Spin-1/2 kagome compounds: volborthite vs herbertsmithite (2008)
Hiroi, Z, Yoshida, H, Okamoto, Y, Takigawa, M
Two kagome compounds, volborthite Cu3V2O7(OH)2-2H2O and herbertsmithite ZnCu3(OH)6Cl2, are compared in order to derive information about the intrinsic properties of the spin-1/2 kagome...
Just a brief comment on the chemical formulae of the rare earth iron arsenide oxide superconductors
Shibauchi, T., Konczykowski, M., Van Der Beek, C. J., Okazaki, R., Matsuda, Y., Yamaura, J., ...
A miniature Hall sensor array was used to detect magnetic induction locally in the vortex states of the $\beta$-pyrochlore superconductor KOs$_2$O$_6$. Below the first-order transition at $T_{\rm...
Superconductivity in Rh$_2$Ga$_9$ and Ir$_2$Ga$_9$ without Inversion Symmetry (2007)
Shibayama, T., Nohara, M., Katori, H. Aruga, Okamoto, Y., Hiroi, Z., Takagi, H.
Superconductivity with $T_{\rm c}$ $\simeq$ 2 K was discovered in the intermetallic binary compounds Rh$_2$Ga$_9$ and Ir$_2$Ga$_9$. This is the first observation of superconductivity in the Rh-Ga and...
Shimono, Y., Shibauchi, T., Kasahara, Y., Kato, T., Hashimoto, K., Matsuda, Y., ...
Microwave penetration depth $\lambda$ and surface resistance at 27 GHz are measured in high quality crystals of KOs$_2$O$_6$. Firm evidence for fully-gapped superconductivity is provided from...
Hiroi, Z., Yonezawa, S., Nagao, Y., Yamaura, J.
Superconducting and normal-state properties of the beta-pyrochlore oxide KOs2O6 are studied by means of thermodynamic and transport measurements. It is shown that the superconductivity is of...
Koda, A., Kadono, R., Ohishi, K., Saha, S. R., Higemoto, W., Yonezawa, S., ...
We report on the muon spin rotation/relaxation study of a pyrochlore oxide, Cd2Os2O7, which exhibits a metal-insulator (MI) transition at T_{MI}~225 K without structural phase transition. It reveals...
Tabata, Y., Kadowaki, H., Matsuhira, K., Hiroi, Z., Aso, N., Ressouche, E., ...
We have investigated the kagom\'{e} ice state in the frustrated pyrochlore oxide Dy_{2}Ti_{2}O_{7} under magnetic field along a [111] axis. Spin correlations have been measured by neutron scattering...
Photoemission study of TiO2/VO2 interfaces (2006)
Maekawa, K., Takizawa, M., Wadati, H., Yoshida, T., Fujimori, A., Kumigashira, H., ...
We have measured photoemission spectra of two kinds of TiO$_2$-capped VO$_2$ thin films, namely, that with rutile-type TiO$_2$ (r-TiO$_2$/VO$_2$) and that with amorphous TiO$_2$ (a-TiO$_2$/VO$_2$)...
NMR Observation of Rattling Phonons in the Pyrochlore Superconductor KOs2O6 (2006)
Yoshida, M., Arai, K., Kaido, R., Takigawa, M., Yonezawa, S., Muraoka, Y., ...
We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of electric field gradient,...
Kagom\'{e} ice state in the dipolar spin ice Dy_{2}Ti_{2}O_{7} (2006)
Tabata, Y., Kadowaki, H., Matsuhira, K., Hiroi, Z., Aso, N., Ressouche, E., ...
We have investigated the kagom\'{e} ice behavior of the dipolar spin-ice compound Dy_{2}Ti_{2}O_{7} in magnetic field along a [111] direction using neutron scattering and Monte Carlo simulations. The...
Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO$_2$ (2006)
Eguchi, R., Taguchi, M., Matsunami, M., Horiba, K., Yamamoto, K., Ishida, Y., ...
The temperature ($T$) dependent metal-insulator transition (MIT) in VO$_2$ is investigated using bulk sensitive hard x-ray ($\sim$ 8 keV) valence band, core level, and V 2$p-3d$ resonant...
A second phase transition and superconductivity in the beta-pyrochlore oxide KOs2O6 (2006)
Hiroi, Z, Yonezawa, S, Yamaura, J
Another phase transition that is probably of first order is found in the beta-pyrochlore oxide superconductor KOs2O6 with a superconducting transition temperature Tc of 9.6 K. It takes place at...
Incommensurate magnetic order in Ag$_{2}$NiO$_{2}$ (2006)
Sugiyama, J., Ikedo, Y., Mukai, K., Brewer, J. H., Ansaldo, E. J., Morris, G. D., ...
