Evolution of magnetic domain structures and coercivity in high-performance SmCo 2:17-type permanent magnets

• Published in: Acta materialia Vol. 54; no. 4; pp. 997 - 1008
• Main Authors: Gutfleisch, O., Müller, K.-H., Khlopkov, K., Wolf, M., Yan, A., Schäfer, R., Gemming, T., Schultz, L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2006; Elsevier Science
• Subjects: Applied sciences; Coarsening; Coercive force; Coercivity; Evolution; Exact sciences and technology; Magnetic domain structure; Magnetic domains; Magnetic force microscopy; Magnets; Metals. Metallurgy; Optimization; Permanent magnets; Quenching; SmCo alloys; SmCo alloys; Permanent magnets; Magnetic domain structure; Magnetic force microscopy; Coercivity; Coercive force; Magnetic domain; Magnetic structure; Permanent magnet; Microstructure; Magnetic properties
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2005.10.026

The magnetic domain structure of SmCo 2:17-type magnets has been found to be very sensitive to details of the processing procedure. In optimally processed high-temperature Sm(Co 0.784Fe 0.100Cu 0.088Zr 0.028) 7.19 magnets, the typical domain width is less than 1 μm, but significantly larger than the typical size of 2:17R cells of about 100 nm. However, quenching straight from the aging temperature of 850 °C, i.e. omitting slow cooling, leads to a much coarser domain structure (domain width ∼10 μm) and a small coercivity (<0.1 T). The fine domain structure of the optimally processed bulk magnet can be considered as interaction domains – an alternative phenomenon compared to the zigzag-shaped domain walls known for thinned specimens. Another, commercially available 2:17-type magnet, developed for low room temperature coercivity and high second quadrant squareness, has a much coarser domain structure, even when slowly cooled from 780 to 400 °C.