Structure and magnetization of a magnetoactive ferrocomposite

Abstract

This work is devoted to the theoretical study of the structural and magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles immobilized in a non-magnetic medium. This model is typical for describing magnetically active soft materials, “smart” polymer ferrocomposites, which have been applied in science-intensive industrial and biomedical technologies. It is assumed that the ferrocomposite is obtained by solidification of the carrier medium in a ferrofluid under an external magnetic field, the intensity of which is determined by the Langevin parameter α_p; after the solidification of the carrier liquid, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes. The features of the orientational texture formed in the sample are analyzed depending on the intensity of the magnetic field α_p and interparticle dipole–dipole interactions. The magnetization of a textured ferrocomposite in the magnetic field α is also investigated. Our results show that in the case of a co-directional arrangement of the considered fields and if α < α_p, the ferrocomposites are magnetized much more efficiently than ferrofluids due to their texture. In the fields α > α_p, the ferrocomposite is magnetized less efficiently than the ferrofluid due to the internal magnetic anisotropy of the nanoparticles. The analytical expressions presented here make it possible to predict the magnetization of a ferrocomposite depending on its internal structure and synthesis conditions, which is the theoretical basis for the synthesis of ferrocomposites with a predetermined magnetic response in a given magnetic field.