Temperature dependence of magnetization in the superconducting mixed state of CeRu₂: evidence of a First order phase transition

Abstract

We present results of magnetization measurements in very close temperature intervals in the superconducting mixed state of CeRu₂. While the temperature (T) dependence of magnetization in low applied magnetic fields (H) is typical of that of a type-II superconductor with moderate pinning, the character changes markedly in high applied H, showing clear evidence of a first-order phase transition. Isothermal field-dependent magnetization studies have suggested earlier the possibility of such a first-order phase transition in the low-T high-H part of the superconducting mixed state of CeRu₂. The present results for the first time provide the evidence of this first-order phase transition in a temperature-dependent study of magnetization. The possible role of paramagnetic impurities in the observed phase transition is discussed.