Formation of hyperfine fields in alloys

This paper deals with the analysis of experimental data on the average magnetization of Fe1-xMex (Me = Sn, Si) disordered alloys and the average and local hyperfine fields (HFF) of the Fe nuclei. The effect of the metalloid concentration on the HFF is studied with the help of the results of the first-principles calculations of ordered alloys. The disorder is taken into account by means of model systems. The dependences obtained correspond to those that were observed experimentally. Experimental data on the ratio of the average HFF of Fe nuclei to the average magnetisation in alloys with sp elements show that the ratio decreases in proportion to the metalloid concentration. This change in the ratio is related to three factors. First, the contribution of the valence electron polarization by neighboring atoms, which is positive (unlike the polarization by its own magnetic moment), increases with the change in the degree of disorder (increase in concentration). Second, the appearance of the impurities, i.e. metalloid atoms, in the nearest environment of the Fe nuclei leads to an increase in the orbital moment. Finally, the change in the degree of disorder, as in the first case, results in an increase in the orbital magnetic moment and its positive contribution to the HFF. The value and the degree of influence of these contributions to the HFF is discussed.