The measurements of the electrical resistivity and the low temperature heat capacity in the superconducting (La//1// minus //yM//y)//3S//4 compounds with M equals vacancy, Sc, Y, Ce, Lu, and Th were made in zero field and in magnetic fields up to 16 and 10T, respectively. The optimum superconducting properties appear in the cubic La//0//. //9//7Th//0//. //0//3S//1//. //3//3//3, which has approximately 10% higher T//c and about a threefold higher H//c//2(0)than the hypothetical values in the tetragonal LaS//1//3//3//3//3. The relationship between H//c//2(0) and T//c (i. e. H//c//2(0) equals C//0T//c, where C//0 equals 1. 96 and 1. 32 T/K for the cubic and tetragonal phases, respectively) is found in a series of La//1// plus //yM//yS//x compounds. The high H//c//2(0) values for the cubic compounds originate in the anomalously large values of the residual resistivity, which may reflect the instability of the cubic lattice.
|Number of pages||3|
|Publication status||Published - 1985|
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