Study of minor hysteresis loops in the usual and anomalous superconducting regime of (Ce 0.95Nd 0.05)Ru 2: evidence of a first-order transition

Abstract

We present a detailed study of minor hysteresis loops (MHLs) in the usual and anomalous superconducting (SC) regime of (Ce 0.95Nd 0.05)Ru 2. MHLs in the usual SC regime follow the predictions of critical state models (CSM) for a hard type-II SC with field-dependent critical current ( J c). At the onset of the anomalous SC regime, the behaviour of the MHLs cannot be explained by CSM alone. Our results present strong evidence of a first-order transition from the usual to the anomalous SC phase. MHLs are used to track the growth of the domains or nuclei of the anomalous SC phase across this first-order transition. Well inside the anomalous regime where the first-order transition is complete, MHLs are again as expected from CSM and this behaviour persists until one reaches the reversible regime below H c2, indicating that the upper transition is of second order.