A5007728432- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Magneto-Optical Properties and Applications
- Iron-based superconductors research
- Rare-earth and actinide compounds
- X-ray Spectroscopy and Fluorescence Analysis
- Magnetic Properties and Applications
- High-pressure geophysics and materials
- Transition Metal Oxide Nanomaterials
- Electron and X-Ray Spectroscopy Techniques
- Semiconductor materials and devices
- Advanced X-ray Imaging Techniques
- Advancements in Battery Materials
- Magnetic Properties of Alloys
- Crystallography and Radiation Phenomena
- Ferroelectric and Piezoelectric Materials
- 2D Materials and Applications
- Advanced Chemical Physics Studies
- ZnO doping and properties
- X-ray Diffraction in Crystallography
- Semiconductor materials and interfaces
University of Hyogo
2019-2025
Osaka University
2021-2024
SPring-8
2024
Institute for Laser Technology
2023-2024
The University of Tokyo
2013-2022
Kyoto Bunkyo University
2021
Kyoto University
2021
Tohoku University
2021
High Energy Accelerator Research Organization
2021
International Summer School of Photography
2017-2019
We demonstrate a method of x-ray absorption spectroscopy (XAS) that is bulk sensitive, like traditional fluorescence yield measurements, but not affected by self-absorption or saturation effects. This measure XAS achieved scanning the incident photon energy through an edge and using energy-sensitive detector to partial (PFY). The emission from any element core-hole excitation resonant with under investigation selected PFY. It found inverse this PFY spectrum, which we term (IPFY), linearly...
In 5d Ir oxides with an interplay of spin-orbit coupling and electron correlations, we have tailored a spin-orbital magnetic insulator out semimetal SrIrO(3) by tuning the structure through superlattices [(SrIrO(3))(m), SrTiO(3)] (m=1,2,3,4, ∞). We observed systematic decrease ordering temperature resistivity as function m. The transition from to is found be closely linked appearance magnetism at m≃3. Long range was realized even in m=1 single layer superlattice, implying that design...
The fundamental electronic structure of the widely used battery material ${\mathrm{Li}}_{x}{\mathrm{CoO}}_{2}$ still remains a mystery. Soft x-ray absorption spectroscopy reveals that holes with strong O $2p$ character play an essential role in conductivity ${\mathrm{Co}}^{3+}/{\mathrm{Co}}^{4+}$ mixed valence ${\mathrm{CoO}}_{2}$ layer. oxygen are bound to ${\mathrm{Co}}^{4+}$ sites and Li-ion vacancy, suggesting flow can be stabilized by hole back flow. Such state is unique among various...
Transition-metal substitution in Fe pnictides leading to superconductivity is usually interpreted terms of carrier doping the system. We report on a density functional calculation local substitute electron and demonstrate that substitutions like Co Ni for do not dope but rather are isovalent Fe. find extra $d$ electrons almost totally located within muffin-tin sphere substituted site. suggest act more random scatterers scrambling momentum space washing out parts Fermi surface.
We have studied the electronic structure of epitaxially grown thin films La$_{1-x}$Sr$_x$FeO$_3$ by {\it in-situ} photoemission spectroscopy (PES) and x-ray absorption (XAS) measurements. The Fe 2$p$ valence-band PES spectra O $1s$ XAS LaFeO$_3$ been successfully reproduced configuration-interaction cluster-model calculation and, except for satellite structure, band-structure calculation.From shift binding energies core levels, chemical potential was found to be shifted downward as $x$...
Resonant soft X-ray scattering with photon energies near the O K and Cu L3 edges was used to study charge ordering in system La_{1.8-x}Eu_{0.2}Sr_xCuO_4 as a function of temperature for x = 0.125 0.15. From superstructure diffraction intensities doping dependent wave vector is derived which this well below transition low-temperature tetragonal phase but above onset spin ordering. This indicates that primary driving force formation stripe-like phases two-dimensional doped cuprates. Analysis...
