Magnetoresistance in asymmetric ferromagnet/superconductor/ferromagnet double tunnel junctions

We investigate theoretically the spin-dependent transport in a ferromagnet/superconductor/ferromagnet double tunnel junction taking into account the junction asymmetry. The spin-polarized tunneling current induces spin imbalance in the superconductor giving rise to suppression of superconductivity. We find that this pair breaking effect exhibits sensitive dependence on the asymmetric natures of the tunnel junction. We show, in particular, that the junction asymmetry can result in substantial changes in the magnetoresistive behavior.