arXiv subjects

O. Suzuki

Publications and source records attributed to O. Suzuki.

3 recordsLinked to original sources

arXiv2005

Valence and Na content dependences of superconductivity in NaxCoO2.yH2O

Various samples of sodium cobalt oxyhydrate with relatively large amounts of Na$^{+}$ ions were synthesized by a modified soft-chemical process in which a NaOH aqueous solution was added in the final step of the procedure. From these samples, a superconducting phase diagram was determined for a section of a cobalt valence of $\sim$+3.48, which was compared with a previously obtained one of $\sim$+3.40. The superconductivity was significantly affected by the isovalent exchanger of Na$^{+}$ and H$_{3}$O$^{+}$, rather than by variation of Co valence, suggesting the presence of multiple kinds of Fermi surface. Furthermore, the high-field magnetic susceptibility measurements for one sample up to 30 T indicated an upper critical field much higher than the Pauli limit supporting the validity of the spin-triplet pairing mechanism.

cond-mat.supr-con↗

arXiv2005

Field-induced magnetic ordering in the Haldane system PbNi2V2O8

The Haldane system PbNi2V2O8 was investigated by the temperature dependent magnetization M(T) measurements at fields higher than H_c, with H_c the critical fields necessary to close the Haldane gap. It is revealed that M(T) for H > H_c exhibits a cusp-like minimum at T_{min}, below which M(T) increases with decreasing T having a convex curve. These features have been observed for both $H \parallel c$ and $H \perp c$, with c-axis being parallel to the chain. These data indicate the occurrence of field-induced magnetic ordering around T_{min}. Phase boundaries for $H \parallel c$ and $H \perp c$ do not cross each other, consistent with the theoretical calculation for negative single-ion anisotropy D.

cond-mat.str-el↗

arXiv2002

Field-Induced Magnetic Ordering in the Quantum Spin System KCuCl$_3$

KCuCl$_3$ is a three-dimensional coupled spin-dimer system and has a singlet ground state with an excitation gap $Δ/k_{\rm B}=31$ K. High-field magnetization measurements for KCuCl$_3$ have been performed in static magnetic fields of up to 30 T and in pulsed magnetic fields of up to 60 T. The entire magnetization curve including the saturation region was obtained at $T=1.3$ K. From the analysis of the magnetization curve, it was found that the exchange parameters determined from the dispersion relations of the magnetic excitations should be reduced, which suggests the importance of the renormalization effect in the magnetic excitations. The field-induced magnetic ordering accompanied by the cusplike minimum of the magnetization was observed as in the isomorphous compound TlCuCl$_3$. The phase boundary was almost independent of the field direction, and is represented by the power law. These results are consistent with the magnon Bose-Einstein condensation picture for field-induced magnetic ordering.

cond-mat.str-el↗