A cubic discretization procedure of the micromagnetic energy functional
is used to carry out numerical studies of the magnetization process
in ferromagnetic cubes. Equilibrium magnetization configurations
and their switching behavior are calculated for particle sizes in
the range from 100 to 550 A In the model calculations the particles
are assumed to have uniaxial crystalline anisotropy with an anisotropy
constant of 18 500 erg/cm3, a saturation magnetization of 370 emu/cm3,
and an exchange constant of 10 - 6 erg/cm. For particle sizes smaller
than 520 A the remanent state has a flowerlike magnetization configuration.
Beyond 520 A this state is replaced by a vortex structure about the
easy axis. For particles smaller than 450 A switching occurs by approximately
uniform rotation of the flower state. The switching fields are larger
than the corresponding Stoner�Wohlfarth value. Beyond 450 A the application
of an external field leads to the formation of a vortex configuration.
The switching of the vortex configuration involves rotation of the
vortex axis at a reduced value of the switching field. The angular
dependence of the coercive field is calculated for particle sizes
of 200, 400, and 550 A.
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