INTRINSIC MAGNETIC-PROPERTIES OF NEW RARE-EARTH IRON INTERMETALLIC SERIES

New rare-earth iron intermetallic compounds have been generated from existing series by the reaction of powder with an appropriate gas at about 500-degrees-C. Interstitial atoms occupy sites adjacent to the rare earth, thereby creating a crystal field that reflects the new local symmetry. They also expand the lattice, which greatly modifies the Fe-Fe exchange interactions and may increase the iron moment by narrowing the 3d bands. These effects are discussed with reference to three systems: R2Fe17N3-delta, R2Fe17C3-delta and R(Fe11Ti)N1-delta. Increases of Curie temperature of 300-400 K are achieved on nitrogenation or carbonation of R2Fe17, whereas the increases in the 1:12 compounds are approximately 200 K. The sign of A2(0), the second-order crystal-field coefficient at rare-earth sites, is opposite in the 2:17 and 1:12 interstitial compounds.