Thermally activated magnetization reversal in monatomic magnetic chains on surfacesstudied by classical atomistic spin-dynamics simulations

Abstract

We analyse the spontaneous magnetization reversal of supported monatomic chains of finitelength due to thermal fluctuations via atomistic spin-dynamics simulations. Our approachis based on the integration of the Landau–Lifshitz equation of motion of a classical spinHamiltonian in the presence of stochastic forces. The associated magnetizationlifetime is found to obey an Arrhenius law with an activation barrier equal to thedomain wall energy in the chain. For chains longer than one domain wall width, thereversal is initiated by nucleation of a reversed magnetization domain primarilyat the chain edge followed by a subsequent propagation of the domain wall tothe other edge in a random-walk fashion. This results in a linear dependence ofthe lifetime on the chain length, if the magnetization correlation length is notexceeded. We studied chains of uniaxial and triaxial anisotropy and found that atriaxial anisotropy leads to a reduction of the magnetization lifetime due to ahigher reversal attempt rate, even though the activation barrier is not changed.