Clustering of Fe3+ in the Li-1-3xFexMgPO4 (0≤x<0.1) solid solution

The Li1-3xFexMgPO4 (0 < x < 0.1) solid solution has been prepared by solid state synthesis. The structure of these phases has been determined by X-ray diffraction on polycrystalline samples, being isostructural with LiMgPO4. Fe3+ substitutes part of the Li+ ions in the channels of the LiMgPO4 structure along the [010] direction, creating cation vacancies. The IR bands corresponding to the vibrational modes of the phosphate groups undergo a gradual widening with the amount of inserted iron as a consequence of the increase of disorder in the structure. The EPR spectra show signals with an effective g' = 4.0. This fact can be attributed to the presence of high spin Fe3+ ions in orthorhombic symmetry. The increase of Fe3+ in the compounds leads to a broadening of the Lorentzian EPR signals indicating the existence of magnetic interactions between the Fe3+ ions. Magnetic susceptibility measurements on the Li1-3xFexMgPO4 (0 < x < 0.1) solid solution show antiferromagnetic behaviors which can be explained considering that the doped Fe3+ ions exhibit a short range magnetic order, forming clusters associated with the vacancies in the structure. (C) 2001 Published by Elsevier Science Ltd.