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Aqeel A, Sahliger J, Taniguchi T, Mändl S, Mettus D, Berger H, Bauer A, Garst M, Pfleiderer C, Back CH. Microwave Spectroscopy of the Low-Temperature Skyrmion State in Cu_{2}OSeO_{3}. PHYSICAL REVIEW LETTERS 2021; 126:017202. [PMID: 33480751 DOI: 10.1103/physrevlett.126.017202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 12/01/2020] [Indexed: 06/12/2023]
Abstract
In the cubic chiral magnet Cu_{2}OSeO_{3} a low-temperature skyrmion state (LTS) and a concomitant tilted conical state are observed for magnetic fields parallel to ⟨100⟩. Here, we report on the dynamic resonances of these novel magnetic states. After promoting the nucleation of the LTS by means of field cycling, we apply broadband microwave spectroscopy in two experimental geometries that provide either predominantly in-plane or out-of-plane excitation. By comparing the results to linear spin-wave theory, we clearly identify resonant modes associated with the tilted conical state, the gyrational and breathing modes associated with the LTS, as well as the hybridization of the breathing mode with a dark octupole gyration mode mediated by the magnetocrystalline anisotropies. Most intriguingly, our findings suggest that under decreasing fields the hexagonal skyrmion lattice becomes unstable with respect to an oblique deformation, reflected in the formation of elongated skyrmions.
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Affiliation(s)
- Aisha Aqeel
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Jan Sahliger
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Takuya Taniguchi
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Stefan Mändl
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Denis Mettus
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Helmuth Berger
- École Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Andreas Bauer
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - Markus Garst
- Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
- Institute for quantum materials and technology, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
| | | | - Christian H Back
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), D-80799 München, Germany
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2
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Pöllath S, Aqeel A, Bauer A, Luo C, Ryll H, Radu F, Pfleiderer C, Woltersdorf G, Back CH. Ferromagnetic Resonance with Magnetic Phase Selectivity by Means of Resonant Elastic X-Ray Scattering on a Chiral Magnet. PHYSICAL REVIEW LETTERS 2019; 123:167201. [PMID: 31702336 DOI: 10.1103/physrevlett.123.167201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/24/2019] [Indexed: 06/10/2023]
Abstract
Cubic chiral magnets, such as Cu_{2}OSeO_{3}, exhibit a variety of noncollinear spin textures, including a trigonal lattice of spin whirls, the so-called skyrmions. Using magnetic resonant elastic x-ray scattering (REXS) on a crystalline Bragg peak and its magnetic satellites while exciting the sample with magnetic fields at gigahertz frequencies, we probe the ferromagnetic resonance (FMR) modes of these spin textures by means of the scattered intensity. Most notably, the three eigenmodes of the skyrmion lattice are detected with large sensitivity. As this novel technique, which we label REXS FMR, is carried out at distinct positions in reciprocal space, it allows us to distinguish contributions originating from different magnetic states, providing information on the precise character, weight, and mode mixing as a prerequisite of tailored excitations for applications.
