Article
Chemistry, Multidisciplinary
Xiuzhen Yu, Yizhou Liu, Konstantin V. Iakoubovskii, Kiyomi Nakajima, Naoya Kanazawa, Naoto Nagaosa, Yoshinori Tokura
Summary: 3D topological spin textures, called hopfions, have been theoretically predicted but not experimentally confirmed in helimagnetic systems. By using an external magnetic field and electric current, researchers successfully realized the existence of 3D topological spin textures, including fractional hopfions with non-zero topological index, in a skyrmion-hosting helimagnet FeGe. The dynamics of the expansion, contraction, and current-driven Hall motion of a bundle composed of a skyrmion and a fractional hopfion were controlled by microsecond current pulses. This research has demonstrated the novel electromagnetic properties of fractional hopfions and their ensembles in helimagnetic systems.
ADVANCED MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Ricardo Zarzuela, Jairo Sinova
Summary: Magnetically frustrated platforms are considered as optimal candidates for hosting topological spin textures and defects. However, these have not been observed experimentally due to the lack of probes coupling directly to the exotic rotation-matrix order parameter. In this work, the spin-transfer and topological Hall physics of metallic frustrated magnets are examined, and new contributions mediated by SO(3) solitons and magnetic disclinations are identified. The effect of symmetry reduction on the spin-transfer and topological Hall responses is also discussed, as well as experimental setups for detecting Hall currents.
Article
Chemistry, Multidisciplinary
Ryan A. Murphy, Lucy E. Darago, Michael E. Ziebel, Elizabeth A. Peterson, Edmond W. Zaia, Michael W. Mara, Daniel Lussier, Ever O. Velasquez, David K. Shuh, Jeffrey J. Urban, Jeffrey B. Neaton, Jeffrey R. Long
Summary: The discovery of conductive and magnetic 2D materials, such as the Mn-3(C6S6) metal-organic kagome lattice, represents a versatile route through coordination chemistry. This work demonstrates the potential utility of geometric frustration in the design of new nanoscale spintronic materials, providing a new strategy for engineering exchange bias systems using single-phase, crystalline lattices.
ACS CENTRAL SCIENCE
(2021)
Review
Physics, Condensed Matter
Satoru Hayami, Yukitoshi Motome
Summary: This paper reviews new types of topological spin textures in itinerant magnets, focusing on their stabilization mechanisms. By analyzing the interplay between charge and spin degrees of freedom, it is demonstrated that itinerant frustration plays a central role in stabilizing various topological spin crystals.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Chemistry, Multidisciplinary
Sae Young Han, Evan J. Telford, Asish K. Kundu, Sylvia J. Bintrim, Simon Turkel, Ren A. Wiscons, Amirali Zangiabadi, Eun-Sang Choi, Tai-De Li, Michael L. Steigerwald, Timothy C. Berkelbach, Abhay N. Pasupathy, Cory R. Dean, Colin Nuckolls, Xavier Roy
Summary: TaFe1+yTe3 possesses strong magnetic and electronic properties, making it a potential platform for two-dimensional spintronics, which may overcome the limitations of current materials.
Article
Materials Science, Multidisciplinary
Yonggi Sim, Hyunhee Choi
Summary: Liquid crystals are anisotropic fluids with long-range directional order. Creating controlled topological defects in liquid crystals is challenging, but this study successfully generated disclinations in an azo dye-doped nematic liquid crystal cell through photoisomerization and symmetry-breaking isotropic-nematic phase transition. This method represents a starting point for easier control of topological defects in liquid crystals.
OPTICAL MATERIALS EXPRESS
(2022)
Article
Materials Science, Multidisciplinary
Zizhao Gong, Wei Zhang, Jianan Liu, Zongkai Xie, Xu Yang, Jin Tang, Haifeng Du, Na Li, Xiangqun Zhang, Wei He, Zhao-hua Cheng
Summary: This study investigates the ultrafast demagnetization processes of FeGe film with different magnetic structures by using time-resolved magneto-optical Kerr effect (TRMOKE) measurements. The results show a transition from one-step to two-step ultrafast demagnetization process in the skyrmion phase region, which is mainly due to the weak electron-phonon coupling.
Article
Chemistry, Physical
Jonas Ronning, Julian Renaud, Amin Doostmohammadi, Luiza Angheluta
Summary: Polar active matter sustains spontaneous flows through topological defects. We study the flow profiles around ±1 defects induced by polar and dipolar active forces. Dipolar forces induce vortical flows around the +1 defect, while the flow around the -1 defect has an 8-fold rotational symmetry. The polarity of the flow near the +1 defect changes in the absence of friction.
