1
|
Ishii Y, Yamasaki Y, Kozuka Y, Lustikova J, Nii Y, Onose Y, Yokoyama Y, Mizumaki M, Adachi JI, Nakao H, Arima TH, Wakabayashi Y. Microscopic evaluation of spin and orbital moment in ferromagnetic resonance. Sci Rep 2024; 14:15504. [PMID: 38969719 PMCID: PMC11226459 DOI: 10.1038/s41598-024-66139-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/27/2024] [Indexed: 07/07/2024] Open
Abstract
Time-resolved X-ray magnetic circular dichroism under the effects of ferromagnetic resonance (FMR), known as X-ray ferromagnetic resonance (XFMR) measurements, enables direct detection of precession dynamics of magnetic moment. Here we demonstrated XFMR measurements and Bayesian analyses as a quantitative probe for the precession of spin and orbital magnetic moments under the FMR effect. Magnetization precessions in two different Pt/Ni-Fe thin film samples were directly detected. Furthermore, the ratio of dynamical spin and orbital magnetic moments was evaluated quantitatively by Bayesian analyses for XFMR energy spectra around the Ni L 2 , 3 absorption edges. Our study paves the way for a microscopic investigation of the contribution of the orbital magnetic moment to magnetization dynamics.
Collapse
Affiliation(s)
- Yuta Ishii
- Department of Physics, Tohoku University, Sendai, 980-8578, Japan.
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Japan.
| | - Yuichi Yamasaki
- National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yusuke Kozuka
- National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
| | - Jana Lustikova
- Center for Science and Innovation in Spintronics, Tohoku University, Sendai, 980-8577, Japan
| | - Yoichi Nii
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Yoshinori Onose
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Yuichi Yokoyama
- Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Sayo, 679-5198, Japan
| | - Masaichiro Mizumaki
- Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Sayo, 679-5198, Japan
- Faculty of Science, Course for Physical Sciences, Kumamoto University, Kumamoto, 860-0862, Japan
| | - Jun-Ichi Adachi
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, 305-0801, Japan
| | - Hironori Nakao
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, 305-0801, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | | |
Collapse
|
2
|
Zhou Y, Li S, Liang X, Zhou Y. Topological Spin Textures: Basic Physics and Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2312935. [PMID: 38861696 DOI: 10.1002/adma.202312935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 05/24/2024] [Indexed: 06/13/2024]
Abstract
In the face of escalating modern data storage demands and the constraints of Moore's Law, exploring spintronic solutions, particularly the devices based on magnetic skyrmions, has emerged as a promising frontier in scientific research. Since the first experimental observation of skyrmions, topological spin textures have been extensively studied for their great potential as efficient information carriers in spintronic devices. However, significant challenges have emerged alongside this progress. This review aims to synthesize recent advances in skyrmion research while addressing the major issues encountered in the field. Additionally, current research on promising topological spin structures in addition to skyrmions is summarized. Beyond 2D structures, exploration also extends to 1D magnetic solitons and 3D spin textures. In addition, a diverse array of emerging magnetic materials is introduced, including antiferromagnets and 2D van der Waals magnets, broadening the scope of potential materials hosting topological spin textures. Through a systematic examination of magnetic principles, topological categorization, and the dynamics of spin textures, a comprehensive overview of experimental and theoretical advances in the research of topological magnetism is provided. Finally, both conventional and unconventional applications are summarized based on spin textures proposed thus far. This review provides an outlook on future development in applied spintronics.
Collapse
Affiliation(s)
- Yuqing Zhou
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, China
| | - Shuang Li
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, China
| | - Xue Liang
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, China
| | - Yan Zhou
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong, 518172, China
| |
Collapse
|
3
|
Liu Q, Lin X, Zhu L. Absence of Spin-Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2301409. [PMID: 37485640 PMCID: PMC10520638 DOI: 10.1002/advs.202301409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 06/29/2023] [Indexed: 07/25/2023]
Abstract
Exploration of exotic spin polarizations in single crystals is of increasing interest. A current of longitudinal spins, the so-called "Dresselhaus-like" spin current, which is forbidden in materials lacking certain inversion asymmetries, is implied to be generated by a charge current at the interface of single-crystal CoFe. This work reports unambiguous evidence that there is no indication of spin current of any spin polarizations from the interface or bulk of single-crystalline CoFe and that the sin2φ second harmonic Hall voltage, which is previously assumed to signify Dresselhaus-like spin current, is not related to any spin currents but rather a planar Nernst voltage induced by a longitudinal temperature gradient within the sample. Such sin2φ signal is independent of large applied magnetic fields and interfacial spin-orbit coupling, inversely correlated to the heat capacity of the substrates and overlayers, quadratic in charge current, and appears also in polycrystalline ferromagnets. Strikingly, the planar Nernst effect (PNE) in the CoFe single crystal has a strong fourfold anisotropy and varies with the crystalline orientation. Such strong, anisotropic PNE has widespread impacts on the analyses of a variety of spintronic experiments and opens a new avenue for the development of PNE-based thermoelectric battery and sensor applications.
Collapse
Affiliation(s)
- Qianbiao Liu
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
| | - Xin Lin
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
- College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of SciencesBeijing100049China
| | - Lijun Zhu
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
- College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of SciencesBeijing100049China
| |
Collapse
|
4
|
Balan C, van de Jagt JW, Fassatoui A, Peña Garcia J, Jeudy V, Thiaville A, Bonfim M, Vogel J, Ranno L, Ravelosona D, Pizzini S. Improving Néel Domain Walls Dynamics and Skyrmion Stability Using He Ion Irradiation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2302039. [PMID: 37178408 DOI: 10.1002/smll.202302039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/14/2023] [Indexed: 05/15/2023]
Abstract
Ion irradiation with light ions is an appealing way to finely tune the magnetic properties of thin magnetic films and in particular the perpendicular magnetic anisotropy (PMA). In this work, the effect of He+ irradiation on the magnetization reversal and on the domain wall dynamics of Pt/Co/AlOx trilayers is illustrated. Fluences up to 1.5 × 1015 ions cm-2 strongly decrease the PMA, without affecting neither the spontaneous magnetization nor the strength of the interfacial Dzyaloshinskii-Moriya interaction (DMI). This confirms experimentally the robustness of the DMI interaction against interfacial chemical intermixing, already predicted by theory. In parallel with the decrease of the PMA, a strong decrease of the domain wall depinning field is observed after irradiation. This allows the domain walls to reach large maximum velocities with a lower magnetic field compared to that needed for the pristine films. Decoupling PMA from DMI can, therefore, be beneficial for the design of low energy devices based on domain wall dynamics. When the samples are irradiated with larger He+ fluences, the magnetization gets close to the out-of-plane/in-plane reorientation transition, where ≈100nm size magnetic skyrmions are stabilized. It is observed that as the He+ fluence increases, the skyrmion size decreases while these magnetic textures become more stable against the application of an external magnetic field, as predicted by theoretical models developed for ultrathin films with labyrinthine domains.