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Affiliation(s)
- S Pöllath
- Institut für Experimentelle Physik, Universität Regensburg, D-93040 Regensburg, Germany
| | - A Aqeel
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - A Bauer
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
| | - C Luo
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
- Helmholtz-Zentrum Berlin für Materialien and Energie, D-12489 Berlin, Germany
| | - H Ryll
- Helmholtz-Zentrum Berlin für Materialien and Energie, D-12489 Berlin, Germany
| | - F Radu
- Helmholtz-Zentrum Berlin für Materialien and Energie, D-12489 Berlin, Germany
| | - C Pfleiderer
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, D-80799 München, Germany
| | - G Woltersdorf
- Institut für Physik, Universität Halle-Wittenberg, D-06120 Halle (Saale), Germany
| | - C H Back
- Institut für Experimentelle Physik, Universität Regensburg, D-93040 Regensburg, Germany
- Physik-Department, Technische Universität München, D-85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, D-80799 München, Germany
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3
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Van Lich L, Shimada T, Wang J, Kitamura T. Self-ordering of nontrivial topological polarization structures in nanoporous ferroelectrics. NANOSCALE 2017; 9:15525-15533. [PMID: 28980678 DOI: 10.1039/c7nr04661h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Topological field structures, such as skyrmions, merons, and vortices, are important features found in ordered systems with spontaneously broken symmetry. A plethora of topological field structures have been discovered in magnetic and ordered soft matter systems due to the presence of inherent chiral interactions, and this has provided a fruitful platform for unearthing additional groundbreaking functionalities. However, despite being one of the most important classes of ordered systems, ferroelectrics scarcely form topological polarization structures due to their lack of intrinsic chiral interactions. In the present study, we demonstrate using multiphysics phase-field modelling based on the Ginzburg-Landau theory that a rich assortment of nontrivial topological polarization structures, including hedgehogs, antivortices, multidirectional vortices, and vortex arrays, can be spontaneously formed in three-dimensional nanoporous ferroelectric structures. We realize that confining ferroelectrics to trivial geometries that are incompatible with the orientation symmetry may impose extrinsic frustration to the polarization field through the enhancement of depolarization fields at free porous surfaces. This frustration gives rise to symmetry breaking, resulting in the formation of nontrivial topological polarization structures as the ground state. We further topologically characterize the local accommodation of polarization structures by viewing them in a new perspective, in which polarization ordering can be mapped on the order parameter space, according to the topological theory of defects and homotopy theory. The results indicate that the nanoporous structures contain composite topological objects composed of two or more elementary topological polarization structures. The present study therefore offers a playground for exploring novel physical phenomena in ferroelectric systems as well as a novel nanoelectronics characterization platform for future topology-based nanotechnologies.
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Affiliation(s)
- Le Van Lich
- Department of Mechanical Engineering and Science, Kyoto University, Nishikyo-ku, Kyoto 615-8540, Japan.
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4
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Langner MC, Roy S, Huang SW, Koralek JD, Chuang YD, Dakovski GL, Turner JJ, Robinson JS, Coffee RN, Minitti MP, Seki S, Tokura Y, Schoenlein RW. Nonlinear Ultrafast Spin Scattering in the Skyrmion Phase of Cu_{2}OSeO_{3}. PHYSICAL REVIEW LETTERS 2017; 119:107204. [PMID: 28949160 DOI: 10.1103/physrevlett.119.107204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Indexed: 05/26/2023]
Abstract
Ultrafast x-ray scattering studies of the topological Skyrmion phase in Cu_{2}OSeO_{3} show the dynamics to be strongly dependent on the excitation energy and fluence. At high photon energies, where the electron-spin scattering cross section is relatively high, the excitation of the topological Skyrmion phase shows a nonlinear dependence on the excitation fluence, in contrast to the excitation of the conical phase which is linearly dependent on the excitation fluence. The excitation of the Skyrmion order parameter is nonlinear in the magnetic excitation resulting from scattering during electron-hole recombination, indicating different dominant scattering processes in the conical and Skyrmion phases.
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Affiliation(s)
- M C Langner
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S Roy
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
| | - S W Huang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
| | - J D Koralek
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Y-D Chuang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA
| | - G L Dakovski
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J J Turner
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J S Robinson
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - R N Coffee
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - M P Minitti
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - S Seki
- RIKEN, Center for Emergent Matter Science, Wako 351-0198, Japan
- PRESTO, Japan Science and Technology Agency, Tokyo 102-0075, Japan
| | - Y Tokura
- RIKEN, Center for Emergent Matter Science, Wako 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - R W Schoenlein
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
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5
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Araque A, Castillo PE, Manzoni OJ, Tonini R. Synaptic functions of endocannabinoid signaling in health and disease. Neuropharmacology 2017. [PMID: 28625718 DOI: 10.1016/j.neuropharm.2017.06.017] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Endocannabinoids (eCBs) are a family of lipid molecules that act as key regulators of synaptic transmission and plasticity. They are synthetized "on demand" following physiological and/or pathological stimuli. Once released from postsynaptic neurons, eCBs typically act as retrograde messengers to activate presynaptic type 1 cannabinoid receptors (CB1) and induce short- or long-term depression of neurotransmitter release. Besides this canonical mechanism of action, recent findings have revealed a number of less conventional mechanisms by which eCBs regulate neural activity and synaptic function, suggesting that eCB-mediated plasticity is mechanistically more diverse than anticipated. These mechanisms include non-retrograde signaling, signaling via astrocytes, participation in long-term potentiation, and the involvement of mitochondrial CB1. Focusing on paradigmatic brain areas, such as hippocampus, striatum, and neocortex, we review typical and novel signaling mechanisms, and discuss the functional implications in normal brain function and brain diseases. In summary, eCB signaling may lead to different forms of synaptic plasticity through activation of a plethora of mechanisms, which provide further complexity to the functional consequences of eCB signaling. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".
