A5091816472- Magnetic and transport properties of perovskites and related materials
- Thermal Expansion and Ionic Conductivity
- Advanced Condensed Matter Physics
- Ferroelectric and Piezoelectric Materials
- Physics of Superconductivity and Magnetism
- Advanced Battery Materials and Technologies
- Rare-earth and actinide compounds
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Iron-based superconductors research
- Multiferroics and related materials
- Topological Materials and Phenomena
- Microwave Dielectric Ceramics Synthesis
- Shape Memory Alloy Transformations
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Superconductivity in MgB2 and Alloys
- Advanced Thermoelectric Materials and Devices
- Magnesium Oxide Properties and Applications
- Crystallography and molecular interactions
- Inorganic Chemistry and Materials
- 2D Materials and Applications
- Superconducting Materials and Applications
- Heusler alloys: electronic and magnetic properties
- Thermal properties of materials
Nagoya University
2016-2025
Japan Science and Technology Agency
2005-2011
Suzuki (Japan)
2011
Japan Synchrotron Radiation Research Institute
2011
RIKEN
2004-2010
National Institute for Materials Science
2010
Sophia University
2008-2009
RIKEN Advanced Science Institute
2005-2009
Nippon Soken (Japan)
2007
Institute of Physical and Organic Chemistry
2006
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...
We report the discovery of a large negative thermal expansion (NTE) up to α=−25×10−6K−1 (α: coefficient linear expansion) in Ge-doped anti-perovskite manganese nitrides Mn3AN (A=Cu,Zn,Ga). This gigantic NTE is several ten times higher than that commercially available materials. The discontinuous lattice seen pure broadened by Ge substitution over wide temperature window, at widest ΔT∼100K, around room temperature. Such large, isotropic and nonhysteretic desirable for practical applications.
The experimental results are presented on the in-plane resistivity for Zn-substituted single crystals of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$ and ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ with various hole densities. primary effect Zn is to produce a large residual ( ${\ensuremath{\rho}}_{0}$) as potential scatterer in unitarity limit. In underdoped regime, due also low carrier density ${\mathrm{CuO}}_{2}$ plane, only few percent...
We have investigated the anisotropic resistivities of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$ using detwinned crystals with various oxygen contents (6.68 \ensuremath{\le}7-y\ensuremath{\le} 6.93). The out-of-plane resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$ shows a crossover from high-T metallic to low-T semiconducting behavior while in-plane ${\mathrm{\ensuremath{\rho}}}_{\mathit{a}}$ deviates in region T-linear dependence. find...
Giant negative thermal expansion (NTE) recently discovered in antiperovskite manganese nitrides Mn3AN (A=Zn,Ga, etc.) is achieved by doping Ge on A as “relaxant” of the sharp volume change at magnetic transition. To promote wider applications, we synthesized NTE antiperovskites without expensive Ge. We that Sn broadens change, though less effective than Simultaneous substitution for and C N expands operation-temperature window almost broad Ge-doped counterpart. discuss relation between...
Discovery of large magnetostriction in an antiperovskite Mn3CuN is reported. undergoes the first-order transition from high-temperature (high-T) paramagnetic to low-temperature ferromagnetic (FM) phase at Curie temperature TC=143K, accompanied by cubic-to-tetragonal structural deformation. In tetragonally distorted FM phase, Mn3CuN, even a polycrystalline form, expands 0.2% and shrinks 0.1% direction parallel perpendicular external field 90kOe, respectively. This possibly due rearrangement...
The absence of resistivity saturation in many strongly correlated metals, including the high-temperature superconductors, is critically examined from viewpoint optical conductivity measurements. Coherent quasiparticle conductivity, form a Drude peak centred at zero frequency, found to disappear as mean free path (at $\omega$ = 0) becomes comparable interatomic spacing. This basic loss coherence so-called Mott-Ioffe-Regel (MIR) limit suggests that universality MIR criterion preserved even...
Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering broadened by substitution. In this Letter, we address unique role of ``magic'' element, Ge, for such broadening ${\mathrm{Mn}}_{3}{\mathrm{Cu}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}\mathrm{N}$. We present evidence a local lattice distortion well described low-temperature tetragonal (${T}_{4}$) structure ${\mathrm{Mn}}_{3}\mathrm{GeN}$ range $x$, where...
Abstract Large negative thermal expansion (NTE) has been discovered during the last decade in materials of various kinds, particularly associated with a magnetic, ferroelectric or charge-transfer phase transition. Such NTE have attracted considerable attention for use as thermal-expansion compensators. Here, we report discovery giant reduced layered ruthenate. The total volume change related to reaches 6.7% dilatometry, value twice large largest reported date. We observed coefficient linear...
