A5029796688- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Multiferroics and related materials
- Corporate Taxation and Avoidance
- Intellectual Capital and Performance Analysis
- Superconductivity in MgB2 and Alloys
- Ferroelectric and Piezoelectric Materials
- Ga2O3 and related materials
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Inorganic Fluorides and Related Compounds
- Magneto-Optical Properties and Applications
- ZnO doping and properties
- Semiconductor materials and devices
- Copper-based nanomaterials and applications
- Electronic and Structural Properties of Oxides
- Underwater Acoustics Research
- Advanced Photocatalysis Techniques
- Superconducting Materials and Applications
- Crystal Structures and Properties
- Magnetic Properties of Alloys
- Magnetism in coordination complexes
National Institute of Advanced Industrial Science and Technology
2015-2024
Self-Defense Forces Central Hospital
2022
Osaka University
1990-2018
Iwate University
2018
Waseda University
2015
Institute for Materials Research, Tohoku University
2015
Japan Aerospace Exploration Agency
2005-2015
Tohoku University
2015
National Institute for Materials Science
2015
Sophia University
2015
The measurement of the Cu-O distances by a local and fast probe, polarized Cu K-edge extended x-ray absorption fine structure (EXAFS) in L${\mathrm{a}}_{1.85}$S${\mathrm{r}}_{0.15}$Cu${\mathrm{O}}_{4}$ crystal shows two different conformations Cu${\mathrm{O}}_{6}$ octahedra below 100 K assigned to types stripes with lattice. This experiment supports model ``two components'' spatially separated superlattice quantum for anomalous properties cuprate superconductors.
The in-plane resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}\mathit{b}}$(T) and Hall coefficient ${\mathit{R}}_{\mathit{H}}$(T) have been measured for ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$ single crystals with various oxygen concentrations. We find that oxygen-depleted samples deviates from T-linear behavior 1/T below a temperature ${\mathit{T}}_{\mathit{o}}$ well above ${\mathit{T}}_{\mathit{c}}$. deviation coincides the development...
The crystal structure of LnFeAsO 1- y (Ln = La, Nd) has been studied by the powder neutron diffraction technique. superconducting phase diagram NdFeAsO is established as a function oxygen content which determined Rietveld refinement. small As–Fe bond length suggests that As and Fe atoms are connected covalently. FeAs 4 -tetrahedrons transform toward regular shape with increasing deficiency. Superconducting transition temperatures seem to attain maximum values for -tetrahedrons.
An ordered phase showing remarkable electronic anisotropy in proximity to the superconducting is now a hot issue field of high-transition-temperature superconductivity. As case copper oxides, superconductivity iron arsenides competes or coexists with such an phase. Undoped and underdoped have magnetostructural exhibiting stripe-like antiferromagnetic spin order accompanied by orthorhombic lattice distortion; both distortion break tetragonal symmetry crystals these compounds. In this state,...
We recently reported a phenotypic association between reduced susceptibility to zinc and methicillin resistance in Staphylococcus aureus CC398 isolates from Danish swine (F. M. Aarestrup, L. Cavaco, H. Hasman, Vet. Microbiol. 142:455-457, 2009). The aim of this study was identify the genetic determinant causing examine its prevalence animal human origin. Based on sequence staphylococcal cassette chromosome mec (SCCmec) element methicillin-resistant S. (MRSA) strain SO385, putative metal gene...
We report the 75As nuclear quadrupole resonance (NQR) and specific heat measurements of heavily hole-doped superconductor KFe2As2 (Tc = 3.5 K). The spin-lattice relaxation rate 1/T1 in superconducting state exhibits quite gradual temperature dependence with no coherence peak below Tc. quasi-particle C_QP/T shows small jump which is about 30% electronic coefficient just In addition, it suggests existence low-energy excitation at lowest measurement T 0.4 K \simeq Tc/10. These can be explained...
We investigated the optical spectrum of Ba(Fe1-xCox)2As2 single crystals with various doping levels. It is found that low-energy conductivity this system can be decomposed into two components: a sharp Drude term and broad "incoherent" term. For compounds showing magnetic order, gap appears predominantly in component, while an s-wave like superconducting opens both components for highly doped compounds. The weight steadily increases as proceeds, consistent electron system. On other hand,...
Centimeter-sized platelet single crystals of KFe 2 As were grown using a self-flux method. An encapsulation technique commercial stainless steel container allowed the stable crystal growth to last for more than weeks. Ternary K–Fe–As systems with various starting compositions examined determine optimal conditions. The employment KAs flux led large typical size as 15 ×10 ×0.4 mm 3 . exhibit sharp superconducting transition at 3.4 K width 0.2 K, well very residual resistivity ratio exceeding...
Numerous attempts have been made to realize crossed coupling between ferroelectricity and magnetism in multiferroic materials at room temperature. BiFeO3 is the most extensively studied material that shows multiferroicity temperatures significantly above Here we present high-field experiments on high-quality mono-domain crystals reveal substantial electric polarization orthogonal widely recognized one along trigonal c axis. This novel appears couple with domains of cycloidal spin order and,...
Surface-functionalized β-Ga2O3 and diamond substrates were directly bonded by annealing at 250 °C in atmospheric air. Prior to bonding, the surfaces OH-terminated oxygen plasma irradiation H2SO4/H2O2 cleaning, respectively. After contacting with each other, direct bonding was formed a thermal dehydration reaction. The annealed specimen had shear strength of 14 MPa because generation chemical bonds between surfaces. analysis interface structures revealed that atomically without nano-voids,...
Polarized optical reflectivity spectra of untwinned ${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ are reported. The show a large ab-plane anisotropy in the infrared region with higher along chain direction. For polarization, spectrum is similar to that deoxygenated tetragonal ${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$, an energy gap about 1.5 eV, indicating it difficult dope holes into ${\mathrm{CuO}}_{2}$ planes by addition...
