Anomalous magnetic properties of the nano-size residual amorphous phase innanocrystals

The composition dependence of the Curie temperature and the magnetic moment of the nano-size residual amorphous phase in partially crystallized Fe92-x Zr7B,Cu-1 (2 less than or equal to x less than or equal to 23) amorphous al loys were determined by Fe-57 Mossbauer spectroscopy. Both quantities show broad minima and for increasing relative Zr content (i.e, for decreasing B concentration) surpass the usual monotonic decrease observed for the bulk c ounterparts. The deviation does not scale with the characteristic size of t he residual amorphous regions, which was found to be constant, ruling out e xplanations based on interphase exchange interaction. A magnetovolume origi n of the observed anomalous composition dependence and the improved soft-ma gnetic characteristics of these nanocrystals is proposed.