Spin-Polarised Transport and Evidence for Novel Spin Valve Behaviour in YBCO/LSMO/YBCO Hybrid Structures

Anisotropic RBa₂Cu₃O_7-delta; high temperature superconductors (RBCO), where R represents the rare earth elements Y, Nd and Pr, as well as the layered manganite La_2/3Sr_1/3MnO₃ (LSMO) are layered metallic systems where the interlayer current transport occurs via sequential tunneling of charge carriers. The authors presents here experimental results of interlayer spin polarized transport studies carried out on YBa₂Cu₃O_7-delta/La_2/3Sr _1/3MnO₃/YBa₂Cu₃O _7-delta thin film multilayers. The tunneling of spin polarized charge carriers between the YBCO layers through LSMO leads to a novel spin valve effects at high temperatures. The samples showed large magneto-resistance with a sharp switching between the high and low resistance states, which assumes corresponds to antiparallel and parallel alignment of the moments of these hybrid structures. The temperature dependence of the resistance for different applied fields shows that these heterostructures are clearly influenced by both the insulator-to-metal transition of the LSMO layers at 330 K and the stripe fluctuations in the conductivity of the YBCO layers at the onset of electronic inhomogeneity at ~ 240 K. The investigation of these promising hybrid structures is aimed at understanding the science of new spin-based devices, laying the foundation for a new generation of ultra-fast, nonvolatile electronics