Metallurgical explanation of ‘‘double magnetic transitions’’ and allied phenomena in AuFe alloys

Publisher Website
Google Scholar
Abstract
Evidence for two magnetic ordering temperatures in AuFe alloys (0.1<XFe<0.28) is given by ac and static susceptibility measurements and Mössbauer experiments. These data have given rise to a variety of qualitative to semiquantitative theories based upon fluctuations in the random distribution of Fe atoms. Our explanation of the two ordering temperatures is based upon the precipitation of metastable Fe-enriched regions which arise via a decomposition and which magnetically couple to the spin-glass matrix. The high temperature transition denotes the onset of ferromagnetic order within the ‘‘precipitate’’ whose field is then coupled to the paramagnetic matrix. When the temperature of the system is decreased below the spin-glass ordering temperature, the apparent high temperature ferromagnetic character is destroyed, attesting to the dominance of the random spin-glass structure and the strength of the coupling between the two phases. Hence, it is the temperature dependence of the coupling between distinguishable ‘‘phases,’’ as well as the nature of the magnetic order, which produces the double transition.