NITROGEN ATOM LOCATION IN RHOMBOHEDRAL AND HEXAGONAL RE2FE17NX COMPOUNDS

High resolution neutron powder diffraction studies were performed on Nd2Fe17N(x) and Y2Fe17N(x). A strong preferential site occupation of the N atoms on the 9e position of the rhombohedral compound Nd2Fe17N(x) was observed. In the hexagonal compound Y2Fe17N(x) the N atoms occupy primarily the 6h sites (82%) and only a small fraction goes into the 12i site (12%). The refined nitrogen occupation numbers correspond to the formula compositions Nd2Fe17N2.6 and Y2Fe17N2.9.