arXiv subjects

Tatsuo Goko

Publications and source records attributed to Tatsuo Goko.

3 recordsLinked to original sources

arXiv2010

The magnetic structure of the $zigzag$ chain family Na$_{x}$Ca$_{1-x}$V$_2$O$_4$ determined by muon-spin rotation

We present muon-spin rotation measurements on polycrystalline samples of the complete family of the antiferromagnetic (AF) $zigzag$ chain compounds, Na$_x$Ca$_{1-x}$V$_2$O$_4$. In this family, we explore the magnetic properties from the metallic NaV$_2$O$_4$ to the insulating CaV$_2$O$_4$. We find a critical $x_c(\sim0.833)$ which separates the low and high Na-concentration dependent transition temperature and its magnetic ground state. In the $x x_c$ compounds, multiple sub-phases appear with temperature and $x$. Based on the muon data obtained in zero external magnetic field, a careful dipolar field simulation was able to reproduce the muon behavior and indicates a modulated helical incommensurate spin structure of the metallic AF phase. The incommensurate modulation period obtained by the simulation agrees with that determined by neutron diffraction.

cond-mat.str-el↗

arXiv2002

From Mott insulator to ferromagnetic metal: a pressure study of Ca$_{2}$RuO$_{4}$

We show that the pressure-temperature phase diagram of the Mott insulator Ca$_{2}$RuO$_{4}$ features a metal-insulator transition at 0.5GPa: at 300K from paramagnetic insulator to paramagnetic quasi-two-dimensional metal; at $T \leq$ 12K from antiferromagnetic insulator to ferromagnetic, highly anisotropic, three-dimensional metal. % We compare the metallic state to that of the structurally related p-wave superconductor Sr$_{2}$RuO$_{4}$, and discuss the importance of structural distortions, which are expected to couple strongly to pressure.

cond-mat.str-el↗

arXiv1999

Role of two-dimensional electronic state in superconductivity in La$_{2-x}$Sr$_{x}$CuO$_{4}$

We have measured out-of-plane resistivity $ρ_c$ for La$_{2-x}$Sr$_{x}$CuO$_{4}$ under anisotropic pressure. c-axis compression, which decreases $ρ_c$, reduces $T_{\rm c}$ drastically, whereas c-axis extention, which increases $ρ_c$, enhances $T_{\rm c}$ from 38K at ambient pressure to 51.6K at 8GPa. We find that the variation of $T_{\rm c}$ scales as a function of $ρ_c$, and that the c-axis pressure coefficient is much stronger than the ab-axis one. These imply that $T_{\rm c}$ depends primarily on the interlayer, rather than the in-plane, lattice parameter.

cond-mat.supr-con↗