Manganese-based permanent magnet materials

Manganese-based permanent magnetic materials have become an area of significant research activity in recent years as a potential alternative to permanent magnets based on Rare Earth (RE) metals. Manganese compounds are capable of achieving a relatively high energy product, BH, when processed to have a strong texture. Research has identified three promising compounds for Mn-based permanent magnets: Mn-Ga, Mn-Bi, and Mn-Al. While calculations show that these compounds cannot achieve the theoretical maximum energy products, (BH)max, of RE magnets, current research suggests than they can fill the property gap between inexpensive, but low-performance, ferrites and expensive high-performance RE magnets. Many researchers have produced Mn-based magnets through a variety of methods that fall into three basic categories: bulk processing, particulate processing, and thin film deposition. This review discusses the various processing methods for each compound and their impact on the microstructure and resulting magnetic properties. We also present unresolved questions and outline opportunities for future research.