A5012256218- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Multiferroics and related materials
- Crystal Structures and Properties
- High-pressure geophysics and materials
- Corporate Taxation and Avoidance
- Thermal Expansion and Ionic Conductivity
- Nuclear materials and radiation effects
- Magnetic Properties of Alloys
- Intellectual Capital and Performance Analysis
- Perovskite Materials and Applications
- Inorganic Chemistry and Materials
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Topological Materials and Phenomena
- Magnetic properties of thin films
- Superconductivity in MgB2 and Alloys
- Magneto-Optical Properties and Applications
- Solid-state spectroscopy and crystallography
- Magnetism in coordination complexes
- Catalytic Processes in Materials Science
- Heusler alloys: electronic and magnetic properties
Tohoku University
2015-2024
The University of Tokyo
2010-2020
Laboratoire National des Champs Magnétiques Intenses
2017
Université Toulouse III - Paul Sabatier
2017
Université Grenoble Alpes
2017
Centre National de la Recherche Scientifique
2017
Japan Science and Technology Agency
2012-2013
Ehime University
2013
RIKEN Advanced Science Institute
2011
RIKEN
2009
A ferromagnet with spin anisotropies on the 2D Kagome lattice is theoretically studied. This a typical example of flat-band ferromagnet. The Berry phase induced by tilting spins opens band gap and quantized Hall conductance \sigma_{xy}=\pm e^2/h realized without external magnetic field. most realistic chiral state based ferromagnetism. We also discuss implication our results to anomalous effect observed in metallic pyrochlore ferromagnets R_2Mo_2O_7(R=Nd, Sm, Gd).
This paper reports angle-resolved photoemission spectroscopy and first-principles band calculations for MnTe, a candidate an altermagnet that is now emerging as new type of magnet, distinct from conventional ferromagnets antiferromagnets. The authors provide direct experimental evidence exchange splitting reaches 0.8 eV. was found to show strong anisotropy multiple nodal lines in momentum space associated with the PT symmetry breaking characteristic altermagnets.
This study presents experimental results of the piezomagnetic effect in MnTe, one candidate materials for altermagnets. The is a cross-correlation between magnetization and stress that allowed with broken time-reversal symmetry. authors observed proportional to below antiferromagnetic transition temperature, indicating MnTe has characteristics They also demonstrated altermagnetic domains can be controlled via effect.
We report results of 75As nuclear magnetic resonance (NMR) experiments on a self-flux grown single crystal BaFe2As2. A first-order antiferromagnetic (AF) transition near 135 K was detected by the splitting NMR lines, which is accompanied simultaneous structural as evidenced sudden large change electric field gradient tensor at As site. The lead almost uniquely to stripe spin structure in AF phase. data spin-lattice relaxation rate indicate development anisotropic fluctuations stripe-type...
Laser angle-resolved photoemission spectroscopy (ARPES) is employed to investigate the temperature ($T$) dependence of electronic structure in ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ across magnetostructural transition at ${T}_{N}\ensuremath{\sim}140\text{ }\text{ }\mathrm{K}$. A drastic transformation Fermi surface (FS) shape ${T}_{N}$ observed, as expected by first-principles band calculations. Polarization-dependent ARPES and calculations consistently indicate that observed FSs...
Bulk photoemission studies of iron pnictides suggest a role for orbital fluctuations in creating the superconducting state.
Big and cold: Strong internal compression of the Sr ion in novel perovskite SrCu3Fe4O12 (see structure) leads to giant negative thermal expansion (NTE) between 170 270 K. Mössbauer spectroscopy shows charge disproportionation FeIV FeIII FeV below 200 Thus, isoelectric substitution A-site cation can induce a drastic change structural electronic properties ACu3Fe4O12 perovskites. Detailed facts importance specialist readers are published as "Supporting Information". Such documents...
