Intensive structural investigation of R_2Fe_(17-x)M_x intermetallic compounds using high resolution powder neutron diffractometer

摘要

The crystallographic and magnetic structure of R_2Fe_(17-x)M_x intermetallic compounds system were refined by Rietveld analyses of the high resolution neutron powder diffraction data. The analyses results show that the substituent atoms were not distributed randomly over the Fe sites, but preferentially occupied some Fe sites. More further, it was also found that the substituent atoms which atomic radius smaller than Fe tend to avoid the 6c site at low concentration while the larger substituent atom tend to replace the Fe atom at this 6c site corresponding to their concentration. From these crystallographic data, it was suggested that the change of magnetic ordering temperature Tc, is not mainly determined by the change of short bond distance between this "dumb-bell" atoms, but it was also influenced by the nearest coordinated atoms to this site.