arXiv subjects

T. Goto

Publications and source records attributed to T. Goto.

96 records · Page 6Linked to original sources

arXiv2002

Hall coefficient of La$_{1.88-y}$Y$_y$Sr$_{0.12}$CuO$_4$ ($y=0, 0.04$) at low temperatures under high magnetic fields

The Hall coefficient in the low-temperature tetragonal phase and the mid-temperature orthorhombic phase of La$_{1.88-y}$Y$_y$Sr$_{0.12}$CuO$_4$ ($y=0, 0.04$) single crystals is measured under high magnetic fields up to 9 T in order to investigate the detailed behavior of the transport properties at low temperatures in the stripe phase. When the superconductivity is suppressed by high magnetic fields, the Hall coefficient has negative values in low temperatures, and the temperature region of the negative values spreads as increasing magnetic fields. This result indicates that the Hall coefficient in the stripe phase around $x=0.12$ is a finite negative value, not zero.

cond-mat.supr-con↗

arXiv2002

Magnetic Phase Transition and Magnetization Plateau in Cs$_2$CuBr$_4$

The crystal structure of Cs$_2$CuBr$_4$ is the same as that of Cs$_2$CuCl$_4$, which has been characterized as a spin-1/2 quasi-two-dimensional frustrated system. The magnetic properties of Cs$_2$CuBr$_4$ were investigated by magnetization and specific heat measurements. The phase transition at zero magnetic field was detected at $T_{\rm N}=1.4$ K. It was observed that the magnetization curve has a plateau at about one-third of the saturation magnetization for magnetic field $H$ parallel to the $b$- and $c$-axes, while no plateau was observed for $H\parallel a$. The field-induced phase transition to the plateau state appears to be of the first order. The mechanism leading to the magnetization plateau is discussed.

cond-mat.str-el↗

arXiv2001

Field-Induced Two-Step Phase Transitions in the Singlet Ground State Triangular Antiferromagnet CsFeBr$_3$

The ground state of the stacked triangular antiferromagnet CsFeBr$_3$ is a spin singlet due to the large single ion anisotropy $D(S^z)^2$. The field-induced magnetic ordering in this compound was investigated by the magnetic susceptibility, the magnetization process and specific heat measurements for an external field parallel to the $c$-axis. Unexpectedly, two phase transitions were observed in the magnetic field $H$ higher than 3 T. The phase diagram for temperature versus magnetic field was obtained. The mechanism leading to the successive phase transitions is discussed.

cond-mat.str-el↗

arXiv2001

Singlet Ground State and Magnetization Plateaus in Ba$_3$Mn$_2$O$_8$

Magnetic susceptibility and the magnetization process have been measured in \green polycrystal. In this compound, the magnetic manganese ion exists as Mn$^{5+}$ in a tetrahedral environment, and thus the magnetic interaction can be described by an S=1 Heisenberg model. The ground state was found to be a spin singlet with an excitation gap $Δ/k_{\rm B}=11.2$ K. Magnetization plateaus were observed at zero and at half of the saturation magnetization. These results indicate that the present system can be represented by a coupled antiferromagnetic dimer model.

cond-mat.str-el↗

arXiv1998

Magnetization under High Pressure in MnSi

The magnetization M(H) has been measured in the weakly helimagnetic itinerant compound MnSi under high pressure up to 10.2 kbar and high magnetic field up to 9 Tesla. We interpret the simultaneous decrease under pressure of the saturated magnetization, $p_s$, and the Curie temperature, $% T_c$ in the frame of the self-consistent renormalization theory (SCR) of spin fluctuations. From the analysis of the so-called Arrot-plot ($H/p [ H,T ] $ versus $p^2[ H,T ] $) and the respective volume dependence of $p_s$ and $T_c$, we estimate the evolution of the characteristic spin fluctuation temperatures, $T_0$ and $T_A$ when the system approaches its critical pressure, $P_c$=15 kbar, corresponding to the disappearance of the long range magnetic order at T=0.

cond-mat.str-el↗

arXiv1995

Model-independent analysis of $\bbox{B}$-$\bbox{\bar B}$ mixing and $\bbox{CP}$ violation in $\bbox{B}$ decays

We present a framework to analyze effects of new physics beyond the standard model on $B$-$\bar B$ mixing and $CP$ violation in $B$ decays in a model-independent manner. Assuming that tree level decay amplitudes are dominated by the standard model ones, new physics contribution to the $B$-$\bar B$ mixing can be extracted from several measurements at $B$ factories. Using this framework, we show the present constraint on new physics contribution to the $B$-$\bar B$ mixing, and illustrate constraints expected to be given by future experiments at $B$ factories. We also point out a possibility that $CP$ asymmetries in $B\rightarrowψK_S$, $B\rightarrowππ$, and $B\rightarrow DK$ modes look consistent with the standard model, even if a large new physics contribution is present in the $B$-$\bar B$ mixing.

hep-ph↗