REENTRANT SUPERCONDUCTIVITY OF CERU2

Magnetization curves [MC] and temperature dependence of the AC susceptibility [TS] were measured in the superconducting phase of CeRu2 with T(c) = 6.55 K in zero field. For fields higher than 0.8 T in [TS], the superconducting susceptibility behaves normally up to the lowest transition temperature T(cL) where it decreases suddenly; the field-induced reentrant superconductivity occurs at T(cL) and breaks very sharply to the normal state at T(cH) (the highest transition temperature). In [MC], an anomaly appears when the magnetization reaches to the extrapolated magnetization of the normal state at H(R) (reentrant field). Magnetization drops suddenly to negative in the field-increasing process for temperatures below 3.9 K, and it only increases for temperatures above 4.0 K. Reentrant superconductivity occurs between, H(R) and H(c2). The reentrant phase has positive magnetization in the background.