  Magnetic nanoparticles are useful biological probes as well as therapeutic
agents. There have been several approaches used to model nanoparticle
magnetization dynamics for both Brownian as well as N\'eel rotation. The
magnetizations are often of interest and can be compared with experimental
results. Here we summarize these approaches including the Stoner-Wohlfarth
approach, and stochastic approaches including thermal fluctuations.
Non-equilibrium related temperature effects can be described by a distribution
function approach (Fokker-Planck equation) or a stochastic differential
equation (Langevin equation). Approximate models in several regimes can be
derived from these general approaches to simplify implementation.
