THEORETICAL-ANALYSIS OF LOCALIZED MAGNETIC-FLUX MEASUREMENT BY NEEDLEPROBE

Analytical study of the needle probe measurement of magnetic nux was p erformed on the basis of the electromagnetic theory to provide an adva nced theoretical backbone for the measuring method. Provided that the nux change in the specimen is homogeneous, the electromotive force ind uced between the needles represents exactly the nux change in the area between the needles. The measuring error in the needle probe measurem ent is caused by lack of homogeneity in the nux change postulated in t he theory. Among several possible causes of flux non-homogeneity, the existence of domain structure is most intrinsic in localized area meas urements, so that in this study the measuring error due to this cause was calculated theoretically in detail It can be concluded that even i n the cases of large domain size often occurring in oriented core mate rials, the localized measurements by the needle probe provide fairly r eliable measure of the nux change in the area.