Forced Volume Magnetostriction of Ferromagnetic and Cluster Glass Fe-Al Alloys

The forced volume magnetostriction of Fe-Al alloys in the concentration range from 15 to 36.5 at %Al has been measured at 4.2 K, 77 K and room temperature. The results were analyzed on the basis of a phenomenological theory of magneto-volume effects, where the volume change is classified into two contributions, the 3d band polarization and the volume dependence of exchange interaction between local moments. It is shown that the band polarization effect is dominant for volume magnetostrictions in cluster glass alloys (Al>30 at%) as well as in ferromagnetic alloys (Al< 30 at %). The analysis gives a rough estimate of the intrinsic band susceptibility, which is strongly enhanced around the critical concentration for the collapse of a long range ferromagnetic order.