Fe3GaTe2/Ga2Ge2Te2/Fe3GaTe2: a promising van der Waals magnetic tunnel junction with giant tunnel magnetoresistance.

The development of all-two-dimensional van der Waals (vdW) magnetic tunnel junctions (MTJs) hold great promise for next-generation spintronic devices. Here, we propose a fully vdW MTJ composed of ferromagnetic Fe3GaTe2(FGT) as electrodes and a monolayer Ga2Ge2Te2(GGT) as the insulating barrier. Through first-principles quantum transport calculations, we demonstrate that the FGT/GGT/FGT heterostructure exhibits a giant tunnel magnetoresistance (TMR) ratio of 9.15 × 106% and nearly perfect spin polarization (∼99.5%) at equilibrium. The high-performance stems from the strong spin polarization of FGT around theKpoint and the wide bandgap of GGT near the same momentum region, which collectively suppress unpolarized carrier transmission. Furthermore, the lattice mismatch between FGT and GGT is only 1.5%, and their stacking sequences are symmetry-compatible, leading to atomically sharp interfaces that minimize spin scattering. Spin-resolved local density of states profiles further illustrate the mechanism for high TMR: in the parallel state, a pronounced spin-up density extends across the junction, supporting a low-resistance conducting path, while the spin-down channel and both channels in the anti-parallel state show negligible density within the barrier, indicating high-resistance tunneling states. In addition, the TMR is electrically tunable by bias voltage and remains above 4000% at low biases (<300 mV), indicating robust performance under operational conditions. These results highlight FGT/GGT/FGT as a highly promising system for room-temperature spin valves.