A5030848954- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Magnetic properties of thin films
- Nuclear Physics and Applications
- Rare-earth and actinide compounds
- Ferroelectric and Piezoelectric Materials
- High-pressure geophysics and materials
- Crystal Structures and Properties
- Atomic and Subatomic Physics Research
- Nuclear materials and radiation effects
- Inorganic Fluorides and Related Compounds
- Iron-based superconductors research
- Solid-state spectroscopy and crystallography
- Magnetic Properties and Synthesis of Ferrites
- Thermal Expansion and Ionic Conductivity
- Theoretical and Computational Physics
- Dielectric properties of ceramics
- Quantum, superfluid, helium dynamics
- Topological Materials and Phenomena
- Magnetism in coordination complexes
- Electronic and Structural Properties of Oxides
- Earthquake Detection and Analysis
- Magneto-Optical Properties and Applications
Ochanomizu University
2020-2023
RIKEN Center for Emergent Matter Science
2018-2023
The University of Tokyo
2012-2021
University of Regensburg
2009-2012
Institute for Solid State Physics and Optics
2012
Nagoya Institute of Technology
2011
Osaka University
2009-2011
Osaka Health Science University
2010
Nagoya University
2003-2007
Measurements of polarized neutron scattering were performed on a S=1/2 chain multiferroic LiCu2O2. In the ferroelectric ground state with spontaneous polarization along c axis, existence transverse spiral spin component in bc plane was confirmed. When direction electric is reversed, vector chirality as defined by C_(ij)=S_(i)xS_(j) (i and j being neighboring sites) observed to be indicating that spin-current model or inverse Dzyaloshinskii-Moriya mechanism applicable even this e_(g)-electron...
The origin of a room-temperature magnetoelectric (ME) effect has been examined by means neutron powder diffraction measurements for Z-type hexaferrite Sr(3)Co(2)Fe(24)O(41). temperature and magnetic-field dependence the electric polarization P several magnetic Bragg reflections show that commensurate order with (0,0,1) propagation vector an intimate connection ME effect. can be understood in terms appearance which is induced transverse conical spin structure through inverse...
We report on structural, magnetic, and magnetoelectric (ME) properties of a U-type hexaferrite Sr4Co2Fe36O60 prepared by solid state reaction. Samples sintered at 1150–1180 °C in oxygen contain the fewest impurity phases show highly insulating behavior. Powder neutron diffraction results reveal that commensurate magnetic order with (0,0,3/2) propagation vector develops below TN2∼350 K. Corresponding to appearance order, sample shows small ME effect. These suggest is room-temperature material...
We report a polarized-neutron-diffraction study on single crystal sample of ${\text{MnWO}}_{4}$, wherein the ferroelectricity and spiral magnetic order coexist. The direction electric polarization controls sense helix that can be detected from difference in intensities satellites for parallel antiparallel spin directions incident neutrons with respect to scattering vector. temperature dependence agrees well polarization. These results corroborate an inverse effect Dzyaloshinskii-Moriya...
We have carried out a spin-polarized-neutron study on multiferroic CuCrO 2 to clarify the origin of ferroelectricity. The neutron results demonstrate that an incommensurate proper-screw magnetic structure induces electric polarization. Not only but also oxygen location contributes ferroelectricity . polarization can be explained not by conventional spin-current model theoretical prediction proposed Arima. spin helicities reversed reversal field E in phase.
R2Ti2O7 (R = Y and various rare earth elements) has pyrochlore type structure, which consists of two kinds three-dimensional networks individually formed by the corner-sharing R4and Ti4-tetrahedra, respectively. Due to this structural characteristic, magnetic moments at R sites are expected be frustrated, if their nearest neighbor interaction is antiferromagnetic. For Tb, value Weiss temperature w 19K, indicating Tb3þ have antiferromagnetic system does not exhibit clear evidence for...
