Gate-controlled spin polarized current in ferromagnetic single electron transistors

Gate voltage can be used to tune polarization of current passing through a ferromagnetic single electron transistor when spin accumulate in the central electrode. The shift in spin chemical potential acts as charge offset in the island and alternates the gate dependence of spin current. We demonstrate this phenomenon by applying master equation calculations to ferromagnetic/normal metal/ferromagnetic single electron transistors. Taking advantage of this effect, one can use ferromagnetic single electron transistors as a tunable current polarizer.