Effects of heat treatment and magnetoannealing on nanocrystalline Co-ferrite powders

Abstract

This work consists of three parts: the effects of heat treatment (slow cooling and quenching), magnetoannealing, and postannealing of samples with induced anisotropy. It has been found that noncomplete inverse spinel structure was the result after annealing at higher temperature and quenching. Our Mössbauer spectroscopy study confirmed noncomplete inverse structure after quenching, while inverse spinel structure was formed after slow cooling. The kinetics of the formation of induced anisotropy during magnetoannealing has been investigated in this study. Reduction of crystalline magnetic anisotropy was observed, as coercivity decreased after magnetoannealing. The change of remanence ratio and coercivity followed the expected equations for ion diffusion. A relative large anisotropy in magnetization was evident. A postannealing resulted in the conversion into the initial isotropic stage. The process could be well described using the equations of ion diffusion. © 2005 American Institute of Physics.