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Singh D, Fujishiro Y, Hayami S, Moody SH, Nomoto T, Baral PR, Ukleev V, Cubitt R, Steinke NJ, Gawryluk DJ, Pomjakushina E, Ōnuki Y, Arita R, Tokura Y, Kanazawa N, White JS. Transition between distinct hybrid skyrmion textures through their hexagonal-to-square crystal transformation in a polar magnet. Nat Commun 2023; 14:8050. [PMID: 38052859 DOI: 10.1038/s41467-023-43814-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 11/21/2023] [Indexed: 12/07/2023] Open
Abstract
Magnetic skyrmions, topological vortex-like spin textures, garner significant interest due to their unique properties and potential applications in nanotechnology. While they typically form a hexagonal crystal with distinct internal magnetisation textures known as Bloch- or Néel-type, recent theories suggest the possibility for direct transitions between skyrmion crystals of different lattice structures and internal textures. To date however, experimental evidence for these potentially useful phenomena have remained scarce. Here, we discover the polar tetragonal magnet EuNiGe3 to host two hybrid skyrmion phases, each with distinct internal textures characterised by anisotropic combinations of Bloch- and Néel-type windings. Variation of the magnetic field drives a direct transition between the two phases, with the modification of the hybrid texture concomitant with a hexagonal-to-square skyrmion crystal transformation. We explain these observations with a theory that includes the key ingredients of momentum-resolved Ruderman-Kittel-Kasuya-Yosida and Dzyaloshinskii-Moriya interactions that compete at the observed low symmetry magnetic skyrmion crystal wavevectors. Our findings underscore the potential of polar magnets with rich interaction schemes as promising for discovering new topological magnetic phases.
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Affiliation(s)
- Deepak Singh
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland.
| | - Yukako Fujishiro
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - Satoru Hayami
- Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Samuel H Moody
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland
| | - Takuya Nomoto
- Research Center for Advanced Science and Technology, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Priya R Baral
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland
| | - Victor Ukleev
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109, Berlin, Germany
| | - Robert Cubitt
- Institut-Laue-Langevin, 6 rue Jules Horowitz, Grenoble, 38000, France
| | | | - Dariusz J Gawryluk
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institut (PSI), CH-5232, Villigen PSI, Switzerland
| | - Ekaterina Pomjakushina
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institut (PSI), CH-5232, Villigen PSI, Switzerland
| | - Yoshichika Ōnuki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - Ryotaro Arita
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Research Center for Advanced Science and Technology, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Naoya Kanazawa
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan
| | - Jonathan S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland.
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Chen K, Luo C, Zhao Y, Baudelet F, Maurya A, Thamizhavel A, Rößler UK, Makarov D, Radu F. Evidence of the Anomalous Fluctuating Magnetic State by Pressure-Driven 4f Valence Change in EuNiGe 3. J Phys Chem Lett 2023; 14:1000-1006. [PMID: 36693119 PMCID: PMC9900636 DOI: 10.1021/acs.jpclett.2c03569] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 01/19/2023] [Indexed: 06/17/2023]
Abstract
In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu3+ atomic shell with J = 0, due to intra-atomic exchange and spin-orbital coupling interactions with the Eu2+ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in EuNiGe3 single crystals is probed. Magnetic polarization is observed for both valence states of Eu2+ and Eu3+ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.
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Affiliation(s)
- K. Chen
- National
Synchrotron Radiation Laboratory, University
of Science and Technology of China, Hefei 230026, Anhui, China
| | - C. Luo
- Helmholtz-Zentrum
Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - Y. Zhao
- Center
for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China
| | - F. Baudelet
- Synchrotron
SOLEIL, L’Orme des Merisiers, Saint-Aubin-BP48, 91192 GIF-sur-Yvette, France
| | - A. Maurya
- Department
of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India
| | - A. Thamizhavel
- Department
of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India
| | - U. K. Rößler
- Leibniz-Institut
für Festkörper- und Werkstoffforschung Dresden e. V.