${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ shows a peculiar metal-insulator transition at 227 K with magnetic ordering in frustrated pyrochlore lattice, but its structure the ordered state and origin are yet uncovered. We observed commensurate peak by resonant x-ray scattering high-quality single crystal. X-ray diffraction Raman experiments confirmed that is not accompanied any spatial symmetry breaking. propose noncollinear all-in--all-out spin arrangement on tetrahedral network...
Dynamical properties of the lattice structure were studied by optical spectroscopy in $A$Cr${}_{2}$O${}_{4}$ chromium spinel oxide magnetic semiconductors over a broad temperature region $T=10$--335 K. The systematic change $A$-site ions ($A=$ Mn, Fe, Co, Ni and Cu) showed that occupancy 3$d$ orbitals on $A$ site has strong impact dynamics. For compounds with orbital degeneracy (FeCr${}_{2}$O${}_{4}$, NiCr${}_{2}$O${}_{4}$, CuCr${}_{2}$O${}_{4}$), clear splitting infrared-active phonon modes...
Ultrafast photoinduced spin dynamics has been investigated by time-resolved magneto-optical Kerr spectroscopy for various ferromagnetic and ferrimagnetic compounds: ${\mathrm{F}\mathrm{e}\mathrm{C}\mathrm{r}}_{2}{\mathrm{S}}_{4}$, ${\mathrm{C}\mathrm{o}\mathrm{C}\mathrm{r}}_{2}{\mathrm{S}}_{4}$, ${\mathrm{C}\mathrm{u}\mathrm{C}\mathrm{r}}_{2}{\mathrm{S}\mathrm{e}}_{4}$, ${\mathrm{C}\mathrm{d}\mathrm{C}\mathrm{r}}_{2}{\mathrm{S}\mathrm{e}}_{4}$,...
We have grown single crystals of a triangular lattice antiferromagnet (TLA), ${\text{CuCrO}}_{2}$, and investigated the correlation between magnetic dielectric properties. Two phase transitions are observed at ${T}_{\text{N}2}\ensuremath{\approx}24.2\text{ }\text{K}$ ${T}_{\text{N}1}\ensuremath{\approx}23.6\text{ }\text{K}$. It was found that ferroelectric polarization along plane develops ${T}_{\text{N}1}$, suggesting system undergoes transition into an out-of-plane...
A comprehensive study of magnetic, optical, and magnetooptical properties was carried out for single crystals the spinel-type Cr 2 X 4 ( =Mn, Fe, Co, Cu, Zn, Cd; =O, S, Se). The optical reflectivity measurements 0.1–30 eV revealed a wide variation in electronic structures on large energy scale between oxides =O) chalcogenides =S For =Fe we observed intra-atomic d – transitions 2+ ions with tetrahedral coordination, successfully deduced crystal field splitting Δ E , Racah parameter B...
We demonstrate that the onset of complex spin orders in ACr2O4 spinels with magnetic and Jahn-Teller active A=Fe Cu ions lowers lattice symmetry. This is clearly indicated by emergence anisotropic dynamics-i.e., pronounced phonon splittings-even when experiments probing static distortions fail. The crystal symmetry phase reduced from tetragonal to orthorhombic for both compounds. conical ordering FeCr2O4 also manifested hardening frequencies. In contrast, multiferroic CoCr2O4 no orbital...
The nature of the pseudogap (PG) in high transition temperature (high Tc) superconducting cuprates has been a major issue condensed matter physics. It is still unclear whether Tc superconductivity can be universally associated with PG formation. Here we provide direct evidence existence phase via angle-resolved photoemission spectroscopy another family superconductor, iron pnictides. Our results reveal composition-dependent formation multiband electronic structure BaFe2(As1−xPx)2. develops...
We performed high-pressure study for a Mott insulator BaFe_{2}S_{3}, by measuring dc resistivity and ac susceptibility up to 15 GPa. found that the antiferromagnetic insulating state at ambient pressure is transformed into metallic critical pressure, P_{c}=10 GPa, superconductivity with optimum T_{c}=24 K emerges above P_{c}. Furthermore, we metal-insulator transition (Mott transition) boundary terminates point around 10 GPa 75 K. The obtained pressure-temperature (P-T) phase diagram similar...
