Bandopadhyay, S and Chaudhuri, Debasish and Jayannavar, A M
(2014)
Macrospin in external magnetic field: Entropy production and
fuctuation theorems.
Condensed Matter.
pp. 1-8.
(Submitted)
Abstract
We consider stochastic rotational dynamics of a single magnetic domain in an external magnetic
field, at constant temperature. Starting from the appropriate Langevin equation of motion, we calculate
entropy production along stochastic trajectories to obtain
uctuation theorems, by presenting
several possibilities of choosing conjugate trajectories. One of these choices gives entropy production
in the reservoir that is consistent with prediction from Fokker-Planck equation. We further show
the relation between heat absorbed and entropy production in the reservoir, using stochastic energy
balance. For a time-independent field, the magnetization obeys Boltzmann distribution, however,
also supports an azimuthal current making the dynamics inherently non-equilibrium. We use numerical
simulations to obtain distribution functions for entropy production along trajectories which
show good agreement with the detailed
uctuation theorem.
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