Stochastic dynamics of magnetization in a ferromagnetic nanoparticle out of equilibrium

摘要

We consider a small metallic particle (quantum dot) where ferromagnetismarises as a consequence of Stoner instability. When the particle is connectedto electrodes, exchange of electrons between the particle and the electrodesleads to a temperature- and bias-driven Brownian motion of the direction of theparticle magnetization. Under certain conditions this Brownian motion isdescribed by the stochastic Landau-Lifshitz-Gilbert equation. As an example ofits application, we calculate the frequency-dependent magnetic susceptibilityof the particle in a constant external magnetic field, which is relevant forferromagnetic resonance measurements.