A5054430046- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Multiferroics and related materials
- Advanced Chemical Physics Studies
- Physics of Superconductivity and Magnetism
- ZnO doping and properties
- Iron-based superconductors research
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Magnetic Properties and Synthesis of Ferrites
- Magnetic Properties of Alloys
- Electron and X-Ray Spectroscopy Techniques
- Transition Metal Oxide Nanomaterials
- Copper-based nanomaterials and applications
- Inorganic Chemistry and Materials
- Iron oxide chemistry and applications
- X-ray Spectroscopy and Fluorescence Analysis
- Heusler alloys: electronic and magnetic properties
- Chalcogenide Semiconductor Thin Films
- Ga2O3 and related materials
- Atomic and Molecular Physics
- Ferroelectric and Piezoelectric Materials
- Magnetism in coordination complexes
- 2D Materials and Applications
Hiroshima University
2015-2024
Osaka University
1992-2018
University of Hyogo
2018
Hiroshima University of Economics
2009
National Institute of Technology, Kure College
2005
National Institute for Materials Science
1999
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-${L}_{2,3}$ edge, we reveal that spin state transition in ${\mathrm{LaCoO}}_{3}$ can be well described by a low-spin ground triply degenerate high-spin first excited state. From temperature dependence of spectral line shapes, find finite temperatures is an inhomogeneous mixed-spin system. It crucial signal paramagnetic carries large orbital momentum. This directly shows currently accepted low- or...
We found direct experimental evidence for an orbital switching in the V $3d$ states across metal-insulator transition ${\mathrm{VO}}_{2}$. have used soft-x-ray absorption spectroscopy at ${L}_{2,3}$ edges as a sensitive local probe and determined quantitatively polarizations. These results strongly suggest that, going from metallic to insulating state, occupation changes manner that charge fluctuations effective bandwidths are reduced, system becomes more one dimensional susceptible...
We report direct experimental evidence for a room-temperature, $\ensuremath{\sim}130\text{ }\text{ }\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}^{2}$ ferroelectric polarization from the tetragonal-like ${\mathrm{BiFeO}}_{3}$ phase. The physical origin of this remarkable enhancement has been investigated by combination x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to oxygen...
We present calculated 3 d , p and s resonant photoemission (RPE) spectra in the transition metal (TM) compounds CuO, NiO, CoO, FeO, MnO TiO 2 at TM core threshold on basis of a cluster model. Our model includes intraatomic multipole electron-electron interactions hybridization between ions ligand. The imaginary part self-energy matrix intermediate state is by taking into account Coster-Kronig decay, which guarantees sum rule integrated RPE absorption spectra. dependence incident photon...
A gradual spin-state transition occurs in ${\mathrm{LaCoO}}_{3}$ around $T\ensuremath{\sim}80--120\text{ }\text{ }\mathrm{K}$, whose detailed nature remains controversial. We studied this by means of inelastic neutron scattering and found that with increasing temperature an excitation at $\ensuremath{\sim}0.6\text{ }\mathrm{meV}$ appears, intensity increases temperature, following the bulk magnetization. Within a model including crystal-field interaction spin-orbit coupling, we interpret as...
A deviation from the X-ray magnetic circular dichroism (MCD) spin sum rule, which is derived assuming well separated core spin-orbit multiplets in final state of absorption, calculated for L 2,3 edge magnetized Ni, Co, Fe and Mn ions on basis an atomic model including full multiplet crystal field with O h symmetry. Due to Coulomb interaction between electrons, mixes so-called 3 2 regions each other, it found that can be ∼10 percent former three ions, while 2+ amounts more than 30 percent....
We have investigated the valence, spin, and orbital state of Co ions in one-dimensional cobaltate Ca3Co2O6 using x-ray absorption magnetic circular dichroism at Co-L2,3 edges. The both octahedral Co_oct trigonal Co_trig sites are found to be a 3+ state. From analysis we established low-spin for high-spin with an anomalously large moment 1.7 muB Co3+ trig ions. This along c-axis chain unusually magnetocrystalline anisotropy can traced back double occupancy d2 crystal field.
