Symmetry and hyperfine magnetic fields in Nd-based intermetallics

Intermetallics of the type NdCo9−xFexSi2Cy (x=3; 5; 6; 7 and y=0; 1) and Nd2Co15−xFexSi2Cy (x=7; 9; 12 and y=0; 1) were prepared by arc melting in order to study the competing effects of Fe and Co substitutions on the magnetic hyperfine fields as well as the effects of interstitial carbon additions on the symmetry and local magnetic properties in these systems. The investigations were performed by X-ray diffraction, Mössbauer spectroscopy and hysteresis loop measurements. Both site and average hyperfine magnetic field values were analyzed in order to discriminate between the Fe and Co contributions to the local atomic environments in these systems. While a higher Fe content as well as a higher Co content can both lead to an increase in the site magnetic fields, it was found that the model based on hyperfine field distributions provides a better description of the trends observed in hyperfine magnetic fields in these compounds.