Magnetic Domain Analysis of Ferrite-Sintered Magnets in Thermally Demagnetized and AC Demagnetized States Using Multiple Distances Observation of MFM and Image Processing

The magnetic domain structure is an important factor in discussing the coercivity development mechanism. We have researched on the new observation method of magnetic domain structures using multiple distances observation of magnetic force microscope (MFM) and image processing. We observed magnetic domain structures in thermally demagnetized state and alternating current (ac) demagnetized state of ferrite-sintered magnets using this method. In addition, the initial magnetization curve was measured in each demagnetized state. There were differences in the domain structures and the initial magnetization curves in each demagnetized state. These differences suggest that irreversible multi-domain gains (IRMDGs) confirmed in rare-earth magnets are present even in sintered ferrite magnets.