Role of magnetostatic interactions in assemblies of Fe nanoparticles

It has recently become possible to synthesize a class of nanostructured materials by ion implantation. The implanted ions aggregate into crystallographically oriented nanoscale inclusions in the host material. We have performed simulations of the magnetization curves for such assemblies of nanoscale Fe inclusions in a nonmagnetic host. We use random positions for the magnetic particles (not a regular grid) and include magnetostatic interactions in detail. We find that these materials are not adequately described by standard noninteracting theories-interactions have a significant effect. In particular, interactions can mask the effects of crystallite orientation, producing nearly isotropic hysteresis curves. The use of a noninteracting model could thus lead one to conclude, incorrectly, that the inclusions are randomly oriented. (C) 2001 American Institute of Physics.