Dependence of the Spin Transfer Torque Switching Current Density on the Exchange Stiffness Constant

TL;DR

This study uses micromagnetic simulations to show that the switching current density in spin transfer torque magnetic tunnel junctions depends on the exchange stiffness constant, influenced by shape anisotropy and domain structures.

Contribution

It reveals the dependence of switching current density on exchange stiffness, challenging the macro-spin model assumption of no such dependence, and suggests optimization avenues.

Findings

Switching current density varies with exchange stiffness constant.

Domain structures influence switching behavior.

Optimization of current density is possible through material and fabrication control.

Abstract

We investigate the dependence of the switching current density on the exchange stiffness constant in the spin transfer torque magnetic tunneling junction structure with micromagnetic simulations. Since the widely accepted analytic expression of the switching current density is based on the macro-spin model, there is no dependence of the exchange stiffness constant. When the switching is occurred, however, the spin configuration forms C-, S-type, or complicated domain structures. Since the spin configuration is determined by the shape anisotropy and the exchange stiffness constant, the switching current density is very sensitive on their variations. It implies that there are more rooms for the optimization of the switching current density with by controlling the exchange stiffness constant, which is determined by composition and the detail fabrication processes.