PERMANENT-MAGNET MATERIALS BASED ON TETRAGONAL RARE-EARTH COMPOUNDS OF THE TYPE-RFE12-XMX

A review is given of the occurrence and composition of ternary rare earth compounds RT12-xMx based on the tetragonal ThMn12 structure. Most of the compounds form with T = Fe but there are also examples with T = Co, Ni or Mn. Particular attention is paid to the site preference of the nonmagnetic component M, (Al, Si, Ti, V, Cr, Mo, W, Re). A discussion is given of the magnetic properties of the RT12-xMx compounds and the corresponding nitrides obtained after charging with nitrogen gas. The important role played by the intersublattice coupling on the magnetocrystalline anisotropy of these materials is stressed. Advantages and disadvantages of the RFe12-xMx compounds as permanent magnet materials are discussed.