Supercooling and giant relaxation of the disordered vortex state in a doped CeRu₂ alloy

Giant relaxation in magnetization of metastable (supercooled) states in Ce(Ru_0.95Nd_0.05)₂ alloy in the vortex solid-solid transition regime is reported. The metastable states were prepared by cooling the alloy sample from a temperature well above the T_C, in the presence of different magnetic fields. This was followed by an isothermal field change to set up a critical state in the entire bulk of the sample. Relaxation in magnetization was measured isothermally in this critical state. Through such a choice of experimental protocol, the relaxation in magnetization contributed by supercooled states is clearly distinguished. Variation of the relaxation rates with respect to the fields applied for producing the field-cooled states is explained in terms of supercooling of the disordered vortex phase.