The nature of the magnetic transition of the half-filled triangular antiferromagnet Ag$_{2}$NiO$_2$ with $T_{\rm N}$=56K was studied with positive muon-spin-rotation and relaxation ($\mu^+$SR)...
Okazaki, K., Sugai, S., Muraoka, Y., Hiroi, Z.
We have investigated the charge dynamics of VO_2 by optical reflectivity measurements. Optical conductivity clearly shows a metal-insulator transition. In the metallic phase, a broad Drude-like...
Okazaki, K., Sugai, S., Muraoka, Y., Hiroi, Z.
We have investigated the charge dynamics of VO2 by optical reflectivity measurements. Optical conductivity clearly shows a metal-insulator transition. In the metallic phase, a broad Drude-like...
Uncommonly High Upper Critical Field in the Superconducting KOs$_2$O$_6$ Pyrochlore (2006)
Shibauchi, T., Krusin-Elbaum, L., Kasahara, Y., Shimono, Y., Matsuda, Y., McDonald, R. D., ...
The entire temperature dependence of the upper critical field $H_{\rm c2}$ in the $\beta$-pyrochlore KOs$_2$O$_6$ is obtained from high-field resistivity and magnetic measurements. Both techniques...
Kasahara, Y., Shimono, Y., Shibauchi, T., Matsuda, Y., Yonezawa, S., Muraoka, Y., ...
To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (Tc=9.6K), the thermal conductivity was measured down to low temperatures (~Tc/100). We...
Spin-1/2 triangular lattice with orbital degeneracy in a metallic oxide Ag2NiO2 (2006)
Yoshida, H., Muraoka, Y., Sörgel, T., Jansen, M., Hiroi, Z.
A metallic and magnetic transition metal oxide Ag2NiO2 is studied by means of resistivity, magnetic susceptibility, specific heat, and x-ray diffraction. The crystal structure is characterized by an...
Spin-1/2 Triangular Lattice with Orbital Degeneracy in a Metallic Oxide Ag2NiO2 (2005)
Yoshida, H., Muraoka, Y., Soergel, T., Jansen, M., Hiroi, Z.
A novel metallic and magnetic transition metal oxide Ag2NiO2 is studied by means of resistivity, magnetic susceptibility, specific heat and X-ray diffraction. The crystal structure is characterized...
High pressure effects on the superconductivity of beta-pyrochlore oxides AOs2O6 (2005)
Muramatsu, T., Takeshita, N., Terakura, C., Takagi, H., Tokura, Y., Yonezawa, S., ...
High pressure effects on the superconducting transitions of beta-pyrochlore superconductors AOs2O6 (A = Cs, Rb, K) are studied by measuring resistivity under high pressures up to 10 GPa. The...
39K and 87Rb Nuclear Magnetic Resonance in the Pyrochlore Superconductors AOs2O6 (A=K, Rb) (2004)
Arai, K., Kikuchi, J., Kodama, K., Takigawa, M., Yonezawa, S., Muraoka, Y., ...
This paper has been withdrawn by the authors, since a crucial assumption in the analysis of the data was found to be incorrect from the later experiments.
Sampathkumaran, E. V., Hiroi, Z., Rayaprol, S., Uwatoko, Y.
Heat-capacity behavior in the presence of externally applied magnetic field (H) up to 140 kOe is investigated (2-35 K) for the quasi-1-dimensional compound, Ca3Co2O6, believed to order magnetically...
New Pyrochlore Oxide Superconductor RbOs2O6 (2004)
Yonezawa, S., Muraoka, Y., Matsushita, Y., Hiroi, Z.
We report the discovery of a new pyrochlore oxide superconductor RbOs2O6. The compound crystallizes in the same beta-pyrochlore structure as the recently discovered superconductor KOs2O6, where Os...
Koda, A., Higemoto, W., Ohishi, K., Saha, S. R., Kadono, R., Yonezawa, S., ...
Magnetic penetration depth ($\lambda$) in a pyrochlore superconductor KOs$_2$O$_6$ was studied by means of muon spin rotation (\msr). The temperature dependence of transverse spin relaxation rate,...
Unprecedented Superconductivity in the beta-Pyrochlore Osmate KOs2O6 (2004)
Hiroi, Z., Yonezawa, S., Muraoka, Y.
Superconductivity in the potassium osmium oxide KOs2O6 crystallizing in the beta-pyrochlore structure is studied by means of electrical resistivity, magnetic susceptibility and specific heat. It is...
Okazaki, K., Wadati, H., Fujimori, A., Onoda, M., Muraoka, Y., Hiroi, Z.
