Magnon-assisted tunnelling in van der Waals heterostructures based on CrBr 3

Recently, the family of two-dimensional materials has been expanded to include ferromagnets. It was shown that CrI₃ exhibits ferromagnetism down to thicknesses of a single monolayer [Huang, B. et al. Nature 546, 270 (2017)]. CrI₃ is part of a group of materials known as the chromium trihalides, CrX₃ (where X=Cl, Br or I). I will report on a few layers of exfoliated CrBr₃ (2-6 layers) that are also ferromagnetic by fabricating and characterising functional tunnelling devices where the CrBr₃ layer is sandwiched in between two graphene electrodes. I will also report a new type of tunnelling mechanism in van der Waals heterostructures by demonstrating that electrons in our device tunnel between the graphene layers via the emission (and, at high temperature, absorption) of magnons in the CrBr₃ barrier.