Data taken by various methods including NMR/NQR and neutron scattering are presented for Na x CoO 2 , particularly 0.5 . Attention has also been paid to the dependence of electronic nature this system. The pseudo-gap-like behavior observed in region < c ∼0.6 is emphasized. For samples with ≤0.6, signals from two kinds Co sites different quadrupole frequencies ν Q ∼4.1 ∼2.8 MHz were observed, former which nearly equal that superconducting system 0.3 · y H O, becomes dominant decreasing 0.3....
We have established the relationship between electric polarization vector and local spin arrangement including chirality in delafossite multiferroic $\mathrm{Cu}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}{\mathrm{O}}_{2}$. The results of polarized neutron diffraction pyroelectric measurements demonstrate that proper helical magnetic ordering $\mathrm{Cu}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}{\mathrm{O}}_{2}$ induces a spontaneous parallel to chirality. This result cannot be...
We refined the magnetic structure of a ferroelectric (FE) phase multiferroic ${\text{CuFe}}_{1\ensuremath{-}x}{\text{Ga}}_{x}{\text{O}}_{2}$ with $x=0.035$ by complementary use spherical neutron polarimetry and four-circle neutron-diffraction measurement, revealing that proper-screw-type in has finite ellipticity $\ensuremath{\sim}0.9$. By means polarized in-situ pyroelectric measurements, we also investigated quantitative relationship between macroscopic polarization $(P)$ asymmetry volume...
This study is motivated by a challenge to the third law of thermodynamics: how does degenerated ground state in textbook example behave real compound? At very low temperatures, nature tries preserve basic using small perturbations and novel quantum should appear. The authors here classic frustrated magnet Ba${}_{3}$Yb${}_{2}$Zn${}_{5}$O${}_{11}$, spin tetrahedron having two-fold degeneracy realized breathing pyrochlore lattice. They measure inelastic neutron scattering low-energy excitations...
Neutron diffraction studies have been carried out in the temperature(T) range between 10 K and 130 on a single crystal of YBaCo4O7, which has stacking kagome triangular lattices CoO4 tetrahedra along c-axis. Structural transitions found at two temperatures Tc1~70 Tc2~105 K. With decreasing T, magnetic order appears with transition Tc2, but it does not grow to an ideal long-range even lowest T studied (~10 K). Two groups diffuse reflections, originate from Co-moments lattices, are observed...
We studied the magnetic and magnetoelectric properties of Ba2-xSrxNi2Fe12O22 single crystals over a wide composition range (0 ≤ x 1.5). All show ferrimagnetic order at around 660 K. While Sr-free crystal is simply down to lowest temperature, transition from into screw ordered state was observed temperatures below 300 K in Sr-substituted crystals. The temperature monotonically increases with increasing Sr content, meaning that stabilized by Sr-substitution. By applying field perpendicular...
We demonstrate the existence of spin-nematic interactions in an easy-plane type antiferromagnet ${\mathrm{Ba}}_{2}{\mathrm{CoGe}}_{2}{\mathrm{O}}_{7}$ by exploring magnetic anisotropy and spin dynamics. The combination neutron scattering susceptibility measurements reveals that origin in-plane is antiferro-type interaction operator. relation between nematic operator electric polarization ligand symmetry this compound presented. introduction useful to understand physics dipole multiferroic compounds.
Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite TbBaCo 2 O 5.5 in the temperature range 7–370 K. There observed several magnetic or structural transitions. Among these, existence transitions to insulating phase from metallic one at ∼340 K, with ferromagnetic moment ∼280 K and possibly antiferromagnetic ∼260 decreasing T correspond those reported former works. We studied structures 270 250 found that all Co 3+ ions CoO 6 octahedra are low...
Using neutron scattering, we elucidate the origins of magnetoelectric effects observed in a triangular lattice antiferromagnet, ${\text{CuCrO}}_{2}$, showing ferroelectricity associated with spiral-spin order $({T}_{\text{N}1}\ensuremath{\sim}24\text{ }\text{K})$. Below ${T}^{\ensuremath{\ast}}\ensuremath{\sim}16\text{ }\text{K}$, remarkable difference magnetic Bragg reflection and electric polarization $P$ between their zero-field-cooling (ZFC) field-cooling procedures, suggesting that...
