Magnetization Switching in Nanoscale Ferromagnetic Grains:
MFM Observables from Monte Carlo Simulations
H. L. Richards, S. W. Sides, M. A. Novotny,
and P. A. Rikvold
In Physical Phenomena at High Magnetic Fields II,
edited by Z. Fisk, L. Gor'kov, D. Meltzer,
and R. Schrieffer
(World Scientific, Singapore, 1996), pp. 386-391.
Recently experimental techniques, such as magnetic force microscopy
(MFM), have enabled the magnetic state of individual sub-micron
particles to be resolved.
Motivated by these experimental developments,
we use Monte Carlo simulations of two-dimensional kinetic
Ising ferromagnets to study the magnetic relaxation
in a negative applied field of a grain with an initial
magnetization m0 = +1.
We use classical droplet theory to predict the functional
forms for some quantities which can be observed by MFM.
An example is the probability that the magnetization is positive,
which is a function of time, field, grain size, and grain
The qualitative agreement between experiments and our simulations
of switching in individual single-domain ferromagnets
indicates that the switching mechanism in such particles may involve
local nucleation and subsequent growth of droplets of the stable