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Zakeri K, Ernst A. Generation and Propagation of Ultrafast Terahertz Magnons in Atomically Architectured Nanomagnets. NANO LETTERS 2024; 24:9528-9534. [PMID: 38899856 DOI: 10.1021/acs.nanolett.4c01982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Utilizing ultrafast terahertz (THz) magnons, the quanta of collective magnetic excitations, as carriers may provide a promising alternative to overcome the problems associated with electrical losses in nanoelectronic devices and circuits. However, efficient excitation of propagating coherent THz magnons in magnonic nanowaveguides is an essential requirement for the development of such devices. Here, by growing ultrathin ferromagnetic nanostructures on a reconstructed surface, we create well-ordered periodic magnetic nanostripes. We demonstrate that such atomically architectured nanowaveguides not only provide a versatile platform for an efficient generation of THz magnons but also allow for their fast propagation. Our results reveal the complex nature of the spin dynamics within such designed nanowaveguides and pave the way for designing ultrafast magnon-based logic devices with THz operation frequencies.
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Affiliation(s)
- Khalil Zakeri
- Heisenberg Spin-Dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, D-76131 Karlsruhe, Germany
| | - Arthur Ernst
- Institute for Theoretical Physics, Johannes Kepler University, Altenberger Strasse 69, A-4040 Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
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2
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Moradifar P, Liu Y, Shi J, Siukola Thurston ML, Utzat H, van Driel TB, Lindenberg AM, Dionne JA. Accelerating Quantum Materials Development with Advances in Transmission Electron Microscopy. Chem Rev 2023. [PMID: 37979189 DOI: 10.1021/acs.chemrev.2c00917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2023]
Abstract
Quantum materials are driving a technology revolution in sensing, communication, and computing, while simultaneously testing many core theories of the past century. Materials such as topological insulators, complex oxides, superconductors, quantum dots, color center-hosting semiconductors, and other types of strongly correlated materials can exhibit exotic properties such as edge conductivity, multiferroicity, magnetoresistance, superconductivity, single photon emission, and optical-spin locking. These emergent properties arise and depend strongly on the material's detailed atomic-scale structure, including atomic defects, dopants, and lattice stacking. In this review, we describe how progress in the field of electron microscopy (EM), including in situ and in operando EM, can accelerate advances in quantum materials and quantum excitations. We begin by describing fundamental EM principles and operation modes. We then discuss various EM methods such as (i) EM spectroscopies, including electron energy loss spectroscopy (EELS), cathodoluminescence (CL), and electron energy gain spectroscopy (EEGS); (ii) four-dimensional scanning transmission electron microscopy (4D-STEM); (iii) dynamic and ultrafast EM (UEM); (iv) complementary ultrafast spectroscopies (UED, XFEL); and (v) atomic electron tomography (AET). We describe how these methods could inform structure-function relations in quantum materials down to the picometer scale and femtosecond time resolution, and how they enable precision positioning of atomic defects and high-resolution manipulation of quantum materials. For each method, we also describe existing limitations to solve open quantum mechanical questions, and how they might be addressed to accelerate progress. Among numerous notable results, our review highlights how EM is enabling identification of the 3D structure of quantum defects; measuring reversible and metastable dynamics of quantum excitations; mapping exciton states and single photon emission; measuring nanoscale thermal transport and coupled excitation dynamics; and measuring the internal electric field and charge density distribution of quantum heterointerfaces- all at the quantum materials' intrinsic atomic and near atomic-length scale. We conclude by describing open challenges for the future, including achieving stable sample holders for ultralow temperature (below 10K) atomic-scale spatial resolution, stable spectrometers that enable meV energy resolution, and high-resolution, dynamic mapping of magnetic and spin fields. With atomic manipulation and ultrafast characterization enabled by EM, quantum materials will be poised to integrate into many of the sustainable and energy-efficient technologies needed for the 21st century.
