Conduction mechanisms in c-axis oriented YBCO based trilayer junctions with ferromagnetic A(0.7)B(0.3)MnO(3) manganite barriers

The mixed-valence manganites (A(0.7)B(0.3))MnO3 are prospective barrier materials for high-T-c junctions. They exhibit colossal magnetoresistance (CMR) and are chemically and structurally compatible with YBa2Cu3O7 (YBCO). The resistivity can be varied by an impressive 11 orders of magnitude upon substitution of the cations A and B. We have studied the magnetisation and resistivity of La0.7Ca0.3MnO3 (LCMO) thin films in grown epitaxially with YBCO by pulsed-laser deposition. We report here on the fabrication of c-axis oriented YBCO trilayer junctions employing LCMO as a barrier material. The crystal structure and surface morphology of a series of heterostructures has been studied using XRD and atomic force microscopy. The current-voltage characteristics have been measured as a function of temperature and magnetic field. In contrast to previously reported results the resulting devices exhibit no supercurrents. We propose the Glazman-Matveev inelastic tunnelling via localised stated as a possible conduction mechanism for quasiparticle transport through the manganite barrier.