Thermal hysteresis in magnetization of single crystal URu₂Si₂

We present low field magnetization results of URu₂Si₂ single crystals, measured after zero-field cooling and field cooling with fields applied along the a- and c-axes. To investigate heat treatment effects on magnetization, we prepared both unannealed and annealed single crystals. In all the samples we studied, we found thermal hysteresis in the low field magnetization, and temperatures where the hysteresis starts differ for the a- and c-axes samples. However it tends to disappear with increasing fields. There are also subtle, but measurable, effects of annealing on the low field magnetization in all the samples. We compare our results with a previous similar study of polycrystalline URu₂Si₂, and heat treatment effects found in neutron diffraction. @ 1998 Elsevier Science B.V. All rights reserved.