Reentrant Superconductivity of CeRu2

Magnetization curves [MC] and temperature dependence of the AC susceptibility [TS] were measured in the superconducting phase of CeRu 2 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.