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Affiliation(s)
- Parivash Moradifar
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Yin Liu
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jiaojian Shi
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | | | - Hendrik Utzat
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aaron M Lindenberg
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | - Jennifer A Dionne
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Radiology, Stanford University, Stanford, California 94305, United States
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3
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Luo J, Li S, Ye Z, Xu R, Yan H, Zhang J, Ye G, Chen L, Hu D, Teng X, Smith WA, Yakobson BI, Dai P, Nevidomskyy AH, He R, Zhu H. Evidence for Topological Magnon-Phonon Hybridization in a 2D Antiferromagnet down to the Monolayer Limit. NANO LETTERS 2023; 23:2023-2030. [PMID: 36797055 DOI: 10.1021/acs.nanolett.3c00351] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Topological phonons and magnons potentially enable low-loss, quantum coherent, and chiral transport of information and energy at the atomic scale. Van der Waals magnetic materials are promising to realize such states due to their recently discovered strong interactions among the electronic, spin, and lattice degrees of freedom. Here, we report the first observation of coherent hybridization of magnons and phonons in monolayer antiferromagnet FePSe3 by cavity-enhanced magneto-Raman spectroscopy. The robust magnon-phonon cooperativity in the 2D limit occurs even in zero magnetic field, which enables nontrivial band inversion between longitudinal and transverse optical phonons caused by the strong coupling with magnons. The spin and lattice symmetry theoretically guarantee magnetic-field-controlled topological phase transition, verified by nonzero Chern numbers calculated from the coupled spin-lattice model. The 2D topological magnon-phonon hybridization potentially offers a new route toward quantum phononics and magnonics with an ultrasmall footprint.
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Affiliation(s)
- Jiaming Luo
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
- Applied Physics Graduate Program, Rice University, Houston, Texas 77005, United States
| | - Shuyi Li
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Zhipeng Ye
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Rui Xu
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
| | - Han Yan
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Junjie Zhang
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
| | - Gaihua Ye
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Lebing Chen
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Ding Hu
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Xiaokun Teng
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - William A Smith
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
| | - Boris I Yakobson
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Andriy H Nevidomskyy
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
| | - Rui He
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Hanyu Zhu
- Department of Materials Science and Nano Engineering, Rice University, Houston, Texas 77005, United States
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Kimura SI, Kawabata T, Matsumoto H, Ohta Y, Yoshizumi A, Yoshida Y, Yamashita T, Watanabe H, Ohtsubo Y, Yamamoto N, Jin X. Bulk-sensitive spin-resolved resonant electron energy-loss spectroscopy (SR-rEELS): Observation of element- and spin-selective bulk plasmons. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:093103. [PMID: 34598542 DOI: 10.1063/5.0055435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 09/05/2021] [Indexed: 06/13/2023]
Abstract
We have developed spin-resolved resonant electron energy-loss spectroscopy with the primary energy of 0.3-1.5 keV, which corresponds to the core excitations of 2p-3d absorption of transition metals and 3d-4f absorption of rare-earths, with the energy resolution of about 100 meV using a spin-polarized electron source as a GaAs/GaAsP strained superlattice photocathode. Element- and spin-selective carrier and valence plasmons can be observed using the resonance enhancement of core absorptions and electron spin polarization. Furthermore, bulk-sensitive electron energy-loss spectroscopy spectra can be obtained because the primary energy corresponds to the mean free path of 1-10 nm. The methodology is expected to provide us with novel information about elementary excitations by resonant inelastic x-ray scattering and resonant photoelectron spectroscopy.
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Affiliation(s)
- Shin-Ichi Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Taishi Kawabata
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Hiroki Matsumoto
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Yu Ohta
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Ayuki Yoshizumi
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Yuto Yoshida
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Takumi Yamashita
- Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Hiroshi Watanabe
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yoshiyuki Ohtsubo
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Naoto Yamamoto
- High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - Xiuguang Jin
- High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
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5
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Vasconcelos MS, Cottam MG. Magnon-polaritons in ferromagnetic magnonic crystals with graphene at the interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:315802. [PMID: 34015778 DOI: 10.1088/1361-648x/ac0385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 05/20/2021] [Indexed: 06/12/2023]
Abstract
We present a theoretical study for the surface and bulk magnon-polaritons in magnonic crystals (or semi-infinite layered superlattices), which are formed from an array of ferromagnetic materials and nonmagnetic spacers with graphene sheets interposed between them. The external medium is taken to be vacuum. The Fermi energies in the graphene can be varied by employing different electronic doping levels, resulting in a strong influence exerted by the presence of graphene on the surface magnon-polariton modes. These effects include localization of the modes and control of the group velocities of the modes as the Fermi energies of the graphene sheets are varied, along with an important role for the phenomenological damping in the graphene sheets.