We have made a detailed temperature-dependent photoemission study of VO_2/TiO_2(001) thin films, which show a metal-insulator transition at \sim 300 K. Clean surfaces were obtained by annealing the...
Fukaya, A., Fudamoto, Y., Gat, I. M., Ito, T., Larkin, M. I., Savici, A. T., ...
Muon spin relaxation ($\mu$SR) and magnetic susceptibility measurements have been performed on the pure and diluted spin 1/2 kagom\'{e} system (Cu$_x$Zn$_{1-x}$)$_{3}$V$_{2}$O$_7$(OH)$_{2}$ 2H$_2$O....
Longitudinal magnon in the tetrahedral spin system Cu2Te2O5Br2 near quantum criticality (2003)
Gros, C., Lemmens, P., Vojta, M., Valenti, R., Kageyama, H., ...
We present a comprehensive study of the coupled tetrahedra-compound Cu2Te2O5Br2 by theory and experiments in external magnetic fields. We report the observation of a longitudinal magnon in Raman...
Photocarrier Injection to Transition Metal Oxides (2003)
This paper has been withdrawn by the author(s), due a crucial error in the data.
Longitudinal magnon in the tetrahedral spin system Cu2Te2O5Br2 near quantum criticality (2003)
Gros, C., Lemmens, P., Vojta, M., ValentÃ, R., Kageyama, H., ...
Correlations and Semimetallic Behaviors in Pyrochlore Oxide Cd2Re2O7 (2002)
Hiroi, Z., Hanawa, M., Muraoka, Y., Harima, H.
Electronic properties of the metallic pyrochlore oxide Cd2Re2O7 are studied by means of electrical resistivity and Hall measurements. Semimetallic band structures are revealed as expected from band...
Specific Heat of Kagome Ice in the Pyrochlore Oxide Dy2Ti2O7 (2002)
Hiroi, Z., Matsuhira, K., Takagi, S., Tayama, T., Sakakibara, T.
A novel macroscopically degenerate state called kagome ice, which was recently found in a spin ice compound Dy2Ti2O7 in a magnetic field applied along the [111] direction of the cubic unit cell, is...
Magnetic and superconducting properties of Cd2Re2O7: Cd NMR and Re NQR (2002)
Vyaselev, O., Arai, K., Kobayashi, K., Yamazaki, J., Kodama, K., Takigaawa, M., ...
We report Cd NMR and Re NQR studies on Cd2Re2O7, the first superconductor among pyrochlore oxides Tc=1 K. Re NQR spectrum at zero magnetic field below 100 K rules out any magnetic or charge order....
Kadono, R., Higemoto, W., Koda, A., Kawasaki, Y., Hanawa, M., Hiroi, Z.
The quasiparticle excitations in the mixed state of Cd2Re2O7 have been studied by means of muon spin rotation/relaxation. The temperature dependence of the magnetic penetration depth (lambda) is...
Spin-1/2 Kagome Like Lattice in Volborthite Cu3V2O7(OH)2-H2O (2001)
Hiroi, Z., Hanawa, M., Kobayashi, N., Nohara, M., Takagi, H., Kato, Y., ...
A novel cuprate Volborthite, Cu3V2O7(OH)2-2H2O, containing an S-1/2 (Cu 2+ spin) kagome-like lattice is studied by magnetic susceptibility, specific heat, and 51 V NMR measurements. Signs for neither...
Superconducting properties of the pyrochlore oxide Cd2Re2O7 (2001)
We report the superconducting properties of the pyrochlore oxide Cd2Re2O7. The bulk superconducting transition temperature Tc is about 1.0 K, and the upper critical field Hc2 determined by the...
Structural Phase Transition in the Superconducting Pyrochlore Oxide Cd2Re2O7 (2001)
Hanawa, M., Yamaura, J., Muraoka, Y., Sakai, F., Hiroi, Z.
We report a structural phase transition found at Ts = 200 K in a pyrochlore oxide Cd2Re2O7 which shows superconductivity at Tc = 1.0 K. X-ray diffractionexperiments indicate that the phase transition...
Superconductivity at 1 K in Cd2Re2O7 (2001)
Hanawa, M., Muraoka, Y., Tayama, T., Sakakibara, T., Yamaura, J., Hiroi, Z.
We report the first pyrochlore oxide superconductor Cd2Re2O7. Resistivity,magnetic susceptibility,and specific heat measurements on single crystals evidence a bulk superconductivity at 1 K. Another...
Johnston, D. C., Troyer, M., Miyahara, S., Lidsky, D., Ueda, K., Azuma, M., ...
A comprehensive theoretical and experimental study is presented of the magnetic susceptibility versus temperature \chi(T) of spin S = 1/2 two- and three-leg Heisenberg ladders and ladder oxide...