arXiv subjects

J. Takeya

Publications and source records attributed to J. Takeya.

22 records · Page 2Linked to original sources

arXiv2000

Thermal Conductivity of Mg-doped CuGeO_3

The thermal conductivity $κ$ is measured in a series of Cu_1-xMg_xGeO_3 single crystals in magnetic fields up to 16 T. It has turned out that heat transport by spin excitations is coherent for lightly doped samples, in which the spin-Peierls (SP) transition exists, at temperatures well above the SP transition temperature T_SP. Depression of this spin heat transport appears below T^*, at which the spin gap locally opens. T^* is not modified with Mg-doping and that T^* for each Mg-doped sample remains as high as T_SP of pure CuGeO_3, in contrast to T_SP which is strongly suppressed with Mg-doping. The spin-gap opening enhances phonon part of the heat transport because of reduced scattering by the spin excitations, producing an unusual peak. This peak diminishes when the spin gap is suppressed both in magnetic fields and with the Mg-doping.

cond-mat.str-el↗

arXiv1999

Magnetoresistance in Heavily Underdoped YBa_2Cu_3O_{6+x}: Antiferromagnetic Correlations and Normal-State Transport

We report on a contrasting behavior of the in-plane and out-of-plane magnetoresistance (MR) in heavily underdoped antiferromagnetic (AF) YBa_2Cu_3O_{6+x} (x<0.37). The out-of-plane MR (I//c) is positive over most of the temperature range and shows a sharp increase, by about two orders of magnitude, upon cooling through the Neel temperature T_N. A contribution associated with the AF correlations is found to dominate the out-of-plane MR behavior for H//c from far above T_N, pointing to the key role of spin fluctuations in the out-of-plane transport. In contrast, the transverse in-plane MR (I//a(b);H//c) appears to be small and smooth through T_N, implying that the development of the AF order has little effect on the in-plane resistivity.

cond-mat.supr-con↗

arXiv1998

Normal-state magnetotransport in La_{1.905}Ba_{0.095}CuO_{4} single crystals

The normal-state magnetotransport properties of La_{2-x}Ba_{x}CuO_{4} single crystals with x=0.095 are measured; at this composition, a structural transition to a low-temperature-tetragonal (LTT) phase occurs without suppression of superconductivity. None of the measured properties (in-plane and out-of-plane resistivity, magnetoresistance, and Hall coefficient) shows any sudden change at the LTT phase transition, indicating that the occurrence of the LTT phase does not necessarily cause an immediate change in the electronic state such as the charge-stripe stabilization.

cond-mat.supr-con↗

arXiv1998

Thermal Conductivity of the Spin Peierls Compound CuGeO_3

The thermal conductivity of the Spin-Peierls (SP) compound CuGeO_3 was measured in magnetic fields up to 16 T. Above the SP transition, the heat transport due to spin excitations causes a peak at around 22 K, while below the transition the spin excitations rapidly diminish and the heat transport is dominated by phonons; however, the main scattering process of the phonons is with spin excitations, which demonstrates itself in an unusual peak in the thermal conductivity at about 5.5 K. This low-temperature peak is strongly suppressed with magnetic fields in excess of 12.5 T.

cond-mat.str-el↗