Domain structure of polycrystalline MnZn ferrites

The magnetic domain structure of sintered MnZn ferrites was observed using the Bitter method, Lorentz microscopy and Colloid-SEM method. The Bitter method revealed that the domain structure of the surface is stripe-like. Under an external magnetic field, the Bitter method showed the domain wall motion during the initial magnetization process and the irregular motion of domain wall near the saturation magnetic field (90∼120 Oe). Using Lorentz microscopy, the closure domain, which is characteristic of the soft magnetic materials, and the bulging of the domain wall were directly observed. In the Colloid-SEM method, the domain structure was observed as a function of the oxygen partial pressure during the sintering process. As atmospheric parameter, a, increased, the roughness of the domain wall increased, while the initial permeability decreased.