We report muon spin relaxation $(\ensuremath{\mu}\mathrm{SR})$ measurements using single crystals of oxygen-intercalated stage-4 ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4.11}$ (LCO:4.11) and ${\mathrm{La}}_{1.88}{\mathrm{Sr}}_{0.12}{\mathrm{CuO}}_{4}$ (LSCO:0.12), in which neutron scattering studies have found incommensurate magnetic Bragg reflections. In both systems, zero-field $\ensuremath{\mu}\mathrm{SR}$ show precession below the N\'eel temperature ${T}_{N}$ with frequency 3.6 MHz at...
We report an inelastic-neutron-scattering experiment on single crystals of the one-dimensional spin-one antiferromagnet ${\mathrm{Y}}_{2}$BaNi${\mathrm{O}}_{5}$. The data show that this compound is a nearly ideal material for studying Haldane conjecture in Heisenberg limit. In particular, gap at $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}=\ensuremath{\pi}$ almost isotropic, taking values 7.5(1), 8.6(1), and 9.6(1) meV polarizations parallel to three principal orthorhombic axes...
We report the observation of bulk superconductivity in PrBa 2 Cu 3 O x single crystals for first time. These samples were grown by travelling-solvent floating-zone (TSFZ) method oxygen-reduced atmosphere. The as-grown crystal has a longer c -axis lattice constant an than any values previously reported . After oxygen annealing, resistivity becomes zero below T =80 K, and zero-field-cooled magnetization shows diamagnetism with full volume fraction. X-ray energy dispersion spectrum diffraction...
High-energy spin excitations up to above 8000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ were measured by polarized Raman scattering in the insulating phases of S=1/2 copper oxides, ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.2}$, ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{0.5}$${\mathrm{Y}}_{0.5}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathit{y}}$, ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$, and...
We report 75As-NQR/NMR studies on the oxygen-deficient iron(Fe)-based oxypnictide superconductors LaFeAsO_{0.6} (T_c=28 K) along with results LaFeAsO, LaFeAsO_{0.75}(T_c=20 and NdFeAsO_{0.6}(T_c=53 K). Nuclear spin-lattice relaxation rate 1/T_1 of 75As NQR at zero field has revealed a T^3 dependence below T_c upon cooling without coherence peak just T_c, evidencing unconventional superconducting state line-node gap. have found an intimate relationship between nuclear quadrupole frequencyof...
We report on a band structure calculation and de Haas–van Alphen measurements of KFe 2 As . Three cylindrical Fermi surfaces are found. Effective masses electrons range from 6 to 18 m e , being the free electron mass. Remarkable discrepancies between calculated observed surface areas large mass enhancement (\({\gtrsim}3\)) highlight importance electronic correlations in determining structures iron pnicitide superconductors.
We have succeeded in synthesizing single-phase polycrystalline samples of oxygen-deficient oxypnictide superconductors, Ln FeAsO 1- y ( : lanthanide elements) with = La, Ce, Pr, Nd, Sm, Gd, Tb, and Dy using high-pressure technique. It is found out that the synthesis pressure a key parameter for samples, particular heavier 's, such as Tb Dy. The lattice parameters systematically decrease atomic number , reflecting shrinkage ionic radius. For lighter 's (La, Nd), T c increases monotonously...
We report that the $(\mathrm{Ba},\mathrm{K}){\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ superconductor (transition temperature, ${T}_{c}\ensuremath{\sim}38\text{ }\text{ }\mathrm{K}$) has an inverse iron isotope coefficient ${\ensuremath{\alpha}}_{\mathrm{Fe}}=\ensuremath{-}0.18(3)$ (where ${T}_{c}\ensuremath{\sim}{M}^{\ensuremath{-}\ensuremath{\alpha}\mathrm{Fe}}$ and $M$ is mass); i.e., sample containing large mass depicts a higher ${T}_{c}$. Systematic shifts in ${T}_{c}$ were clearly observed...
We investigated the in-plane resistivity anisotropy for underdoped Ba(Fe(1-x)Co(x))(2)As(2) single crystals with improved quality. demonstrate that in magnetostructural ordered phase arises from residual component which increases proportion to Co concentration x. This gives evidence originates impurity scattering by atoms substituted Fe sites, rather than so far proposed mechanisms such as of Fermi velocities reconstructed surface pockets. As doping proceeds paramagnetic-tetragonal phase, a...
We have performed electrical resistivity measurements on single-crystal ${\text{BaFe}}_{2}{\text{As}}_{2}$ under high pressure $P$ up to 16 GPa with a cubic anvil apparatus, and 3 modified Bridgman cell. The samples were obtained from the same batch, which was grown self-flux method. A apparatus provides highly hydrostatic pressure, cell, contains liquid-pressure transmitting medium, quasihydrostatic pressure. For crystal phase magnetic-transition temperature decreases robustly disappears at...
We show that the Fermi surface (FS) in antiferromagnetic phase of ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ is composed one hole and two electron pockets, all which are three dimensional closed, sharp contrast to FS observed by angle-resolved photoemission spectroscopy. Considerations on carrier compensation Sommerfeld coefficient rule out existence unobserved pockets significant sizes. A standard band structure calculation reasonably accounts for FS, despite overestimated ordered moment. The...
We have determined the full magnetic dispersion relations of multiferroic ${\mathrm{BiFeO}}_{3}$. In particular, two excitation gaps originating from anisotropies been clearly observed. The direct observation enables us to accurately determine Dzyaloshinskii-Moriya (DM) interaction and single ion anisotropy. DM supports a sizable magnetoelectric coupling in this compound.
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...