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Schlitz R, Grammer M, Wimmer T, Gückelhorn J, Flacke L, Goennenwein STB, Gross R, Huebl H, Kamra A, Althammer M. Electrically Induced Angular Momentum Flow between Separated Ferromagnets. PHYSICAL REVIEW LETTERS 2024; 132:256701. [PMID: 38996263 DOI: 10.1103/physrevlett.132.256701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 04/17/2024] [Indexed: 07/14/2024]
Abstract
Converting angular momentum between different degrees of freedom within a magnetic material results from a dynamic interplay between electrons, magnons, and phonons. This interplay is pivotal to implementing spintronic device concepts that rely on spin angular momentum transport. We establish a new concept for long-range angular momentum transport that further allows us to address and isolate the magnonic contribution to angular momentum transport in a nanostructured metallic ferromagnet. To this end, we electrically excite and detect spin transport between two parallel and electrically insulated ferromagnetic metal strips on top of a diamagnetic substrate. Charge-to-spin current conversion within the ferromagnetic strip generates electronic spin angular momentum that is transferred to magnons via electron-magnon coupling. We observe a finite angular momentum flow to the second ferromagnetic strip across a diamagnetic substrate over micron distances, which is electrically detected in the second strip by the inverse charge-to-spin current conversion process. We discuss phononic and dipolar interactions as the likely cause to transfer angular momentum between the two strips. Moreover, our Letter provides the experimental basis to separate the electronic and magnonic spin transport and thereby paves the way towards magnonic device concepts that do not rely on magnetic insulators.
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Affiliation(s)
- Richard Schlitz
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Matthias Grammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
| | - Tobias Wimmer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
| | - Janine Gückelhorn
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
| | - Luis Flacke
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
| | | | - Rudolf Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), 80799 München, Germany
| | - Hans Huebl
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), 80799 München, Germany
| | - Akashdeep Kamra
- Condensed Matter Physics Center (IFIMAC) and Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Matthias Althammer
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physics Department, TUM School of Natural Sciences, Technische Universität München, 85747 Garching, Germany
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Pantazopoulos PA, Feist J, García-Vidal FJ, Kamra A. Unconventional magnetism mediated by spin-phonon-photon coupling. Nat Commun 2024; 15:4000. [PMID: 38734667 PMCID: PMC11088681 DOI: 10.1038/s41467-024-48404-z] [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: 10/10/2023] [Accepted: 04/30/2024] [Indexed: 05/13/2024] Open
Abstract
Magnetic order typically emerges due to the short-range exchange interaction between the constituent electronic spins. Recent discoveries have found a crucial role for spin-phonon coupling in various phenomena from optical ultrafast magnetization switching to dynamical control of the magnetic state. Here, we demonstrate theoretically the emergence of a biquadratic long-range interaction between spins mediated by their coupling to phonons hybridized with vacuum photons into polaritons. The resulting ordered state enabled by the exchange of virtual polaritons between spins is reminiscent of superconductivity mediated by the exchange of virtual phonons. The biquadratic nature of the spin-spin interaction promotes ordering without favoring ferro- or antiferromagnetism. It further makes the phase transition to magnetic order a first-order transition, unlike in conventional magnets. Consequently, a large magnetization develops abruptly on lowering the temperature which could enable magnetic memories admitting ultralow-power thermally-assisted writing while maintaining a high data stability. The role of photons in the phenomenon further enables an in-situ static control over the magnetism. These unique features make our predicted spin-spin interaction and magnetism highly unconventional paving the way for novel scientific and technological opportunities.
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Affiliation(s)
- Petros Andreas Pantazopoulos
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Johannes Feist
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Francisco J García-Vidal
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Akashdeep Kamra
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
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Choi YG, Jo D, Ko KH, Go D, Kim KH, Park HG, Kim C, Min BC, Choi GM, Lee HW. Observation of the orbital Hall effect in a light metal Ti. Nature 2023; 619:52-56. [PMID: 37407680 DOI: 10.1038/s41586-023-06101-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 04/19/2023] [Indexed: 07/07/2023]
Abstract
The orbital Hall effect1 refers to the generation of electron orbital angular momentum flow transverse to an external electric field. Contrary to the common belief that the orbital angular momentum is quenched in solids, theoretical studies2,3 predict that the orbital Hall effect can be strong and is a fundamental origin of the spin Hall effect4-7 in many transition metals. Despite the growing circumstantial evidence8-11, its direct detection remains elusive. Here we report the magneto-optical observation of the orbital Hall effect in the light metal titanium (Ti). The Kerr rotation by the orbital magnetic moment accumulated at Ti surfaces owing to the orbital Hall current is measured, and the result agrees with theoretical calculations semi-quantitatively and is supported by the orbital torque12 measurement in Ti-based magnetic heterostructures. This result confirms the orbital Hall effect and indicates that the orbital angular momentum is an important dynamic degree of freedom in solids. Moreover, this calls for renewed studies of the orbital effect on other degrees of freedom such as spin2,3,13,14, valley15,16, phonon17-19 and magnon20,21 dynamics.
