A micromagnetic theory of skyrmion lifetime in ultrathin ferromagnetic films

TL;DR

This paper develops a micromagnetic theory to calculate the lifetime of skyrmions in ultrathin ferromagnetic films, accounting for thermal noise and material parameters, providing explicit formulas for collapse rates.

Contribution

It introduces a novel micromagnetic framework for skyrmion lifetime estimation, especially in cases lacking a saddle point, with explicit formulas linking collapse rates to material properties.

Findings

Derived explicit Arrhenius collapse rate formulas.

Identified collapse as 'capture by an absorber' in absence of saddle point.

Provided dynamical paths to skyrmion collapse.

Abstract

We use the continuum micromagnetic framework to derive the formulas for compact skyrmion lifetime due to thermal noise in ultrathin ferromagnetic films with relatively weak interfacial Dzyaloshinskii-Moriya interaction. In the absence of a saddle point connecting the skyrmion solution to the ferromagnetic state, we interpret the skyrmion collapse event as ``capture by an absorber'' at microscale. This yields an explicit Arrhenius collapse rate with both the barrier height and the prefactor as functions of all the material parameters, as well as the dynamical paths to collapse.