Evidence for impurity phase superconductivity in EuMo6S8 under pressure

Magnetization measurements in a static field as a function of temperature (2.5–20K) and pressure to 14 kbar are reported for a series of well characterized samples of EuMo_6+xS_8?y. From these d.c. magnetization data, we find no evidence for bulk superconductivity in any of our samples, although some of them exhibit a strong diamagnetic anomaly in the a.c. susceptibility under pressure, similar to that reported in the literature. An explanation for this anomaly is presented in terms of the presence of a granular superconducting impurity on the grain boundaries of the Chevrel phase compound EuMo₆S₈.