Magnetization processes of irregular dendrite structures - a Monte Carlo study

Abstract

The paper refers to micromagnetic simulations of magnetization processes of dendrite-like object. The objects were generated by the DLA fractal algorithm that allows obtaining fractals with different ratio of the spins attributed to the surface to volume. The simulations were carried out using the cluster Monte Carlo algorithm designed for spin continuous and multiphase magnetic systems. The presented researches include different magnetic anisotropy of the surface and volume reflected magnetically soft, hard and ultra-high coercive phases. As it was shown, the influence of microstructure on the coercivity mechanism is a complex phenomenon. In the case of the fractals with magnetically soft volume the increasing surface contribution causes either increse or decrease of the coercive field for relatively high or low magnetic anisotropy of the surface, respectively. For the fractals with ultra-high coercive volume the occurrence of the surface anisotropy leads to the significant deterioration of their hard magnetic properties. The obtained spin configurations show that this effect is related to non-colinear directions of the surface anisoropy and strong enough exchange coupling between the surface and volume.