Thermally activated magnetization reversal in monoatomic magnetic chains on surfaces studied by classical atomistic spin-dynamics simulations

TL;DR

This study uses atomistic spin-dynamics simulations to investigate thermally induced magnetization reversal in monoatomic magnetic chains on surfaces, revealing how chain length, anisotropy, and domain wall dynamics influence reversal times.

Contribution

It introduces a detailed simulation approach to analyze thermal magnetization reversal mechanisms and quantifies the effects of anisotropy and chain length on reversal lifetimes.

Findings

Reversal lifetime follows an Arrhenius law with the domain wall energy as activation barrier.

Reversal is initiated at chain edges and propagates as a domain wall in a random walk.

Tri-axial anisotropy reduces magnetization lifetime despite unchanged activation barrier.

Abstract

We analyze the spontaneous magnetization reversal of supported monoatomic chains of finite length due to thermal fluctuations via atomistic spin-dynamics simulations. Our approach is based on the integration of the Landau-Lifshitz equation of motion of a classical spin Hamiltonian at the presence of stochastic forces. The associated magnetization lifetime is found to obey an Arrhenius law with an activation barrier equal to the domain wall energy in the chain. For chains longer than one domain-wall width, the reversal is initiated by nucleation of a reversed magnetization domain primarily at the chain edge followed by a subsequent propagation of the domain wall to the other edge in a random-walk fashion. This results in a linear dependence of the lifetime on the chain length, if the magnetization correlation length is not exceeded. We studied chains of uniaxial and tri-axial anisotropy and found that a tri-axial anisotropy leads to a reduction of the magnetization lifetime due to a higher reversal attempt rate, even though the activation barrier is not changed.