The discoveries of intrinsic ferromagnetism in atomically-thin van der Waals crystals have opened up a new research field enabling fundamental studies on magnetism at two-dimensional (2D) limit as well development magnetic heterostructures. To date, variety 2D has been explored mainly by mechanically exfoliating 'originally ferromagnetic (FM)' crystals, while bottom-up approach thin film growth technique demonstrated emergent non-FM' materials. Here we demonstrate that V5Se8 epitaxial films...
In a conventional magnetic material, long-range order develops in three dimensions, and reducing layer number weakens its magnetism. Here we demonstrate anomalous layer-number-independent ferromagnetism down to the two-dimensional (2D) limit metastable phase of Cr3Te4. We fabricated Cr3Te4 thin films by molecular-beam epitaxy found that could host two distinct ferromagnetic phases characterized with different Curie temperatures (TC). One is bulk-like "high-TC phase" showing room-temperature...
We have made a detailed temperature-dependent photoemission study of ${\mathrm{VO}}_{2}/{\mathrm{TiO}}_{2}(001)$ thin films, which show metal-insulator transition at \ensuremath{\sim}300 K. Clean surfaces were obtained by annealing the films in an oxygen atmosphere. Spectral weight transfer between coherent and incoherent parts accompanying was clearly observed. also observed hysteretic behavior spectra for heating-cooling cycles. derived ``bulk'' spectrum metallic phase found that it has...
We have measured photoemission spectra of SrTiO3/LaTiO3 superlattices with a topmost SrTiO3 layer variable thickness. A finite coherent spectral weight clear Fermi cutoff was observed at chemically abrupt interfaces, indicating that an "electronic reconstruction" occurs the interface between Mott insulator LaTiO3 and band SrTiO3. For interfaces annealed high temperatures (approximately 1000 degrees C), which leads to Sr/La atomic interdiffusion hence formation La(1-x)Sr(x)TiO3-like material,...
We have performed an angle-resolved photoemission spectroscopy study of ${\text{SrVO}}_{3}$ thin films. Utilizing films prepared in situ, with well-defined and atomically flat surfaces, contributions from surface states centered at $\ensuremath{\sim}\ensuremath{-}1.5\text{ }\text{eV}$ were dramatically reduced, enabling us to the bulklike $\text{V}\text{ }3d$ states, including incoherent part. A clear band dispersion is observed not only coherent part but also spectral weight larger within...
We investigated the magnetic structure of an orthorhombic YMnO(3) thin film by resonant soft x-ray and hard diffraction. observed a temperature-dependent incommensurate reflection below 45 K commensurate lattice-distortion 35 K. These results demonstrate that ground state is composed coexisting E-type cycloidal states. Their different ordering temperatures clarify origin large polarization to be caused antiferromagnetic states in film.
We report magnetotransport properties for epitaxial thin films of SrFeO${}_{3}$ and SrFe${}_{0.99}$Co${}_{0.01}$O${}_{3}$ with possible skyrmion-related spin textures. Resonant soft x-ray diffraction measurements revealed formation helical structures both samples ($Q//\ensuremath{\langle}111\ensuremath{\rangle}$). From we found several distinct helimagnetic phases multiple/single $Q$ vectors. A steep suppression Hall resistivity is observed above the critical field to reach high-field...
Effects of electron doping on the BiS$_2$-based superconductors Sr$_{1-x}$La$_x$FBiS$_2$ ($0\le x\le 0.6$) have been investigated using systematically synthesized polycrystals. The pristine compound is a band insulator with BiS$_2$ layer, which accommodates carriers through La substitution for Sr, as evidenced by change in x-ray absorption spectra reflecting occupancy Bi 6$p$ orbitals. With increasing carrier density, resistivity progressively decreases and bad metallic state appears...
We evaluate the utilities of fluorescence-yield (FY) modes in soft X-ray absorption spectroscopy (XAS) several cathode materials for Li-ion batteries. In case total-FY (TFY) XAS LiNi0.5Mn1.5O4, line shape Mn L3-edge was largely distorted by self-absorption and saturation effects, while distortions were less pronounced at Ni L3 edge. The suppressed inverse-partial-FY (IPFY) spectra. found that, materials, IPFY is highly effective Cr, Mn, Fe L edges TFY PFY are useful enough edge which far from O K
We investigate near-Fermi-energy (${E}_{F}$) element-specific electronic and spin states of ferromagnetic van der Waals (vdW) metal ${\mathrm{Fe}}_{5}\mathrm{Ge}{\mathrm{Te}}_{2}$. The soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) measurement provides spectroscopic evidence localized Fe $3d$ band. also find prominent hybridization between the band delocalized Ge/Te $p$ bands. This picture is strongly supported from direct observation remarkable polarization ligand bands...
