Peculiarities of the stochastic motion in antiferromagnetic nanoparticles

TL;DR

This paper derives stochastic equations for antiferromagnetic nanoparticles, revealing unique noise-induced dynamics and energy distributions that differ from ferromagnetic systems, with implications for spintronic device stability.

Contribution

It introduces stochastic Langevin and Fokker-Planck equations for AFM vectors, analyzing noise effects in AFM particles under spin-polarized currents, a novel approach in the field.

Findings

Energy distribution functions near equilibrium states are characterized.

Noise-induced dynamics in AFM differ from ferromagnets.

Distinct behaviors in sub- and super-critical regimes.

Abstract

Antiferromagnetic (AFM) materials are widely used in spintronic devices as passive elements (for stabilization of ferromangetic layers) and as active elements (for information coding). In both cases switching between the different AFM states depends in a great extent from the environmental noise. In the present paper we derive the stochastic Langevin equations for an AFM vector and corresponding Fokker-Planck equation for distribution function in the phase space of generalised coordinate and momentum. Thermal noise is modeled by a random delta-correlated magnetic field that interacts with the dynamic magnetisation of AFM particle. We analyse in details a particular case of the collinear compensated AFM in the presence of spin-polarised current. The energy distribution function for normal modes in the vicinity of two equilibrium states (static and stationary) in sub- and super-critical regimes is found. It is shown that the noise-induced dynamics of AFM vector has pecuilarities compared to that of magnetisation vector in ferromagnets.