DEPENDENCE OF THE CRITICAL TEMPERATURE OF YBCO THIN FILMS ON SPINPOLARIZED QUASIPARTICLE INJECTION

Abstract

Heterostructures consisting of ferromagnetic La 2/3 Ca 1/3 MnO 3 and superconducting YBa 2 Cu 3 O 7- x layers were fabricated by conventional pulsed laser deposition in conjunction with shadow mask techniques to define appropriate sample geometries. Using standard dc- four probe measurements we observe a 2% decrease of T c for injection current densities of 5.10-2 A/cm2 in the case of unpolarized quasiparticles whereas highly spin polarized quasiparticles show a much stronger decrease of 14%. This result clearly demonstrates that the spin plays a crucial role in the T c reduction. The results are discussed within the frame of a theoretical model based on the Owen-Scalapino approach for nonequilibrium effects in superconductors.