⁵⁷ Fe Mössbauer Lineshapes in Disordered Ni₃/Mn

Mössbauer studies of 57 Co doped disordered Ni 3 Mn are presented in the temperature range 77 to 500 K. The spectra consist of a well resolved six‐line pattern a t 77 K, becoming complex and showing hyperfine structure at higher temperatures, and finally collapsing t o a single line around 473 K. 57 Fe Mössbauer line shapes in disordered Ni 3 Mn have been computed in this temperature range using a model which assigns an average exchange integral to an atom depending on its nearest neighbour (nn) atoms. Owing to the distribution of T c of the various nn configuration clusters for a given central atom, there is a distribution in hyperfine fields, and the spectrum a t any temperature is the superposition of the different fields suitably weighted. The spectra simulated basing on this model agree with the experimental spectra.