Enhancement of Exchange Coupling in MM–Fe–B Nanocrystalline Ribbons Through Spontaneous Formation of Dual Hard-Magnetic Main Phases

To enhance the comprehensive utilization of high-abundance La and Ce, misch metal (MM)–Fe–B magnets have become the research focus. Herein, considerable differences were observed in the magnetic properties and microstructure of rare earth (RE)–Fe–B ribbons prepared using natural or artificial MM with varying La/Ce ratios. With increasing La content, the total magnetic properties of the involved thin RE–Fe–B strip deteriorated; meanwhile, the MM–Fe–B ribbon exhibited high coercivity and maximum magnetic-energy-product values of 9.2 kOe and 9.28 MGOe, respectively. Notably, the La utilization rate increased to 28 wt.% (La/TRE). A conspicuous heterogeneous distribution of RE elements and dual hard-magnetic phases in the MM–Fe–B ribbon were noted based on transmission electron microscopy microanalysis and first-principles calculations, unlike for the (Ce, Pr, Nd)–Fe–B ribbon. Henkel plot measurements confirmed a strong exchange-coupling interaction within the MM–Fe–B ribbon, attributed to the spontaneous formation of dual hard-magnetic main phases—La–Ce-poor and La–Ce-rich.