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 appli ed along the a- and c-axes. To investigate heat treatment effects on m agnetization, we prepared both unannealed and annealed single crystals . In all the samples we studied, we found thermal hysteresis in the lo w held magnetization, and temperatures where the hysteresis starts dif fer for the a- and c-axes samples. However it tends to disappear with increasing fields. There are also subtle, but measurable, effects of a nnealing 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. (C) 1998 Els evier Science B.V. All rights reserved.