Non-Linear Local Environment Effect in Ni₃Fe Observed by Mössbauer Effect of Fe⁵⁷

Abstract

In order to study the local environment effect, measurements of the Mössbauer effect of Fe⁵⁷ were made for Ni_79.5Fe_20.5, Ni_75.4Fe_24.6 and Ni_69.7Fe_30.3 alloys with various degrees of long range order. We have analysed the Mössbauer pattern with 7 or 8 configurations without any assumption of the functional relation between the hyperfine field and the number of Fe atoms in the nearest neighbor shell and determined the value of the hyperfine field for each environment from which the values of the magnetic moment on Fe atoms could be deduced in a self-consistent way. The results show that the variations of the hyperfine field and the magnetic moment are not linear, especially for highly ordered alloys. This behavior is discussed in terms of the cluster CPA theory.