PC, Shafer P, Fabbris G, Hu W, Arenholz E, Karapetrova E, Dean MPM, Green RJ, May SJ. Depth-Resolved Modulation of Metal-Oxygen Hybridization and Orbital Polarization across Correlated Oxide Interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1902364. [PMID: 31515864 DOI: 10.1002/adma.201902364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/22/2019] [Indexed: 06/10/2023]
Abstract
Interface-induced modifications of the electronic, magnetic, and lattice degrees of freedom drive an array of novel physical properties in oxide heterostructures. Here, large changes in metal-oxygen band hybridization, as measured in the oxygen ligand hole density, are induced as a result of interfacing two isovalent correlated oxides. Using resonant X-ray reflectivity, a superlattice of SrFeO3 and CaFeO3 is shown to exhibit an electronic character that spatially evolves from strongly O-like in SrFeO3 to strongly Fe-like in CaFeO3 . This alternating degree of Fe electronic character is correlated with a modulation of an Fe 3d orbital polarization, giving rise to an orbital superstructure. At the SrFeO3 /CaFeO3 interfaces, the ligand hole density and orbital polarization reconstruct in a single unit cell of CaFeO3 , demonstrating how the mismatch in these electronic parameters is accommodated at the interface. These results provide new insight into how the orbital character of electrons is altered by correlated oxide interfaces and lays out a broadly applicable approach for depth-resolving band hybridization.
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Affiliation(s)
- Paul C Rogge
- Department of Materials Science and Engineering, Drexel University, 3141 Chestnut St., Philadelphia, PA, 19104, USA
| | - Padraic Shafer
- Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA, 94720, USA
| | - Gilberto Fabbris
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, 98 Rochester St., Upton, NY, 11973, USA
| | - Wen Hu
- National Synchrotron Light Source II, Brookhaven National Laboratory, 98 Rochester St., Upton, NY, 11973, USA
| | - Elke Arenholz
- Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA, 94720, USA
- Cornell High Energy Synchrotron Source, Cornell University, 161 Wilson Laboratory, Synchrotron Drive, Ithaca, NY, 14853, USA
| | - Evguenia Karapetrova
- Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Ave, Lemont, IL, 60439, USA
| | - Mark P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, 98 Rochester St., Upton, NY, 11973, USA
| | - Robert J Green
- Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Pl, Saskatoon, Saskatchewan, S7N 5E2, Canada
- Stewart Blusson Quantum Matter Institute, University of British Columbia, 111-2355 E Mall, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Steven J May
- Department of Materials Science and Engineering, Drexel University, 3141 Chestnut St., Philadelphia, PA, 19104, USA
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14
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The interfacial nature of proximity-induced magnetism and the Dzyaloshinskii-Moriya interaction at the Pt/Co interface. Sci Rep 2017; 7:16835. [PMID: 29203797 PMCID: PMC5715054 DOI: 10.1038/s41598-017-17137-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 11/22/2017] [Indexed: 11/08/2022] Open
Abstract
The Dzyaloshinskii-Moriya interaction has been shown to stabilise Nèel domain walls in magnetic thin films, allowing high domain wall velocities driven by spin current effects. The interfacial Dzyaloshinskii-Moriya interaction (IDMI) occurs at the interface between ferromagnetic and heavy metal layers with strong spin-orbit coupling, but details of the interaction remain to be understood and the role of proximity induced magnetism (PIM) in the heavy metal is unknown. Here IDMI and PIM are reported in Pt determined as a function of Au and Ir spacer layers in Pt/Co/Au,Ir/Pt. Both interactions are found to be sensitive to sub-nanometre changes in the spacer thickness, correlating over sub-monolayer spacer thicknesses, but not for thicker spacers where IDMI continues to change even after PIM is lost.
