In this chapter a brief overview of the micromagnetic
model [3,4] is presented. The discussion starts
with the introduction of the different interactions that occur
within ferromagnetic bodies at different spatial scales. The
expressions of the energies related to each analyzed interaction
are reported. As second step, the Brown's equations are
derived by imposing micromagnetic equilibrium as a `stationary
point' of the free energy functional. As a further step, the
semiclassical dynamic model for damped gyromagnetic precession,
described by the Landau-Lifshitz and
Landau-Lifshitz-Gilbert equations [3,18], is
introduced on the basis of physical considerations on spin
magnetic momentum of electrons and the well-known relationship
with angular momentum through the gyromagnetic ratio. The
dimensionless form of the free energy and Landau-Lifshitz-Gilbert
equation is presented. The fundamental properties of magnetization
dynamics, magnetization magnitude conservation and energy balance,
are derived. General introduction of the phenomenological Gilbert
damping is also explained.
Subsections