Collapse
Affiliation(s)
- Cristina Balan
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| | - Johannes W van de Jagt
- Spin-Ion Technologies, 10 Boulevard Thomas Gobert, Palaiseau, 91120, France
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Saclay, 10 boulevard Thomas Gobert, Palaiseau, 91120, France
| | - Aymen Fassatoui
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| | - Jose Peña Garcia
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| | - Vincent Jeudy
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, Orsay, 91405, France
| | - André Thiaville
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, Orsay, 91405, France
| | - Marlio Bonfim
- Dep. de Engenharia Elétrica, Universidade Federal do Parana, Curitiba, PR 81531-990, Brasil
| | - Jan Vogel
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| | - Laurent Ranno
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| | - Dafiné Ravelosona
- Spin-Ion Technologies, 10 Boulevard Thomas Gobert, Palaiseau, 91120, France
- Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Saclay, 10 boulevard Thomas Gobert, Palaiseau, 91120, France
| | - Stefania Pizzini
- Univ. Grenoble Alpes, CNRS, Institut Néel, Grenoble, 38042, France
| |
Collapse
|
5
|
Chen CJ, Chao YC, Lin YH, Zhuang YH, Lai YM, Huang ST, MacDonald AH, Shih CK, Wang BY, Su JJ, Hsu PJ. Single-Atomic-Layer Stanene on Ferromagnetic Co Nanoislands with Topological Band Structures. ACS NANO 2023; 17:7456-7465. [PMID: 37014733 DOI: 10.1021/acsnano.2c12144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Introducing magnetism to two-dimensional topological insulators is a central issue in the pursuit of magnetic topological materials in low dimensionality. By means of low-temperature growth at 80 K, we succeeded in fabricating a monolayer stanene on Co/Cu(111) and resolving ferromagnetic spin contrast by field-dependent spin-polarized scanning tunneling microscopy (SP-STM). Increases of both remanence to saturation magnetization ratio (Mr/Ms) and coercive field (Hc) due to an enhanced perpendicular magnetic anisotropy (PMA) are further identified by out-of-plane magneto-optical Kerr effect (MOKE). In addition to ultraflat stanene fully relaxed on bilayer Co/Cu(111) from density functional theory (DFT), characteristic topological properties including an in-plane s-p band inversion and a spin-orbit coupling (SOC) induced gap about 0.25 eV at the Γ̅ point have also been verified in the Sn-projected band structure. Interfacial coupling of single-atomic-layer stanene with ferromagnetic Co biatomic layers allows topological band features to coexist with ferromagnetism, facilitating a conceptual design of atomically thin magnetic topological heterostructures.
Collapse
Affiliation(s)
- Chia-Ju Chen
- Department of Physics, National Tsing Hua University, 300044 Hsinchu, Taiwan
| | - Yung-Chun Chao
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Yen-Hui Lin
- Department of Physics, National Tsing Hua University, 300044 Hsinchu, Taiwan
| | - Yi-Hao Zhuang
- Department of Physics, National Tsing Hua University, 300044 Hsinchu, Taiwan
| | - Yen-Ming Lai
- Department of Physics, National Changhua University of Education, Changhua 500, Taiwan
| | - Shih-Tang Huang
- Department of Physics, National Tsing Hua University, 300044 Hsinchu, Taiwan
| | - Allan H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Chih-Kang Shih
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Bo-Yao Wang
- Department of Physics, National Changhua University of Education, Changhua 500, Taiwan
| | - Jung-Jung Su
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Pin-Jui Hsu
- Department of Physics, National Tsing Hua University, 300044 Hsinchu, Taiwan
- Center for Quantum Technology, National Tsing Hua University, Hsinchu 300044, Taiwan
| |
Collapse
|
6
|
Miura Y, Okabayashi J. Understanding magnetocrystalline anisotropy based on orbital and quadrupole moments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:473001. [PMID: 36137512 DOI: 10.1088/1361-648x/ac943f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Understanding magnetocrystalline anisotropy (MCA) is fundamentally important for developing novel magnetic materials. Therefore, clarifying the relationship between MCA and local physical quantities observed by spectroscopic measurements, such as the orbital and quadrupole moments, is necessary. In this review, we discuss MCA and the distortion effects in magnetic materials with transition metals (TMs) based on the orbital and quadrupole moments, which are related to the spin-conserving and spin-flip terms in the second-order perturbation calculations, respectively. We revealed that orbital moment stabilized the spin moment in the direction of the larger orbital moment, while the quadrupole moment stabilized the spin moment along the longitudinal direction of the spin-density distribution. The MCA of the magnetic materials with TMs and their interfaces can be determined from the competition between these two contributions. We showed that the perpendicular MCA of the face-centered cubic Ni with tensile tetragonal distortion arose from the orbital moment anisotropy, whereas that of Mn-Ga alloys originated from the quadrupole moment of spin density. In contrast, in the Co/Pd(111) multilayer and Fe/MgO(001), both the orbital moment anisotropy and quadrupole moment of spin density at the interfaces contributed to the perpendicular MCA. Understanding the MCA of magnetic materials and interfaces based on orbital and quadrupole moments is essential to design MCA of novel magnetic applications.
Collapse
Affiliation(s)
- Yoshio Miura
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba 305-0047, Japan
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560-8531, Japan
| | - Jun Okabayashi
- Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| |
Collapse
|
7
|
Kim S, Pathak S, Rhim SH, Cha J, Jekal S, Hong SC, Lee HH, Park S, Lee H, Park J, Lee S, Steinrück H, Mehta A, Wang SX, Hong J. Giant Orbital Anisotropy with Strong Spin-Orbit Coupling Established at the Pseudomorphic Interface of the Co/Pd Superlattice. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201749. [PMID: 35748161 PMCID: PMC9403640 DOI: 10.1002/advs.202201749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 05/22/2022] [Indexed: 06/15/2023]
Abstract
Orbital anisotropy at interfaces in magnetic heterostructures has been key to pioneering spin-orbit-related phenomena. However, modulating the interface's electronic structure to make it abnormally asymmetric has been challenging because of lack of appropriate methods. Here, the authors report that low-energy proton irradiation achieves a strong level of inversion asymmetry and unusual strain at interfaces in [Co/Pd] superlattices through nondestructive, selective removal of oxygen from Co3 O4 /Pd superlattices during irradiation. Structural investigations corroborate that progressive reduction of Co3 O4 into Co establishes pseudomorphic growth with sharp interfaces and atypically large tensile stress. The normal component of orbital to spin magnetic moment at the interface is the largest among those observed in layered Co systems, which is associated with giant orbital anisotropy theoretically confirmed, and resulting very large interfacial magnetic anisotropy is observed. All results attribute not only to giant orbital anisotropy but to enhanced interfacial spin-orbit coupling owing to the pseudomorphic nature at the interface. They are strongly supported by the observation of reversal of polarity of temperature-dependent Anomalous Hall signal, a signature of Berry phase. This work suggests that establishing both giant orbital anisotropy and strong spin-orbit coupling at the interface is key to exploring spintronic devices with new functionalities.
Collapse
Affiliation(s)
- Sanghoon Kim
- Department of Materials Science and EngineeringYonsei UniversitySeoul03722Korea
- Present address:
Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Sachin Pathak
- Department of Materials Science and EngineeringYonsei UniversitySeoul03722Korea
| | - Sonny H. Rhim
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Jongin Cha
- Department of Materials Science and EngineeringYonsei UniversitySeoul03722Korea
| | - Soyoung Jekal
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | | | | | - Sung‐Hun Park
- Department of PhysicsPohang University of Science and TechnologyPohang37673Korea
| | - Han‐Koo Lee
- Pohang Acceleration LaboratoryPohang37673Korea
| | - Jae‐Hoon Park
- Department of PhysicsPohang University of Science and TechnologyPohang37673Korea
| | - Soogil Lee
- Department of Materials Science and EngineeringYonsei UniversitySeoul03722Korea
| | | | - Apurva Mehta
- SSRL Materials Science DivisionSLAC National Accelerator LaboratoryCA94025USA
| | - Shan X. Wang
- Department of Materials Science and Engineeringand Electrical EngineeringStanford UniversityCA94305USA
| | - Jongill Hong
- Department of Materials Science and EngineeringYonsei UniversitySeoul03722Korea
| |
Collapse
|
8
|
Shaw JM, Knut R, Armstrong A, Bhandary S, Kvashnin Y, Thonig D, Delczeg-Czirjak EK, Karis O, Silva TJ, Weschke E, Nembach HT, Eriksson O, Arena DA. Quantifying Spin-Mixed States in Ferromagnets. PHYSICAL REVIEW LETTERS 2021; 127:207201. [PMID: 34860034 DOI: 10.1103/physrevlett.127.207201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
We quantify the presence of spin-mixed states in ferromagnetic 3D transition metals by precise measurement of the orbital moment. While central to phenomena such as Elliot-Yafet scattering, quantification of the spin-mixing parameter has hitherto been confined to theoretical calculations. We demonstrate that this information is also available by experimental means. Comparison of ferromagnetic resonance spectroscopy with x-ray magnetic circular dichroism results show that Kittel's original derivation of the spectroscopic g factor requires modification, to include spin mixing of valence band states. Our results are supported by ab initio relativistic electronic structure theory.
