Science http://doi.org/cpz8 (2018)

The promise of low power consumption combined with the continued scaling of its components to higher density could see magnetoresistive random-access memory (MRAM) become a dominant type of memory technology in the foreseeable future. To this end, the recent discovery of 2D magnetism in chromium triiodide (CrI3) creates opportunities for realizing atomically thin magnetic devices. To further illustrate this point, Song et al. have now reported layer-dependent tunnelling magnetoresistance (TMR) in a multiple-spin-filter magnetic tunnel junction (sf-MTJ) based on a 2D magnetic insulator CrI3.

The proposed van der Waals sf-MTJ device consists of a thin bilayer, trilayer or four-layer CrI3 tunnel barrier sandwiched between few-layer graphene and hexagonal boron nitride. In each case, CrI3 acts as a spin filter in which the spin orientation of constituent layers can be tuned by a magnetic field, creating multiple magnetic states of thickness-dependent complexity. The tunnelling current in the sf-MTJs is highly sensitive to the net spin polarization in CrI3 and can be greatly enhanced in the sample with fully aligned magnetization. The effect is especially pronounced in a four-layer CrI3 that shows TMR of up to 19,000% for a magnetic field of 9 T at 2 K.