Transport properties of HTS/CMR/HTS multilayers for spin injection devices
YBa2Cu3O7-δ high temperature superconductors (YBCO), as well as the layered manganite La2/3Sr1/3MnO3 (LSMO) are layered metallic systems where the interlayer current transport occurs via sequential tunneling of charge carriers. We present in this paper experimental results of magneto-transport studies carried out on YBa2Cu3O7-δ/La2/3Sr1/3MnO3/YBa2Cu3O7-δ (YBCO/LSMO/YBCO) thin film multilayers. The YBCO/LSMO/YBCO heterostructures were grown on SrTiO3 (STO) substrates by pulsed laser deposition. The close lattice match among the constituent layers of the perovskite YBCO/LSMO/YBCO and the substrate facilitates epitaxial film growth, thus minimizing strong spin-flip scattering at the interface. The temperature dependence of the resistance for different bias currents 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 samples show a drop between 19% and 22% in the resistance for the c-axis tunneling currents varying from I = 0.05-1.0 mA at the critical temperature T* ~ 240 K. This behavior could be related to the opening of a pseudogap. The investigation of these promising hybrid structures is aimed at understanding the science of new spin-based devices.