Proximity effect in La_0.7Sr_0.3MnO₃/Bi₂Sr₂CaCu₂O₈hybrid bi-layers

Abstract

The electrical resistivity and magnetization of half-metallic/superconducting La 0.7 Sr 0.3 MnO 3 /Bi 2 Sr 2 CaCu 2 O 8 (LSMO/Bi-2212) heterostructures are investigated with the thickness of Bi-2212 top layer fixed at 50 nm and that of the LSMO underlayer (t) being 40, 80 and 160 nm. Both the normal state resistivity ρ(290 K) and the superconducting transition width (δT C ) increase with increasing t. On the other hand, the superconducting transition onset temperature (T con ) of Bi-2212 monotonically decreases with increasing t, which is attributed to pair breaking via the polarized spins from the ferromagnetic LSMO due to strengthening of the magnetization. However, the rate of reduction of T con in Bi-2212 with respect to the thickness of LSMO is found to be much less in LSMO(t)/Bi-2212 compared with that of YBCO in the analogous system PCMO(t)/YBCO. From the qualitative analysis of the electrical and magnetic data we conclude that growing domains enhancing the magnetization is the reason for the thickness-dependent suppression of superconductivity in LSMO(t)/Bi-2212 bi-layers.