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Affiliation(s)
- Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461, USA.
| | - Olivier J Manzoni
- Institut National de la Santé et et de la Recherche Médicale U901 Marseille, France, Université de la Méditerranée UMR S901 Aix-Marseille Marseille, France, INMED Marseille, France.
| | - Raffaella Tonini
- Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy.
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Dussaux A, Schoenherr P, Koumpouras K, Chico J, Chang K, Lorenzelli L, Kanazawa N, Tokura Y, Garst M, Bergman A, Degen CL, Meier D. Local dynamics of topological magnetic defects in the itinerant helimagnet FeGe. Nat Commun 2016; 7:12430. [PMID: 27535899 PMCID: PMC4992142 DOI: 10.1038/ncomms12430] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 07/01/2016] [Indexed: 11/24/2022] Open
Abstract
Chiral magnetic interactions induce complex spin textures including helical and conical spin spirals, as well as particle-like objects such as magnetic skyrmions and merons. These spin textures are the basis for innovative device paradigms and give rise to exotic topological phenomena, thus being of interest for both applied and fundamental sciences. Present key questions address the dynamics of the spin system and emergent topological defects. Here we analyse the micromagnetic dynamics in the helimagnetic phase of FeGe. By combining magnetic force microscopy, single-spin magnetometry and Landau–Lifschitz–Gilbert simulations we show that the nanoscale dynamics are governed by the depinning and subsequent motion of magnetic edge dislocations. The motion of these topologically stable objects triggers perturbations that can propagate over mesoscopic length scales. The observation of stochastic instabilities in the micromagnetic structure provides insight to the spatio-temporal dynamics of itinerant helimagnets and topological defects, and discloses open challenges regarding their technological usage. Topological defects may strongly influence the evolution of a materials' micromagnetic structure whilst their manipulation forms the basis for emerging technological concepts. Here, the authors study the depinning and motion of magnetic edge dislocations in the domain structure of helimagnetic FeGe.
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Affiliation(s)
- A Dussaux
- Department of Physics, ETH Zürich, Otto Stern Weg 1, Zurich 8093, Switzerland
| | - P Schoenherr
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 4, Zurich 8093, Switzerland
| | - K Koumpouras
- Department of Physics and Astronomy, Uppsala University, PO Box 516, Uppsala 75120, Sweden
| | - J Chico
- Department of Physics and Astronomy, Uppsala University, PO Box 516, Uppsala 75120, Sweden
| | - K Chang
- Department of Physics, ETH Zürich, Otto Stern Weg 1, Zurich 8093, Switzerland
| | - L Lorenzelli
- Department of Physics, ETH Zürich, Otto Stern Weg 1, Zurich 8093, Switzerland
| | - N Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Y Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - M Garst
- Institute for Theoretical Physics, Universität zu Köln, Köln D-50937, Germany
| | - A Bergman
- Department of Physics and Astronomy, Uppsala University, PO Box 516, Uppsala 75120, Sweden
| | - C L Degen
- Department of Physics, ETH Zürich, Otto Stern Weg 1, Zurich 8093, Switzerland
| | - D Meier
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 4, Zurich 8093, Switzerland.,Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim 7491, Norway
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7
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Generic Aspects of Skyrmion Lattices in Chiral Magnets. TOPOLOGICAL STRUCTURES IN FERROIC MATERIALS 2016. [DOI: 10.1007/978-3-319-25301-5_1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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8
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Schwarze T, Waizner J, Garst M, Bauer A, Stasinopoulos I, Berger H, Pfleiderer C, Grundler D. Universal helimagnon and skyrmion excitations in metallic, semiconducting and insulating chiral magnets. NATURE MATERIALS 2015; 14:478-483. [PMID: 25730395 DOI: 10.1038/nmat4223] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/21/2015] [Indexed: 06/04/2023]
Abstract
