Superconducting and Magnetic Properties of Pb1.2-xEuxMo6S8

Abstract
Effect of magnetic ions on the superconductivity is investigated in the pseudo ternary compounds Pb 1.2- x Eu x Mo 6 S 8 by measuring the electrical resistance and magnetization in the field up to 650 kOe. The superconducting and structural transformation temperatures, T c and T s , are obtained as a function of Eu-concentration. A clear enhancement of H c 2 defined as the onset of superconductivity is found around the composition Pb 0.7 Eu 0.5 Mo 6 S 8 and the H c 2 (0) is estimated to be 630 kOe. The dependences of T c and H c 2 on the temperature and Eu-concentration are successfully explained by the theory of Maekawa and Tachiki with the antiferromagnetic coupling of -3.2±0.6 meV between the conduction electrons and Eu-spins. Valence mixing of Eu 2+ and Eu 3+ is suggested in Eu 1.2 Mo 6 S 8 from the high field magnetization data.

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