Developments in rare earth intermetallics

The magnetic properties of rare earth intermetallics have been the subject of numerous investigations in recent years. However, while the preparation of hew intermetallic compounds and the determination of their properties have been the prime concern in former years, more recently the analysis and theoretical explanation of the available data has become most important. Furthermore single crystals have now become available, which permit new experiments. Also many investigations on pseudo-binary systems have permitted the systematic determination of the primary magnetic properties. The rare earth intermetallics with the formula RaBbare divided according to the magnetic moment of the B-atom (s). Typical R-B compounds with a B-moment equal to zero are e.g. the RAl2compounds. Of all intermetallics with nonzero B-moment the R-3d intermetallics are the most important. These intermetallics can be formed with Mn, Fe, Co and Ni. In these systems there exist in principle three interactions, namely between the R-R, R-3d and 3d-3d atoms. The most important is usually the latter interaction. After a summary of the magnetic properties of intermetallics where the B-moment is zero and nonzero, some examples of pseudobinary systems and especially applications of R-3d multicomponent systems as the basis for advanced permanent magnets are discussed. Finally RE-3d alloys with metalloids and non-metals are discussed with emphasis on the newly developed R-Fe-B permanent magnets.