Concentration Fluctuations and Anomalous Properties of the Invar Alloy

Abstract

It is pointed out that concentration fluctuations affect the magnetic properties of Fe-Ni Invar alloys, which behaves as collection of cells containing equally 60 atoms whose mean concentrations are different from cell to cell. The fluctuation can be expressed by a Gaussian distribution law when the proportion of the number of the cells having the same concentration is plotted against the mean concentration. The saturation magnetization vs. nickel concentration relation, the deviation of the magnetic saturation moment σ vs temperature T curves form the standard Brillouin function, the small thermal expansion coefficient around room temperature and other anomalous physical properties of the alloy were accounted for on the basis of the present model of the concentration fluctuations.