(IFW Dresden), 01069 Dresden, Germany
| | - D. Makarov
- Helmholtz-Zentrum
Dresden-Rossendorf e.V., Institute of Ion Beam Physics and Materials
Research, 01328 Dresden, Germany
| | - F. Radu
- Helmholtz-Zentrum
Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
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Giovannini M, Čurlík I, Freccero R, Solokha P, Reiffers M, Sereni J. Crystal Structure and Magnetism of Noncentrosymmetric Eu 2Pd 2Sn. Inorg Chem 2021; 60:8085-8092. [PMID: 34028265 PMCID: PMC8277132 DOI: 10.1021/acs.inorgchem.1c00678] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The new intermetallic
compound Eu2Pd2Sn has
been investigated. A single crystal was selected from the alloy and
was analyzed by single-crystal X-ray diffraction, revealing that this
compound possesses the noncentrosymmetric Ca2Pd2Ge structure type being, so far, the only rare-earth-based representative.
Bonding analysis, performed on the basis of DOS and (I)COHP, reveals
the presence of strong covalent Sn–Pd bonds in addition to
linear and equidistant Pd–Pd chains. The incomplete ionization
of Eu leads to its participation in weaker covalent interactions.
The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μeff = 7.87
μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum
of χ(T) at TN ∼
13 K indicates an antiferromagnetic behavior below this temperature.
A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered
at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate
antiferromagnetic phase below TN followed
by a commensurate configuration below 10 K is suggested. A new intermetallic compound, Eu2Pd2Sn, is so far the only rare-earth representative of the Ca2Pd2Ge structure type. Synthesis and characterization of
the structure, together with magnetic properties, are discussed.
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Affiliation(s)
- Mauro Giovannini
- Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova, Italy
| | - Ivan Čurlík
- Faculty of Humanities and Natural Sciences, University of Prešov, 17 Novembra 1, 080 01 Prešov, Slovakia
| | - Riccardo Freccero
- Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova, Italy
| | - Pavlo Solokha
- Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova, Italy
| | - Marian Reiffers
- Faculty of Humanities and Natural Sciences, University of Prešov, 17 Novembra 1, 080 01 Prešov, Slovakia.,Institute of Experimental Physics, Slovak Academy of Science, Watsonova 47, 040 01 Košice, Slovakia
| | - Julian Sereni
- Department of Physics, CAB-CNEA, CONICET, IB-UNCuyo, 8400 S. C. de Bariloche, Argentina
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Abstract
Abstract
In this article, we focus on (1) type-II multiferroics driven by spiral spin orderings and (2) magnetoelectric couplings in multiferroic skyrmion-hosting materials. We present both phenomenological understanding and microscopic mechanisms for spiral spin state, which is one of the essential starting points for type-II multiferroics and magnetic skyrmions. Two distinct mechanisms of spiral spin states (frustration and Dzyaloshinskii–Moriya [DM] interaction) are discussed in the context of the lattice symmetry. We also discuss the spin-induced ferroelectricity on the basis of the symmetry and microscopic atomic configurations. We compare two well-known microscopic models: the generalized inverse DM mechanism and the metal-ligand d-p hybridization mechanism. As a test for these models, we summarize the multiferroic properties of a family of triangular-lattice antiferromagnets. We also give a brief review of the magnetic skyrmions. Three types of known skyrmion-hosting materials with multiferroicity are discussed from the view point of crystal structure, magnetism, and origins of the magnetoelectric couplings. For exploration of new skyrmion-hosting materials, we also discuss the theoretical models for stabilizing skyrmions by magnetic frustration in centrosymmetric system. Several basic ideas for material design are given, which are successfully demonstrated by the recent experimental evidences for the skyrmion formation in centrosymmetric frustrated magnets.
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Affiliation(s)
- Takashi Kurumaji
- Physics , Massachusetts Institute of Technology , Cambridge , MA, USA
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