MAGNETIC-PROPERTIES OF SUPERPARAMAGNETIC PARTICLES BY A MONTE-CARLO METHOD

We develop and carry out Monte Carlo simulations for an ensemble of su perparamagnetic particles uniformly distributed in a nonmagnetic matri x. We find the magnetization below the blocking temperature T-B when i t shows hysteresis and above T-B in the superparamagnetic region. We d etermine the blocking temperature for a set of anisotropy strengths fr om the magnetization and the susceptibility of the particles. A fixed number of Monte Carlo steps with a constrained acceptance rate is show n to be equivalent to an observation time in the simulations that is m uch shorter than experimental observation times. We show how the block ing temperature obtained in the simulations can be converted into the corresponding experimentally measurable blocking temperature by using this difference in the observation times. This provides a method to co mpare Monte Carlo simulation results with experiments, such as recent ones on fcc Co particles.