Defect scattering in high Tc and colossal magnetoresistive tunnel junctions

Disorder causes both superconducting cuprate and colossal magnetoresistive manganite based tunnel junctions to depart from properties based solely on the superconductivity or magnetism inherent in the materials. Amorphous barrier layers cause diffuse reflection of quasiparticle states at the insulator-superconductor interface, resulting in a local quenching of the d-wave order parameter. A subdominant order parameter evolves at low temperatures in these layers. In manganites, interface disorder reduces spin polarization and causes the tunneling magnetoresistance in spin valve devices to be smaller than in junctions with less disorder.