Some Measurements of Inhomogeneous Permanent Magnets by the Pole-Coil Method

The pole-coil method for measuring demagnetization curves of permanent magnets is applied to inhomogeneous magnets. It allows the analysis of different causes of inhomogeneities: differences in the intrinsic magnetic properties within one test sample, in the degree of orientation of otherwise homogeneous material, in the effectiveness of magnetic heat and annealing treatment; inclusion of holes or nonmagnetic contaminations; unequal cross sections of the tested magnet, for example, with conical shape.

By the pole-coil method inhomogeneities can be recognized by differences in remanence and coercivity. But in the case of serial arrangement of different components the resulting coercivity of an inhomogeneous sample is an average value of the coercivities of the components and nearly unaffected by the location of the measuring spot. The measurement of a magnet with different cross-sectional areas on both faces yields data for immediate magnetic circuit design.