Local and non-local spin valve effects in Fe₃Si/FeSi₂/Fe₃Si vertical trilayer films at room temperature

Local and non-local vertical trilayer spin valve films comprising ferromagnetic Fe3Si layers and semiconducting nanocrystalline FeSi2 interlayers were prepared by sputtering combined with a mask method, and spin valve signals were measured at room temperature. The local spin valve signals were observed at different FeSi2 interlayer thicknesses of 5, 10, 50, and 100 nm. Spin-polarized currents were generated from ferromagnetic Fe3Si layers into semiconducting nanocrystalline FeSi2 layers at room temperature. They might be because carriers in the FeSi2 layers are transported in hopping conduction. On the other hand, the non-local spin valve signals were also observed at the FeSi2 film thickness of 10 nm. Spin accumulation, so-called pure spin current, was generated from ferromagnetic Fe3Si layers into semiconducting FeSi2 layers at room temperature. Nanocrystalline FeSi2 that can be deposited technically easily is a new spin transport semiconductor and hopping conduction does not drastically lessen the spin transport length.