Theoretical study of the intrinsic magnetic properties of disordered Fe_(1-x)Ru_x alloys: a mean-field approach

The magnetic properties of the $Fe_{1-x}Ru_x$ alloy system for 0 $\leq$ x $\leq$ 0.10 are studied by using a mean-field approximation based on the Bogoliubov inequality. Ferromagnetic Fe-Fe spin correlations and antiferromagnetic Fe-Ru and Ru-Ru exchanges have been considered to describe the temperature dependence of the Curie temperature and low temperature magnetization. A composition dependence has been imposed in the exchange couplings, as indicated by experiments. From a least-square fitting procedure to the experimental results an estimation of the interaction parameters was obtained, which yielded the low temperature dependence of the magnetization and of the ferromagnetic Curie temperature. A good agreement was obtained with available experimental results.