Observation of room-temperature magnetoresistance effect in Co2Fe(Al,Si)/Ge/Co2FeSi vertical spin-valve devices on Si

Using low-temperature growth techniques and an intermediate Ge layer with Sn doping, we experimentally demonstrate an epitaxial Co 2 Fe(Al,Si)/Ge/Co 2 FeSi heterostructure on a Si platform, where Co 2 Fe(Al,Si) and Co 2 FeSi are Heusler compounds that exhibit half-metallic properties. The Sn doping only at the initial growth stage of Ge effectively affects the suppression of surface segregation of Sn and the atomic interdiffusion at the Ge/Co 2 FeSi heterointerface. By fabricating current-perpendicular-to-the-plane spin-valve devices, we observe a magnetoresistance (MR) effect with an MR ratio of ∼ 0.11 % at room temperature, showing evidence of a nonvolatile memory effect at room temperature, even in a vertical semiconductor spintronic device structure with Co-based Heusler compounds. This study presents crucial findings for high-performance Ge-based vertical spin-valve devices on a Si platform.