Ferromagnetic interaction and superconductivity of CeCu 2Si 2

Abstract

We have recently reported our finding of a weakly ferromagnetic phase and two superconducting phases in the Cu-deficient and Cu-rich region of the homogeneity range, respectively, for the heavy-electron compound CeCu 2Si 2. We herein report more detailed results of the specific heat, magnetic susceptibility, resistivity ( R), magnetoresistance (Δ R) and thermopower for many different compositions. We confirmed the slightly re-entrant behavior in the H c2( T) curve and a change of regime in the Δ R at about 0.35 K above H c2( T) for the low- T c phase. Above about 0.75 K, the normal state of this phase exhibited no magnetoresistance up to 70 kOe, while that of high- T c phase and the weakly ferromagnetic phase did a slightly positive Δ R. These differences in the three phases may provide an important clue to better understanding of the heavy-electron superconductivity of CeCu 2Si 2.