Improved Spin Transport in Co₂FeAl Magnetic Tunnel Junctions with Symmetric Hybrid MgO/WSe₂/MgO Barriers

This work reports a first-principles study of a hybrid-barrier magnetic tunnel junction (MTJ) with the stack Co₂FeAl/MgO/WSe₂/MgO/Co₂FeAl, modeled using density-functional theory (DFT) combined with a non-equilibrium Green’s-function (NEGF) transport framework in QuantumATK. The symmetric device yields a tunneling magnetoresistance (TMR) of about 170% at 300 K, indicating strong spin-dependent tunneling suitable for room-temperature spintronic operation. To assess the impact of structural asymmetry, two modified hybrid-barrier junctions were examined in which the left-side (skip-L) or right-side (skip-R) MgO sublayer was removed, giving WSe₂/MgO and MgO/WSe₂ hybrid-barrier. In these asymmetric configurations, the TMR drops to ~ 19% at 300 K, demonstrating that the loss of symmetric MgO confinement substantially weakens Δ₁-like coherent tunneling and spin-selective transmission. Overall, the results show that a symmetric MgO/WSe₂/MgO barrier can effectively merge the coherent tunneling characteristics of MgO with the spin-filtering behavior of WSe₂, leading to a thermally robust, high-TMR Co₂FeAl-based MTJ that is well suited for spintronic memory applications.