A 57Fe Mössbauer study of four pyrite compounds: CoS2, NiS2, CoSe2 and NiSe2

Mössbauer spectra of ⁵⁷Fe-doped CoS₂, NiS₂, CoSe₂ and NiSe₂ have been taken at various temperatures between 300 and 16 K, and the hyperfine parameters H and θ measured for those substances showing magnetic hyperfine splitting. Quadrupole splitting $\text{QS}\text{(=}\text{1}\text{2}\text{e}{}^2\text{qQ)}$ was also measured and for NiS₂ and CoS₂ the sign of QS was determined.The room temperature value of QS showed a similar behaviour in the series FeS₂CoS₂NiS₂ to that in the series FeSe₂CoSe₂NiSe₂. The absolute value of QS decreased slightly below the magnetic transition temperature in those compounds which showed magnetic ordering.