A5069518795- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- 2D Materials and Applications
- Ferroelectric and Piezoelectric Materials
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Advanced Thermoelectric Materials and Devices
- Magnetic Properties and Synthesis of Ferrites
- Thermal Expansion and Ionic Conductivity
- Magneto-Optical Properties and Applications
- Heusler alloys: electronic and magnetic properties
- Inorganic Fluorides and Related Compounds
- X-ray Diffraction in Crystallography
- Crystal Structures and Properties
- Inorganic Chemistry and Materials
- Crystallization and Solubility Studies
- Chemical Synthesis and Characterization
- Graphene research and applications
- Quantum and electron transport phenomena
- Chalcogenide Semiconductor Thin Films
Osaka University
2019-2025
Spintronics Research Network of Japan
2020-2025
The University of Tokyo
2014-2023
Japan Synchrotron Radiation Research Institute
2023
Kindai University
2023
RIKEN Center for Emergent Matter Science
2015-2023
SPring-8
2023
Japan Science and Technology Agency
2005-2020
Material Physics Center
2019
Waseda University
2005-2011
A magnetic skyrmion is a topologically stable particle-like object that appears as vortex-like spin texture at the nanometer scale in chiral-lattice magnet. Skyrmions have been observed metallic materials, where they are controllable by electric currents. Here, we report experimental discovery of magnetoelectric skyrmions an insulating magnet Cu(2)OSeO(3) through Lorentz transmission electron microscopy and susceptibility measurements. We find can magnetically induce polarization. The...
We have observed an unconventional, likely topological, Hall effect over a wide temperature region in the magnetization process of chiral-lattice helimagnet MnGe. The magnitude topological resistivity is nearly temperature-independent below 70 K, which reflects real-space fictitious magnetic field proportional to geometric quantity (scalar spin chirality) underlying texture. From neutron diffraction study, it anticipated that relatively short-period (3-6 nm) noncoplanar structure stabilized...
The unusual property of negative thermal expansion is fundamental interest and may be used to fabricate composites with zero or other controlled values. Here we report that colossal (defined as linear <−10−4 K−1 over a temperature range ~100 K) accessible in perovskite oxides showing charge-transfer transitions. BiNiO3 shows 2.6% volume reduction under pressure due Bi/Ni charge transfer shifted ambient through lanthanum substitution for Bi. Changing proportions coexisting low-...
A newly designed ferromagnetic, ferroelectric compound, Bi(2)NiMnO(6), was prepared by high-pressure synthesis at 6 GPa. The crystal structure, as determined synchrotron X-ray powder diffraction, is a heavily distorted double perovskite with Ni(2+) and Mn(4+) ions ordered in rock-salt configuration. presence of 6s(2) lone pairs Bi(3+) the covalent Bi-O bonds give properties T(CE) 485 K, while -Ni(2+)-O-Mn(4+)-O-Ni(2+)- magnetic paths lead to ferromagnetism T(CM) 140 K. This simple material...
The mutual control of the electric and magnetic properties a solid is currently great interest because possible application for novel electronic devices. We report on low-magnetic-field (for example, B values +/-30 milliteslas) polarization (P) vector in hexaferrite, Ba2Mg2Fe12O22, which shows helimagnetic spin structure with propagation k0 parallel to [001]. B-induced transverse conical carries P directing perpendicular both k0, accord recently proposed spin-current model. Then, oscillating...
We have investigated the low-energy dynamics of triangular lattice Skyrmions in a helimagnetic insulator Cu2OSeO3 terms microwave response. observed two elementary excitations Skyrmion with different polarization characteristics: counterclockwise circulating mode at 1 GHz magnetic field parallel to plane and breathing 1.5 perpendicular polarization. These modes reflect topological nature may play central role dynamics.
Magnetic and magnetoelectric (ME) properties have been studied for single crystals of Sc-doped M-type barium hexaferrites. Magnetization (M) neutron diffraction measurements revealed that by tuning Sc concentration a longitudinal conical state is stabilized up to above room temperatures. ME shown transverse magnetic field (H) can induce electric polarization (P) at lower temperatures the spin helicity nonvolatile endurable near transition temperature. It was also response (reversal or...
Quantum transport of quasi–two-dimensional Dirac fermions is largely controlled by magnetic order in a layered magnet.
We report a 139La-NMR study of polycrystalline samples multi(n)-layered nickelates, La3Ni2O7−δ (n = 2) and La4Ni3O10−δ 3), at ambient pressure. Measurements the nuclear magnetic resonance (NMR) spectra spin relaxation rate (1/T1) indicate emergence density wave order with gap below T* ∼ 150 K for ∼130 La4Ni3O10−δ. The finite value 1/T1 indicates metallic ground states remaining Fermi level (EF) under order. These features are attributed to multiple d electron bands different characteristics....
