Giant tunneling magnetoresistance induced by bias voltage in spin-filter van der Waals magnetic tunnel junctions with an interlayer antiferromagnetic semiconductor barrier

Spin-filter van der Waals Magnetic tunnel junctions (sf-vdW MTJs) formed by an interlayer antiferromagnetic (AFM) vdW semiconductor as a barrier have exhibited promising prospects in achieving a high tunneling magnetoresistance (TMR) ratio in MTJs. Here, using first-principles calculations, we investigate the spin-dependent transport and the TMR effect of sf-vdW MTJs formed by sandwiching bilayer and trilayer NiBr₂ barriers between two graphite electrodes (Gr/NiBr₂/Gr sf-vdW MTJs). Similar to the experimental results of sf-vdW MTJs formed by a few-layer CrI₃ barrier, the TMR ratios of the Gr/NiBr₂/Gr sf-vdW MTJs increase first with the increase of bias voltage and decrease with the further increase of bias voltage after reaching the highest points because the conduction bands of the interlayer ferromagnetic (FM) NiBr₂ barrier at the K points go into the bias window earlier than those of the interlayer AFM NiBr₂ barrier with the increase of bias voltage. Compared to the TMR ratios of about 170% and 206% at zero bias voltage, the TMR ratios of the Gr/NiBr₂/Gr sf-vdW MTJs with bilayer and trilayer NiBr₂ barriers are largely increased about 34 and 67 times by the optimized bias voltage, respectively. Correspondingly, a giant TMR ratio of about 6000% and 14 000% can be achieved in the Gr/NiBr₂/Gr sf-vdW MTJs with bilayer and trilayer NiBr₂ barriers at 0.14 and 0.125 V bias voltage, respectively. Our results elucidate the mechanism of bias voltage induced giant TMR ratio in the Gr/NiBr₂/Gr sf-vdW MTJs and provide promising routes for developing MTJs with a high TMR ratio.