We have fabricated a spin-polarized tunneling device based on half metallic manganites incorporating $Ba_{ 2}LaNbO_{ 6}$ as insulating barrier. An anomalous bias dependence of tunnel magnetoresistance (TMR) has been observed, the first of its kind in a symmetric electrode tunnel junction with single insulating barrier. The bias dependence of TMR shows an extremely sharp zero bias anomaly, which can be considered as a demonstration of the drastic density of states variation around the Fermi level of the half metal. This serves as a strong evidence for the existence of minority spin tunneling states at the half-metal insulator interface.
Categories: cond-mat.mtrl-sci cond-mat.mes-hall