Article
Chemistry, Multidisciplinary
Peggy Schoenherr, Mariia Stepanova, Erik Nikolai Lysne, Naoya Kanazawa, Yoshinori Tokura, Anders Bergman, Dennis Meier
Summary: The study reveals that the motion of magnetic topological defects, such as edge dislocations, significantly impacts the formation of nanoscale spin structures in chiral magnets, disturbing the stability of helimagnetic spin structures.
Article
Multidisciplinary Sciences
Ryoji Masuda, Yoshio Kaneko, Yoshinori Tokura, Youtarou Takahashi
Summary: The resonantly enhanced natural optical activity on the electrically active magnetic excitation in multiferroic cupric oxide demonstrates electric field control through magnetically induced chirality endowed with magnetoelectric coupling. These inherent optical properties of multiferroics may lead to optical devices based on the control of chirality.
Article
Materials Science, Multidisciplinary
A. S. Sukhanov, Y. V. Tymoshenko, A. A. Kulbakov, A. S. Cameron, V. Kocsis, H. C. Walker, A. Ivanov, J. T. Park, V. Pomjakushin, S. E. Nikitin, I. V. Morozov, I. O. Chernyavskii, S. Aswartham, A. U. B. Wolter, A. Yaresko, B. Buechner, D. S. Inosov
Summary: FeP is a special material with complex noncollinear spin order. By measuring the spin-excitation spectra, we found that the magnons in FeP have strong anisotropic dispersions. The dominant antiferromagnetic interactions between rigid ferromagnetic spin chains drive the magnetic frustration in FeP.
Article
Physics, Applied
H. L. Lin, K. L. Yang, Y. Huang, L. Lin, Z. B. Yan, J. -m. Liu
Summary: Although the dynamics of domain growth in ferroic systems have been studied extensively, there are still no realistic systems that strictly follow the scaling laws for two extreme types of defects. However, the ferroelectric hexagonal manganite family provides a unique platform to investigate these scaling laws as it exhibits a topological vortex-antivortex domain structure.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Multidisciplinary
Wen-Ti Guo, Zhigao Huang, Jian-Min Zhang
Summary: Defects significantly affect the properties of intrinsic magnetic topological insulators, and substituting Te atomic sites with Se can lead to changes in structure, magnetic moment, and result in topological phase transitions.
NEW JOURNAL OF PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Y. Miyagi, J. Jiang, K. Ohishi, Y. Kawamura, J. Suzuki, D. R. Alshalawi, J. Campo, Y. Kousaka, Y. Togawa
Summary: Chiral helimagnetism was investigated in MnTa3S6, revealing the presence of harmonic chiral helimagnetic order and chiral soliton lattice phase. The observed features in MnTa3S6 are distinct from other dichalcogenides. The tunable capability of the number of chiral solitons in CSL system at zero magnetic field may be useful for memory device applications.
Article
Chemistry, Physical
Kamil Nowak, Michal Jurczyszyn, Maciej Chrobak, Krzysztof Mackosz, Andrii Naumov, Natalia Olszowska, Marcin Rosmus, Ireneusz Miotkowski, Andrzej Kozlowski, Marcin Sikora, Marek Przybylski
Summary: In this study, we used STM/STS, ARPES, and magnetotransport techniques to investigate the surface topography and electronic structure of pristine Bi2Se3, as well as doped Bi1.96Mg0.04Se3 and Bi1.98Fe0.02Se3. We found a large number of complex, triangle-shaped defects on the surface and observed that the local electronic structure at the defects was influenced by doping in the same way as the electronic structure of the undefected surface. ARPES measurements provided additional information about the electronic structure, showing the dependence of bulk and surface electronic bands on doping. Magneto-transport measurements confirmed the subtle changes in the surface electronic structure induced by doping.
Review
Nanoscience & Nanotechnology
Dawei Zhang, Peggy Schoenherr, Pankaj Sharma, Jan Seidel
Summary: Van der Waals ferroelectrics have stable layered structures with strong intralayer forces and weak interlayer forces. They are easily stackable and can be integrated with different materials without interfacial issues. This review discusses the experimentally verified van der Waals ferroelectrics, their unique characteristics, and their potential applications in post-Moore's law electronics.
NATURE REVIEWS MATERIALS
(2023)
Article
Physics, Multidisciplinary
Aki Kitaori, Naoya Kanazawa, Takanori Kida, Yasuo Narumi, Masayuki Hagiwara, Koichi Kindo, Tetsuya Takeuchi, Ai Nakamura, Dai Aoki, Yoshinori Haga, Yoshio Kaneko, Yoshinori Tokura, Yoshichika O. Nuki
Summary: We have successfully grown single crystalline Tb5Sb3 with a hexagonal structure, which exhibits complex spiral magnetic structures with changing temperature. Specific heat and magnetization measurements revealed one clear magnetic transition at 133 K. The magnetic structure is oriented in the hexagonal basal plane with a hard axis corresponding to the [0001] direction. Below 50 K, the magnetic structure undergoes a transformation, leading to a rapid decrease in magnetic susceptibility for H II [1010] and a kink behavior in low-field magnetization, while showing hysteresis in the magnetization curve.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2023)
Letter
Physics, Multidisciplinary
Minoru Kawamura, Masataka Mogi, Ryutaro Yoshimi, Takahiro Morimoto, Kei S. Takahashi, Atsushi Tsukazaki, Naoto Nagaosa, Masashi Kawasaki, Yoshinori Tokura
Summary: Adiabatic charge pumping is observed in a thin-film magnetic heterostructure of topological insulators, confirming the theoretical prediction of topological magnetoelectric effect. The pumped charge is proportional to the surface Hall conductivity, providing clues for its direct observation.