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Affiliation(s)
- M S Vasconcelos
- Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, 59078-970, Natal, RN, Brazil
| | - M G Cottam
- Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada
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6
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Zakeri K, Hjelt A, Maznichenko IV, Buczek P, Ernst A. Nonlinear Decay of Quantum Confined Magnons in Itinerant Ferromagnets. PHYSICAL REVIEW LETTERS 2021; 126:177203. [PMID: 33988456 DOI: 10.1103/physrevlett.126.177203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/06/2021] [Indexed: 06/12/2023]
Abstract
Quantum confinement leads to the emergence of several magnon modes in ultrathin layered magnetic structures. We probe the lifetime of these quantum confined modes in a model system composed of three atomic layers of Co grown on different surfaces. We demonstrate that the quantum confined magnons exhibit nonlinear decay rates, which strongly depend on the mode number, in sharp contrast to what is assumed in the classical dynamics. Combining the experimental results with those of linear-response density-functional calculations we provide a quantitative explanation for this nonlinear damping effect. The results provide new insights into the decay mechanism of spin excitations in ultrathin films and multilayers and pave the way for tuning the dynamical properties of such structures.
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Affiliation(s)
- Kh Zakeri
- Heisenberg Spin-Dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, D-76131 Karlsruhe, Germany
| | - A Hjelt
- Heisenberg Spin-Dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, D-76131 Karlsruhe, Germany
| | - I V Maznichenko
- Department of Engineering and Computer Sciences, Hamburg University of Applied Sciences, Berliner Tor 7, D-20099 Hamburg, Germany
| | - P Buczek
- Department of Engineering and Computer Sciences, Hamburg University of Applied Sciences, Berliner Tor 7, D-20099 Hamburg, Germany
| | - A Ernst
- Institute for Theoretical Physics, Johannes Kepler University, Altenberger Strasse 69, A-4040 Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
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7
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Pelliciari J, Lee S, Gilmore K, Li J, Gu Y, Barbour A, Jarrige I, Ahn CH, Walker FJ, Bisogni V. Tuning spin excitations in magnetic films by confinement. NATURE MATERIALS 2021; 20:188-193. [PMID: 33462465 DOI: 10.1038/s41563-020-00878-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Accepted: 11/12/2020] [Indexed: 06/12/2023]
Abstract
Spin excitations of magnetic thin films are the founding element for magnetic devices in general. While spin dynamics have been extensively studied in bulk materials, the behaviour in mesoscopic films is less known due to experimental limitations. Here, we employ resonant inelastic X-ray scattering to investigate the spectrum of spin excitations in mesoscopic Fe films, from bulk-like films down to three unit cells. In bulk samples, we find isotropic, dispersive ferromagnons consistent with previous neutron scattering results for bulk single crystals. As the thickness is reduced, these ferromagnetic spin excitations renormalize to lower energies along the out-of-plane direction while retaining their dispersion in the in-plane direction. This thickness dependence is captured by simple Heisenberg model calculations accounting for the confinement in the out-of-plane direction through the loss of Fe bonds. Our findings highlight the effects of mesoscopic scaling on spin dynamics and identify thickness as a knob for fine tuning and controlling magnetic properties.
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Affiliation(s)
- Jonathan Pelliciari
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA.
| | - Sangjae Lee
- Department of Physics, Yale University, New Haven, CT, USA
| | - Keith Gilmore
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA
| | - Jiemin Li
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Yanhong Gu
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Andi Barbour
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Ignace Jarrige
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA
| | - Charles H Ahn
- Department of Applied Physics, Yale University, New Haven, CT, USA
| | | | - Valentina Bisogni
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, USA.
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8
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Zakeri K. Magnonic crystals: towards terahertz frequencies. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:363001. [PMID: 32289765 DOI: 10.1088/1361-648x/ab88f2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 04/14/2020] [Indexed: 06/11/2023]
Abstract
This topical review presents an overview of the recent experimental and theoretical attempts on designing magnonic crystals for operation at different frequencies. The focus is put on the microscopic physical mechanisms involved in the formation of the magnonic band structure, allowed as well as forbidden magnon states in various systems, including ultrathin films, multilayers and artificial magnetic structures. The essential criteria for the formation of magnonic bandgaps in different frequency regimes are explained in connection with the magnon dynamics in such structures. The possibility of designing small-size magnonic crystals for operation at ultrahigh frequencies (terahertz and sub-terahertz regime) is discussed. Recently discovered magnonic crystals based on topological defects and using periodic Dzyaloshinskii-Moriya interaction, are outlined. Different types of magnonic crystals, capable of operation at different frequency regimes, are put within a rather unified picture.
