A COMPARISON OF THE MAGNETIC PROPERTIES OF COMMERCIAL HDDR POWDER WITH THOSE OF OTHER COMMERCIAL SINTERED RARE-EARTH MAGNETS

摘要

Rare-earth permanent magnet motors are being used increasingly in electrical machines and modern production methods frequently require in situ magnetization of the magnets. Magnetic measurements have been performed on magnetically anisotropic Nd2Fe14B powder (Magnequench MQA-T), sintered Nd2Fe14B and sintered Sm2Co17 and were compared in order to study the influence of the magnetizing field strength on the measured values of the remanence and intrinsic coercivity. For thermally de-magnetized material, the internal magnetic field necessary to obtain limiting values of the remanence and intrinsic coercivity varies with magnet type. For example, the Nd2Fe14B and Sm2Co17 magnets studied have similar values of remanence (approximate to 1.14 T) and intrinsic coercivity (approximate to 2 MA m(-1)), but the latter requires an internal magnetizing field three times larger than does the former in order for one to attain limiting values of the remanence and coercivity. Further insight into the magnetization processes in these three materials has been gained from the determination of the magnetic viscosity parameter, S, and the irreversible susceptibility, chi(irr). [References: 16]