The role of finite magnetic clusters in Au-Fe alloys near the percolation concentration

Au-Fe alloys have been studied by magnetic measurements of various types in the composition range where ferromagnetism evolves from spin-glass character. The percolation limit identified from the results and other data is 15.5 + 0.3 at.% Fe. Between this composition and ∼28% Fe, finite clusters co-exist in significant concentrations with the infinite cluster, and a fairly well-defined temperature observed in the magnetic properties is ascribed to a freezing of these clusters that parallels that of finite clusters in the pre-percolation alloys. Magnetic resonance is observed in alloys with more than about 13% Fe (i.e. in alloys containing large nearest-neighbour clusters) and the temperature dependence of the linewidth correlates with the interpretation given of the magnetization data.