The excess free energy due to the composition gradient for ferromagnetic alloys

The magnetic free energy for alloy systems contains the magnetic alloying e xcess free energy that is thermodynamically described by using the magnetic interaction parameter. We reveal the statistical meaning of this parameter by using the Ising model and Weiss's molecular field approximation. Ginzbu rg-Landau-type free energy, which includes the excess free energy of the co mposition gradient, is often used in order to simulate the phase separation process. Using the magnetic interaction parameter, we estimated the gradie nt energy due to spatial distribution of ferromagnetic atoms in the alloy. This study made possible the accurate simulation of phase separation in fer romagnetic alloys. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Sc ience Ltd. All rights reserved.