Size dependence of the thermal stability factor in a perpendicular CoFeB/MgO magnetic tunnel junction studied by micromagnetic simulations

Abstract

Size dependence of the thermal stability factor (Δ) for perpendicular CoFeB/MgO-based magnetic tunnel junctions (p-MTJs) was investigated using the string method in the framework of finite element micromagnetics. The simulation revealed that Δ showed significant size dependence, and the reversal mode changed from coherent rotation to domain wall (DW) motion as MTJ size increased. It also elucidated that Δ depended on the exchange stiffness constant in DW mediated reversal region. These Δ simulations can reproduce the experimental data and can be helpful for MTJ device design.