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15
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Bougiatioti P, Klewe C, Meier D, Manos O, Kuschel O, Wollschläger J, Bouchenoire L, Brown SD, Schmalhorst JM, Reiss G, Kuschel T. Quantitative Disentanglement of the Spin Seebeck, Proximity-Induced, and Ferromagnetic-Induced Anomalous Nernst Effect in Normal-Metal-Ferromagnet Bilayers. PHYSICAL REVIEW LETTERS 2017; 119:227205. [PMID: 29286760 DOI: 10.1103/physrevlett.119.227205] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Indexed: 06/07/2023]
Abstract
We identify and investigate thermal spin transport phenomena in sputter-deposited Pt/NiFe_{2}O_{x} (4≥x≥0) bilayers. We separate the voltage generated by the spin Seebeck effect from the anomalous Nernst effect (ANE) contributions and even disentangle the ANE in the ferromagnet (FM) from the ANE produced by the Pt that is spin polarized due to its proximity to the FM. Further, we probe the dependence of these effects on the electrical conductivity and the band gap energy of the FM film varying from nearly insulating NiFe_{2}O_{4} to metallic Ni_{33}Fe_{67}. A proximity-induced ANE could only be identified in the metallic Pt/Ni_{33}Fe_{67} bilayer in contrast to Pt/NiFe_{2}O_{x} (x>0) samples. This is verified by the investigation of static magnetic proximity effects via x-ray resonant magnetic reflectivity.
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Affiliation(s)
- Panagiota Bougiatioti
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Christoph Klewe
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Daniel Meier
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Orestis Manos
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Olga Kuschel
- Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, Barbarastrasse 7, 49076 Osnabrück, Germany
| | - Joachim Wollschläger
- Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, Barbarastrasse 7, 49076 Osnabrück, Germany
| | - Laurence Bouchenoire
- XMaS, European Synchrotron Radiation Facility, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
| | - Simon D Brown
- XMaS, European Synchrotron Radiation Facility, Grenoble 38043, France
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom
| | - Jan-Michael Schmalhorst
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Günter Reiss
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - Timo Kuschel
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
- Physics of Nanodevices, Zernike Institue for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
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16
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Thielemann-Kühn N, Schick D, Pontius N, Trabant C, Mitzner R, Holldack K, Zabel H, Föhlisch A, Schüßler-Langeheine C. Ultrafast and Energy-Efficient Quenching of Spin Order: Antiferromagnetism Beats Ferromagnetism. PHYSICAL REVIEW LETTERS 2017; 119:197202. [PMID: 29219516 DOI: 10.1103/physrevlett.119.197202] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Indexed: 06/07/2023]
Abstract
By comparing femtosecond laser pulse induced ferro- and antiferromagnetic dynamics in one and the same material-metallic dysprosium-we show both to behave fundamentally different. Antiferromagnetic order is considerably faster and much more efficiently reduced by optical excitation than its ferromagnetic counterpart. We assign the fast and extremely efficient process in the antiferromagnet to an interatomic transfer of angular momentum within the spin system. Our findings imply that this angular momentum transfer channel is effective in other magnetic metals with nonparallel spin alignment. They also point out a possible route towards energy-efficient spin manipulation for magnetic devices.
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Affiliation(s)
- Nele Thielemann-Kühn
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
| | - Daniel Schick
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Niko Pontius
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Christoph Trabant
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Rolf Mitzner
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Karsten Holldack
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Hartmut Zabel
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Alexander Föhlisch
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
| | - Christian Schüßler-Langeheine
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
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17
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Hamann-Borrero JE, Macke S, Gray B, Kareev M, Schierle E, Partzsch S, Zwiebler M, Treske U, Koitzsch A, Büchner B, Freeland JW, Chakhalian J, Geck J. Site-selective spectroscopy with depth resolution using resonant x-ray reflectometry. Sci Rep 2017; 7:13792. [PMID: 29061996 PMCID: PMC5653850 DOI: 10.1038/s41598-017-12642-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 09/13/2017] [Indexed: 11/21/2022] Open
Abstract
Combining dissimilar transition metal oxides (TMOs) into artificial heterostructures enables to create electronic interface systems with new electronic properties that do not exist in bulk. A detailed understanding of how such interfaces can be used to tailor physical properties requires characterization techniques capable to yield interface sensitive spectroscopic information with monolayer resolution. In this regard resonant x-ray reflectivity (RXR) provides a unique experimental tool to achieve exactly this. It yields the element specific electronic depth profiles in a non-destructive manner. Here, using a YBa2Cu3O7−δ (YBCO) thin film, we demonstrate that RXR is further capable to deliver site selectivity. By applying a new analysis scheme to RXR, which takes the atomic structure of the material into account, together with information of the local charge anisotropy of the resonant ions, we obtained spectroscopic information from the different Cu sites (e.g., chain and plane) throughout the film profile. While most of the film behaves bulk-like, we observe that the Cu-chains at the surface show characteristics of electron doping, whereas the Cu-planes closest to the surface exhibit an orbital reconstruction similar to that observed at La1−xCaxMnO3/YBCO interfaces.
