On staircase like magnetization curve of UGe2

Pressure-induced ferromagnetic superconductor UGe2 shows a staircase like magnetization curve below about 1 K. We have carried out static magnetization measurements under various conditions, and found that the origin of the multi-step curves can be attributed to the demagnetization field effect. More than 1000 times magnetization measurements indicate that a coercive force H-C is almost independent of the magnetic field sweeping rate and temperature within the statistical distribution. It seems that none of these results are incompatible with the field-tuned resonant tunneling which is a kind of macroscopic quantum tunneling. (C) 2003 Elsevier B.V. All rights reserved.