Collapse
Affiliation(s)
- Justin M Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - Ronny Knut
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - Abigail Armstrong
- Department of Physics, University of South Florida, Tampa, Florida 33620, USA
| | - Sumanta Bhandary
- School of Physics and CRANN Institute, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Yaroslav Kvashnin
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - Danny Thonig
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | | | - Olof Karis
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - T J Silva
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - Eugen Weschke
- Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, D-12489 Berlin, Germany
| | - Hans T Nembach
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Olle Eriksson
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | - Dario A Arena
- Department of Physics, University of South Florida, Tampa, Florida 33620, USA
| |
Collapse
|
9
|
Magnetic anisotropic of thermally evaporated FeNi thin film: A soft X‐ray magnetic circular dichroism study. SURF INTERFACE ANAL 2021. [DOI: 10.1002/sia.6982] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
10
|
Fallarino L, Kirby BJ, Fullerton EE. Graded magnetic materials. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2021; 54:10.1088/1361-6463/abfad3. [PMID: 38915790 PMCID: PMC11194700 DOI: 10.1088/1361-6463/abfad3] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Graded magnetic materials represent a promising new avenue in modern material science from both fundamental and application points of view. Over the course of the last few years, remarkable results have been obtained in (epitaxial) heterostructures based on thin alloy films featuring diverse compositional depth profiles. As a result of the precise tailoring of such profiles, the exchange coupling, and the corresponding effective or local Curie temperatures can be controlled over tens of nm with an excellent precision. This topical review article reports the most recent advances in this emerging research field. Several aspects are covered, but the primary focus lies in the study of compositional gradients being transferred into depth dependent magnetic states in ferromagnets, while also reviewing other experimental attempts to create exchange graded films and materials in general. We account for the remarkable progress achieved in each sample and composition geometry by reporting the recent developments and by discussing the research highlights obtained by several groups. Finally, we conclude the review article with an outlook on future challenges in this field.
Collapse
Affiliation(s)
| | - Brian J Kirby
- NIST Center for Neutron Research, Gaithersburg, MD 20899, United States of America
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California, San Diego, La Jolla, CA 92093-0401, United States of America
- Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0407, United States of America
| |
Collapse
|
11
|
Lima MP. Spatial anisotropy of the quantum spin liquid system YbMgGaO 4 revealed by ab initio calculations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:025505. [PMID: 31581147 DOI: 10.1088/1361-648x/ab4ab6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
YbMgGaO4 was recently proposed as a promising quantum-spin-liquid candidate material. However, some details of its structure, such as those related to a spatial anisotropy, were not completely understood. In this work, we perform ab initio calculations based on density-functional-theory to investigate the structural, the electronic and the magnetic properties of YbMgGaO4. The geometrical model was constructed to take into account disorder effects produced by the random distribution of Ga and Mg along the lattice. We found a substantial spatial anisotropy revealed by variations up to 8% in the Mg-O and Ga-O bond lengths, which results in variations up to 3% in the Yb-Yb distances along its triangular lattice. Thus, the Yb lattice was not perfectly triangular. Furthermore, we demonstrate an out-of-plane magnetization at the Yb atoms with magnetic anisotropy energy of [Formula: see text] eV/Yb and a small interlayer exchange of [Formula: see text] eV/Yb, demonstrating that the system is only approximately two-dimensional. The presented results provide insights for an atomic-scale understanding of YbMgGaO4 with density-functional-theory calculations.
Collapse
Affiliation(s)
- Matheus P Lima
- Department of Physics, Federal University of São Carlos, CEP 13565-905, São Carlos, SP, Brazil
| |
Collapse
|
12
|
Kikuchi Y, Tanaka T. Strengthen of magnetic anisotropy of Au/Co/Au nanostructure by surface plasmon resonance. Sci Rep 2019; 9:8630. [PMID: 31201342 PMCID: PMC6570655 DOI: 10.1038/s41598-019-45122-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 05/29/2019] [Indexed: 11/24/2022] Open
Abstract
We experimentally demonstrated the increase of in-plane magnetic anisotropy in Au/Co/Au nanostructures by localized surface plasmon resonance (LSPR). When an array of Au/Co/Au square patch nanostructures was illuminated with linearly polarized light whose wavelength was 750 nm, the localized surface plasmons were resonantly excited in the nanostructures. From the measurement results of polar magneto-optical Kerr effect curves, we observed the magnetic anisotropy field increase in the Au/Co/Au nanostructure due to the excited surface plasmons. The in-plane magnetic anisotropy energy density was increased about 24%.
Collapse
Affiliation(s)
- Yusuke Kikuchi
- School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguroku, Tokyo, 152-8550, Japan
- Metamaterials Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Takuo Tanaka
- School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguroku, Tokyo, 152-8550, Japan.
- Metamaterials Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
- Innovative Photon Manipulation Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
| |
Collapse
|
13
|
Zhang W, Wong PKJ, Zhou X, Rath A, Huang Z, Wang H, Morton SA, Yuan J, Zhang L, Chua R, Zeng S, Liu E, Xu F, Chua DHC, Feng YP, van der Laan G, Pennycook SJ, Zhai Y, Wee ATS. Ferromagnet/Two-Dimensional Semiconducting Transition-Metal Dichalcogenide Interface with Perpendicular Magnetic Anisotropy. ACS NANO 2019; 13:2253-2261. [PMID: 30775909 DOI: 10.1021/acsnano.8b08926] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ferromagnet/two-dimensional transition-metal dichalcogenide (FM/2D TMD) interfaces provide attractive opportunities to push magnetic information storage to the atomically thin limit. Existing work has focused on FMs contacted with mechanically exfoliated or chemically vapor-deposition-grown TMDs, where clean interfaces cannot be guaranteed. Here, we report a reliable way to achieve contamination-free interfaces between ferromagnetic CoFeB and molecular-beam epitaxial MoSe2. We show a spin reorientation arising from the interface, leading to a perpendicular magnetic anisotropy (PMA), and reveal the CoFeB/2D MoSe2 interface allowing for the PMA development in a broader CoFeB thickness-range than common systems such as CoFeB/MgO. Using X-ray magnetic circular dichroism analysis, we attribute generation of this PMA to interfacial d-d hybridization and deduce a general rule to enhance its magnitude. We also demonstrate favorable magnetic softness and considerable magnetic moment preserved at the interface and theoretically predict the interfacial band matching for spin filtering. Our work highlights the CoFeB/2D MoSe2 interface as a promising platform for examination of TMD-based spintronic applications and might stimulate further development with other combinations of FM/2D TMD interfaces.
