Avalanches in UGe2

In UGe2 ferromagnetisim and superconductivity co-exist for pressures in the range 1.0-1.6 GPa. The magnetic state, however, has several unusual properties. Here we report measurements of hysteresis loops for fields parallel to the easy-axis at low temperature and ambient pressure, measured for two separate UGe2 single crystals. Steps in the magnetization as the field is changed at low temperature are observed for both crystals. The general phenomenology associated with the steps strongly suggests that they correspond to avalanches of domain-wall motion. (C) 2003 Elsevier B.V. All rights reserved.