NMR and Mössbauer Studies in Ternary Superconductors

Nuclear magnetic resonance (NMR) played an important historical role [7.1] in the early microscopic confirmation of the Bardeen, Cooper, Schrieffer (BCS) [7.2] theory of superconductivity. Hyperfine techniques, particularly the Mossbauer effect and NMR, are making important contributions to the microscopic picture developing for the ternary superconductors. Shortly after the discovery of superconductivity in the Chevrel phases [7.3] by Matthias and coworkers [7.4], Mossbauer studies of the localized vibrations of 119Sn in SnMo6S8 led to a description of the soft, anharmonic, resonance modes of the loosely bound tin atom in the network of Mo6S8 units [7.5]. This work led to other efforts using heat capacity and inelastic neutron scattering to characterize the lattice modes of the Chevrel phases. In Sect.7.1 we present a brief survey of the structural and localized vibrational properties of a number of Chevrel phase compounds studied by the Mossbauer effect.