Spin-filter induced large magnetoresistance in 2D van der Waals magnetic tunnel junctions

Two-dimensional (2D) van der Waals (vdW) heterostructures, known as layer-by-layer stacked 2D materials in a precisely chosen sequence, have received more and more attention in spintronics for their ultra-clean interface, unique electronic properties and 2D ferromagnetism. Motivated by the recent synthesis of monolayer 1T-VSe2 with ferromagnetic ordering and a high Curie temperature above room temperature, we investigate the bias-voltage driven spin transport properties of 2D magnetic tunnel junctions (MTJs) based on VSe2 utilizing density functional theory combined with the nonequilibrium Green's function method. In the device 1T-MoSe2/1T-VSe2/2H-WSe2/1T-VSe2/1T-MoSe2, the tunneling magneto-resistance (TMR) is incredibly satisfactory up to 5600%. Based on the analysis of evanescent states, this large TMR is attributed to the spin filter effect at the interface between 1T-VSe2 and 2H-WSe2, which overcomes the low spin polarization of 1T-VSe2. Furthermore, by inserting 2H-MoSe2, the spin filter effect is enhanced with decreasing current and the TMR is drastically improved to 1.7 × 10⁵%. This work highlights the feasibility of 2D vdW heterostructures for ultra-low power spintronic applications by electronic structural engineering.