Collapse
Affiliation(s)
- Wen Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Xiaochao Zhou
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Ashutosh Rath
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Zhaocong Huang
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Hongyu Wang
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Simon A Morton
- Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jiaren Yuan
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Lei Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Rebekah Chua
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , National University of Singapore , Centre for Life Sciences, #05-01, 28 Medical Drive , Singapore 117456 Singapore
| | - Shengwei Zeng
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- NUSSNI-NanoCore , National University of Singapore , 5A Engineering Drive 1 , Singapore 117411 , Singapore
| | - Er Liu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Feng Xu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Daniel H C Chua
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Yuan Ping Feng
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | | | - Stephen J Pennycook
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Ya Zhai
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Andrew T S Wee
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| |
Collapse
|
14
|
Salaheldeen M, Vega V, Ibabe A, Jaafar M, Asenjo A, Fernandez A, Prida VM. Tailoring of Perpendicular Magnetic Anisotropy in Dy 13Fe 87 Thin Films with Hexagonal Antidot Lattice Nanostructure. NANOMATERIALS 2018; 8:nano8040227. [PMID: 29642476 PMCID: PMC5923557 DOI: 10.3390/nano8040227] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 03/31/2018] [Accepted: 04/05/2018] [Indexed: 11/16/2022]
Abstract
In this article, the magnetic properties of hexagonally ordered antidot arrays made of Dy13Fe87 alloy are studied and compared with corresponding ones of continuous thin films with the same compositions and thicknesses, varying between 20 nm and 50 nm. Both samples, the continuous thin films and antidot arrays, were prepared by high vacuum e-beam evaporation of the alloy on the top-surface of glass and hexagonally self-ordered nanoporous alumina templates, which serve as substrates, respectively. By using a highly sensitive magneto-optical Kerr effect (MOKE) and vibrating sample magnetometer (VSM) measurements an interesting phenomenon has been observed, consisting in the easy magnetization axis transfer from a purely in-plane (INP) magnetic anisotropy to out-of-plane (OOP) magnetization. For the 30 nm film thickness we have measured the volume hysteresis loops by VSM with the easy magnetization axis lying along the OOP direction. Using magnetic force microscopy measurements (MFM), there is strong evidence to suggest that the formation of magnetic domains with OOP magnetization occurs in this sample. This phenomenon can be of high interest for the development of novel magnetic and magneto-optic perpendicular recording patterned media based on template-assisted deposition techniques.
Collapse
Affiliation(s)
- Mohamed Salaheldeen
- Physics Department, Faculty of Science, Sohag University, 82524 Sohag, Egypt.
- Depto. Física, Universidad de Oviedo, C/Federico Garcia Lorca 18, 33007 Oviedo, Asturias, Spain.
| | - Victor Vega
- Depto. Física, Universidad de Oviedo, C/Federico Garcia Lorca 18, 33007 Oviedo, Asturias, Spain.
- Laboratorio Membranas Nanoporosas, Servicios Científico-Técnicos, Universidad de Oviedo, Campus El Cristo s/n, 33006 Oviedo, Asturias, Spain.
| | - Angel Ibabe
- Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
| | - Miriam Jaafar
- Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
| | - Agustina Asenjo
- Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
| | - Agustin Fernandez
- Depto. Física, Universidad de Oviedo, C/Federico Garcia Lorca 18, 33007 Oviedo, Asturias, Spain.
| | - Victor M Prida
- Depto. Física, Universidad de Oviedo, C/Federico Garcia Lorca 18, 33007 Oviedo, Asturias, Spain.
| |
Collapse
|
15
|
Hellman F, Hoffmann A, Tserkovnyak Y, Beach GSD, Fullerton EE, Leighton C, MacDonald AH, Ralph DC, Arena DA, Dürr HA, Fischer P, Grollier J, Heremans JP, Jungwirth T, Kimel AV, Koopmans B, Krivorotov IN, May SJ, Petford-Long AK, Rondinelli JM, Samarth N, Schuller IK, Slavin AN, Stiles MD, Tchernyshyov O, Thiaville A, Zink BL. Interface-Induced Phenomena in Magnetism. REVIEWS OF MODERN PHYSICS 2017; 89:025006. [PMID: 28890576 PMCID: PMC5587142 DOI: 10.1103/revmodphys.89.025006] [Citation(s) in RCA: 192] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.
Collapse
Affiliation(s)
- Frances Hellman
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Axel Hoffmann
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Geoffrey S D Beach
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0401, USA
| | - Chris Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Allan H MacDonald
- Department of Physics, University of Texas at Austin, Austin, Texas 78712-0264, USA
| | - Daniel C Ralph
- Physics Department, Cornell University, Ithaca, New York 14853, USA; Kavli Institute at Cornell, Cornell University, Ithaca, New York 14853, USA
| | - Dario A Arena
- Department of Physics, University of South Florida, Tampa, Florida 33620-7100, USA
| | - Hermann A Dürr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Peter Fischer
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; Physics Department, University of California, 1156 High Street, Santa Cruz, California 94056, USA
| | - Julie Grollier
- Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Avenue Fresnel, 91767 Palaiseau, France
| | - Joseph P Heremans
- Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210, USA; Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA; Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Tomas Jungwirth
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Praha 6, Czech Republic; School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Alexey V Kimel
- Radboud University, Institute for Molecules and Materials, Nijmegen 6525 AJ, The Netherlands
| | - Bert Koopmans
- Department of Applied Physics, Center for NanoMaterials, COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Ilya N Krivorotov
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Steven J May
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA
| | - Amanda K Petford-Long
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208, USA
| | - James M Rondinelli
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Nitin Samarth
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California, San Diego, La Jolla, California 92093, USA; Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093, USA
| | - Andrei N Slavin
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
| | - Mark D Stiles
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6202, USA
| | - Oleg Tchernyshyov
- Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - André Thiaville
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405 Orsay, France
| | - Barry L Zink
- Department of Physics and Astronomy, University of Denver, Denver, CO 80208, USA
| |
Collapse
|
16
|
Kim KW, Lee KJ, Lee HW, Stiles MD. Perpendicular magnetic anisotropy of two-dimensional Rashba ferromagnets. PHYSICAL REVIEW. B 2016; 94:184402. [PMID: 28596998 PMCID: PMC5460678 DOI: 10.1103/physrevb.94.184402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We compute the magnetocrystalline anisotropy energy within two-dimensional Rashba models. For a ferromagnetic free-electron Rashba model, the magnetic anisotropy is exactly zero regardless of the strength of the Rashba coupling, unless only the lowest band is occupied. For this latter case, the model predicts in-plane anisotropy. For a more realistic Rashba model with finite band width, the magnetic anisotropy evolves from in-plane to perpendicular and back to in-plane as bands are progressively filled. This evolution agrees with first-principles calculations on the interfacial anisotropy, suggesting that the Rashba model captures energetics leading to anisotropy originating from the interface provided that the model takes account of the finite Brillouin zone. The results show that the electron density modulation by doping or an external voltage is more important for voltage-controlled magnetic anisotropy than the modulation of the Rashba parameter.
Collapse
Affiliation(s)
- Kyoung-Whan Kim
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA
- Basic Science Research Institute, Pohang University of Science and Technology, Pohang 37673, Korea
- PCTP and Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Kyung-Jin Lee
- Department of Materials Science and Engineering, Korea University, Seoul 02841, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
| | - Hyun-Woo Lee
- PCTP and Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - M D Stiles
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| |
Collapse
|
17
|
Ferromagnetic Multilayers: Magnetoresistance, Magnetic Anisotropy, and Beyond. MAGNETOCHEMISTRY 2016. [DOI: 10.3390/magnetochemistry2020022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
18
|
Jhajhria D, Pandya DK, Chaudhary S. Orbital moment probed spin orbit coupling effects on anisotropy and damping in CoFeB thin films. RSC Adv 2016. [DOI: 10.1039/c6ra19837f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Spin orbit coupling based direct correlation between magnetic anisotropy and damping is established in CoFeB thin films on compositional and stress variations.
