Inhomogeneous Spin Diffusion in Thickness-Controlled La 0 . 6 7 Sr 0 . 3 3 MnO 3 /YBa 2 Cu 3 O 7 − δ /La 0 . 6 7 Sr 0 . 3 3 MnO 3 Trilayers

Abstract

La0.67Sr0.33MnO3/YBa2Cu3O7 − δ /La0.67Sr0.33 MnO3 (LSMO/YBCO/LSMO) trilayers are prepared on single-crystal LaAlO3 (LAO) substrates by pulsed laser deposition (PLD) with the thicknesses of LSMO layers fixed at 50 nm, and the thickness of YBCO sandwich varied from 10 to 40 nm. X-ray diffraction (XRD) and pole figure measurements disclose that all the trilayers are c-oriented and there is little change in the textures of YBCO layer for both in-plane and out-of-plane. Based on inductive, transport, and magnetic measurements, obvious suppression of superconductivity with a decrease in YBCO thickness is observed, particularly at thickness below 20 nm. Importantly, there are great disparities in the superconducting transition temperature (T c) and transition width (ΔT c) values for both inductive and transport measurements. The T c values from an inductive method are much smaller than those from transport measurements, with ΔT c in the opposite direction. The results are explained by the nonuniform diffusion of spin-polarized quasiparticles due to the comparable length scales of the spin diffusion length and the superconducting film thickness.