ac susceptibility of AuFe near the percolation limit

A detailed study of the ac susceptibility of a Au-15 at.% Fe sample in both a quenched and aged state is reported as a function of dc biasing field over a wide range of temperature. Both the quenched and aged samples exhibit considerable structure in their susceptibility-versus-temperature curves which might be taken as indicating various "transitions." However, unlike the situation reported recently for a variety of systems, we find that the predictions of scaling behavior are not followed at either transition; instead these data exhibit features which might be qualitatively interpreted in terms of a recently proposed triple-transition process in this system. The quantitative aspects of this latter model have yet to be worked out and tested, and so any definitive assignments still cannot be made.