Collapse
Affiliation(s)
- Deepika Jhajhria
- Thin Film Laboratory
- Department of Physics
- Indian Institute of Technology Delhi
- New Delhi 110016
- India
| | - Dinesh K. Pandya
- Thin Film Laboratory
- Department of Physics
- Indian Institute of Technology Delhi
- New Delhi 110016
- India
| | - Sujeet Chaudhary
- Thin Film Laboratory
- Department of Physics
- Indian Institute of Technology Delhi
- New Delhi 110016
- India
| |
Collapse
|
19
|
Gräfe J, Haering F, Tietze T, Audehm P, Weigand M, Wiedwald U, Ziemann P, Gawroński P, Schütz G, Goering EJ. Perpendicular magnetisation from in-plane fields in nano-scaled antidot lattices. NANOTECHNOLOGY 2015; 26:225203. [PMID: 25969389 DOI: 10.1088/0957-4484/26/22/225203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Investigations of geometric frustrations in magnetic antidot lattices have led to the observation of interesting phenomena like spin-ice and magnetic monopoles. By using highly focused magneto-optical Kerr effect measurements and x-ray microscopy with magnetic contrast we deduce that geometrical frustration in these nanostructured thin film systems also leads to an out-of-plane magnetization from a purely in-plane applied magnetic field. For certain orientations of the antidot lattice, formation of perpendicular magnetic domains has been found with a size of several μm that may be used for an in-plane/out-of-plane transducer.
Collapse
Affiliation(s)
- Joachim Gräfe
- Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Saravanan K, Kao CH, Shao YC, Wang YF, Wang BY, Wang HT, Tsai CJ, Lin WC, Pao CW, Tsai HM, Jang LY, Lin HJ, Lee JF, Pong WF. Magnetic anisotropic properties of Pd/Co/Pd trilayer films studied by X-ray absorption spectroscopy and magnetic circular dichroism. RSC Adv 2015. [DOI: 10.1039/c4ra15683h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Strong perpendicular magnetic anisotropy (PMA) is observed in annealed Pd/Co/Pd trilayer film. The effect of temperature on alloy formation, the relationship among the atomic/electronic structures, magnetic moments and PMA has been studied.
Collapse
|
21
|
van der Laan G, Figueroa AI. X-ray magnetic circular dichroism—A versatile tool to study magnetism. Coord Chem Rev 2014. [DOI: 10.1016/j.ccr.2014.03.018] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
|
22
|
Macke S, Goering E. Magnetic reflectometry of heterostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:363201. [PMID: 25121937 DOI: 10.1088/0953-8984/26/36/363201] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Measuring the magnetic configuration at complex buried layers and interfaces is an important task, which requires especially a non-destructive probing technique. X-ray resonant magnetic reflectometry (XRMR) combines the non-destructive depth profiling potential of x-ray reflectometry with the excellent sensitivity for magnetic phenomena, utilizing the x-ray magnetic circular dichroism effect. It provides the magnetic spatial distribution with a precision down to the angstrom scale, combined with element and symmetry specificity, sub-monolayer sensitivity, and the possible separation of spin and orbital magnetic moments. This review provides an overview to the XRMR technique in a tutorial way. We focus on the introduction to the theory, measurement types, and data simulation. We provide related experimental examples and show selected applications.
Collapse
Affiliation(s)
- 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
| | | |
Collapse
|
23
|
Dąbrowski M, Peixoto TRF, Pazgan M, Winkelmann A, Cinal M, Nakagawa T, Takagi Y, Yokoyama T, Bisio F, Bauer U, Yildiz F, Przybylski M, Kirschner J. Oscillations of the orbital magnetic moment due to d-band quantum well states. PHYSICAL REVIEW LETTERS 2014; 113:067203. [PMID: 25148348 DOI: 10.1103/physrevlett.113.067203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Indexed: 06/03/2023]
Abstract
The effect of electron confinement on the magnetocrystalline anisotropy of ultrathin bcc Fe films is explored by combining photoemission spectroscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements. Pronounced thickness-dependent variations in the magnetocrystalline anisotropy are ascribed to periodic changes in the density of states at the Fermi level, induced by quantization of d(xz), d(yz) out-of-plane orbitals. Our results reveal a direct correlation between quantum well states, the orbital magnetic moment, and the magnetocrystalline anisotropy.
Collapse
Affiliation(s)
- M Dąbrowski
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - T R F Peixoto
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Pazgan
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - A Winkelmann
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Cinal
- Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
| | - T Nakagawa
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - Y Takagi
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - T Yokoyama
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - F Bisio
- CNR-SPIN Corso Perrone 24, I-16152 Genova, Italy
| | - U Bauer
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - F Yildiz
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Przybylski
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany and Faculty of Physics and Applied Computer Science, and Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, 30-059 Kraków, Poland
| | - J Kirschner
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany and Naturwissenschaftliche Fakultät II, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany
| |
Collapse
|
24
|
Schmitz D, Schmitz-Antoniak C, Warland A, Darbandi M, Haldar S, Bhandary S, Eriksson O, Sanyal B, Wende H. The dipole moment of the spin density as a local indicator for phase transitions. Sci Rep 2014; 4:5760. [PMID: 25041757 PMCID: PMC4104392 DOI: 10.1038/srep05760] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/02/2014] [Indexed: 11/17/2022] Open
Abstract
The intra-atomic magnetic dipole moment - frequently called 〈Tz〉 term - plays an important role in the determination of spin magnetic moments by x-ray absorption spectroscopy for systems with nonspherical spin density distributions. In this work, we present the dipole moment as a sensitive monitor to changes in the electronic structure in the vicinity of a phase transiton. In particular, we studied the dipole moment at the Fe2+ and Fe3+ sites of magnetite as an indicator for the Verwey transition by a combination of x-ray magnetic circular dichroism and density functional theory. Our experimental results prove that there exists a local change in the electronic structure at temperatures above the Verwey transition correlated to the known spin reorientation. Furthermore, it is shown that measurement of the dipole moment is a powerful tool to observe this transition in small magnetite nanoparticles for which it is usually screened by blocking effects in classical magnetometry.
Collapse
Affiliation(s)
- D Schmitz
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - C Schmitz-Antoniak
- 1] Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany [2]
| | - A Warland
- Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany
| | - M Darbandi
- 1] Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany [2]
| | - S Haldar
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120 Uppsala, Sweden
| | - S Bhandary
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120 Uppsala, Sweden
| | - O Eriksson
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120 Uppsala, Sweden
| | - B Sanyal
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120 Uppsala, Sweden
| | - H Wende
- Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany
| |
Collapse
|
25
|
Rau IG, Baumann S, Rusponi S, Donati F, Stepanow S, Gragnaniello L, Dreiser J, Piamonteze C, Nolting F, Gangopadhyay S, Albertini OR, Macfarlane RM, Lutz CP, Jones BA, Gambardella P, Heinrich AJ, Brune H. Reaching the magnetic anisotropy limit of a 3d metal atom. Science 2014; 344:988-92. [PMID: 24812206 DOI: 10.1126/science.1252841] [Citation(s) in RCA: 269] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism.
