Magnetostatic interactions in various magnetosome clusters

Abstract

Hysteretic properties of dilute assemblies of various types of magnetosome clusters, i.e., linear chains, closed rings, and random three-dimensional (3D) configurations are studied by means of numerical simulation. It is shown that after averaging over random particle positions and random orientations of the particle easy anisotropy axes, there remain only several physical parameters that determine the shape of the assembly hysteresis loop: the cluster topology, the characteristic value of the magnetostatic interaction field, and the number of the nanoparticles within the cluster. The strong magnetostatic interaction between the particles increases significantly the coercive force of an assembly of linear chains or circular rings. On the other hand, for these assemblies, the type of the random anisotropy assumed as well as the number of the particles within the cluster has only minor effect on the hysteresis loop shape. For an assembly of 3D magnetosome clusters, the remanent magnetization shows strong dependence on the volume fractions of magnetic nanoparticles, contrary to the coercive force behavior.