Gold Substitution Effect on Structure and Superconductivity Properties in Filled Skutterudite La(Pt<SUB>1−<I>x</I></SUB>Au<I><SUB>x</SUB></I>)<SUB>4</SUB>Ge<SUB>12</SUB>

Abstract

A series of single-phased La(Pt 1-x Au x ) 4 Ge 12 compounds were prepared by an arc-melting method. The crystal structure and basic superconductivity parameters have been systematically investigated by X-ray diffraction and by examining the temperature and field dependences of electrical resistivity, magnetization and heat capacity. The lattice parameter a increases and the superconducting transition temperature T c decreases gradually with increasing Au content x. The low critical field H c1 (T) and the upper critical field H c2 (T) were estimated from the isothermal magnetization (M-H-T) and electrical transport (p-H-T) measurements, respectively. The evaluated H c1 (0) and H c2 (0) indicate a decrease tendency with increasing x, and enable us to deduce the coherence length ξ(0), penetration depth λ(0), Ginzburg-Landau parameter κ(0) and thermodynamic critical field H c (0). The present results are compared with those of the related systems.