Interface imperfection effects on spin transfer torque switching: an atomistic approach

Abstract

The further commercialization of spintronic memory devices depends on the development of methods by which to assess performance. This paper presents an approach to the atomistic investigation of switching performance in spin transfer torque magneto-resistive random access memory (MRAM) devices with the use of interface imperfection model. Switching simulation in the nanosecond regime was made possible under this model, and we first time demonstrate that switching time is inversely proportional to interface imperfection (i.e. roughness). In investigating the damping of CoFeB/MgO films, we analyzed the effective damping constant α eff, which cannot be accurately predicted for ferromagnetic layers of less than 2 nm using existing micromagnetic models. The proposed model includes a roughness parameter, which has nearly no effect on the effective damping constant in films of >2 nm, but a profound effect in films of <2 nm, reaching a 27% decrease in a 1.0 nm CoFeB film. Our finding is supported by the experimental data of classic references. We expect that these results will prove valuable in magnetic simulation and research on MRAM with ultrathin films.