Interaction Domains as Cooperative Phenomena in SmCo 2:17 Magnets

Application temperatures above 400degC are now possible for SmCo 2:17-type magnets. In this work, the evolution of magnetic microstructure of newly developed high temperature grades of sintered SmCo 2:17-type magnets is correlated with the development of coercivity and subtle microchemical changes occurring during the slow cooling ramp from the aging temperature of 850degC. In this context, the SmCo 2:17-type magnets are regarded as highly textured nanostructures.A systematic analysis of the evolution of the magnetic domain structure by magnetic force microscopy (MFM) and coercivity during slow cooling (0.7 K/min) from the aging temperature of 850degC confirmed not only that high performance 2:17-type SmCo magnets are generally pinning-dominated magnets but also revealed, for the first time, that the nature of the magnetic domain structure (in particular the domain width) is very sensitive. The fine domain structure of the optimally processed magnet is considered as a cooperative phenomenon similar and akin to interaction domains well known for fine grained, highly textured, ferromagnetic materials. It is quite possible that the interaction-domain-like magnetic microstructures show similar zigzag shaped walls as the domains observed in thinned specimen for TEM.