First-Principles Studies of Influences of Capping Layers on Perpendicular Magnetic Anisotropy (K_i) in X/Co₂FeAl/MgO (X = 4d/5d transition metals) Structures

The Co₂FeAl/MgO based magnetic tunnel junctions (MTJs) with interfacial perpendicular magnetic anisotropy (K_i) have attracted extensive interests because of their potential utilization in spin-transfer-torque magnetic random-access memory (STT-MRAM). In this study, we systematically investigated the capping layer impact on the K_i magnitude in Co₂FeAl/MgO system with 4d/5d transition metals (TMs) using density functional theory calculations. Our results show that TM capping layers, such as W, Pb, and Bi can effectively increase the K_i values as compared to the uncapped structures. The results are explained in terms of atomic resolved K_i contributions due to different orbital hybridizations. This work shed light on research and development of novel MTJs with high thermal stability during data storage in STT-MRAM in the future.