https://doi.org/10.1007/s100510170318
On dissipation mechanisms in micromagnetics
Dipartimento di Ingegneria Civile, Università di Roma "Tor Vergata",
Via di Tor Vergata 110, 00133 Roma, Italy
Corresponding author: a ppg@uniroma2.it
Received:
31
October
2000
Published online: 15 February 2001
Within the framework of a dynamic version of
micromagnetics [1,2], the space-time evolution of
magnetization 
in a rigid, saturated ferromagnet is governed
by the following equation:
where the interaction couple 
and the couple stress
are to be constitutively specified. Under
constitutive assumptions for 
, , and the free energy ψ,
that allow for equilibrium response and viscosity out of
equilibrium and agree with the dissipation principle
the above evolution equation yields a broad generalization of the
standard Gilbert equation. In particular, while the standard
Gilbert equation only incorporates relativistic dissipation, it is
shown that the dissipation mechanisms compatible with the
generalized Gilbert equation include exchange dissipation [2],
dry-friction dissipation [3], and others. It is
also shown that the additional term proposed in [4] to
account for exchange dissipation, rather than having a genuine
dissipative nature, modifies instead the nature of possible
equilibria; and that such a modification is an automatic side
effect when dry-friction dissipation is incorporated in the manner
of [3].
PACS: 75.40.Gb – Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.) / 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001
