Methods to induce perpendicular magnetic anisotropy in full-Heusler Co2FeSi thin layers in a magnetic tunnel junction structure

摘要

In this study, to obtain perpendicular magnetic tunnel junctions (p-MTJs)using half-metallic ferromagnets (HMFs), several methods were developed toinduce perpendicular magnetic anisotropy (PMA) in full-Heusler Co2FeSi (CFS)alloy thin layers in an MTJ multilayer composed of a layered CFS/MgO/CFSstructure. Oxygen exposure at 2.0 Pa for 10 min after deposition of the bottomCFS layer was effective for obtaining PMA in the CFS layer. One of the reasonsfor the PMA is the formation of nearly ideal CFS/MgO interfaces due to oxygenexposure before the deposition of the MgO layer. The annealing process waseffective for obtaining PMA in the top CFS layer capped with a Pd layer. PMAwas clearly observed in the top CFS layer of a Cr(40 nm)/Pd(50 nm)/bottomCFS(0.6 nm)/MgO(2.0 nm)/top CFS(0.6 nm)/Pd(10 nm) multilayer, where the top CFSand Pd thin films were deposited at RT and subsequently annealed at 300{\deg}C.In addition to the continuous layer growth of the films, the crystallineorientation alignment at the top CFS/Pd interface probably attributes to theorigin of PMA at the top CFS layer.