Two-dimensional Mn ₂ CF ₂ MXene-based magnetic tunnel junctions with giant spin filter tunnel magnetoresistance

The discovery of two-dimensional (2D) intrinsic ferromagnets has opened new avenues for realizing van der Waals (vdW) magnetic tunnel junctions (MTJs) that overcome the limitations of conventional MTJs through atomic-scale thickness, reduced spin scattering, and superior interfacial quality, thereby preserving high spin polarization. Using first-principles density functional theory calculations combined with the non-equilibrium Green's function (DFT + NEGF) formalism, we investigated the spin-dependent transport properties of 2D MXene Mn₂CF₂-based vdW heterostructures. In lateral 2H-MoS₂/Mn₂CF₂ devices, we observe an ohmic contact with perfect spin filtering and a linear current-voltage (I-V) response. In vertical MTJs, Mn₂CF₂ acts as the spin-filter barrier, 1T-MoS₂ as the electrode, and tunnel magnetoresistance (TMR) is calculated for metallic, semiconducting, and hybrid barriers of varying thickness and stacking configurations. A four-layer 2H-MoS₂ barrier yields the highest TMR of 7.21 × 10⁵% with a large peak-to-valley current ratio, while even a single-layer 2H-MoS₂ retains a substantial TMR of 10³% under higher bias. In contrast, a five-layer 1T-MoS₂ barrier strongly suppresses TMR due to reduced spin-injection efficiency and exhibits spin-flip transitions above a certain bias. These results establish Mn₂CF₂-based 2D vdW heterostructures as promising platforms for next-generation spintronic devices, combining higher TMR with pronounced negative differential resistance and providing a robust theoretical foundation for experimental realization.