High upper critical field in the Chevrel phase superconductor lead-molybdenum-sulphide doped with europium

Chevrel phase superconductors have high upper critical fields, which make them candidate materials for the next generation of high field magnets operating at fields significantly above 25 T. The effect of doping lead-molybdenum-sulphide with europium ((Pb_1-xEu _x)Mo₆S₈ with x=0.0, 0.25, 0.5, 0.75 and 1.0) has been investigated. Bulk materials were fabricated using different heat-treatment procedures, followed by hot isostatic pressing at a pressure of 2000 Bar and a temperature of 800°C, X-ray diffraction data have been taken. Resistivity and susceptibility measurements have been made in magnetic fields up to 15 T, and temperatures from 3.5 K to 18 K. Single-phase samples were fabricated with x=0.0, 0.25 and 0.5. The x=0.0 sample has an onset critical temperature of 15.16 K. For x=0.25, the critical temperature decreased to 12.62 K but the upper critical field calculated for zero temperature increased from 51 T to 57 T