A large-size single crystal of nearly stoichiometric SrCoO(3) was prepared with a two-step method combining the floating-zone technique and subsequent high oxygen pressure treatment. crystallizes in cubic perovskite structure space group Pm3m, displays an itinerant ferromagnetic behavior Curie temperature 305 K. The easy magnetization axis is found to be along [111] direction, saturation moment 2.5 µ(B)/f.u., accord picture intermediate spin state. resistivity at low temperatures (T)...
Small-angle neutron scattering experiments were performed on a bulk single crystal of chiral-lattice multiferroic insulator Cu${}_{2}$OSeO${}_{3}$. In the absence an external magnetic field, helical spin order with modulation vector $q\ensuremath{\parallel}\ensuremath{\langle}001\ensuremath{\rangle}$ was identified. When field is applied, triple-$q$ structure emerges normal to in A phase just below ordering temperature ${T}_{c}$, which suggests formation triangular lattice skyrmions....
We have investigated the thermal Hall effect of magnons for various ferromagnetic insulators. For pyrochlore insulators Lu${}_{2}$V${}_{2}$O${}_{7}$, Ho${}_{2}$V${}_{2}$O${}_{7}$, and In${}_{2}$Mn${}_{2}$O${}_{7}$, finite conductivities been observed below Curie temperature ${T}_{C}$. From magnetic-field dependencies, it is concluded that are responsible effect. The can be well explained by theory based on Berry curvature in momentum space induced Dzyaloshinskii-Moriya (DM) interaction....
Dielectric properties were investigated under various magnitudes and directions of magnetic field ($H$) for a chiral insulator Cu${}_{2}$OSeO${}_{3}$. We found that the skyrmion crystal induces electric polarization ($P$) along either in-plane or out-of-plane direction spin vortices depending on applied $H$ direction. The observed dependence $P$ in ferrimagnetic, helimagnetic, state can be consistently described by $d$-$p$ hybridization model, highlighting an important role relativistic...
Complete magnetoelectric (ME) phase diagrams of orthorhombic $R{\text{MnO}}_{3}$ with and without magnetic moments on the $R$ ions have been established. Three kinds multiferroic ground states, $ab$-cycloidal, $bc$-cycloidal, collinear $E$-type phases, identified by distinct ME responses. The electric polarization dominated symmetric spin exchange $({\mathbit{S}}_{i}\ensuremath{\cdot}{\mathbit{S}}_{j})$ is more than ten times as large that $bc$-cycloidal antisymmetric one...
A helical spin texture is of great current interest for a host novel spin-dependent transport phenomena. We report rich variety nontrivial helimagnetic phases in the simple cubic perovskite ${\mathrm{SrFeO}}_{3}$ under magnetic fields up to 42 T. Magnetic and resistivity measurements revealed that proper-screw phase proposed can be subdivided into at least five kinds ordered phases. Near multicritical point, an unconventional anomalous Hall effect was found show interpreted as due possible...
We have investigated the magnetic structure in a polycrystalline sample of $B20$-type MnGe by means small-angle neutron scattering. On projected diffraction plane normal to incoming beam, Debye-ring-like pattern appears due random orientation spin helix $q$ vectors ($\ensuremath{\parallel}\ensuremath{\langle}100\ensuremath{\rangle}$). When an external field is applied intense peak with wave vector ($q$) perpendicular observed as hallmark formation skyrmion lattice multiple-$q$ wide...
We have spectroscopically investigated the thermally and doping-induced metal-insulator transitions for pyrochlore-type ${\mathrm{Nd}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ as well its Rh-doped analogs ${\mathrm{Nd}}_{2}({\mathrm{Ir}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{)}_{2}{\mathrm{O}}_{7}$, where spin-orbit interaction electron correlation is effectively tuned by doping level ($x$). The charge dynamics dramatically changes on an energy scale of 1 eV in course transitions, while...
The authors unveil topological spin structures composed of skyrmion strings in a cubic centrosymmetric iron oxide that provides the missing experimental link between lattices and rich variety helimagnetic order. This is first observation three-dimensional texture bulk perovskite-type oxide, one most ubiquitous important systems for electronics. study enlarges family textures offers promising route toward design novel skyrmionics.
A new triclinic perovskite, BiNiO3, has been synthesized at a high pressure of 6 GPa in an oxidizing atmosphere. Structure refinements based on synchrotron X-ray powder diffraction and bond-valence calculations revealed disproportionation the Bi ions into Bi3+ Bi5+, both being located distorted oxygen octahedra. Because presence oxidation state Ni was +2, rather than +3 as had expected; BiNiO3 thus showed insulating behavior with localized spins S = 1.
The valence state change of BiNiO3 perovskite under pressure has been investigated by a powder neutron diffraction study and electronic-state calculations. At ambient pressure, the unusual charge distribution Bi(3+)(0.5)Bi(5+)(0.5)Ni(2+)O3 with ordering Bi(3+) Bi(5+)charges on A sites highly distorted structure. High-pressure measurements bond sum calculations show that pressure-induced melting disproportionated leads to simultaneous transfer from Ni Bi, so high-pressure phase is metallic...