Magnetization processes of fractal-like core shell nanoparticles

Abstract

The paper refers to micromagnetic simulations of magnetization processes of fractal-like core–shell nanoparticles. The objects were generated using the 3D diffusion limited aggregation (DLA) algorithm for obtaining fractals with two kinds of magnetic phases – magnetically soft core and magnetically hard shell. The simulations were carried out using the cluster Monte Carlo algorithm designed for spin continuous and multiphase magnetic systems. The presented research includes different degrees of branch development, different strengths of the exchange coupling between the phases, as well as different soft phase contents. As was shown, the influence of microstructure on the coercivity mechanism is a complex phenomenon. The core–shell coupling and the magnetic properties of the entire system can be controlled by fractal development. The spring-exchange mechanism and high surface development of the fractals makes it possible to obtain a value of the |BH|max parameter higher than 300 kJ/m3. For K = 5 × 10􀀀 5 eV and K = 5 × 10􀀀 4 eV, it requires about 30% and 7% contribution of the hard magnetic phase, respectively.