The role of Co substitution in the low-energy electronic structure $\mathrm{Ca}({\mathrm{Fe}}_{0.944}{\mathrm{Co}}_{0.056}{)}_{2}{\mathrm{As}}_{2}$ is investigated by resonant photoemission spectroscopy and density-functional theory. $3d$ state center mass observed at 250 meV higher binding energy than that Fe, indicating possesses one extra valence electron Fe are same oxidation state. Yet, significant character detected for Bloch wave functions chemical potential, revealing electrons part...
We investigate the electronic structure of a perovskite-type Pauli paramagnet ${\mathrm{SrMoO}}_{3}$ (${{t}_{2g}}^{2}$) thin film using hard x-ray photoemission spectroscopy and compare results to realistic calculations that combine density functional theory within local-density approximation (LDA) with dynamical mean-field (DMFT). Despite clear signature electron correlations in specific heat, narrowing quasiparticle bands is not observed spectrum. This explained terms characteristic effect...
Static charge-density wave (CDW) and spin-density (SDW) order has been convincingly observed in La-based cuprates for some time. However, more recently it suggested by quantum oscillation, transport thermodynamic measurements that density is generic to underdoped plays a significant role YBa_2Cu_3O_{6+delta} (YBCO). We use resonant soft x-ray scattering at the Cu L O K edges search evidence of Ortho-II Ortho-VIII oxygen-ordered YBCO. report null result -- no static CDW both ordered While...
We investigated the electronic and magnetic properties of fully oxidized ${\mathrm{BaFeO}}_{3}$ thin films, which show ferromagnetic-insulating with cubic crystal structure, by hard x-ray photoemission spectroscopy (HAXPES), absorption (XAS), soft circular dichroism (XMCD). analyzed results configuration-interaction (CI) cluster-model calculations for ${\mathrm{Fe}}^{4+}$, showed good agreement experimental results. also studied ${\mathrm{SrFeO}}_{3}$ have an ${\mathrm{Fe}}^{4+}$ ion helical...
The spin states of ${\mathrm{Co}}^{3+}$ ions in perovskite-type ${\mathrm{LaCoO}}_{3}$, governed by the complex interplay between electron-lattice interactions and strong electron correlations, still remain controversial due to lack experimental techniques which can directly detect them. In this Letter, we revealed tensile-strain dependence states, i.e., ratio high- low-spin epitaxial thin films a bulk crystal ${\mathrm{LaCoO}}_{3}$ via resonant inelastic soft x-ray scattering. A tensile...
Abstract Here, an unprecedented phenomenon in which 7‐coordinate lanthanide metallomesogens, align via hydrogen bonds mediated by coordinated H 2 O molecules, form micellar cubic mesophases at room temperature, creating body‐centered (BCC)‐type supramolecular spherical arrays, is reported. The results of experiments and molecular dynamics simulations reveal that assemblies three complexes surrounded amorphous alkyl domain spontaneously energetically stable orientation to the BCC structure....
Within a homologous series of cuprate superconductors, variations in the stacking CuO$_2$ layers influence collective charge dynamics through long-range Coulomb interactions. We use O $K$-edge resonant inelastic x-ray scattering to reveal plasmon excitations optimally-doped trilayer Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$. The observed exhibits nearly $q_z$-independent dispersion and large excitation gap approximately 300 meV. This mode is primarily ascribed $\omega_{-}$ mode, where density...
The crystal structure of La4Ge3S12 has been known to be noncentrosymmetric for almost four decades. This characteristic inversion symmetry breaking suggests the presence nonlinear optical (NLO) properties. Yet, experimental observations such phenomena, including second harmonic generation (SHG) have reported only in recent studies. In this study, we synthesized using one‐step melting method, which is more straightforward than conventional two‐step growth method. We characterized composition,...