We use inelastic neutron scattering to study the low-energy spin excitations of 112-type iron pnictide ${\mathrm{Ca}}_{0.82}{\mathrm{La}}_{0.18}{\mathrm{Fe}}_{0.96}{\mathrm{Ni}}_{0.04}{\text{As}}_{2}$ with bulk superconductivity below ${T}_{c}=22\text{ }\text{ }\mathrm{K}$. A two-dimensional resonance mode is found around $E=11\text{ }\mathrm{meV}$, where energy almost temperature independent and linearly scales ${T}_{c}$ along other iron-based superconductors. Polarized analysis reveals...
Transport and magnetic measurements have been carried out on perovskite Co-oxides R1-xAxCoO3 (R=La, Pr, Nd; A=Ba, Sr Ca; 0<x<0.5: All sets of the R A species except Nd1-xBaxCoO3 studied.). With increasing Sr- or Ba-concentration x, system becomes metallic ferromagnet with rather large moments. For R=Pr Nd A=Ca, approaches metal- insulator phase boundary but does not become metallic. The moments Ca-doped systems measured field H=0.1 T are much smaller than those Ba- Sr-doped systems....
Hybridization of phase and amplitude fluctuations an order parameter is evidenced by neutron scattering technique.
We investigate the magnetic order of buckled honeycomb lattice antiferromagnet ${\mathrm{Ba}}_{2}{\mathrm{NiTeO}}_{6}$ and its related ${\mathrm{Ba}}_{3}{\mathrm{NiTa}}_{2}{\mathrm{O}}_{9}$ by neutron diffraction measurements. observe Bragg peaks below transition temperatures, identify propagation vectors for these oxides. A combination representation analysis Rietveld refinement leads to a collinear ${120}^{\ensuremath{\circ}}$ structure...
Inelastic neutron scattering measurement is performed on a breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11. The observed dispersionless excitations are explained by crystalline electric field (CEF) Hamiltonian of Kramers ion Yb3+ which the local symmetry exhibits C3v point group symmetry. magnetic susceptibility previously reported consistently reproduced energy scheme CEF excitations. obtained wave functions ground state doublet exhibit planer-type anisotropy. result demonstrates that...
Neutron diffraction studies have been carried out on a single crystal of oxygen-deficient perovskite NdBaCo 2 O 5 in the temperature range 7–370 K. There observed, with decreasing T , two magnetic transitions accompanied structural changes, to antiferromagnetic phase at ∼360 K and charge ordered one ∼250 We studied structures 300 7 At these temperatures Co-moments so-called G-type structure, Co ions are considered be high spin state over whole below N
We performed inelastic neutron scattering measurements on single crystals of ${\mathrm{NdFe}}_{3}(^{11}\mathrm{BO}_{3}){}_{4}$ to explore the magnetic excitations, establish underlying Hamiltonian, and reveal detailed nature hybridization between $4f$ $3d$ magnetism. The observed spectra exhibiting a couple key features, i.e., anticrossing Nd Fe excitations anisotropy gap at antiferromagnetic zone center, are explained by model including spin interaction in framework weakly coupled...
We have studied the pressure-induced quantum phase transition in singlet-ground-state antiferromagnet ${\mathrm{CsFeCl}}_{3}$. Neutron diffraction experiments under pressure evidence magnetic long-range order at low temperatures. Magnetic structure analysis reveals a ${120}^{\ensuremath{\circ}}$ with propagation vector of ${\mathbit{k}}_{\mathrm{mag}}=(1/3,1/3,0)$. The estimated critical exponent parameter suggests that ${\mathrm{CsFeCl}}_{3}$ belongs to universality class...