Critical current density for spin transfer torque switching with composite free layer structure

TL;DR

This paper investigates the critical current density needed for spin transfer torque switching in composite free layers of magnetic tunnel junctions, analyzing how coupling strength and torque efficiency influence switching behavior.

Contribution

It introduces an analytic spin wave excitation model to determine the instability condition of coupled ferromagnetic layers under spin transfer torque, validated by macro-spin simulations.

Findings

Critical current density depends on coupling strength and torque efficiency.

Analytic model accurately predicts instability conditions.

Results inform design of more efficient magnetic memory devices.

Abstract

Critical current density of composite free layer (CFL) in magnetic tunneling junction is investigated. CFL consists of two exchange coupled ferromagnetic layers, where the coupling is parallel or anti-parallel. Instability condition of the CFL under the spin transfer torque, which is related with critical current density, is obtained by analytic spin wave excitation model and confirmed by macro-spin Landau-Lifshitz-Gilbert equation. The critical current densities for the coupled two identical layers are investigated with various coupling strengths, and spin transfer torque efficiencies.