MOSSBAUER-SPECTROSCOPY OF FE-57 IN THE COMPOUNDS R(NI0.99FE0.01)(2)B2C (R=Y,GD,TB,DY,HO,ER) - THEORY AND EXPERIMENT

Fe-57 Mossbauer spectroscopy measurements were performed for the Fe im purities in the substituted compounds R(Ni0.99Fe0.01)(2)B2C (R=Y,Gd,Tb ,Dy,Ho,Er). Isomer shifts and quadrupole splittings were obtained; the latter were seen to correlate to the ratio cia of the lattice constan ts. Isomer shifts show very similar values for compounds with differen t rare earths. First-principles density-functional calculations for 71 -atom embedded clusters representing the compounds were performed. Qua drupole splittings at the Fe site were obtained from the calculations, and the origin of the trend observed was elucidated.