Spectroscopic and magnetic properties of Fe3IIFe4III(AsO4)6

The infrared (IR) and 57Fe-Mössbauer spectra of Fe3IIFe4III(AsO4)6 were recorded and analyzed on the basis of its structural characteristics. The IR spectrum presents a high complexity, showing an important number of bands and splittings, as a consequence of the presence of three structurally independent AsO43− groups. The analysis of the four quadrupole signals shown by the Mössbauer spectrum allowed to attain a detailed insight into the cation distribution over the available crystallographic sites. The alternating current susceptibility measurements indicate a paramagnetic to ferrimagnetic transition in the material at about 59 K.