EXCHANGE INTERACTIONS IN DYXTM1-XFE10SI2 COMPOUNDS

Mossbauer measurements were performed on DyxTm1-xFe10Si2 samples (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). The hyperfine magnetic fields at Fe-57 nu clei were investigated, their changes caused by replacement of Tm by D y atoms. Measurements were performed in transmission geometry using a constant acceleration Mossbauer spectrometer. The substitution of Tm a toms by the Dy atoms causes an increase of internal magnetic fields. I n pure TmFe10Si2 the hyperfine magnetic fields at 8(i), 8(j) and 8(f) positions are respectively equal to 25.3, 23.0 and 21.2 T. The complet e substitution of Tm by Dy gives the average increase of hyperfine mag netic field magnitude equal to 0.6 T. The molecular field approximatio n was applied to calculate the intra- and intersublattice exchange int eractions considering experimental Curie temperatures of the investiga ted compounds. The calculated exchange coupling constants between rare earth and iron sublattices increase when substituting Tm by Dy.