Collapse
Affiliation(s)
- Ileana G Rau
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | - Susanne Baumann
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA. Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Stefano Rusponi
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Fabio Donati
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Sebastian Stepanow
- Department of Materials, Eidgenössische Technische Hochschule (ETH) Zürich, Hönggerbergring 64, CH-8093 Zürich, Switzerland
| | - Luca Gragnaniello
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Jan Dreiser
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland. Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Frithjof Nolting
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | | | - Oliver R Albertini
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA. Department of Physics, Georgetown University, 3700 O Street NW, Washington, DC 20057, USA
| | | | | | - Barbara A Jones
- IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA
| | - Pietro Gambardella
- Department of Materials, Eidgenössische Technische Hochschule (ETH) Zürich, Hönggerbergring 64, CH-8093 Zürich, Switzerland.
| | | | - Harald Brune
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland.
| |
Collapse
|
26
|
|
27
|
Wang BY, Wang HT, Singh SB, Shao YC, Wang YF, Chuang CH, Yeh PH, Chiou JW, Pao CW, Tsai HM, Lin HJ, Lee JF, Tsai CY, Hsieh WF, Tsai MH, Pong WF. Effect of geometry on the magnetic properties of CoFe2O4–PbTiO3 multiferroic composites. RSC Adv 2013. [DOI: 10.1039/c3ra00104k] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
28
|
Cheng XM, Keavney DJ. Studies of nanomagnetism using synchrotron-based x-ray photoemission electron microscopy (X-PEEM). REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2012; 75:026501. [PMID: 22790347 DOI: 10.1088/0034-4885/75/2/026501] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
As interest in magnetic devices has increased over the last 20 years, research into nanomagnetism has experienced a corresponding growth. Device applications from magnetic storage to magnetic logic have compelled interest in the influence of geometry and finite size on magnetism and magnetic excitations, in particular where the smallest dimensions reach the important magnetic interaction length scales. The dynamical behavior of nanoscale magnets is an especially important subset of research, as these phenomena are both critical for device physics and profoundly influenced by finite size. At the same time, nanoscale systems offer unique geometries to promote and study model systems, such as magnetic vortices, leading to new fundamental insights into magnetization dynamics. A wide array of experimental and computational techniques have been applied to these problems. Among these, imaging techniques that provide real-space information on the magnetic order are particularly useful. X-ray microscopy offers several advantages over scanning probe or optical techniques, such as high spatial resolution, element specificity and the possibility for high time resolution. Here, we review recent contributions using static and time-resolved x-ray photoemission electron microscopy to nanomagnetism research.
Collapse
Affiliation(s)
- X M Cheng
- Department of Physics, Bryn Mawr College, Bryn Mawr, PA, USA
| | | |
Collapse
|
29
|
|
30
|
Distinguishing the ultrafast dynamics of spin and orbital moments in solids. Nature 2010; 465:458-61. [PMID: 20505724 DOI: 10.1038/nature09070] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 04/06/2010] [Indexed: 11/08/2022]
|
31
|
Clavero C, Yang K, Skuza JR, Lukaszew RA. Magnetic field modulation of intense surface plasmon polaritons. OPTICS EXPRESS 2010; 18:7743-7752. [PMID: 20588615 DOI: 10.1364/oe.18.007743] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We present correlated experimental and theoretical studies on the magnetic field modulation of Surface Plasmon Polaritons (SPPs) in Au/Co/Au trilayers. The trilayers were grown by sputter deposition on glass slides with the Co films placed at different distances from the surface and with different thickness. We show that it is possible to tailor Au/Co/Au trilayers with the critical thickness needed for optimum excitation of SPPs leading to large localized electromagnetic fields. The modification of the SPP wave vector by externally applied magnetic fields was investigated by measuring the magneto-optical activity in transverse configuration. In addition, using magneto-optics as a tool we determined the spatial distribution of the SPP generated electromagnetic fields within Au/Co/Au samples by analyzing the field-dependent optical response, demonstrating that it is possible to excite SPPs that exhibit large electromagnetic fields that are also magneto-optically active and therefore can be modulated by externally applied magnetic fields.
Collapse
Affiliation(s)
- C Clavero
- Department of Applied Science, College of William & Mary, Williamsburg, Virginia 23187, USA.
| | | | | | | |
Collapse
|
32
|
Błoński P, Hafner J. Density-functional theory of the magnetic anisotropy of nanostructures: an assessment of different approximations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:426001. [PMID: 21715860 DOI: 10.1088/0953-8984/21/42/426001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We discuss the multiple technical choices that have to be made in ab initio density-functional calculations of the magnetic anisotropy of supported nanostructures: (i) choice of the exchange-correlation functional, (ii) degree of optimization of the geometry of the adsorbate/substrate complex, (iii) magnetic anisotropy energy calculated self-consistently or via the 'force theorem', (iv) calculations based on slab models of the substrate or using a Green's function describing a semi-infinite substrate, (v) full potential approach or atomic-sphere approximation. Using isolated Fe and Co atoms on Pt(111) as an example we demonstrate that by using a judicious combination of relatively crude approximations (complete neglect of structural relaxation, local exchange-correlation functional,...) seemingly good agreement with experimental anisotropy energies can be achieved, while the calculated orbital moments remain small. At a higher level of theory (relaxed adsorbate/substrate complex, gradient-corrected functionals,...) providing a realistic geometry of the adsorbate/substrate complex and hence a correct description of the interaction between the magnetic adatom and its ligands, anisotropy energies are also in semi-quantitative agreement with experiment, while the orbital moments of the adatoms are much too small. We suggest that the anisotropy energies provided by both approaches should be considered as lower limits of the real anisotropies. Without relaxation the ligand effect coupling the orbital moments of the adatom to the heavy atoms of the substrate is underestimated, while in a relaxed adsorbate/substrate complex the lack of orbital dependence of the exchange potential combined with a strong hybridization of adatom and substrate states leads to a strong underestimation of the orbital moment. We have briefly explored the influence of post-density-functional corrections. Adding a modest on-site Coulomb repulsion to the d states of the adatom (in a DFT+U approach) leads to a modest increase of spin and orbital moments of the adatom accompanied by a slow decrease of the induced moments, leaving the anisotropy energy almost unchanged.
Collapse
Affiliation(s)
- Piotr Błoński
- Fakultät für Physik and Center for Computational Materials Science, Universität Wien, Sensengasse 8/12, A-1090 Wien, Austria
| | | |
Collapse
|
33
|
Andersson C, Sanyal B, Eriksson O, Nordström L, Karis O, Arvanitis D, Konishi T, Holub-Krappe E, Dunn JH. Influence of ligand states on the relationship between orbital moment and magnetocrystalline anisotropy. PHYSICAL REVIEW LETTERS 2007; 99:177207. [PMID: 17995367 DOI: 10.1103/physrevlett.99.177207] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Indexed: 05/25/2023]
Abstract
The spin and orbital moments of Au/Co/Au trilayers grown on a W(110) single crystal substrate have been investigated by means of x-ray magnetic circular dichroism. Our findings suggest that the orbital moment of Co does not obtain a maximum value along the easy axis, in contrast with previous experience. This is attributed to the large spin-orbit interaction within the Au caps. Both second order perturbation theory and first principles calculations show how the magnetocrystalline anisotropy (MCA) is dramatically influenced by this effect, and how this leads to the fact that the orbital moment anisotropy is not proportional to the MCA.
Collapse
Affiliation(s)
- C Andersson
- Department of Physics, Uppsala University, Box 530, 751 21 Uppsala, Sweden
| | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Angle-resolved soft X-ray magnetic circular dichroism in a monatomic Fe layer facing an MgO(001) tunnel barrier. Radiat Phys Chem Oxf Engl 1993 2006. [DOI: 10.1016/j.radphyschem.2005.07.042] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
35
|
Schattschneider P, Rubino S, Hébert C, Rusz J, Kunes J, Novák P, Carlino E, Fabrizioli M, Panaccione G, Rossi G. Detection of magnetic circular dichroism using a transmission electron microscope. Nature 2006; 441:486-8. [PMID: 16724061 DOI: 10.1038/nature04778] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2005] [Accepted: 03/29/2006] [Indexed: 11/09/2022]
Abstract
A material is said to exhibit dichroism if its photon absorption spectrum depends on the polarization of the incident radiation. In the case of X-ray magnetic circular dichroism (XMCD), the absorption cross-section of a ferromagnet or a paramagnet in a magnetic field changes when the helicity of a circularly polarized photon is reversed relative to the magnetization direction. Although similarities between X-ray absorption and electron energy-loss spectroscopy in a transmission electron microscope (TEM) have long been recognized, it has been assumed that extending such equivalence to circular dichroism would require the electron beam in the TEM to be spin-polarized. Recently, it was argued on theoretical grounds that this assumption is probably wrong. Here we report the direct experimental detection of magnetic circular dichroism in a TEM. We compare our measurements of electron energy-loss magnetic chiral dichroism (EMCD) with XMCD spectra obtained from the same specimen that, together with theoretical calculations, show that chiral atomic transitions in a specimen are accessible with inelastic electron scattering under particular scattering conditions. This finding could have important consequences for the study of magnetism on the nanometre and subnanometre scales, as EMCD offers the potential for such spatial resolution down to the nanometre scale while providing depth information--in contrast to X-ray methods, which are mainly surface-sensitive.
