Comparing h-BN and MgO tunnel barriers for scaled magnetic tunnel junctions

Magnetic tunnel junctions (MTJ) with MgO/Fe based interfaces and perpendicular spin directions form the basis of present-day spin-transfer torque magnetic random-access memories. Many semiconductor devices, such as CMOS transistors, have undergone fundamental changes in materials design as dimensional scaling has progressed. Here, we consider how future scaling of MTJs might affect materials choices, comparing different tunnel barriers, such as 2D h-BN materials with existing MgO tunnel barriers. The different interfacial sites of h-BN on Ni or Co are compared in terms of their physisorptive or chemisorptive bonding and how this affects their transmission magnetoresistance, ability to create perpendicular magnetic isotropy, and unusual factors such as the "pillow effect." These effects are balanced by the beneficial chemical thermodynamics of the existing MgO barriers and MgO/Fe interfaces.