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

The mixed-valence manganites (A/sub 0.7/B/sub 0.3/)MnO/sub 3/ are prospective barrier materials for high-T/sub c/ junctions. They exhibit colossal magnetoresistance (CMR) and are chemically and structurally compatible with YBa/sub 2/Cu/sub 3/O/sub 7/ (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 La/sub 0.7/Ca/sub 0.3/MnO/sub 3/ (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 states as a possible conduction mechanism for quasiparticle transport through the manganite barrier.