Recent progress and challenges in magnetic tunnel junctions with 2D materials for spintronic applications

As Moore's law is gradually losing its effectiveness, the development of alternative high-speed and low-energy-consuming information technology with postsilicon-advanced materials is urgently needed. The successful application of tunneling magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) has given rise to a tremendous economic impact on magnetic informatics, including magnetoresistive random access memory (MRAM), radiofrequency sensors, microwave generators, and neuromorphic computing networks. The emergence of two-dimensional (2D) materials brings opportunities for MTJs based on 2D materials, which have many attractive characteristics and advantages. In particular, the recently discovered intrinsic 2D ferromagnetic materials with high spin polarization hold the promise for next-generation nanoscale MTJs. Various 2D materials, such as semimetallic graphene, insulating h-BN, semiconducting MoS2, magnetic semiconducting CrI3, magnetic metallic Fe3GeTe2, and some other recently emerged 2D materials, are discussed as the electrodes and/or central scattering materials of MTJs in this review. We discuss the fundamental and main issues facing MTJs; review the current progress made with 2D MTJs; briefly comment on work with some specific 2D materials and highlight how they address the current challenges in MTJs; and, finally, offer an outlook and perspective of 2D MTJs.