In La_0.7Sr_0.3MnO_3/SrTiO_3/Co tunnel junctions, the half-metallic nature of La_0.7Sr_0.3MnO_3 allows probing the spin polarization of Co. For applied voltage bias around zero volts, an inverse tunnel magnetoresistance is found, indicating the negative spin polarization of Co at the Fermi level as expected from the density of states of the "d" band in Co. The bias dependence of the magnetoresistance reflects the structure of the "d" band density of states of Co. In this article we underline the important consequences for the knowledge of the spin-dependent tunneling in solids brought by these results and describe in detial the effect of temperature and high magnetic field on the magnetoresistance.
展开▼