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Affiliation(s)
- Khalil Zakeri
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, D-76131 Karlsruhe, Germany
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9
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Qin HJ, Tsurkan S, Ernst A, Zakeri K. Experimental Realization of Atomic-Scale Magnonic Crystals. PHYSICAL REVIEW LETTERS 2019; 123:257202. [PMID: 31922781 DOI: 10.1103/physrevlett.123.257202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Indexed: 06/10/2023]
Abstract
We introduce a new approach of materials design for terahertz magnonics making use of quantum confinement of terahertz magnons in layered ferromagnets. We show that in atomically designed multilayers composed of alternating atomic layers of ferromagnetic metals one can efficiently excite different magnon modes associated with the quantum confinement in the third dimension, i.e., the direction perpendicular to the layers. We demonstrate experimentally that the magnonic band structure of these systems can be tuned by changing the material combination and the number of atomic layers. We realize the idea of opening band gaps, with a size of up to several tens of millielectronvolts, between different terahertz magnon bands and thereby report on the first step toward the realization of atomic-scale magnonic crystals.
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Affiliation(s)
- H J Qin
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
- NanoSpin, Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland
| | - S Tsurkan
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
| | - A Ernst
- Institute for Theoretical Physics, Johannes Kepler University, Altenberger Straße 69, 4040 Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
| | - Kh Zakeri
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Straße 1, D-76131 Karlsruhe, Germany
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10
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Abstract
Magnonics, an emerging research field, aims to control and manipulate spin waves in magnetic materials and structures. However, the current understanding of spin waves remains quite limited. This review attempts to provide an overview of the anomalous behaviors of spin waves in various types of magnetic materials observed thus far by inelastic light scattering experiments. The anomalously large asymmetry of anti-Stokes to Stokes intensity ratio, broad linewidth, strong resonance effect, unique polarization selection, and abnormal impurity dependence of spin waves are discussed. In addition, the mechanisms of these anomalous behaviors of spin waves are proposed.
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11
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Wolff M, Devishvili A, Dura JA, Adlmann FA, Kitchen B, Pálsson GK, Palonen H, Maranville BB, Majkrzak CF, Toperverg BP. Nuclear Spin Incoherent Neutron Scattering from Quantum Well Resonators. PHYSICAL REVIEW LETTERS 2019; 123:016101. [PMID: 31386422 PMCID: PMC11135630 DOI: 10.1103/physrevlett.123.016101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 04/12/2019] [Indexed: 06/10/2023]
Abstract
We report the detection and quantification of nuclear spin incoherent scattering from hydrogen occupying interstitial sites in a thin film of vanadium. The neutron wave field is enhanced in a quantum resonator with magnetically switchable boundaries. Our results provide a pathway for the study of dynamics at surfaces and in ultrathin films using inelastic and/or quasielastic neutron scattering methods.
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Affiliation(s)
- Max Wolff
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
| | - Anton Devishvili
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
- Institut Laue Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Joseph A. Dura
- NIST Center for Neutron Research, National Institute for Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
| | - Franz A. Adlmann
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
| | - Brian Kitchen
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
| | - Gunnar K. Pálsson
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
| | - Heikki Palonen
- Department for Physics and Astronomy, Uppsala University, Regementsvägen 1, 75237 Uppsala, Sweden
| | - Brian B. Maranville
- NIST Center for Neutron Research, National Institute for Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
| | - Charles F. Majkrzak
- NIST Center for Neutron Research, National Institute for Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
| | - Boris P. Toperverg
- Petersburg Nuclear Physics Institute, Leningrad Oblast, 188300 Gatchina, Russia
- Institut Laue Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
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12
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Buczek P, Thomas S, Marmodoro A, Buczek N, Zubizarreta X, Hoffmann M, Balashov T, Wulfhekel W, Zakeri K, Ernst A. Spin waves in disordered materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:423001. [PMID: 30182926 DOI: 10.1088/1361-648x/aadefb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present an efficient methodology to study spin waves in disordered materials. The approach is based on a Heisenberg model and enables calculations of magnon properties in spin systems with disorder of an arbitrary kind and concentration of impurities. Disorder effects are taken into account within two complementary approaches. Magnons in systems with substitutional (uncorrelated) disorder can be efficiently calculated within a single-site coherent potential approximation for the Heisenberg model. From the computation point of view the method is inexpensive and directly applicable to systems like alloys and doped materials. It is shown that it performs exceedingly well across all concentrations and wave vectors. Another way is the direct numerical simulation of large supercells using a configurational average over possible samples. This approach is applicable to systems with an arbitrary kind of disorder. The effective interaction between magnetic moments entering the Heisenberg model can be obtained from first-principles using a self-consistent Green function method within the density functional theory. Thus, our method can be viewed as an ab initio approach and can be used for calculations of magnons in real materials.
