Superconducting State in the Ternary Germanide Y2AlGe3 with Related ThCr2Si2-Type Structure

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Superconductivity in a ternary germanide, Y2AlGe3, was revealed at the transition temperature of 4.5 K by electrical resistivity and magnetic susceptibility measurements. The magnetization versus magnetic field (M--H) curve indicated that Y2AlGe3 was a type-II superconductor. The lower critical field H_{\text{c1}}(0) and the upper critical field H_{\text{c2}}(0) were estimated to be 1.66(8) mT and 1.26(15) T. The coherence length \xi(0)_{\text{GL}}, penetration depth \lambda(0)_{\text{GL}}, and Ginzburg--Landau (GL) parameter \kappa(0) obtained from the critical fields were 16.2(5) nm, 631(16) nm, and 38(3), respectively. Specific heat measurements revealed that Y2AlGe3 was a weak-coupling BCS superconductor with an isotropic superconducting gap. The electron--phonon mass enhancement parameter \lambda_{\gamma} was calculated to be 0.13, which was in good agreement with the weak-coupling limit inferred from the specific heat \Delta C_{\text{e}}/\gamma T_{\text{c}} and 2\Delta (0)/k_{\text{B}}T_{\text{c}}.
2011-01-15