Magnetism in the insulating BaFe${}_{2}$Se${}_{3}$ was examined through susceptibility, specific heat, resistivity, and neutron diffraction measurements. After formation of a short-range magnetic correlation, long-range ordering observed below ${T}_{\mathrm{N}}\ensuremath{\sim}255$ K. The transition is obscured by bulk properties. Magnetic moments ($\ensuremath{\parallel}a$) are arranged to form Fe${}_{4}$ ferromagnetic unit, each stacks antiferromagnetically. This block magnetism third type...
In CaIrO3, electronic correlation, spin-orbit coupling, and tetragonal crystal field splitting are predicted to be of comparable strength. However, the nature its ground state is still an object debate, with contradictory experimental theoretical results. We probe CaIrO3 assess effective coupling at play in this system by means resonant inelastic x-ray scattering. conclude that insulating not a j(eff) = 1/2 iridate discuss consequences our finding interpretation previous experiments....
The ruthenium halide $\alpha$-RuCl$_{3}$ is a promising candidate for Kitaev spin liquid. However, the microscopic model describing still debated partly because of lack analogue materials $\alpha$-RuCl$_{3}$, which prevents tracking electronic properties as functions controlled interaction parameters. Here, we report successful synthesis RuBr$_{3}$. material RuBr$_{3}$~possesses BiI$_3$-type structure (space group: $R\overline{3}$) where Ru$^{3+}$ form an ideal honeycomb lattice. Although...
Application of magnetic field ( H ) can produce the ferroelectric polarization P in a proper screw helimagnet, ZnCr 2 Se 4 . While rotating , we observed cyclic generation current arising from change conical spin structure. Versatile variations magnitude and sign are while changing direction The behaviors ascribed to rotation cones conserving or reversing spin-helicity upon flop propagation vector, as affected by competition among anisotropy, inclination cone axis domain-wall stability.
We report results of 75As nuclear magnetic resonance (NMR) experiments on a self-flux grown high-quality single crystal SrFe2As2. The NMR spectra clearly show sharp first-order antiferromagnetic (AF) and structural transitions occurring simultaneously. behavior in the vicinity transition is compared with our previous study BaFe2As2. No significant difference was observed temperature dependence static quantities such as AF splitting electric quadrupole splitting. However, relaxation rate...
We present the results of electrical resistivity, ac specific heat, magnetic susceptibility, X-ray absorption spectroscopy (XAS) and circular dichroism (XMCD) ternary iron arsenide EuFe2As2 single crystal under pressure. Applying pressure leads to a continuous suppression antiferromagnetism associated with Fe moments antiferromagnetic transition temperature becomes zero in vicinity critical Pc ~2.5-2.7 GPa. Pressure-induced re-entrant superconductivity, which is highly sensitive homogeneity...
Unusual electronic phase transitions in the A-site ordered perovskites LnCu3Fe4O12 (Ln: trivalent lanthanide ion) are investigated. All compounds identical valence states of Ln3+Cu2+3Fe3.75+4O12 at high temperature. with larger Ln ions (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) show an intersite charge transfer transition (3Cu2+ + 4Fe3.75+ → 3Cu3+ 4Fe3+) which temperature decreases from 360 to 240 K decreasing ion size. In contrast, smaller Dy, Ho, Er, Tm Yb, Lu) transform into a...
We performed a Laser angle-resolved photoemission spectroscopy (ARPES) study on wide doping range of Ba1-xKxFe2As2 (BaK) and precisely determined the evolution superconducting (SC) gaps in this compound. The gap size outer hole Fermi surface (FS) sheet around Brillioun zone (BZ) center shows an abrupt drop with overdoping (for x > 0.6) while inner middle FS roughly scale Tc. This is accompanied by simultaneous disappearance electron similar orbital character at BZ corner. These results...