MAGNETIZATION REVERSAL IN COBALT-SURFACE-COATED IRON-OXIDE PARTICLES

The reduced critical field hn for magnetization reversal by curling of Co-surface-coated iron-oxide particles has been investigated in terms of the atomic layer model (ALM). The most simple case is a rectangular Co distribution (particle composed of a γ-Fe2O3 core and a shell of CoFe2O4). In this case, the results agree very well with the curves calculated by Aharoni [1] in the frame of micromagnetism. Furthermore, the influence of Co diffusion into the particle core is taken into account. It turns out that hn first increases considerably with proceeding diffusion. Depending on the anisotropy magnitude the further alteration may be either positive or negative. This behaviour offers the possibility to explain the different temperature dependence of the coercivity before and after annealing. © 1990 IEEE