Article
Physics, Multidisciplinary
H. Takagi, R. Takagi, S. Minami, T. Nomoto, K. Ohishi, M. -t. Suzuki, Y. Yanagi, M. Hirayama, N. D. Khanh, K. Karube, H. Saito, D. Hashizume, R. Kiyanagi, Y. Tokura, R. Arita, T. Nakajima, S. Seki
Summary: The spontaneous topological Hall effect in triangular lattice compounds CoTa3S6 and CoNb3S6 is experimentally demonstrated, combining non-coplanar antiferromagnetic order with finite scalar spin chirality in the absence of a magnetic field. These compounds exhibit unconventionally large spontaneous Hall effects despite their small net magnetization, and the mechanism behind this phenomena is explained by the topological Hall effect associated with scalar spin chirality. The results suggest that the scalar spin chirality mechanism offers a promising route for the realization of a giant spontaneous Hall response in compensated antiferromagnets.
Article
Physics, Multidisciplinary
T. Nomura, X. -X. Zhang, R. Takagi, K. Karube, A. Kikkawa, Y. Taguchi, Y. Tokura, S. Zherlitsyn, Y. Kohama, S. Seki
Summary: The nonreciprocal acoustic properties of a room-temperature ferromagnet Co9Zn9Mn2 unveil the phonon magnetochiral effect close to room temperature. In contrast to the insulating Cu2OSeO3, the nonreciprocity in this metallic compound is enhanced at higher temperatures and observed up to 250 K. Ultrasound and microwave-spectroscopy experiments suggest that the magnitude of the phonon magnetochiral effect mostly depends on the Gilbert damping of Co9Zn9Mn2, which increases at low temperatures and hinders the magnon-phonon hybridization. It is also proposed that the phonon nonreciprocity can be further enhanced by engineering the magnon band of materials.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Kamil K. Kolincio, Max Hirschberger, Jan Masell, Taka-hisa Arima, Naoto Nagaosa, Yoshinori Tokura
Summary: Dynamical spin fluctuations in magnets can be influenced by lattice geometry, leading to chiral spin fluctuations and fluctuation-related transport anomalies. This study focuses on the crucial role of lattice geometry on chiral spin fluctuations and the quantum-mechanical phase of conduction electrons. Experimental results and Monte Carlo calculations suggest that lattices with dissimilar plaquettes exhibit the most promising Berry phase phenomena in paramagnets.
PHYSICAL REVIEW LETTERS
(2023)
Article
Multidisciplinary Sciences
Keisuke Matsuura, Yo Nishizawa, Markus Kriener, Takashi Kurumaji, Hiroshi Oike, Yoshinori Tokura, Fumitaka Kagawa
Summary: In some materials, the equilibrium phase-transition line is concealed by the hysteresis region associated with field-induced first-order transitions (FOTs). Phase diagrams are essential in material science, as they provide comprehensive information about thermodynamic quantities. However, determining the equilibrium phase-transition line in a field-induced FOT is challenging, especially in the presence of large hysteresis.
SCIENTIFIC REPORTS
(2023)
Article
Nanoscience & Nanotechnology
N. Takahara, K. S. Takahashi, K. Maruhashi, Y. Tokura, M. Kawasaki
Summary: EuTiO3 (ETO) is a unique magnetic semiconductor with a large localized magnetic moment of Eu2+. By doping high-mobility electrons in the conduction band, peculiar magnetotransport properties have been observed. In this study, the physical properties of high quality ETO films with La3+ or Gd3+ donors grown on nearly lattice matched substrates are examined. These transport properties provide a deeper understanding of the band structure topology in high-mobility, magnetic oxide semiconductors.