Using soft-x-ray absorption spectroscopy at the Co L(2,3) and O K edges, we demonstrate that Co3+ ions with CoO5 pyramidal coordination in layered Sr2CoO3Cl compound are unambiguously high spin state. Our result questions reliability of state assignments made so far for recently synthesized cobalt perovskites calls a reexamination modeling complex fascinating properties these new materials.
We have studied the local electronic structure of $\mathrm{La}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$ using soft-x-ray absorption spectroscopy at $\mathrm{Co}\text{\ensuremath{-}}{L}_{3,2}$ and $\mathrm{Mn}\text{\ensuremath{-}}{L}_{3,2}$ edges. found a high-spin ${\mathrm{Co}}^{2+}\text{\ensuremath{-}}{\mathrm{Mn}}^{4+}$ valence state for samples with optimal Curie temperature. discovered that lower temperatures contain low-spin nonmagnetic ${\mathrm{Co}}^{3+}$ ions. Using...
Using Co-L2,3 and O-K x-ray absorption spectroscopy, we reveal that the charge ordering in La1.5Sr0.5CoO4 involves high spin (S=3/2) Co2+ low (S=0) Co3+ ions. This provides evidence for spin-blockade phenomenon as a source extremely insulating nature of La2-xSrxCoO4 series. The associated e{g}{2} e{g}{0} orbital occupation accounts large contrast Co-O bond lengths and, turn, temperature. Yet, magnetic temperature is naturally explained by presence nonmagnetic From identification bands infer...
The complex metal oxide SrCo0.5Ru0.5O(3-δ) possesses a slightly distorted perovskite crystal structure. Its insulating nature infers well-defined charge distribution, and the six-fold coordinated transition metals have oxidation states +5 for ruthenium +3 cobalt as observed by X-ray spectroscopy. We discovered that Co(3+) ion is purely high-spin at room temperature, which unique in an octahedral oxygen surrounding. attribute this to field interaction being weaker than Hund's-rule exchange...
The strong coupling between antiferromagnetism and ferroelectricity at room temperature found in BiFeO3 generates high expectations for the design development of technological devices with novel functionalities. However, multi-domain nature material tends to nullify properties interest complicates thorough understanding mechanisms that are responsible those properties. Here we report realization a thin film form single-domain behaviour both its magnetism ferroelectricity: entire shows...
This review provides an overview of the different methods and computer codes that are used to interpret 2p x-ray absorption spectra 3d transition metal ions. We first introduce basic parameters give used. start with semi-empirical multiplet compare available. A special chapter is devoted user friendly interfaces have been written on basis these codes. Next we discuss principle based band structure, including a Density Functional theory approaches. also first-principle from cluster...
We report on the results of x-ray absorption (XAS), magnetic circular dichroism (XMCD), and photoemission experiments {\it n}-type Zn$_{1-x}$Co$_x$O ($x=0.05$) thin film, which shows ferromagnetism at room temperature. The XMCD spectra show a multiplet structure, characteristic Co$^{2+}$ ion tetrahedrally coordinated by oxygen, suggesting that comes from Co ions substituting Zn site in ZnO. field temperature dependences imply non-ferromagnetic are strongly coupled antiferromagnetically with...
The origin of both the Ising chain magnetism and ferroelectricity in ${\mathrm{Ca}}_{3}{\mathrm{CoMnO}}_{6}$ is studied by ab initio electronic structure calculations x-ray absorption spectroscopy. We find that has alternate trigonal prismatic ${\mathrm{Co}}^{2+}$ octahedral ${\mathrm{Mn}}^{4+}$ sites spin chain. Both are high-spin state. In addition, a huge orbital moment $1.7{\ensuremath{\mu}}_{B}$ which responsible for significant magnetism. centrosymmetric crystal known so far calculated...
We investigated electronic structure of hexagonal multiferroic YMnO3 using the polarization dependent x-ray absorption spectroscopy (XAS) at O K and Mn L(2,3) edges. The spectra exhibit strong dependence both edges, reflecting anisotropic 3d orbital occupation. Moreover, edge show that Y 4d states are strongly hybridized with 2p ones, resulting in large anomalies Born effective charges on off-centering ions. These results manifest d(0)-ness rehybridization is driving force for...
