Magnetic Properties of the Fe(PO3)3 Metaphosphate

The Fe(PO3)3 compound has been synthesized by solid state reaction. The crystal structure consists of a three-dimensional network, with infinite PO3 chains of PO4 tetrahedra and isolated FeO6 octahedra, where the Fe(III) ions occupy three different crystallographic positions. The IR spectrum of the compound shows bands characteristics of metaphosphate groups with chain structure. The X-band EPR spectra on polycrystalline samples are isotropic with a g value of approximately 2.0, which remains unchanged with variation in temperature. The intensity of the signals increases with decreasing temperature reaching a maximum at about 12 K and at lower temperatures the intensity decreases, becoming silent at 4.2 K. Magnetic measurements at high magnetic fields show a three-dimensional antiferromagnetic behavior, with a J/k value of -0.36 K. However, the magnetic study at less magnetic fields reveals the existence of a weak ferromagnetism intrinsic to the sample.