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Affiliation(s)
- Paweł Buczek
- Hochschule für Angewandte Wissenschaften Hamburg, Fakultät Technik und Informatik, Berliner Tor 7, 20099 Hamburg, Germany
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13
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Zakeri K. Probing of the interfacial Heisenberg and Dzyaloshinskii-Moriya exchange interaction by magnon spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:013001. [PMID: 27831928 DOI: 10.1088/0953-8984/29/1/013001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This Topical Review presents an overview of the recent experimental results on the quantitative determination of the magnetic exchange parameters in ultrathin magnetic films and multilayers grown on different substrates. The experimental approaches for probing both the symmetric Heisenberg and the antisymmetric Dzyaloshinskii-Moriya exchange interaction in ultrathin magnetic films and at interfaces are discussed in detail. It is explained how the experimental spectrum of magnetic excitations can be used to quantify the strength of these interactions.
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Affiliation(s)
- Khalil Zakeri
- Heisenberg Spin-dynamics Group, Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, D-76131 Karlsruhe, Germany. Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
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14
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Sarkar S, Chaudhury R, Paul SK. Semi-phenomenological analysis of neutron scattering results for quasi-two dimensional quantum anti-ferromagnet. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 2017; 421:207-215. [DOI: 10.1016/j.jmmm.2016.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
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15
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Mi BZ. Spin wave dynamics in Heisenberg ferromagnetic/antiferromagnetic single-walled nanotubes. PHYSICA B: CONDENSED MATTER 2016; 497:23-30. [DOI: 10.1016/j.physb.2016.05.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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16
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Etz C, Bergqvist L, Bergman A, Taroni A, Eriksson O. Atomistic spin dynamics and surface magnons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:243202. [PMID: 26030259 DOI: 10.1088/0953-8984/27/24/243202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Atomistic spin dynamics simulations have evolved to become a powerful and versatile tool for simulating dynamic properties of magnetic materials. It has a wide range of applications, for instance switching of magnetic states in bulk and nano-magnets, dynamics of topological magnets, such as skyrmions and vortices and domain wall motion. In this review, after a brief summary of the existing investigation tools for the study of magnons, we focus on calculations of spin-wave excitations in low-dimensional magnets and the effect of relativistic and temperature effects in such structures. In general, we find a good agreement between our results and the experimental values. For material specific studies, the atomistic spin dynamics is combined with electronic structure calculations within the density functional theory from which the required parameters are calculated, such as magnetic exchange interactions, magnetocrystalline anisotropy, and Dzyaloshinskii-Moriya vectors.
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Affiliation(s)
- Corina Etz
- Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden. Department of Engineering Sciences and Mathematics, Luleå University of Technology, 971 87 Luleå, Sweden
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17
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Qin HJ, Zakeri K, Ernst A, Sandratskii LM, Buczek P, Marmodoro A, Chuang TH, Zhang Y, Kirschner J. Long-living terahertz magnons in ultrathin metallic ferromagnets. Nat Commun 2015; 6:6126. [DOI: 10.1038/ncomms7126] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 12/18/2014] [Indexed: 11/09/2022] Open
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18
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Rohart S, Rodary G. Spin waves: close-up on spin dynamics. NATURE MATERIALS 2014; 13:770-771. [PMID: 24997738 DOI: 10.1038/nmat4038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Affiliation(s)
- Stanislas Rohart
- Laboratoire de Physique des Solides, Université Paris-Sud and CNRS, Bâtiment 510, 91405 Orsay cedex, France
| | - Guillemin Rodary
- Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France
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19
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Rajeswari J, Ibach H, Schneider CM. Standing spin waves in ultrathin magnetic films: a method to test for layer-dependent exchange coupling. PHYSICAL REVIEW LETTERS 2014; 112:127202. [PMID: 24724676 DOI: 10.1103/physrevlett.112.127202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Indexed: 06/03/2023]
Abstract
We introduce a method to test theoretical models for the layer dependence of exchange coupling constants in ultrathin magnetic films. The method is based on the observation of high-energy and high-momentum standing spin wave modes using high-resolution electron energy loss spectroscopy. Experimental data are presented for 5-8 layers of fcc cobalt deposited on Cu(100). The power of the method is illustrated by comparison to two theoretical studies predicting rather different results concerning the ratio of the interlayer and intralayer exchange coupling constants near the surface. Only the theory with a large interlayer coupling shows sufficient energy spreading in the layer dependence of the dispersion curves to match the experimental data. We furthermore discuss the reason for the surprising success of the simple nearest-neighbor Heisenberg model with a single exchange constant matched to experiment.
