Distribution of the magnetization reversal duration in sub-ns spin-transfer switching

TL;DR

This paper investigates the distribution of magnetization switching times in spin-transfer devices, revealing a comb-like pattern due to precessional dynamics and thermal fluctuations, with improved reproducibility under biasing.

Contribution

It introduces a model explaining the comb-like distribution of switching times based on precessional and thermal effects, and demonstrates how biasing enhances reproducibility.

Findings

Switching times follow a multiply-peaked, comb-like distribution.

Precessional dynamics cause the multiple peaks in switching durations.

Biasing with a hard axis field improves switching reproducibility.

Abstract

We study the distribution of switching times in spin-transfer switching induced by sub-ns current pulses in pillar-shaped spin-valves. The pulse durations leading to switching follow a comb-like distribution, multiply-peaked at a few most probable, regularly spaced switching durations. These durations reflect the precessional nature of the switching, which occurs through a fluctuating integer number of precession cycles. This can be modeled considering the thermal variance of the initial magnetization orientations and the occurrence of vanishing total torque in the possible magnetization trajectories. Biasing the spin-valve with a hard axis field prevents some of these occurrences, and can provide an almost perfect reproducibility of the switching duration.