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 barrie r materials for high-T-c junctions. They exhibit colossal magnetoresis tance (CMR) and are chemically and structurally compatible with YBa2Cu 3O7 (YBCO). The resistivity can be varied by an impressive 11 orders o f 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 h ere on the fabrication of c-axis oriented YBCO trilayer junctions empl oying LCMO as a barrier material. The crystal structure and surface mo rphology of a series of heterostructures has been studied using XRD an d atomic force microscopy. The current-voltage characteristics have be en measured as a function of temperature and magnetic field. In contra st to previously reported results the resulting devices exhibit no sup ercurrents. We propose the Glazman-Matveev inelastic tunnelling via lo calised stated as a possible conduction mechanism for quasiparticle tr ansport through the manganite barrier.