Spin injection in ferromagnet/superconductor/ferromagnet tunnel junctions

We theoretically study the spin-dependent transport in a ferromagnet/superc onductor/ferromagnet double barrier tunnel junction. The spin-polarized tun neling currents create spin and charge imbalance in a superconductor. Noneq uilibrium effects are dominated by spin imbalance, causing an unusual spin transport and suppression of superconductivity depending on whether the mag netizations of the electrodes are parallel or antiparallel. Recent experime ntal results on the critical current suppression by spin injection are disc ussed.