BIAS DEPENDENCE IN SPIN-POLARIZED TUNNELING

We discuss the transport of electrons through ferromagnetic tunnel jun ctions. The spin-up and spin-down chemical potentials are different at the insulator-ferromagnet interfaces by different amounts between the parallel and the antiparallel configuration. As a result, the tunneli ng probabilities fdr the spin-up and spin-down channels change differe ntly as the external voltages are increased. There is a strong bias de pendence of the magnetoresistance ratio, consistent with experimental results.