Macrospin in external magnetic field: entropy production and fluctuation theorems

Abstract

We consider stochastic rotational dynamics of a macrospin at a constant temperature, in presence of an external magnetic field. Starting from the appropriate Langevin equation which contains multiplicative noise, we calculate entropy production (EP) along stochastic trajectories, and obtain fluctuation theorems. The system remains inherently out of equilibrium due to a spin torque supporting azimuthal current, leading to an excess EP apart from the EP due to heat dissipation. The anomaly may be removed using a redefinition of dissipated heat and stochastic work done. Using numerical simulations, we obtain distribution functions for entropy production along stochastic trajectories to find good agreement with the detailed fluctuation theorem.

On the One‐Dimensional Transition State Theory and the Relation between Statistical and Deterministic Oscillation Frequencies of Anharmonic Energy Wells

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Entropy production and Onsager reciprocal relations describing the relaxation to equilibrium in stochastic thermodynamics

“…Today, thermodynamic theories play a crucial role in the understanding of several nano-systems and physical phenomena, including macromolecular folding and unfolding [48][49][50], molecular motors [51,52], muscles behavior [53,54], adhesion processes [55][56][57], micro-and nano-heat engines [58][59][60], micromagnetism [61][62][63][64][65], and heat transfer in nanostructures [66][67][68], just to name a few.…”