Effect of the magnetic moments of Gd on the superconductivity in the infinite-layer superconductor Sr 0.9Gd 0.1CuO 2

Abstract

We report the synthesis of Sr 0.9Gd 0.1CuO 2 and its superconducting properties. The low-field magnetization, the structural analysis, and the value of the paramagnetic moment of the Gd ion ( μ∼7.6 μ B/Gd) showed a homogeneous doping of the samples. By a comparison of Sr 0.9Gd 0.1CuO 2 with Sr 0.9La 0.1CuO 2, we found that the T c was not sensitive to the presence of the large magnetic moments due to the Ln ions sandwiched between two neighboring CuO 2 planes. This is rather contrasting with the large pair-breaking effect when the magnetic element Ni is between the CuO 2 planes. A correlation of the values of the T c and the tetragonal a-axis lattice constant was discussed between (Ln,Ce) 2CuO 4 and (Sr,Ln)CuO 2. The irreversibility field line and the intragranular critical current density were measured to probe the pinning properties and the pinning strength were nearly the same for Ln=La and Gd.