Significant reduction of critical currents in MRAM designs using dual free layer with perpendicular and in-plane anisotropy

TL;DR

This paper demonstrates that using a dual free layer with perpendicular and in-plane anisotropy in MRAM significantly reduces the critical switching current and enhances spin torque efficiency, based on detailed simulations.

Contribution

It introduces a dual free layer design in MRAM that improves spin torque efficiency by a factor of 3.2 and reduces switching current, supported by comprehensive spin transport and micromagnetic simulations.

Findings

Spin torque efficiency improved by 3.2 times.

Switching current reduced by a factor of 4.

Enhanced spin accumulation due to dynamical magnetization tilting.

Abstract

One essential feature in MRAM cells is the spin torque efficiency, which describes the ratio of the critical switching current to the energy barrier. Within this paper it is reported that the spin torque efficiency can be improved by a factor of 3.2 by the use a of dual free layer device, which consists of one layer with perpendicular crystalline anisotropy and a second layer with in-plane crystalline anisotropy. Detailed simulations solving the spin transport equations simultaneously with the micromagnetics equation were performed in order to understand the origin of the switching current reduction by a factor of 4 for the dual layer structure compared to a single layer structure. The main reason could be attributed to an increased spin accumulation within the free layer due to the dynamical tilting of the magnetization within the in-plane region of the dual free layer.