Study on strongly correlated electron systems by means of angle-resolved magnetization measurements at low temperatures

点击翻译按钮获取中文摘要

1.We developed a new magnetometer that can rotate the field direction continuously at low temperatures below 0.5 K. Using this magnetometer, we examined the phase diagram of an antiferro-quadrupole ordering system PrPb3 and obtained the field-angle variation of the transition temperature. From the results, we could identify the order parameter, which requires the quadrupole interaction to be anisotropic.2.We developed a new calorimeter that can rotate magnetic field direction continuously at low temperatures below 0.5 K. Using this calorimeter, we investigated the low temperature specific heat of the anisotropic superconductor CeCoIn5 in the superconducting mixed state. We observed a clear fourfold angular oscillation of the electronic specific heat, indicating d wave superconductivity. From the angular position of the minima in the specific heat, the d_xy type gap symmetry is concluded.3.Magnetization process of a spin-ice compound Dy2Ti2O7 has been examined in a (111] magnetic field. We observed a clear magnetization plateau in the kagome ice state, followed by a first-order transition to a saturated sate. The transition is found to be of a liquid-gs type, which is new for the localized spin systems.4.Field-temperature phase diagrams of the skutterudite compound PrOs4Sb12 has been examined at low temperatures and a field-induced ordering is observed for all the principal field directions. The results indicate the ground state of this system to be a Gamma_1 singlet.