Powder EPR of Gd 3+ in the superconductors SnMo 6S 8 and PbMo 6S 8

Abstract

EPR spectra at 35 and 60 GHz of Gd 3+ diluted (∼1%) in powdered SnMo 6S 8 and PbMo 6S 8 are presented and interpreted. The crystal field is found to be axial, with D = b 2 0=-760 gauss and -740 Gauss for the tin and lead compounds respectively. Values are obtained for <J(q)> and J(q = 0). Below T c the impurity to conduction electron relaxation rate is no longer proportional to temperature but decreases more rapidly. From this temperature dependence we extract a value for 2Δ kT c of roughly 5 for both compounds.