Relative significance of particle anisotropy in systems of ultrafine ferromagnetic particles

The relative weight of particle anisotropy in systems of dipolarly interacting single-domain ultrafine ferromagnetic particles is investigated based on the comparison between a simple model and a particular variant of it. The latter differs from the former by the absence of particle anisotropy, and both are investigated in parallel by Monte Carlo simulations of zero field cooling and field cooling experiments. By comparing systems characterized by different particle concentrations as well as by various types of particle positions' disorder, it is shown that the relative importance of the particle anisotropy, besides the expected dependence on the particle concentration, crucially depends on the positional disorder. (C) 2002 American Institute of Physics.