Nearly seven decades of research on microwave excitations of magnetic materials have led to a wide range of applications in electronics. The recent discovery of topological spin solitons in chiral magnets, so-called skyrmions, promises high-frequency devices that exploit the exceptional emergent electrodynamics of these compounds. Therefore, an accurate and unified quantitative account of their resonant response is key. Here, we report all-electrical spectroscopy of the collective spin excitations in the metallic, semiconducting and insulating chiral magnets MnSi, Fe1-xCoxSi and Cu2OSeO3, respectively, using broadband coplanar waveguides. By taking into account dipolar interactions, we achieve a precise quantitative modelling across the entire magnetic phase diagrams using two material-specific parameters that quantify the chiral and the critical field energy. The universal behaviour sets the stage for purpose-designed applications based on the resonant response of chiral magnets with tailored electric conductivity and an unprecedented freedom for an integration with electronics.
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Affiliation(s)
- T Schwarze
- Lehrstuhl für Physik funktionaler Schichtsysteme, Technische Universität München, Physik Department, D-85748 Garching, Germany
| | - J Waizner
- Institute of Theoretical Physics, University of Cologne, D-50937 Cologne, Germany
| | - M Garst
- Institute of Theoretical Physics, University of Cologne, D-50937 Cologne, Germany
| | - A Bauer
- Lehrstuhl für Topologie korrelierter Systeme, Technische Universität München, Physik Department, D-85748 Garching, Germany
| | - I Stasinopoulos
- Lehrstuhl für Physik funktionaler Schichtsysteme, Technische Universität München, Physik Department, D-85748 Garching, Germany
| | - H Berger
- Institut de Physique de la Matiére Complexe, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - C Pfleiderer
- Lehrstuhl für Topologie korrelierter Systeme, Technische Universität München, Physik Department, D-85748 Garching, Germany
| | - D Grundler
- 1] Lehrstuhl für Physik funktionaler Schichtsysteme, Technische Universität München, Physik Department, D-85748 Garching, Germany [2] Institut des Matériaux, Faculté Sciences et Technique de l'Ingénieur, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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9
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Abstract
Magnetic skyrmions in an insulating chiral magnet Cu2OSeO3 were studied by all-optical spin wave spectroscopy. The spins in the conical and skyrmion phases were excited by the impulsive magnetic field from the inverse-Faraday effect, and resultant spin dynamics were detected by using time-resolved magneto-optics. Clear dispersions of the helimagnon were observed, which is accompanied by a distinct transition into the skyrmion phase, by sweeping temperature and magnetic field. In addition to the collective excitations of skyrmions, i.e., rotation and breathing modes, several spin precession modes were identified, which would be specific to optical excitation. The ultrafast, nonthermal, and local excitation of the spin systems by photons would lead to the efficient manipulation of nano-magnetic structures.
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Krawczyk M, Grundler D. Review and prospects of magnonic crystals and devices with reprogrammable band structure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:123202. [PMID: 24599025 DOI: 10.1088/0953-8984/26/12/123202] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Research efforts addressing spin waves (magnons) in microand nanostructured ferromagnetic materials have increased tremendously in recent years. Corresponding experimental and theoretical work in magnonics faces significant challenges in that spinwave dispersion relations are highly anisotropic and different magnetic states might be realized via, for example, the magnetic field history. At the same time, these features offer novel opportunities for wave control in solids going beyond photonics and plasmonics. In this topical review we address materials with a periodic modulation of magnetic parameters that give rise to artificially tailored band structures and allow unprecedented control of spin waves. In particular, we discuss recent achievements and perspectives of reconfigurable magnonic devices for which band structures can be reprogrammed during operation. Such characteristics might be useful for multifunctional microwave and logic devices operating over a broad frequency regime on either the macroor nanoscale.
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