HIGH CRITICAL-FIELD CHEVREL PHASES

Some of the Chevrel phase material of the type MxMo6X8 (M = metal, X = S, Se, Te) present extraordinarily high critical fields (Hc2 of PbMo6S8 is about 600 kG). The reason for this is to be found in the particular pseudo molecular crystal structure of these compounds producing narrow bands at the Fermi surface. Single crystal investigations have revealed a surprisingly large anisotropy of about 15-20% in several of these materials. Of particular interest is the possibility in these materials to substitute M by magnetic rare earth ions without destroying the superconductivity. The anomalous behaviour of Hc2 in these latter materials allows us to study the different pairbreaking mechanisms present in the Chevral phases. © 1979.