Fe ₃ GaTe ₂ /Ga ₂ Ge ₂ Te ₂ /Fe ₃ GaTe ₂ : A promising van der Waals magnetic tunnel junction with giant tunnel magnetoresistance

The development of all-two-dimensional van der Waals magnetic tunnel junctions (MTJs) holds great promise for next-generation spintronic devices. Here, we propose a fully van der Waals 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 9.15×10 6 % and nearly perfect spin polarization (~99.5%) at equilibrium. The high-performance stems from the strong spin polarization of FGT around the K-point 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 (LDOS) 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.