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Affiliation(s)
- J Rajeswari
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany and Jülich Aachen Research Alliance, 52425 Jülich, Germany
| | - H Ibach
- Jülich Aachen Research Alliance, 52425 Jülich, Germany and Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - C M Schneider
- Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany and Jülich Aachen Research Alliance, 52425 Jülich, Germany
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20
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Abstract
Collective spin excitations form a fundamental class of excitations in magnetic materials. As their energy reaches down to only a few meV, they are present at all temperatures and substantially influence the properties of magnetic systems. To study the spin excitations in solids from first principles, we have developed a computational scheme based on many-body perturbation theory within the full-potential linearized augmented plane-wave (FLAPW) method. The main quantity of interest is the dynamical transverse spin susceptibility or magnetic response function, from which magnetic excitations, including single-particle spin-flip Stoner excitations and collective spin-wave modes as well as their lifetimes, can be obtained. In order to describe spin waves we include appropriate vertex corrections in the form of a multiple-scattering T matrix, which describes the coupling of electrons and holes with different spins. The electron-hole interaction incorporates the screening of the many-body system within the random-phase approximation. To reduce the numerical cost in evaluating the four-point T matrix, we exploit a transformation to maximally localized Wannier functions that takes advantage of the short spatial range of electronic correlation in the partially filled d or f orbitals of magnetic materials. The theory and the implementation are discussed in detail. In particular, we show how the magnetic response function can be evaluated for arbitrary k points. This enables the calculation of smooth dispersion curves, allowing one to study fine details in the k dependence of the spin-wave spectra. We also demonstrate how spatial and time-reversal symmetry can be exploited to accelerate substantially the computation of the four-point quantities. As an illustration, we present spin-wave spectra and dispersions for the elementary ferromagnet bcc Fe, B2-type tetragonal FeCo, and CrO₂ calculated with our scheme. The results are in good agreement with available experimental data.
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21
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Rózsa L, Udvardi L, Szunyogh L. Relativistic and thermal effects on the magnon spectrum of a ferromagnetic monolayer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:506002. [PMID: 24275952 DOI: 10.1088/0953-8984/25/50/506002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A spin model including magnetic anisotropy terms and Dzyaloshinsky-Moriya interactions is studied for the case of a ferromagnetic monolayer with C2v symmetry like Fe/W(110). Using the quasiclassical stochastic Landau-Lifshitz-Gilbert equations, the magnon spectrum of the system is derived using linear response theory. The Dzyaloshinsky-Moriya interaction leads to asymmetry in the spectrum, while the anisotropy terms induce a gap. It is shown that, in the presence of lattice defects, both the Dzyaloshinsky-Moriya interactions and the two-site anisotropy lead to a softening of the magnon energies. Two methods are developed to investigate the magnon spectrum at finite temperatures. The theoretical results are compared to atomistic spin dynamics simulations and good agreement is found between them.
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Affiliation(s)
- L Rózsa
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
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22
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Zakeri K, Chuang TH, Ernst A, Sandratskii LM, Buczek P, Qin HJ, Zhang Y, Kirschner J. Direct probing of the exchange interaction at buried interfaces. NATURE NANOTECHNOLOGY 2013; 8:853-858. [PMID: 24056902 DOI: 10.1038/nnano.2013.188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 08/20/2013] [Indexed: 06/02/2023]
Abstract
The fundamental interactions between magnetic moments at interfaces have an important impact on the properties of layered magnetic structures. Hence, a direct probing of these interactions is highly desirable for understanding a wide range of phenomena in low-dimensional solids. Here we propose a method for probing the magnetic exchange interaction at buried interfaces using spin-polarized electrons and taking advantage of the collective nature of elementary magnetic excitations (magnons). We demonstrate that, for the case of weak coupling at the interface, the low-energy magnon mode is mainly localized at the interface. Because this mode has the longest lifetime of the modes and has a finite spectral weight across the layers on top, it can be probed by electrons. A comparison of experimental data and first-principles calculations leads to the determination of the interface exchange parameters. This method may help the development of spectroscopy of buried magnetic interfaces.
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Affiliation(s)
- Kh Zakeri
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
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23
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Lobos AM, Cazalilla MA. Easy-axis ferromagnetic chain on a metallic surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:094008. [PMID: 23530267 DOI: 10.1088/0953-8984/25/9/094008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The phases and excitation spectrum of an easy-axis ferromagnetic chain of S = 1/2 magnetic impurities built on the top of a clean metallic surface are studied. As a function of the (Kondo) coupling to the metallic surface and at low temperatures, the spin chain exhibits a quantum phase transition from an Ising ferromagnetic phase with long-range order to a paramagnetic phase where quantum fluctuations destroy the magnetic order. In the paramagnetic phase, the system consists of a chain of Kondo singlets where the impurities are completely screened by the metallic host. In the ferromagnetic phase, the excitations above the Ising gap are damped magnons, with a finite lifetime arising due to the coupling to the substrate. We discuss the experimental consequences of our results to spin-polarized electron energy loss spectroscopy, and we finally analyze possible extensions to spin chains with S > 1/2.
