Demagnetizing Field Caused by Specimen End Gaps in Electromagnet Measurements of Permanent Magnet Materials

The midplane and volume-averaged demagnetizing factors, N mid and Nvol, for a uniformly magnetized cylinder of length l s and radius r s clamped in the pole gap of an electromagnet with end gaps of total length d s are calculated as functions of d s /l s and l s /(2r s ) and used for converting the measured magnetization-field curves of an Alnico specimen for different values of d s . The maximum d s /l s allowed for permanent magnet measurements stated in IEC and ASTM standards are discussed.