The Curie temperature and density of Fe2R amorphous alloys

Various kinds of Fe-R amorphous alloys have been prepared by a high-rate dc sputtering method in order to study the Curie temperature Tcas a function of the de Gennes factor G for Fe2R, and to the difference of the density between amorphous and crystalline states. The exchange interaction between Fe-Fe in iron-light rare earth amorphous alloy systems of Fe2R persists and their Curie temperatures are lower than those crystalline counterparts. It should be noted that Tcof Fe2Ce in the both states is much lower than that expected from the G vs. Tccurve due to the valence fluctuation. In iron-heavy rare earth amorphous alloys of Fe2R, Fe-Fe exchange interaction becomes zero, being consistent with the results previously reported. The concentration dependence of the room temperature density shows a distinct anomaly around the composition corresponding to Fe2R. This difference between these two states is attributed to the denser packing structure of the Laves compounds. With increasing Ce content, the density of Fe-Ce amorphous alloy system increases although the density of Ce is lighter than that of Fe. This behavior is caused by the valence fluctuation of Ce in the alloy system.