ABSTRACT
Nanoscale magnetic devices and particles are being developed for a
wide variety of applications, including magnetic memory, nanoscale
sensors, magnetic resonance imaging (MRI) agents, and therapeutic
agents. Magnetic nanoparticles are also endogenous to the human
body in the form of ferritin. The small volume and anisotropy
energies of these structures make their magnetic moments very
susceptible to thermal fluctuations. The magnetization dynamics of
these structures occur on awide range of time scales, from thermally
activated Arrhenius behavior that may cause an unwanted moment
reversal of a magnetic random access memory bit once in 10 years
to the 100 GHz precessional resonance of a magnetic nanoparticle
in a clinical MRI system. Here we review the stochastic dynamics
of magnetic nanoparticles and devices for both single particles and
for ensembles. We focus on particles whose dimensions are on the
order of 1 nm to 100 nm and have moments on the order of 10 to
100,000 μB.
