Effects of Interfacial States and Strain on Tunnel Magnetoresistance in van der Waals Magnetic Tunnel Junctions
Sakshi Goel, Arti Kashyap, Keisuke Masuda, Terumasa Tadano
Abstract
All-two-dimensional magnetic tunnel junctions promise atomically sharp interfaces, yet the role of interface-induced states in their spin transport is not fully understood. Here, we theoretically investigate spin-dependent transport in van der Waals magnetic tunnel junctions of the structure Cr2C/MY2/Cr2C (M = Mo, W; Y = S, Se) with barrier thicknesses of 3, 5, 7, and 9 layers. The broad features of the k-resolved conductances, namely suppression near the Γ point and enhancement at six off-Γ hot spots, are consistent with the decay of evanescent states in the barrier. However, trilayer WS2, MoSe2, and WSe2 barriers exhibit conductances of the order of e2/h at k points within the hot spots. We attribute these near-unity transmission channels to resonant coupling between the interfacial states at the two electrode--barrier interfaces, as evidenced by their weak but finite residual weight at the barrier center. For thicker barriers, this coupling weakens, which suppresses the residual weight, thereby reducing the tunnel magnetoresistance (TMR) ratio of the MoS2 junction while enhancing those of the other junctions. To exploit the interfacial states for spin-selective tunneling, we further examine biaxial tensile strain applied to the trilayer junctions. At 4\% strain, the TMR ratio increases from 176\% to 540\% for MoS2 and from 98\% to 496\% for WS2, whereas MoSe2 and WSe2 exhibit comparatively weaker enhancement. Our results establish interfacial-state engineering via strain and barrier thickness as effective routes for enhancing the TMR effect in all-two-dimensional magnetic tunnel junctions.