On the Mechanism of the Initial Permeability in MgMnZn-Ferrite

The magnetic permeabiility and the thickness of the socalled %on"magnetic grain boundary were studied for a MgMnZn-femte with composition M~,J~,&ln,lFe,,,03,m For the mono-domain situation the grain size dependence of the effective initial permeability is well described by the nonmagnetic grain boundary model. A gradual increase of permeability with grain size around the transition from monoto two-domain indicates that the permeability is predominantly rotational in origin. The intrinsic initial permeability and the "nonumagneticgrain boundary width were obtained from a fit of permeability versus grain size at different temperatures. It is found that the grain boundary thickness decreases with temperature. This suggests that the grain boundary is hard magnetic rather than nonmagnetic.