Giant tunneling magnetoresistance in van der Waals magnetic tunnel junctions formed by interlayer antiferromagnetic bilayer CoBr2

The discovery of two-dimensional (2D) van der Waals (vdW) intrinsic magnets has opened a promising avenue to design high-performance magnetic tunnel junctions (MTJs) based on 2D materials. In this work, using first-principles calculations, it is demonstrated that bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$ is intrinsically a magnetic semiconductor with intralayer ferromagnetic (FM) and interlayer antiferromagnetic (AFM) couplings and the interlayer AFM coupling in bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$ is independent on the stacking orders. Moreover, using the nonequilibrium Green's function combined with density functional theory, it is found that due to the large difference between interlayer AFM and FM states of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier, the conductance of spin filter (SF) vdW MTJs based on the graphene/bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$/graphene heterostructure for the interlayer FM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier is about 25 times that for the interlayer AFM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier. Consequently, a high tunneling magnetoresistance (TMR) ratio of $2420%$ is achieved in this SF-vdW MTJ at zero bias. In particular, because the current for the interlayer FM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier rapidly increases with the increase of bias voltage, a giant TMR ratio of up to about $38\phantom{\rule{0.16em}{0ex}}000%$ can be achieved in this SF-vdW MTJ at 0.2-V bias. Our results suggest that SF-vdW MTJs formed by the interlayer AFM barrier with variable conductivity hold great potential for developing vdW MTJs with a high TMR ratio.