NEW INTERSTITIAL RARE-EARTH IRON INTERMETALLICS PRODUCED BY GAS-PHASE REACTION

New rare-earth iron intermetallic compounds have been generated from existing series by the reaction of powder with an appropriate gas. Interstitial atoms occupy sites adjacent to the rare earth, creating a crystal field that reflects the new local symmetry. They also expand the lattice, which leads to an increase in iron moment due to narrowing of the 3d bands and modifies the Fe-Fe exchange interactions, resulting in increases of the Curie temperature of 200-400 K. These effects are discussed with reference to the system R2Fe17Z3-delta where Z = N, C, B. The observed volume dependence of the magnetic moment at the four inequivalent iron sites of Y2Fe17, due to interstitial modifications with nitrogen and carbon, are compared to calculated values published for pure Y2Fe17. Details of the nitrogenation process and of the broad line shapes observed in nitrided materials are discussed with reference to the compound Sm(Fe11Ti)N1-delta.