Magnetization of UPd2Al3 in ultra-low temperature and high magnetic fields

Abstract Magnetization processes of a uranium heavy-fermion superconductor UPd 2 Al 3 is studied at temperatures down to 0.4 K in a static high magnetic field. The sweep ratio of a magnetic field is very low, 0.0015 T/min and measurements are done in completely isothermal processes. A sharp isothermal metamagnetic transition and a hysteresis have been first observed at B =17.9 T and at ultra-low temperatures when an external field is applied perpendicular to the c -axis. The hysteresis Δ B is about 0.02 T at 0.4 K. This hysteresis and sharp jump of the magnetization suggest that this transition is a first-order transition.