Magnetic properties of Fe nanocubes with magnetostatic interactions

Recent experiments indicate that the magnetic properties of single domain Fe nanoparticles (dispersed in an insulating matrix) may be dominated by magnetostatic interactions at packing fractions as low as 10%, where the separation between particles is of the same order as the particle size [Sorge , IEEE Trans. Magn. 37, 2197 (2001)]. We use extensive Monte Carlo simulations to calculate the temperature dependence of the remnant magnetization as a direct test of this hypothesis [Sorge , IEEE Trans. Magn. 37, 2197 (2001)]. The particle distribution is constructed with a computer model that imitates the experimental system for which data were obtained from transmission electron microscopy images, and the Fe particles are modeled as point dipoles with cubic anisotropy. Using bulk values for the anisotropy and the Fe magnetization, our simulations reproduce very well the experimental remnant magnetization. Furthermore, we find that the magnetic properties are dominated by the effects of dipole-dipole interactions and that the experimental results cannot be reproduced with noninteracting particles. (C) 2003 American Institute of Physics.