Spontaneous Spin Polarized Currents in Superconductor-Ferromagnetic Metal Heterostructures

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We study a simple microscopic model for thin, ferromagnetic, metallic layers on semi-infinite bulk superconductor. We find that for certain values of the exchange spliting, on the ferromagnetic side, the ground states of such structures feature spontaneously induced spin polarized currents. Using a mean-field theory, which is selfconsistent with respect to the pairing amplitude χ, spin polarization m and the spontaneous current jₛ, we show that not only there are Andreev bound states in the ferromagnet but when their energies Eₙ are near zero they support spontaneous currents parallel to the ferromagnetic-superconducting interface. Moreover, we demonstrate that the spin-polarization of these currents depends sensitively on the band filling.