Dislocation-induced magnetization reversal in a ferromagnetic film

TL;DR

The work addresses how fast local elastic twists generated by moving dislocations can reverse magnetization in a ferromagnetic film through the Barnett effect, formalized within a two-frame Landau-Lifshitz dynamic model that includes exchange, uniaxial anisotropy, Zeeman coupling, and rotation. By computing the dislocation-induced rotation field $\boldsymbol{\Omega}$ and solving the dimensionless LL equations with cobalt-like parameters on a hexagonal lattice, the authors demonstrate magnetization switching on picosecond timescales as the dislocation passes. The key finding is that fast local rotations create strong effective fields $H = \boldsymbol{\Omega}/\gamma$ that drive the system from a metastable to a reversed state, with relaxation occurring over nanoseconds and possible GHz-scale oscillations. This mechanism offers a mechanically driven route to ultrafast magnetization control and motivates experimental exploration of Barnett-induced switching in nanoscale or stressed magnetic films, potentially enabling new memory or multifunctional device concepts.

Abstract

We demonstrate that moving edge dislocations can induce the reversal of magnetization in a ferromagnetic film due to the Barnett effect. The dynamics of magnetization is studied numerically within a discretized Landau-Lifshitz equation on a hexagonal lattice containing over $10^5$ sites. Local coordinate frames coupled to the crystallographic axes for each spin are used together with the laboratory coordinate frame. The parameters of a hexagonal close-packed cobalt lattice have been chosen for illustration. The magnetization reversal from a metastable initial state created by the external magnetic field occurs on a time scale of a few picoseconds. Our results imply that fast local elastic twists generated by moving dislocations serve as an important mechanism of magnetization dynamics in solids subjected to a mechanical stress.

Figures (5)

• Figure 1: Deformed crystal lattice in the presence of an edge dislocation. The rotation of crystallographic axes away from the dislocation core is apparent.
• Figure 2: Existence of meta-stable equilibria opposing the external field, for $h_z>0$. The equilibrium value of $s_{i,z}$ is shown in color.
• Figure 3: Full evolution of the lattice.
• Figure 4: Evolution of the lattice as the dislocation passes.
• Figure 5: Evolution of the lattice after the dislocation has passed, as it relaxes towards the stable equilibrium.