X-RAY-DIFFRACTION STUDY OF LOCAL ATOMIC STRUCTURES IN AMORPHOUS ND-FE-B ALLOYS

Local atomic structures in NdxFe82B18-x (x=0 to 18) and NdxFe100-x (x= 15 to 25) alloy glasses prepared by melt spinning are studied with X-ray diffraction technique. The total radial distribution function G(r) of each alloy is decomposed into partials, G(Fe-Fe)(r) and G(Fe-Nd)(r), and near-neighbour distances and coordination numbers associated with the Fe-Fe and Fe-Nd correlations are determined. The structure of the ternary alloy system is characterized by packing of a trigonal prism of 6 Fe atoms with a B atom at the center and 3 outer Nd atoms capping the rectangular faces, as is found in crystalline Nd2Fe14B compound. X-ray photoemission spectra of these alloys indicate that strong chemical bonding is formed between Fe and B atoms. Variation of the spectra with composition is understood on the basis of this local atomic structure.