High-performance permanent magnets

High-performance permanent magnets (pms) are based on compounds with outsta nding intrinsic magnetic properties as well as on optimized microstructures and alloy compositions. The most powerful pm materials at present are RE-T M intermetallic alloys which derive their exceptional magnetic properties f rom the favourable combination of rare earth metals (RE=Nd, Pr, Sm) with tr ansition metals (TM=Fe, Co), in particular magnets based on (Nd,Pr)(2)Fe14B and Sm-2(Co,Cu,Fe,Zr)(17), Their development during the last 20 years has involved a dramatic improvement in their performance by a factor of >15 com pared with conventional ferrite pms therefore contributing positively to th e ever-increasing demand for pms in many (including new) application fields , to the extent that RE-TM pms now account for nearly half of the worldwide market. This review article first gives a brief introduction to the basics of ferromagnetism to confer an insight into the variety of (permanent) mag nets, their manufacture and application fields. We then examine the rather complex relationship between the microstructure and the magnetic properties for the two highest-performance and most promising pm materials mentioned. By using numerical micromagnetic simulations on the basis of the Finite El ement technique the correlation can be quantitatively predicted, thus provi ding a powerful tool for the further development of optimized high-performa nce pms.