Spin dependent transport perpendicular to CoPt/S/Co (S=Si, Ge) trilayer

In this article, we report spin dependent electron transport perpendicular to a ferromagnet/semiconductor/ferromagnet trilayer with the current perpendicular to the plane (CPP) geometry and fabricated by a photolithographic technique. The CPP current was defined with a contact hole of 20 μm diameter produced in a SiO2 spacing layer. A CoPt/S/Co trilayer was used in the present study. Various film deposition methods were studied for optimum performance. A superior hard magnetic property was obtained in rf sputtered CoPt, which results in a well defined selective magnetization switching between CoPt and Co layers. The magnetoresistance (MR) effects have been confirmed by the measurement of MR hysteresis for various semiconductor layers. The values of MR change ΔR at room temperature observed in sputtered Ge (42 nm), evaporated Si (30 nm), and sputtered Si (16 nm) were 0.40 mΩ (R=1.3 Ω), 0.30 mΩ (R=2.4 Ω), and 5.5 mΩ (R=19 Ω), respectively. The magnetron sputtering was found to be a most promising method for producing a pinhole free semiconductor layer of order 20 nm thickness.