Electric, thermal, and magnetic properties of hexagonal and cubic UPtSn

Resistivity, specific heat, and magnetization measurements have been carried out for polycrystalline UPtSn. Samples as cast and those annealed at temperatures below 300 °C crystallize in a hexagonal structure. The structure of samples annealed between 800 and 935 °C transforms into the cubic MgAgAs phase. The hexagonal UPtSn sample undergoes a ferromagnetic transition at TC=27 K. Below TC both the zero-field-cooled (ZFC) and field-cooled (FC) magnetization data initially increase as the temperature is decreased. However, when the temperature is lowered further, the ZFC magnetization drops significantly whereas the FC magnetization saturates. This irreversible behavior in the ZFC and FC curves could be attributed to intrinsic domain-wall pinning. On the other hand, the cubic UPtSn sample is paramagnetic down to the lowest measured temperature 0.5 K. The resistivity of cubic UPtSn is unusually large and exhibits a semiconductor-like behavior.