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Affiliation(s)
- J E Hamann-Borrero
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany.
| | - S Macke
- Quantum Matter Institute, University of British Columbia, 2355 East Mall, Vancouver, V6T 1Z4, Canada.,Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569, Stuttgart, Germany
| | - B Gray
- Department of Physics, University of Arkansas, Fayetteville, Arkansas, 70701, USA
| | - M Kareev
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| | - E Schierle
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, D-12489, Berlin, Germany
| | - S Partzsch
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany
| | - M Zwiebler
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany
| | - U Treske
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany
| | - A Koitzsch
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany
| | - B Büchner
- Leibniz Institute for Solid State and Materials Research, IFW Dresden, 01171, Dresden, Germany.,Institut für Festkörper- und Materialphysik, TU Dresden, D-01062, Dresden, Germany
| | - J W Freeland
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, 60439, USA
| | - J Chakhalian
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854, USA
| | - J Geck
- Institut für Festkörper- und Materialphysik, TU Dresden, D-01062, Dresden, Germany.
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18
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Gutt C, Sant T, Ksenzov D, Capotondi F, Pedersoli E, Raimondi L, Nikolov IP, Kiskinova M, Jaiswal S, Jakob G, Kläui M, Zabel H, Pietsch U. Probing ultrafast changes of spin and charge density profiles with resonant XUV magnetic reflectivity at the free-electron laser FERMI. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:055101. [PMID: 28713843 PMCID: PMC5500121 DOI: 10.1063/1.4990650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 06/16/2017] [Indexed: 06/07/2023]
Abstract
We report the results of resonant magnetic XUV reflectivity experiments performed at the XUV free-electron laser FERMI. Circularly polarized XUV light with the photon energy tuned to the Fe M2,3 edge is used to measure resonant magnetic reflectivities and the corresponding Q-resolved asymmetry of a Permalloy/Ta/Permalloy trilayer film. The asymmetry exhibits ultrafast changes on 240 fs time scales upon pumping with ultrashort IR laser pulses. Depending on the value of the wavevector transfer Qz , we observe both decreasing and increasing values of the asymmetry parameter, which is attributed to ultrafast changes in the vertical spin and charge density profiles of the trilayer film.
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Affiliation(s)
- C Gutt
- Physics Department, University of Siegen, D-57072 Siegen, Germany
| | - T Sant
- Physics Department, University of Siegen, D-57072 Siegen, Germany
| | - D Ksenzov
- Physics Department, University of Siegen, D-57072 Siegen, Germany
| | - F Capotondi
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | - E Pedersoli
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | - L Raimondi
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | - I P Nikolov
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | - M Kiskinova
- Elettra-Sincrotrone Trieste, 34149 Basovizza, Trieste, Italy
| | | | - G Jakob
- Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
| | - M Kläui
- Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
| | - H Zabel
- Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
| | - U Pietsch
- Physics Department, University of Siegen, D-57072 Siegen, Germany
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19
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Bobowski K, Gleich M, Pontius N, Schüßler-Langeheine C, Trabant C, Wietstruk M, Frietsch B, Weinelt M. Influence of the pump pulse wavelength on the ultrafast demagnetization of Gd(0 0 0 1) thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:234003. [PMID: 28398211 DOI: 10.1088/1361-648x/aa6c92] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We studied the magnetization dynamics of gadolinium metal after femtosecond laser excitation recording the x-ray magnetic circular dichroism in reflection (XMCD-R) at the Gd M 5 absorption edge. Varying the photon energy of the pump pulse allows us to change the initial energy distribution of photoexcited carriers. The overall similar response for excitation with 0.95, 1.55 and 3.10 eV photons at comparable pump fluences indicates that ultrafast ballistic carrier transport leads to a homogeneous energy distribution on the femtosecond timescale in the probed sample volume. Differences are observed in the initial ultrafast demagnetization magnitude. They are attributed to an enhanced spin-flip probability at higher electron energies characterizing the non-thermal electron distribution.
