Evidence for reversal by nucleation in RE-Fe-B die-upset magnets

• Published in: Journal of applied physics 1994-11, Vol.76 (10), p.6235-6237
• Main Authors: Henderson Lewis, L., Zhu, Y., Welch, D. O.
• Format: Article
• Language: English
• Subjects: 360204 - Ceramics, Cermets, & Refractories- Physical Properties; BORIDES; BORON COMPOUNDS; COERCIVE FORCE; DOMAIN STRUCTURE; IRON BORIDES; IRON COMPOUNDS; MAGNETIZATION; MAGNETS; MATERIALS SCIENCE; MICROSTRUCTURE; NUCLEATION; PERMANENT MAGNETS; PHASE STUDIES; RARE EARTH COMPOUNDS; TRANSITION ELEMENT COMPOUNDS
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.358291

Electron microscopy and initial magnetization studies at elevated temperatures were performed on two die-upset rare-earth magnets with bulk compositions Nd13.75Fe80.25B6 and Pr13.75Fe80.25B6. In both compositions the intergranular phase is amorphous and occurs primarily on those surfaces parallel to the tetragonal 2-14-1 phase c axis. The intergranular phase is enriched in iron relative to the bulk grain, with an average width of 8–12 Å in the Nd-based magnet and 15–20 Å in the Pr-based magnet. The initial magnetization curves and the dependence of the coercivity upon maximum magnetizing field both increase linearly with a common slope and then saturate, consistent with nucleation-dominated behavior. These results suggest that the dominant reversal mechanism in these magnets is nucleation of reversed domains in the iron-rich intergranular region of reduced anisotropy.