Stochastic processes in magnetization reversal involving domain wall motion in magnetic memory elements

TL;DR

This paper investigates stochastic effects in magnetization reversal in magnetic memory elements, highlighting the roles of domain wall nucleation and motion, and identifying conditions for quasi-deterministic behavior.

Contribution

It provides experimental evidence and micromagnetic simulations revealing stochastic effects and conditions for deterministic domain wall motion in magnetic tunnel junctions.

Findings

Reproducible ballistic domain wall motion occurs when Bloch and Nél walls are energetically degenerate.

Two stochastic effects dominate reversal: incubation time and Walker regime motion.

Micromagnetic simulations identify pinning contributions and conditions for deterministic motion.

Abstract

We show experimentally through time-resolved conductance measurements that magnetization reversal through domain wall motion in sub-100 nm diameter magnetic tunnel junctions is dominated by two distinct stochastic effects. The first involves the incubation time related to domain wall nucleation, while the second results from stochastic motion in the Walker regime. Micromagnetics simulations reveal several contributions to temporal pinning of the wall near the disk center, including Bloch point nucleation and wall precession. We show that a reproducible ballistic motion is recovered when Bloch and N\'eel wall profiles become degenerate in energy in optimally sized disks, which enables quasi-deterministic motion.