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Affiliation(s)
- Alejandro M Lobos
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, MD 20742-4111, USA.
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24
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Chuang TH, Zakeri K, Ernst A, Sandratskii LM, Buczek P, Zhang Y, Qin HJ, Adeagbo W, Hergert W, Kirschner J. Impact of atomic structure on the magnon dispersion relation: a comparison between Fe(111)/Au/W(110) and Fe(110)/W(110). PHYSICAL REVIEW LETTERS 2012; 109:207201. [PMID: 23215520 DOI: 10.1103/physrevlett.109.207201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Indexed: 06/01/2023]
Abstract
We present a combined experimental and theoretical study of the interplay between the atomic structure and the magnon excitations in low dimensional ferromagnets. Two monolayer thick Fe films on W(110) with and without a Au buffer layer are investigated. Our experiments show that adding the Au layer leads to a significant softening of the magnons. First-principles calculations confirm the experimental results revealing a strong dependency of exchange interactions on the atomic structure. It is observed that the intralayer exchange interactions increase with increasing distance between Fe layers. This unusual relationship is attributed to the complexity of the electronic structure and the contribution of different orbitals to the hybridization and exchange interaction. Our results suggest a way of tailoring magnetic excitations in low-dimensional magnetic structures.
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Affiliation(s)
- T-H Chuang
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
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25
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Sarkar S, Paul S, Chaudhury R. Theoretical analysis of neutron scattering results for quasi-two dimensional ferromagnets. THE EUROPEAN PHYSICAL JOURNAL B 2012; 85:380. [DOI: 10.1140/epjb/e2012-30200-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
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26
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Yan P, Bauer GEW. Magnonic domain wall heat conductance in ferromagnetic wires. PHYSICAL REVIEW LETTERS 2012; 109:087202. [PMID: 23002771 DOI: 10.1103/physrevlett.109.087202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Indexed: 06/01/2023]
Abstract
We present a theoretical study of magnon-mediated heat transport in electrically insulating ferromagnetic wires containing a domain wall (DW). In the regime of validity of continuum micromagnetism, a DW is found to have no effect on the heat conductance. However, spin waves are found to be reflected by DWs with widths of a few lattice spacings, which is associated with emergence of an additional spin wave bound state. The resulting DW heat conductance should be significant for thin films of yttrium iron garnet with sharply defined magnetic domains.
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Affiliation(s)
- Peng Yan
- Kavli Institute of NanoScience, Delft University of Technology, Delft, Netherlands
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27
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Kamble B, Singh A. An effective quantum parameter for strongly correlated metallic ferromagnets. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:086004. [PMID: 22277778 DOI: 10.1088/0953-8984/24/8/086004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The correlated motion of electrons in metallic ferromagnets is investigated in terms of a realistic interacting-electron model with N-fold orbital degeneracy and intra-orbital (U) and inter-orbital (J) Coulomb interactions. Correlation-induced self-energy and vertex corrections are incorporated systematically to provide a non-perturbative Goldstone-mode-preserving scheme. An effective quantum parameter [U2+(N-1)J2]/[U+(N-1)J]2 is obtained which determines, in analogy with 1/S for quantum spin systems and 1/N for the N-orbital Hubbard model, the strength of correlation-induced quantum corrections to magnetic excitations. The rapid suppression of this quantum parameter with Hund's coupling J, especially for large N, provides fundamental insight into the phenomenon of strong stabilization of metallic ferromagnetism by orbital degeneracy and Hund's coupling. Correlation effects are investigated for spin stiffness, magnon dispersion, electronic spectral function, density of states, and finite-temperature spin dynamics using realistic bandwidth, interaction, and lattice parameters for iron.
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Affiliation(s)
- Bhaskar Kamble
- Theoretical Physics III, Ruhr-University Bochum, Bochum, Germany
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28
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Taroni A, Bergman A, Bergqvist L, Hellsvik J, Eriksson O. Suppression of standing spin waves in low-dimensional ferromagnets. PHYSICAL REVIEW LETTERS 2011; 107:037202. [PMID: 21838397 DOI: 10.1103/physrevlett.107.037202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Indexed: 05/31/2023]
Abstract
We examine the experimental absence of standing spin wave modes in thin magnetic films, by means of atomistic spin dynamics simulations. Using Co on Cu(001) as a model system, we demonstrate that by increasing the number of layers, the optical branches predicted from adiabatic first-principles calculations are strongly suppressed, in agreement with spin-polarized electron energy loss spectroscopy measurements reported in the literature. Our results suggest that a dynamical analysis of the Heisenberg model is sufficient in order to capture the strong damping of the standing modes.
