Spectroscopic and magnetic properties of alpha-Li3Fe2(PO4)(3): A two-sublattice ferrimagnet

Spectroscopic and magnetic studies on alpha-Li3Fe2(PO4)(3) show an interest ing behavior blow the transition temperature (29 K). The compound orders an tiferromagnetically, presenting a weak ferromagnetic moment, which diminish es with temperature. In the same-region of temperatures, the Mossbauer spec tra split; in two sextets with slightly different hyperfine fields, and the ESR spectrum reduces its intensity and broadens. These results are interpr eted as the competition between two sublattices of Fe(III) ions, correspond ing to the presence of two independent Fe(III) crystallographic sites in th e structure. The magnetic interaction in each sublattice is ferromagnetic, being coupled antiferromagnetically between them. The observed weak ferroma gnetic component is the result of the ferrimagnetic character in the coupli ng between two Fe(III) sublattices.