Exchange interactions in Dy/sub x/Tm/sub 1-x/Fe/sub 10/Si/sub 2/ compounds

Mossbauer measurements were performed on Dy/sub x/Tm/sub 1-x/iFe/sub 10/Si/sub 2/ samples (x=O, 0.2, 0.4, 0.6, 0.8, 1.0). The hyperfine magnetic fields at /sup 57/Fe nuclei were investigated, their changes caused by replacement of Tm by Dy atoms. Measurements were performed in transmission geometry using a constant acceleration Mossbauer spectrometer. The substitution of Tm atoms by the Dy atoms causes an increase of internal magnetic fields. In pure TmFe/sub 10/Si/sub 2/ 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 complete substitution of Tm by Dy gives the average increase of hyperfine magnetic held magnitude equal to 0.6 T. The molecular field approximation was applied to calculate the intra- and intersublattice exchange interactions considering experimental Curie temperatures of the investigated compounds. The calculated exchange coupling constants between rare earth and iron sublattices increase when substituting Tm by Dy.<
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