Article
Multidisciplinary Sciences
Yoshihiro D. Kato, Yoshihiro Okamura, Max Hirschberger, Yoshinori Tokura, Youtarou Takahashi
Summary: The study reveals the magneto-optical Kerr effect (MOKE) induced by the formation of magnetic skyrmions in Gd2PdSi3, referred to as topological MOKE. The presence of skyrmions leads to a significant enhancement of the optical rotation, exemplifying the light-skyrmion interaction arising from the emergent gauge field. The findings pave the way for photonic technology based on skyrmionics.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Shunsuke Kitou, Yoshio Kaneko, Yuiga Nakamura, Kunihisa Sugimoto, Yusuke Nomura, Ryotaro Arita, Yoshinori Tokura, Hiroshi Sawa, Taka-hisa Arima
Summary: By performing core differential Fourier synthesis (CDFS) analysis of high-energy X-ray diffraction data, we directly observe the distribution state of Mo 4d orbital electrons in a pyrochlore-type oxide Nd2Mo2O7 at subangstrom resolution. The obtained valence electron density (VED) distribution confirms the Mo4+ 4d2 orbital state, and a dip in the radial profile indicates a node of the 4d wave function. The VED distribution around the Nd site is attributed to the hybridization of neighboring O 2p with Nd 6s/6p/5d orbitals and the anisotropic Nd3+ 4f3 electrons, which cannot be explained by simple j-j or LS coupling models. This study demonstrates the usefulness of CDFS analysis in investigating orbital states in crystalline materials.
Article
Materials Science, Multidisciplinary
Y. H. Zhuang, H. W. Liu, Y. H. Li, Y. M. Chang, T. Kurumaji, Y. Tokura, Y. M. Sheu
Summary: This study reveals the crucial role of crystal-field excitations involving spin-flip transitions in controlling switchable optomagnet effects in antiferromagnetic (Fe0.875Zn0.125)2Mo3O8. The photoinduced magnetization does not occur until the flipped spins are in excited states that frustrate the balanced spin moments, and it only starts to grow from a zero moment after the ultrashort pulses disappear. Through Kerr-effect microscopy and application of magnetic fields, the study distinguishes between photoinduced switchable magnetization and nonswitchable demagnetization. The experimental designs uncover essential factors for the development of antiferromagnetic memory devices using insulating oxides.
Article
Materials Science, Multidisciplinary
M. Ogino, Y. Kaneko, Y. Tokura, Y. Takahashi
Summary: We investigate the nonreciprocity of photons caused by enhanced dynamical magnetoelectric (ME) coupling in multiferroic perovskite manganites. The correlation between the optical ME effects and the order parameters is examined by changing the composition of the manganites. Nonreciprocal directional dichroism and gyrotropic birefringence are demonstrated in different spin-cycloidal phases, and their magnitudes show deviations from the relevant coupled order parameters.
Article
Materials Science, Multidisciplinary
Jiwon Ju, Hiraku Saito, Takashi Kurumaji, Max Hirschberger, Akiko Kikkawa, Yasujiro Taguchi, Taka-hisa Arima, Yoshinori Tokura, Taro Nakajima
Summary: We investigated the magnetic structures of Gd2PdSi3, a centrosymmetric skyrmion material, using polarized neutron scattering. Our results confirmed the elliptic screw-type magnetic modulation in zero field with a propagation vector of (q, 0, 0). As the temperature increases, the system undergoes a magnetic phase transition while maintaining the incommensurate q-vector of (q, 0, 0). In the ground state, the system contains equal fractions of left-handed and right-handed screw-type orders, as expected from the centrosymmetric crystal structure.
Article
Materials Science, Multidisciplinary
Aki Kitaori, Jonathan S. White, Naoya Kanazawa, Victor Ukleev, Deepak Singh, Yuki Furukawa, Taka-hisa Arima, Naoto Nagaosa, Yoshinori Tokura
Summary: AC current-driven motions of spiral spin textures can create new electric fields and induce emergent electromagnetic induction effect, potentially realizing quantum inductor elements of micrometer size. Research on YMn6Sn6 helimagnet reveals the optimized conditions for emergent inductors beyond room temperature, achieved by modifying the magnetism through partial substitution of Y by Tb. The study demonstrates the control of both magnitude and sign of emergent electromagnetic inductance, and expands the range of potential candidate materials for emergent inductors.
Article
Materials Science, Multidisciplinary
M. Kondo, M. Ochi, R. Kurihara, A. Miyake, Y. Yamasaki, M. Tokunaga, H. Nakao, K. Kuroki, T. Kida, M. Hagiwara, H. Murakawa, N. Hanasaki, H. Sakai
Summary: In this letter, we introduce a degenerate magnetic semiconductor EuMg2Bi2, which possesses topologically nontrivial Dirac/Weyl points formed by a magnetic exchange interaction with local Eu spins. Quantum oscillations in the resistivity, elastic constant, and surface impedance reveal the position of the Fermi energy EF and the existence of Weyl points near EF when the Eu spins are fully polarized, leading to an energy-dependent anomalous Hall conductivity peak. These findings are supported by first-principles calculations and demonstrate the significant impact of Weyl points on the simple band structure.