Superconducting State in the Ternary Germanide Y2AlGe3with Related ThCr2Si2-Type Structure

Abstract

Superconductivity in a ternary germanide, Y 2 AlGe 3 , 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 Y 2 AlGe 3 was a type-II superconductor. The lower critical field H c1 (0) and the upper critical field H c2 (0) were estimated to be 1.66(8) mT and 1.26(15) T. The coherence length ξ(0) GL , penetration depth λ(0) GL , and Ginzburg–Landau (GL) parameter κ(0) obtained from the critical fields were 16.2(5) nm, 631(16) nm, and 38(3), respectively. Specific heat measurements revealed that Y 2 AlGe 3 was a weak-coupling BCS superconductor with an isotropic superconducting gap. The electron–phonon mass enhancement parameter λ γ was calculated to be 0.13, which was in good agreement with the weak-coupling limit inferred from the specific heat Δ C e /γ T c and 2Δ(0)/ k B T c .