We present a combined experimental and theoretical x-ray absorption spectroscopy study of the class cobaltates ${\text{YBaCo}}_{4}{\text{O}}_{7}$ ${\text{YBaCo}}_{3}M{\text{O}}_{7}$ $(M=\text{Al},\text{ }\text{Fe})$. The focus is on local electronic magnetic properties transition metal ions in these geometrically frustrated kagom\'e compounds. For mixed valence cobaltate ${\text{YBaCo}}_{4}{\text{O}}_{7}$, both ${\text{Co}}^{2+}$ ${\text{Co}}^{3+}$ are found to be high-spin state. stability...
By using x-ray absorption spectroscopy at the $\text{Rh}\text{ }{L}_{2,3}$, $\text{Co}\text{ and $\text{Fe}\text{ }{L}_{2,3}$ edges, we find a valence state of ${\text{Co}}^{2+}/{\text{Rh}}^{4+}$ in ${\text{Ca}}_{3}{\text{CoRhO}}_{6}$ ${\text{Fe}}^{3+}/{\text{Rh}}^{3+}$ ${\text{Ca}}_{3}{\text{FeRhO}}_{6}$. X-ray magnetic circular dichroism edge reveals giant orbital moment about $1.7{\ensuremath{\mu}}_{B}$, which can be attributed to occupation minority-spin ${d}_{0}{d}_{2}$ high-spin...
We investigated the magnetic nature of ${\mathrm{Fe}}_{1/4}{\mathrm{TaS}}_{2}$ using x-ray absorption spectroscopy, photoemission and first principles band calculations. The results show a large unquenched orbital moment ($\ensuremath{\sim}1.0\text{ }\text{ }{\ensuremath{\mu}}_{B}/\mathrm{Fe}$) at intercalated Fe sites, resulting in gigantic anisotropy (${H}_{A}\ensuremath{\simeq}60\text{ }\mathrm{T}$). coupling is well understood terms Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction,...
Significance The ground state of materials with strong electronic correlations depends on a delicate balance among competing interactions. strongly correlated compounds Ce M In 5 , = Co, Rh, and Ir, exhibit superconducting magnetic states as well Fermi surface changes upon substituting one element for another become even higher temperature superconductors when is substituted by Pu. They are therefore recognized important model systems in which search parameters correlating the occurrence...
We have studied the electronic structure of BaCoO$_3$ using soft x-ray absorption spectroscopy at Co-$L_{2,3}$ and O-$K$ edges, magnetic circular dichroism as well valence band hard photoelectron spectroscopy. The quantitative analysis spectra established that Co ions are in formal low-spin tetravalent 3$d^5$ state system is a negative charge transfer Mott insulator. spin-orbit coupling plays also an important role for magnetism system. At same time, trigonal crystal field present with...
The role of transition-metal d and ligand p hybridization continues to be immense interest in Li-ion battery cathode, yet it is still poorly understood. Using combined experimental theoretical soft X-ray absorption spectroscopic study density functional theory calculation, we investigated the fundamental electronic structure high-voltage spinel LiNixMn2–xO4. An oxygen-participating charge rebalance between manganese nickel ions was found; that is, content O 2p holes close Fermi level...
We investigated the influence of interface orientation on magnetic coupling for (110), (001), and (111) interfaces epitaxial NiO thin films single-crystal ${\text{Fe}}_{3}{\text{O}}_{4}$. In our analysis, we combine x-ray spectroscopies with circularly linearly polarized light, i.e., circular linear dichroism (XMCD XMLD). A full treatment anisotropic XMLD in single-crystalline materials backed by theoretical support allows a reliable vectorial magnetometry. Both (110) produce collinear...
In a recent publication Larson et al. reported remarkably clear $d\mathrm{\text{\ensuremath{-}}}d$ excitations for NiO and CoO with x-ray scattering. Here we present an accurate quantitative description based on local many body approach, beyond density approximation $+$ Hubbard U approximations. The magnitude of $\stackrel{\ensuremath{\rightarrow}}{q}$ determines which the allowed multipoles contributes most to spectra. direction respect crystal can be used as equivalent polarization similar...