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Affiliation(s)
- Young-Gwan Choi
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea
| | - Daegeun Jo
- Department of Physics, Pohang University of Science and Technology, Pohang, Korea
| | - Kyung-Hun Ko
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea
| | - Dongwook Go
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Julich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Kyung-Han Kim
- Department of Physics, Pohang University of Science and Technology, Pohang, Korea
| | - Hee Gyum Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, Korea
| | - Changyoung Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, Korea
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea
| | - Byoung-Chul Min
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, Korea
| | - Gyung-Min Choi
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea.
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, Korea.
| | - Hyun-Woo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, Korea.
- Asia Pacific Center for Theoretical Physics, Pohang, Korea.
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Mai TT, Garrity KF, McCreary A, Argo J, Simpson JR, Doan-Nguyen V, Aguilar RV, Walker ARH. Magnon-phonon hybridization in 2D antiferromagnet MnPSe 3. SCIENCE ADVANCES 2021; 7:eabj3106. [PMID: 34714675 PMCID: PMC8555890 DOI: 10.1126/sciadv.abj3106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 09/08/2021] [Indexed: 05/08/2023]
Abstract
Magnetic excitations in van der Waals (vdW) materials, especially in the two-dimensional (2D) limit, are an exciting research topic from both the fundamental and applied perspectives. Using temperature-dependent, magneto-Raman spectroscopy, we identify the hybridization of two-magnon excitations with two phonons in manganese phosphorus triselenide (MnPSe3), a magnetic vdW material that hosts in-plane antiferromagnetism. Results from first-principles calculations of the phonon and magnon spectra further support our identification. The Raman spectra’s rich temperature dependence through the magnetic transition displays an avoided crossing behavior in the phonons’ frequency and a concurrent decrease in their lifetimes. We construct a model based on the interaction between a discrete level and a continuum that reproduces these observations. Our results imply a strong hybridization between each phonon and a two-magnon continuum. This work demonstrates that the magnon-phonon interactions can be observed directly in Raman scattering and provides deep insight into these interactions in 2D magnetic materials.
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Affiliation(s)
- Thuc T. Mai
- Nanoscale Device Characterization Division, Physical Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA
| | - Kevin F. Garrity
- Materials Measurement Science Division, Materials Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA
| | - Amber McCreary
- Nanoscale Device Characterization Division, Physical Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA
| | - Joshua Argo
- Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210, USA
| | - Jeffrey R. Simpson
- Nanoscale Device Characterization Division, Physical Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA
- Physics, Astronomy, and Geosciences, Towson University, Towson, MD 21252, USA
| | - Vicky Doan-Nguyen
- Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43210, USA
- Center for Emergent Materials, Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Rolando Valdés Aguilar
- Center for Emergent Materials, Department of Physics, The Ohio State University, Columbus, OH 43210, USA
| | - Angela R. Hight Walker
- Nanoscale Device Characterization Division, Physical Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA
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Zhang X, Bauer GEW, Yu T. Unidirectional Pumping of Phonons by Magnetization Dynamics. PHYSICAL REVIEW LETTERS 2020; 125:077203. [PMID: 32857579 DOI: 10.1103/physrevlett.125.077203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 07/23/2020] [Accepted: 07/24/2020] [Indexed: 06/11/2023]
Abstract
We propose a method to control surface phonon transport by weak magnetic fields based on the pumping of surface acoustic waves (SAWs) by magnetostriction. We predict that the magnetization dynamics of a nanowire on top of a dielectric films injects SAWs with opposite angular momenta into opposite directions. Two parallel nanowires form a phononic cavity that at magnetic resonances pump a unidirectional SAW current into half of the substrate.
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Affiliation(s)
- Xiang Zhang
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, Netherlands
| | - Gerrit E W Bauer
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, Netherlands
- WPI-AIMR & Institute for Materials Research & CSRN, Tohoku University, Sendai 980-8577, Japan
| | - Tao Yu
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, Netherlands
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
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