Magnetism of Iron Clusters in Noble Metals

Effective magnetic moments Peff and spin glass freezing temperatures Tg were determined by susceptibility measurements for rapidly quenched Cu100-xFex 0¿x¿10) and Au100-xFex (0¿x¿20) alloys. The volume fraction of clusters of Fe atoms in these alloys was estimated by analysis of Mössbauer spectra. On comparing the volume fractions of clusters to Peff and Tg, we obtained the following results. 1) the Peff of dimers and trimers were estimated to be 6.4 ¿B and 11.3 ¿B for the Cu-Fe system, and 7.3 ¿B and 11.2 ¿B for the Au-Fe system, respectively. 2) Both the Cu-Fe and the Au-Fe systems exhibited the same freezing temperature, Tg, for the same total number of Fe atoms involved in isolated atoms and in clusters, dimer and trimer.