Deriving the Ginzburg-Landau parameter from heat-capacity data on magnetic superconductors with Schottky anomalies.

Abstract

The specific heat of the Chevrel phase (CP) magnetic superconductors (Sn0.65Eu0.35)Mo6S8 and (Sn0.50Eu0.50)Mo6S8 have been measured in high magnetic fields. The Schottky contributions, including self-field and exchange terms, were calculated and then subtracted to improve determination of the Ginzburg-Landau parameter. Two approximate high-field specific-heat equations are presented which are used to find the free-ion ground state of these CP compounds and the doublet ground-state properties in some rare-earth high-temperature superconductors without advanced computation. The approximate equations allow simple calculation of the degeneracy and moments of the ground-state multiplet and the ordering temperature.