Superconducting and magnetic interactions in La/sub 1.2-x/Eu/sub x/Mo6S8 pseudoternary compounds

Superconducting and magnetic properties of La/sub 1.2-x/Eu/sub x/Mo6S8 pseudoternary compounds were investigated by means of low-frequency ac and dc magnetic susceptibility measurements under hydrostatic pressure up to 20 kbar and in magnetic fields up to 10 T. At atmospheric pressure, the superconducting transition temperature T/sub c/ is a weak function of Eu concentration x for 0< or =x< or =0.2, and decreases smoothly with x for x>0.2, until it vanishes for x> or approx. =0.95. Hydrostatic pressure was found to lower T/sub c/ in the La-rich compounds and to increase T/sub c/ in the Eu-rich compounds. Pressure also induces superconductivity in compounds with x>0.95 which are not superconducting at atmospheric pressure with maximum T/sub c/'s that are quite high (approx.8 K, midpoint) and comparable to the T/sub c/ values of other ternary molybdenum sulfides with divalent metal atoms. Magnetization data (dc) on a La/sub 0.2/Eu/sub 1.0/Mo6S8 compound revealed a sizable Meissner effect for pressures >7 kbar. At atmospheric pressure, the upper critical magnetic field H/sub c2/ for 0<x< or =0.6 was enhanced above that of La/sub 1.2/Mo6S8