Performance comparison of capping layer materials for double spin-torque magnetic tunnel junctions

We present a computational study of different capping layer materials in double spin-torque MTJ structures. Using fully atomistic calculations based on density functional theory, we calculate key parameters relevant for the read, write, and storage performance of STT-MRAM devices. Among the three candidate materials, Tungsten (W), Tantalum (Ta), and MgO, W is identified as best material for both thermal stability, STT, and TMR, but a very large Gilbert damping can be problematic for reducing the switching current.