Spin-transfer-induced magnetization switching in magnetic tunnel junctions

Micromagnetic simulations for spin-transfer-induced magnetization dynamics in nanoscale low-resistance magnetic tunnel junctions (MTJs) are performed by using the modified Landau-Lifshitz equation in which a spin-transfer model for MTJs is included. Calculations show that critical switching current density (Jc) is about (4-8) × 106 A cm2, consistent with the experimental data, lower than the values found in metallic spin-valve nanopillars (typically in the order of ∼ 107 A cm2). A slight asymmetry of the critical current is observed in the magnetization switching loop, due to the asymmetry of the spin-torque factor. The switching time is related to the applied current, and our calculation results show that a longer switching time, 10-15 ns, is needed when the applied current density J is close to Jc, and it decreases down to 1 ns for J>2× 107 A cm2.