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Affiliation(s)
- Kamil Bobowski
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
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20
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Macke S, Hamann-Borrero JE, Green RJ, Keimer B, Sawatzky GA, Haverkort MW. Dynamical Effects in Resonant X-Ray Diffraction. PHYSICAL REVIEW LETTERS 2016; 117:115501. [PMID: 27661698 DOI: 10.1103/physrevlett.117.115501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Indexed: 06/06/2023]
Abstract
Using resonant magnetic diffraction at the Ni L_{2,3} edge in a LaNiO_{3} superlattice, we show that dynamical effects beyond the standard kinematic approximation can drastically modify the resonant scattering cross section. In particular, the combination of extinction and refraction convert maxima to minima in the azimuthal-angle dependence of the diffracted intensity, which is commonly used to determine orbital and magnetic structures by resonant x-ray diffraction. We provide a comprehensive theoretical description of these effects by numerically solving Maxwell's equations in three dimensions. The understanding and description of dynamical diffraction enhances the capabilities of resonant x-ray scattering as a probe of electronic ordering phenomena in solids.
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Affiliation(s)
- S Macke
- Quantum Matter Institute, Physics and Astronomy Department, The Brimacombe Building, 2355 East Mall, Vancouver V6T 1Z4, Canada
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - J E Hamann-Borrero
- Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstrae 20, 01069 Dresden, Germany
| | - R J Green
- Quantum Matter Institute, Physics and Astronomy Department, The Brimacombe Building, 2355 East Mall, Vancouver V6T 1Z4, Canada
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - B Keimer
- Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - G A Sawatzky
- Quantum Matter Institute, Physics and Astronomy Department, The Brimacombe Building, 2355 East Mall, Vancouver V6T 1Z4, Canada
| | - M W Haverkort
- Quantum Matter Institute, Physics and Astronomy Department, The Brimacombe Building, 2355 East Mall, Vancouver V6T 1Z4, Canada
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
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21
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Audehm P, Schmidt M, Brück S, Tietze T, Gräfe J, Macke S, Schütz G, Goering E. Pinned orbital moments - A new contribution to magnetic anisotropy. Sci Rep 2016; 6:25517. [PMID: 27151436 PMCID: PMC4858686 DOI: 10.1038/srep25517] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/15/2016] [Indexed: 11/19/2022] Open
Abstract
Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy.
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Affiliation(s)
- P Audehm
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - M Schmidt
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - S Brück
- Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - T Tietze
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - J Gräfe
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - S Macke
- Quantum Matter Institute and Department of Physics and Astronomy University of British Columbia 2355 East Mall, Vancouver, V6T 1Z4, Canada.,Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569, Stuttgart, Germany
| | - G Schütz
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - E Goering
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
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22
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Liao Z, Huijben M, Zhong Z, Gauquelin N, Macke S, Green RJ, Van Aert S, Verbeeck J, Van Tendeloo G, Held K, Sawatzky GA, Koster G, Rijnders G. Controlled lateral anisotropy in correlated manganite heterostructures by interface-engineered oxygen octahedral coupling. NATURE MATERIALS 2016; 15:425-31. [PMID: 26950593 DOI: 10.1038/nmat4579] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 01/22/2016] [Indexed: 05/27/2023]
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23
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Antiferromagnetic proximity effect in epitaxial CoO/NiO/MgO(001) systems. Sci Rep 2016; 6:22355. [PMID: 26932164 PMCID: PMC4773757 DOI: 10.1038/srep22355] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/12/2016] [Indexed: 11/08/2022] Open
Abstract
Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices.
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24
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Kuschel T, Klewe C, Schmalhorst JM, Bertram F, Kuschel O, Schemme T, Wollschläger J, Francoual S, Strempfer J, Gupta A, Meinert M, Götz G, Meier D, Reiss G. Static Magnetic Proximity Effect in Pt/NiFe2O4 and Pt/Fe Bilayers Investigated by X-Ray Resonant Magnetic Reflectivity. PHYSICAL REVIEW LETTERS 2015; 115:097401. [PMID: 26371679 DOI: 10.1103/physrevlett.115.097401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Indexed: 06/05/2023]
Abstract
The spin polarization of Pt in Pt/NiFe2O4 and Pt/Fe bilayers is studied by interface-sensitive x-ray resonant magnetic reflectivity to investigate static magnetic proximity effects. The asymmetry ratio of the reflectivity is measured at the Pt L3 absorption edge using circular polarized x-rays for opposite directions of the magnetization at room temperature. The results of the 2% asymmetry ratio for Pt/Fe bilayers are independent of the Pt thickness between 1.8 and 20 nm. By comparison with ab initio calculations, the maximum magnetic moment per spin polarized Pt atom at the interface is determined to be (0.6±0.1) μB for Pt/Fe. For Pt/NiFe2O4 the asymmetry ratio drops below the sensitivity limit of 0.02 μB per Pt atom. Therefore, we conclude, that the longitudinal spin Seebeck effect recently observed in Pt/NiFe2O4 is not influenced by a proximity induced anomalous Nernst effect.