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Affiliation(s)
- Andrea Taroni
- Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
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29
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Zakeri K, Zhang Y, Prokop J, Chuang TH, Tang WX, Kirschner J. Magnon excitations in ultrathin Fe layers: The influence of the Dzyaloshinskii-Moriya interaction. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/303/1/012004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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30
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Buczek P, Ernst A, Sandratskii LM. Interface electronic complexes and Landau damping of magnons in ultrathin magnets. PHYSICAL REVIEW LETTERS 2011; 106:157204. [PMID: 21568609 DOI: 10.1103/physrevlett.106.157204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Indexed: 05/30/2023]
Abstract
The damping of magnons in ultrathin metallic magnets is studied from first-principles. We contrast Fe/Cu(100) and Fe/W(110) systems for which the influence of the substrate on the magnon life time differs strongly. We introduce the concept of Landau map in momentum space to assess the role of different electronic states in the attenuation. The formation of electronic complexes localized at the film-substrate interface leads to hot spots in the Landau maps and enhances the damping. This finding allows tuning the attenuation of high-frequency magnetization dynamics in nanostructures.
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Affiliation(s)
- Paweł Buczek
- Max Planck Institute of Microstructure Physics, Weinberg 2, Halle/S., Germany.
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31
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Papaioannou ET, Kapaklis V, Taroni A, Marcellini M, Hjörvarsson B. Dimensionality and confinement effects in δ-doped Pd(Fe) layers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:236004. [PMID: 21393776 DOI: 10.1088/0953-8984/22/23/236004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We address the dimensionality aspects of the magnetic ordering in δ-doped Pd(Fe) structures. The key property we investigate, via magneto-optic Kerr measurements, is the magnetization induced by iron in palladium, over a wide temperature range 5 K < T < 300 K. The dimensional crossover we observe cannot be rationalized on the basis of structural considerations alone, since we find the dimensionality of the low temperature and of the critical region can differ. We discuss the crossover in terms of the temperature dependence of the magnon modes, giving rise to lower dimensionality at low temperatures.
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Affiliation(s)
- Evangelos Th Papaioannou
- Department of Physics and Astronomy, Materials Physics Division, Uppsala University, Box 516, 751 20 Uppsala, Sweden
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32
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Zakeri K, Zhang Y, Prokop J, Chuang TH, Sakr N, Tang WX, Kirschner J. Asymmetric spin-wave dispersion on Fe(110): direct evidence of the Dzyaloshinskii-Moriya interaction. PHYSICAL REVIEW LETTERS 2010; 104:137203. [PMID: 20481909 DOI: 10.1103/physrevlett.104.137203] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Indexed: 05/29/2023]
Abstract
The influence of the Dzyaloshinskii-Moriya interaction on the spin-wave dispersion in an Fe double layer grown on W(110) is measured for the first time. It is demonstrated that the Dzyaloshinskii-Moriya interaction breaks the degeneracy of spin waves and leads to an asymmetric spin-wave dispersion relation. An extended Heisenberg spin Hamiltonian is employed to obtain the longitudinal component of the Dzyaloshinskii-Moriya vectors from the experimentally measured energy asymmetry.
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Affiliation(s)
- Kh Zakeri
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany.
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Udvardi L, Szunyogh L. Chiral asymmetry of the spin-wave spectra in ultrathin magnetic films. PHYSICAL REVIEW LETTERS 2009; 102:207204. [PMID: 19519069 DOI: 10.1103/physrevlett.102.207204] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Indexed: 05/27/2023]
Abstract
We raise the possibility that the chiral degeneracy of the magnons in ultrathin films can be lifted due to the presence of Dzyaloshinskii-Moriya interactions. By using simple symmetry arguments, we discuss under which conditions such a chiral asymmetry occurs. We then perform relativistic first principles calculations for an Fe monolayer on W(110) and explicitly reveal the asymmetry of the spin-wave spectrum in the case of wave vectors parallel to the (001) direction. Furthermore, we quantitatively interpret our results in terms of a simplified spin model by using calculated Dzyaloshinskii-Moriya vectors. Our theoretical prediction should inspire experiments to explore the asymmetry of spin waves, with a particular emphasis on the possibility to measure the Dzyaloshinskii-Moriya interactions in ultrathin films.
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Affiliation(s)
- L Udvardi
- Department of Theoretical Physics, Budapest University of Technology and Economics, H1111 Budapest, Hungary
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