Collapse
Affiliation(s)
- P Schattschneider
- Service Centre for Transmission Electron Microscopy, Wiedner Hauptstrasse 8-10/052, and Institut für Festkörperphysik, Wiedner Hauptstrasse 8-10/138, Technische Universität Wien, A-1040 Wien, Austria.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Edmonds KW, van der Laan G, Freeman AA, Farley NRS, Johal TK, Campion RP, Foxon CT, Gallagher BL, Arenholz E. Angle-dependent x-ray magnetic circular dichroism from (Ga,Mn)As: anisotropy and identification of hybridized states. PHYSICAL REVIEW LETTERS 2006; 96:117207. [PMID: 16605863 DOI: 10.1103/physrevlett.96.117207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Indexed: 05/08/2023]
Abstract
Remarkably anisotropic Mn L2,3 x-ray magnetic circular dichroism spectra from the ferromagnetic semiconductor (Ga,Mn)As are reported. States with cubic and uniaxial symmetry are distinguished by careful analysis of the angle dependence of the spectra. The multiplet structures with cubic symmetry are qualitatively reproduced by calculations for an atomiclike d5 configuration in tetrahedral environment, and show zero anisotropy in the orbital and spin moments within the experimental uncertainty. However, hybridization with the host valence bands is reflected by the presence of a preedge feature with a uniaxial anisotropy and a marked dependence on the hole density.
Collapse
Affiliation(s)
- K W Edmonds
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Borgonovi F, Celardo GL, Musesti A, Trasarti-Battistoni R, Vachal P. Topological nonconnectivity threshold in long-range spin systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:026116. [PMID: 16605407 DOI: 10.1103/physreve.73.026116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 09/01/2005] [Indexed: 05/08/2023]
Abstract
We demonstrate the existence of a topological disconnection threshold, recently found by Borgonovi [J. Stat. Phys. 116, 1435 (2004)], for generic 1-d anisotropic Heisenberg models interacting with an interparticle potential R(-alpha) when 0<alpha<1(here R is the distance among spins). We also show that alpha if is greater than the embedding dimension then the ratio between the disconnected energy region and the total energy region goes to zero when the number of spins becomes very large. On the other hand, numerical simulations in d=2,3 for the long-range case support the conclusion that such a ratio remains finite for large N values. The disconnection threshold can thus be thought of as a distinctive property of anisotropic long-range interacting systems.
Collapse
Affiliation(s)
- F Borgonovi
- Dipartimento di Matematica e Fisica, Università Cattolica, via Musei 41, 25121 Brescia, Italy
| | | | | | | | | |
Collapse
|
38
|
Giant Spin-Polarization and Magnetic Anisotropy of Nanostructures at Surfaces. E-JOURNAL OF SURFACE SCIENCE AND NANOTECHNOLOGY 2006. [DOI: 10.1380/ejssnt.2006.478] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
39
|
Weiss N, Cren T, Epple M, Rusponi S, Baudot G, Rohart S, Tejeda A, Repain V, Rousset S, Ohresser P, Scheurer F, Bencok P, Brune H. Uniform magnetic properties for an ultrahigh-density lattice of noninteracting co nanostructures. PHYSICAL REVIEW LETTERS 2005; 95:157204. [PMID: 16241757 DOI: 10.1103/physrevlett.95.157204] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Indexed: 05/05/2023]
Abstract
We report on the magnetic properties of two-dimensional Co nanoparticles arranged in macroscopically phase-coherent superlattices created by self-assembly on Au(788). Our particles have a density of 26 Tera/in2 (1 Tera=10(12)), are monodomain, and have uniaxial out-of-plane anisotropy. The distribution of the magnetic anisotropy energies has a half width at half maximum of 17%, a factor of 2 more narrow than the best results reported for superlattices of three-dimensional nanoparticles. Our data show the absence of magnetic interactions between the particles. Co/Au(788) thus constitutes an ideal model system to explore the ultimate density limit of magnetic recording.
Collapse
Affiliation(s)
- N Weiss
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Yamamoto Y, Miura T, Suzuki M, Kawamura N, Miyagawa H, Nakamura T, Kobayashi K, Teranishi T, Hori H. Direct observation of ferromagnetic spin polarization in gold nanoparticles. PHYSICAL REVIEW LETTERS 2004; 93:116801. [PMID: 15447364 DOI: 10.1103/physrevlett.93.116801] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Indexed: 05/24/2023]
Abstract
We report the first direct observation of ferromagnetic spin polarization of Au nanoparticles with a mean diameter of 1.9 nm using x-ray magnetic circular dichroism (XMCD). Owing to the element selectivity of XMCD, only the gold magnetization is explored. Magnetization of gold atoms as estimated by XMCD shows a good agreement with results obtained by conventional magnetometry. This evidences intrinsic spin polarization in nanosized gold.
Collapse
Affiliation(s)
- Y Yamamoto
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Tatsunokuchi, Ishikawa, 923-1292, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Gambardella P, Rusponi S, Veronese M, Dhesi SS, Grazioli C, Dallmeyer A, Cabria I, Zeller R, Dederichs PH, Kern K, Carbone C, Brune H. Giant magnetic anisotropy of single cobalt atoms and nanoparticles. Science 2003; 300:1130-3. [PMID: 12750516 DOI: 10.1126/science.1082857] [Citation(s) in RCA: 314] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The isotropic magnetic moment of a free atom is shown to develop giant magnetic anisotropy energy due to symmetry reduction at an atomically ordered surface. Single cobalt atoms deposited onto platinum (111) are found to have a magnetic anisotropy energy of 9 millielectron volts per atom arising from the combination of unquenched orbital moments (1.1 Bohr magnetons) and strong spin-orbit coupling induced by the platinum substrate. By assembling cobalt nanoparticles containing up to 40 atoms, the magnetic anisotropy energy is further shown to be dependent on single-atom coordination changes. These results confirm theoretical predictions and are of fundamental value to understanding how magnetic anisotropy develops in finite-sized magnetic particles.
Collapse
Affiliation(s)
- P Gambardella
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Dhesi SS, Dürr HA, Münzenberg M, Felsch W. Isolating the interface magnetocrystalline anisotropy contributions in magnetic multilayers. PHYSICAL REVIEW LETTERS 2003; 90:117204. [PMID: 12688964 DOI: 10.1103/physrevlett.90.117204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2002] [Indexed: 05/24/2023]
Abstract
The interface magnetocrystalline anisotropy energy (MAE) in Fe/CeH(2) multilayers has been site and element-specifically isolated by combining soft x-ray resonant magnetic scattering (SXRMS) with soft x-ray standing waves. Using the different temperature evolutions of the Fe and Ce SXRMS contributions, following an in-plane to out-of-plane spin reorientation, the interface Fe 3d MAE and Ce 4f single-ion anisotropy have been separated. The results demonstrate that the transition metal interface MAE dominates the spin reorientation while the rare-earth contribution becomes significant only at much lower temperatures.
