Determination of nanocrystal size distribution in magnetic multicore particles including dipole-dipole interactions and magnetic anisotropy: A Monte Carlo study

Paper in proceedings, 2010

A correct estimate of the size distribution (i.e., median diameter D and geometric standard deviation σ) of the magnetic nanocrystals (MNCs) embedded in magnetic multicore particles is a necessity in most applications relying on the magnetic response of these particles. In this paper we use a Monte Carlo method to simulate the equilibrium magnetization of two types of multicore particles: (I) MNCs fused in a random compact cluster, and (II) MNCs distributed on the surface of a large carrier sphere. The simulated magnetization data are then fitted using a common method based on a Langevin equation weighted with a size distribution function. Finally, the fitting parameters Dm and σm are compared to the real parameters Dp and σp used to generate the MNCs. Our results show that fitting magnetization data with a Langevin model that neglects magnetic anisotropy and dipole-dipole interactions leads to an erroneous estimate of the size distribution of the MNCs in multicore particles. The magnitude of the error depends on the particle morphology, number of MNCs contained in the particle and magnetic properties of the MNCs.