Giant tunneling magnetoresistance in van der Waals magnetic tunnel junctions formed by interlayer antiferromagnetic bilayer CoBr_2

摘要

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 CoBr_2 is intrinsically a magnetic semiconductor with intralayer ferromagnetic (FM) and interlayer antiferromagnetic (AFM) couplings and the interlayer AFM coupling in bilayer CoBr_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 CoBr_2 barrier, the conductance of spin fliter (SF) vdW MTJs based on the graphene/bilayer CoBr_2/graphene heterostructure for the interlayer FM slate of the CoBr_2 barrier is about 25 times that for the interlayer AFM state of the CoBr_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 CoBr_2 barrier rapidly increases with the increase of bias voltage, a giant TMR ratio of up to about 38 000% 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.