Demagnetization processes of Nd-Fe-B sintered magnets and ferrite magnets as demonstrated by soft X-ray magnetic circular dichroism microscopy

Abstract

The demagnetization processes of Nd-Fe-B sintered magnets and ferrite magnets are investigated using X-ray magnetic circular dichroism microscopy (XMCD). The average XMCD demagnetization curves are compared with the demagnetization curves from magnetic measurements. It is found that the magnetization reversal of the magnets proceeds in two steps. First, the grains are discretely demagnetized in a weak demagnetization field. When the strength of the demagnetization field increases, the magnetization of the grains adjacent to the discretely reversed grains is also reversed to form a cluster of reversed grains, and this cluster grows. Coercivity is achieved through the growth of such clusters. The demagnetization curves from XMCD and the demagnetization curves from the magnetic measurements agree well with each other when the self-demagnetization field and the magnetic after-effect in the XMCD measurement are taken into account. This result shows that the information obtained from the XMCD reflects the bulk information.