Effect of exchange interaction in dumbbell Fe-Fe pairs on the curie temperature of the rhombohedral Gd2Fe17 phase

Abstract

One of important problems of improving the magnetic properties of technologically promicing intermetallics R2Fe17 (R is rare-earth metal) with high Fe contents is related to the increase in the Curie temperature TC. There is a hypothesis on the possibility of a marked increase in TC of the alloys, which can be achieved via the synthesis of systems characterized by pairs of atoms coupled by strong exchange interaction similar to that for Fe-Fe pairs situated in the so-called dumbbell position in the R2Fe17 systems. In the present study, based on an example of the rhombohedral Gd2Fe17 phase, it was shown in terms of a classical nearest-neighbor spin Heisenberg model that changes in the exchange interaction for a dimer pair of dumbbell Fe-Fe atoms from zero to infinitely large lead to no more than 10% increase in TC. Thus, the creation of ferromagnetic systems characterized by dimers of magnetic atoms coupled by strong short-range exchange interaction, which, in this case, do not form an infinite magnetic cluster, cannot increase radically the Curie temperature TC.