Recent demonstrations of magnetic ordering and spin transport in two-dimensional heterostructures have opened research venues in these material systems. In order to control and enhance the tunneling magnetoresistance phenomena in 2D magnetic heterostructures beyond phenomenological descriptions, quantitative estimates of tunneling rates in terms of the atomic details are required. Here we combine first principles and quantum ballistic transport calculations to shed important insights from an atomistic viewpoint on the underlying mechanisms governing spin transport in graphene/${\mathrm{CrI}}_3$ junctions. Descriptions of the electronic structure reveal that tunneling is the dominant transport mechanism in these heterostructures and helps differentiate intermediate metamagnetic states present in the switching process. We find that quantum confinement and layer-layer interactions are key to describing transport in these two-dimensional systems. Ballistic transport calculations further support these findings and yield magnetoresistance values in remarkable agreement with experiments. The short width of these barriers limits analysis solely based on the bulk complex band structure often employed in the description of magnetic tunnel junctions. Our work devises mechanisms to attain larger tunneling magnetoresistances, proving valuable to the advancement of spin valves in layered heterostructures.

• Received 14 June 2019
• Revised 23 April 2020
• Accepted 11 May 2020

DOI:https://doi.org/10.1103/PhysRevB.101.195439