A zero thermal expansion material in a pure form is fabricated using an antiperovskite manganese nitride. The isotropic achieved by optimizing the heat treatment and chemical composition. present study suggests that affects mainly via nitrogen content of material. obtained materials exhibit low |α|<0.5×10−6 K−1 (α coefficient linear expansion) over broad temperature range, which includes room temperature. They are desirable for many fields industry as reliable, mechanically hard,...
Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1−xAxN (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb). This class of is attracting great attention because their giant negative thermal expansion, which achieved by doping Ge into the A site as a relaxant sharp volume contraction on heating (spontaneous magnetostriction ωs) magnetovolume effects. The physical background large ωs mechanism how...
One of key challenges in current material research is to search for new topological materials with inverted bulk-band structure. In insulators, the band inversion caused by strong spin-orbit coupling leads opening a gap entire Brillouin zone, whereas an additional crystal symmetry such as point-group and nonsymmorphic symmetries sometimes prohibits at/on specific points or line momentum space, giving rise semimetals. Despite many theoretical predictions insulators/semimetals associated...
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...
Magnetic structures in an antiperovskite system, ${\mathrm{Mn}}_{3}{\mathrm{Cu}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}\mathrm{N}$, with a large magnetovolume effect above $x=0.15$ have been studied by neutron powder diffraction measurement. The present study revealed that not only cubic crystal structure but also ${\ensuremath{\Gamma}}^{5g}$ antiferromagnetic spin are key ingredients of the this itinerant electron system. is possibly ascribed to geometrical frustration originating from...
Electrical resistivity is systematically investigated in Mn3AgN and related compounds with an antiperovskite structure. Despite its overall metallic character, features a broad maximum the temperature-resistivity curve paramagnetic state temperature coefficient of resistance (TCR) negative at higher temperatures. The resistivity-peak was tuned to just room by partial substitution Cu for Ag, TCR as low 10−6 K−1 achieved over wide window including temperature. These peculiar behaviors are...
We constructed a composition–temperature phase diagram for Cu1.8Zn0.2V2–xPxO7 based on structural analysis conducted using synchrotron radiation over the entire compositional range and wide temperature (110–760 K) range. As x increases, structure changes from β-Cu2V2O7 (C2/c) to α-Cu2P2O7 (C2/c), then β-Cu2P2O7 (C2/m). Accordingly, crystallographic negative thermal expansion (NTE) weakens, especially in structure, but it never disappears completely. also discovered that = 0.75–1.0,...
Giant negative thermal expansion (NTE), over α = −30 × 10−6 K−1 (α: coefficient of linear expansion), at room temperature can be achieved in Mn3ZnN-based antiperovskite manganese nitrides by simultaneous substitution C and B for N as well Sn Zn. The developed NTE show larger α, although the width operating-temperature window is comparable to that Mn3CuN-based materials date. Such a large, isotropic, high-stiffness material compensate large positive of, example, even aluminum or plastic materials.
We investigate the electronic structure of chromium nitride (CrN) across first-order magnetostructural transition at ${T}_{N}\ensuremath{\sim}286\text{ }\text{ }\mathrm{K}$. Resonant photoemission spectroscopy (PES) shows a gap in $3d$ partial density states Fermi level and an on-site Coulomb energy $U\ensuremath{\sim}4.5\text{ }\mathrm{eV}$, indicating strong electron-electron correlations. Bulk-sensitive high-resolution (6 meV) laser PES reveals clear edge antiferromagnetic metal below...
We controlled thermal expansion of metal matrix composites (MMCs) that had been blended using antiperovskite manganese nitrides with giant negative (NTE). The NTE the nitrides, which is isotopic, greater than −30 ppm K−1 in α (coefficient linear expansion), several or ten times as large conventional materials. These advantages are desirable for practical application a thermal-expansion compensator, can suppress various materials including metals and even plastics. Powder metallurgy pulsed...
We elucidate the transport properties and electronic structures of distorted rutile-type WO2. Electrical resistivity Hall effect measurements high-quality single crystals revealed property characteristics topological materials; these included an extremely large magnetoresistance 13 200% (2 K 9 T) a very high carrier mobility 25 700 cm2 V−1 s−1 (5 K). First-principles calculations Dirac nodal lines (DNLs) near Fermi energy in structure when spin–orbit interactions (SOIs) were absent. Although...