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Affiliation(s)
- T Kuschel
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - C Klewe
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - J-M Schmalhorst
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - F Bertram
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - O Kuschel
- Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49069 Osnabrück, Germany
| | - T Schemme
- Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49069 Osnabrück, Germany
| | - J Wollschläger
- Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49069 Osnabrück, Germany
| | - S Francoual
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - J Strempfer
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - A Gupta
- Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - M Meinert
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - G Götz
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - D Meier
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
| | - G Reiss
- Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
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25
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Abrudan R, Brüssing F, Salikhov R, Meermann J, Radu I, Ryll H, Radu F, Zabel H. ALICE—An advanced reflectometer for static and dynamic experiments in magnetism at synchrotron radiation facilities. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:063902. [PMID: 26133845 DOI: 10.1063/1.4921716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report on significant developments of a high vacuum reflectometer (diffractometer) and spectrometer for soft x-ray synchrotron experiments which allows conducting a wide range of static and dynamic experiments. Although the chamber named ALICE was designed for the analysis of magnetic hetero- and nanostructures via resonant magnetic x-ray scattering, the instrument is not limited to this technique. The versatility of the instrument was testified by a series of pilot experiments. Static measurements involve the possibility to use scattering and spectroscopy synchrotron based techniques (photon-in photon-out, photon-in electron-out, and coherent scattering). Dynamic experiments require either laser or magnetic field pulses to excite the spin system followed by x-ray probe in the time domain from nano- to femtosecond delay times. In this temporal range, the demagnetization/remagnetization dynamics and magnetization precession in a number of magnetic materials (metals, alloys, and magnetic multilayers) can be probed in an element specific manner. We demonstrate here the capabilities of the system to host a variety of experiments, featuring ALICE as one of the most versatile and demanded instruments at the Helmholtz Center in Berlin-BESSY II synchrotron center in Berlin, Germany.
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Affiliation(s)
- R Abrudan
- Institute for Condensed Matter Physics, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - F Brüssing
- Institute for Condensed Matter Physics, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - R Salikhov
- Institute for Condensed Matter Physics, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - J Meermann
- Institute for Condensed Matter Physics, Ruhr-Universität Bochum, 44780 Bochum, Germany
| | - I Radu
- Helmholtz-Zentrum-Berlin for Materials and Energy, 12489 Berlin, Germany
| | - H Ryll
- Helmholtz-Zentrum-Berlin for Materials and Energy, 12489 Berlin, Germany
| | - F Radu
- Helmholtz-Zentrum-Berlin for Materials and Energy, 12489 Berlin, Germany
| | - H Zabel
- Institute for Condensed Matter Physics, Ruhr-Universität Bochum, 44780 Bochum, Germany
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Nayak M, Pradhan PC, Lodha GS. Element-specific structural analysis of Si/B4C using resonant X-ray reflectivity. J Appl Crystallogr 2015. [DOI: 10.1107/s1600576715005877] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Element-specific structural analysis at the buried interface of a low electron density contrast system is important in many applied fields. The analysis of nanoscaled Si/B4C buried interfaces is demonstrated using resonant X-ray reflectivity. This technique combines information about spatial modulations of charges provided by scattering, which is further enhanced near the resonance, with the sensitivity to electronic structure provided by spectroscopy. Si/B4C thin-film structures are studied by varying the position of B4C in Si layers. Measured values of near-edge optical properties are correlated with the resonant reflectivity profile to quantify the element-specific composition. It is observed that, although Si/B4C forms a smooth interface, there are chemical changes in the sputtered B4C layer. Nondestructive quantification of the chemical changes and the spatial distribution of the constituents is reported.
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