Assessing composition gradient energy effects due to spin interaction on the spinodal decomposition of Fe–Cr

In ferromagnetic alloys, the excess Helmholtz energy due to composition gradients is influenced by the spin interaction among the ferromagnetic atoms. Therefore, the gradient energy coefficient is composition dependent. In order to assess the influence of the composition dependence on the spinodal decomposition process, we reformulated the Langer, Bar-on and Miller theory and simulated the structural change during spinodal decomposition in the Fe–Cr system. The simulation revealed that the periodicity of composition fluctuations becomes more accentuated. However, the influence of composition dependence of the gradient energy coefficient was found to be less important than the composition dependence of the mobility.