Collapse
Affiliation(s)
- S S Dhesi
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France
| | | | | | | |
Collapse
|
43
|
Hochstrasser M, Tobin JG, Rotenberg E, Kevan SD. Spin-resolved photoemission of surface states of W(110)-(1 x 1)H. PHYSICAL REVIEW LETTERS 2002; 89:216802. [PMID: 12443440 DOI: 10.1103/physrevlett.89.216802] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2002] [Indexed: 05/24/2023]
Abstract
The surface electronic states of W(110)-(1 x 1)H have been measured using spin- and angle-resolved photoemission. We directly demonstrate that the surface bands are both split and spin-polarized by the spin-orbit interaction in association with the loss of inversion symmetry near a surface. We observe 100% spin polarization of the surface states, with the spins aligned in the plane of the surface and oriented in a circular fashion relative to the Smacr; symmetry point. In contrast, no measurable polarization of nearby bulk states is observed.
Collapse
Affiliation(s)
- M Hochstrasser
- Chemistry and Material Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | | | | | | |
Collapse
|
44
|
Goering E, Bayer A, Gold S, Schütz G, Rabe M, Rüdiger U, Güntherodt G. Strong anisotropy of projected 3d moments in epitaxial CrO2 films. PHYSICAL REVIEW LETTERS 2002; 88:207203. [PMID: 12005597 DOI: 10.1103/physrevlett.88.207203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2001] [Indexed: 05/23/2023]
Abstract
Soft x-ray magnetic circular dichroism (XMCD) spectra have been investigated for different crystallographic projections of CrO2. Strong anisotropic orbital Cr 3d contributions and a change of sign of the XMCD signal is observed and attributed to t(2g) majority states near the Fermi level. Additionally, moment analysis exhibits anisotropic behavior in the projected spin contributions of CrO2 assigned to a strong magnetic dipole term T(z), consistent with an intrinsic magnetic easy axis behavior along the CrO2 [001] axis. A reduced projected isotropic Cr 3d spin moment has been interpreted in terms of hybridization with oxygen.
Collapse
Affiliation(s)
- E Goering
- MPI für Metallforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | | | | | | | | | | | | |
Collapse
|
45
|
Gambardella P, Dallmeyer A, Maiti K, Malagoli MC, Eberhardt W, Kern K, Carbone C. Ferromagnetism in one-dimensional monatomic metal chains. Nature 2002; 416:301-4. [PMID: 11907571 DOI: 10.1038/416301a] [Citation(s) in RCA: 222] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two-dimensional systems, such as ultrathin epitaxial films and superlattices, display magnetic properties distinct from bulk materials. A challenging aim of current research in magnetism is to explore structures of still lower dimensionality. As the dimensionality of a physical system is reduced, magnetic ordering tends to decrease as fluctuations become relatively more important. Spin lattice models predict that an infinite one-dimensional linear chain with short-range magnetic interactions spontaneously breaks up into segments with different orientation of the magnetization, thereby prohibiting long-range ferromagnetic order at a finite temperature. These models, however, do not take into account kinetic barriers to reaching equilibrium or interactions with the substrates that support the one-dimensional nanostructures. Here we demonstrate the existence of both short- and long-range ferromagnetic order for one-dimensional monatomic chains of Co constructed on a Pt substrate. We find evidence that the monatomic chains consist of thermally fluctuating segments of ferromagnetically coupled atoms which, below a threshold temperature, evolve into a ferromagnetic long-range-ordered state owing to the presence of anisotropy barriers. The Co chains are characterized by large localized orbital moments and correspondingly large magnetic anisotropy energies compared to two-dimensional films and bulk Co.
Collapse
Affiliation(s)
- P Gambardella
- Institut de Physique des Nanostructures, EPF-Lausanne, CH-1015 Lausanne, Switzerland.
| | | | | | | | | | | | | |
Collapse
|
46
|
Gambardella P, Dhesi SS, Gardonio S, Grazioli C, Ohresser P, Carbone C. Localized magnetic states of Fe, Co, and Ni impurities on alkali metal films. PHYSICAL REVIEW LETTERS 2002; 88:047202. [PMID: 11801162 DOI: 10.1103/physrevlett.88.047202] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2001] [Indexed: 05/23/2023]
Abstract
X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) have been used to study transition metal impurities on K and Na films. The multiplet structure of the XAS spectra indicates that Fe, Co, and Ni have localized atomic ground states with predominantly d7, d8, and d9 character, respectively. XMCD shows that the localized impurity states possess large, atomiclike, magnetic orbital moments that are progressively quenched as clusters are formed. Ni impurities on Na films are found to be nonmagnetic, with a strongly increased d10 character of the impurity state. The results show that the high magnetic moments of transition metals in alkali hosts originate from electron localization.
Collapse
Affiliation(s)
- P Gambardella
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | | | | | | | | | | |
Collapse
|
47
|
Koide T, Miyauchi H, Okamoto J, Shidara T, Fujimori A, Fukutani H, Amemiya K, Takeshita H, Yuasa S, Katayama T, Suzuki Y. Direct determination of interfacial magnetic moments with a magnetic phase transition in Co nanoclusters on Au(111). PHYSICAL REVIEW LETTERS 2001; 87:257201. [PMID: 11736602 DOI: 10.1103/physrevlett.87.257201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2000] [Indexed: 05/23/2023]
Abstract
The spin, in-plane and out-of-plane orbital and magnetic dipole moments of almost purely interfacial Co atoms were directly determined for Au/2-monolayer Co nanoclusters/Au(111) by angle-dependent magnetic circular x-ray dichroism (MCXD) measurements. The field- and temperature-dependent MCXD evidences a ferromagnetic(FM)-to-superparamagnetic phase transition in single-domain clusters with decreasing size. The interfacial moments are remarkably enhanced as compared with bulk values, verifying theoretical predictions. The FM clusters show strong perpendicular magnetic anisotropy, providing promise of applications for nanoscale magnetic bits.
Collapse
Affiliation(s)
- T Koide
- Photon Factory, IMSS, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
|
49
|
Dhesi SS, van Der Laan G, Dudzik E, Shick AB. Anisotropic spin-orbit coupling and magnetocrystalline anisotropy in vicinal co films. PHYSICAL REVIEW LETTERS 2001; 87:067201. [PMID: 11497850 DOI: 10.1103/physrevlett.87.067201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2000] [Indexed: 05/23/2023]
Abstract
The anisotropy of the spin-orbit interaction, <lambda(a)>, in vicinal Co films has been measured using x-ray magnetic linear dichroism (XMLD). A linear increase in <lambda(a)> with Co step density is found using a new sum rule and represents the first experimental confirmation that XMLD probes the magnetocrystalline anisotropy energy (MAE). X-ray magnetic circular dichroism is used to confirm that the XMLD arises from changes in the local step-edge electronic structure. The XMLD sum rule gives a larger MAE compared to macroscopic values and is discussed with respect to other local probes of the MAE.
Collapse
Affiliation(s)
- S S Dhesi
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France
| | | | | | | |
Collapse
|
50
|
Mertins HC, Oppeneer PM, Kunes J, Gaupp A, Abramsohn D, Schäfers F. Observation of the x-ray magneto-optical Voigt effect. PHYSICAL REVIEW LETTERS 2001; 87:047401. [PMID: 11461644 DOI: 10.1103/physrevlett.87.047401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2001] [Indexed: 05/22/2023]
Abstract
The existence of the x-ray magneto-optical Voigt effect is demonstrated. By means of polarization analysis the Voigt rotation and ellipticity of linearly polarized synchrotron radiation are measured at the Co L3 edge upon transmission through an amorphous Co film. The observed x-ray Voigt rotation is about 7.5 degrees /microm. On the basis of ab initio calculations it is shown that the x-ray Voigt effect follows sensitively the amount of spin polarization of the 2p core states. Therefore it provides a unique measure of the spin splitting of the core states.
Collapse
Affiliation(s)
- H C Mertins
- BESSY GmbH, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | | | | | | | | | | |
Collapse
|