Spectroscopic and Magnetic Properties of α-Li₃Fe₂(PO₄)₃:  A Two-Sublattice Ferrimagnet

Abstract

Spectroscopic and magnetic studies on α-Li 3 Fe 2 (PO 4 ) 3 show an interesting behavior below the transition temperature (29 K). The compound orders antiferromagnetically, presenting a weak ferromagnetic moment, which diminishes with temperature. In the same region of temperatures, the Mössbauer spectra split in two sextets with slightly different hyperfine fields, and the ESR spectrum reduces its intensity and broadens. These results are interpreted as the competition between two sublattices of Fe(III) ions, corresponding to the presence of two independent Fe(III) crystallographic sites in the structure. The magnetic interaction in each sublattice is ferromagnetic, being coupled antiferromagnetically between them. The observed weak ferromagnetic component is the result of the ferrimagnetic character in the coupling between two Fe(III) sublattices.