Fluorescence extended x-ray absorption fine structure study of silicon in neodymium iron boron rare-earth magnets

Rare-earth transition-metal magnetic materials consisting of Nd2Fe14B with small amounts of Si, produced by melt-spinning, have been studied using fluorescence extended x-ray absorption fine structure. A windowless Si(Li) solid-state detector was used to collect the Si fluorescence. These polycrystalline samples are unusual in that they are magnetically isotropic, yet have a very high remanent magnetization. The silicon atom is bonded to a single shell of iron atoms at a distance of 2.46 +- 0.05 A. The results strongly suggest that (1) Si does not segregate at the grain boundaries or cluster with other Si atoms, and that (2) Si replaces the iron atom at the ''c'' site of the standard Nd2Fe14B structural model within the grains