Structural investigation of the alluaudite-like mixed-valence iron phosphate : Na1.25Mg1.10Fe1.90(PO4)3

• Published in: Journal of alloys and compounds 2008-02, Vol.450 (1-2), p.301-305
• Main Authors: HIDOURI, M, LAJMI, B, WATTIAUX, A, FOURNES, L, DARRIET, J, BEN AMARA, M
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetically ordered materials: other intrinsic properties; Material chemistry; Mössbauer effect; other γ-ray spectroscopy; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Valence fluctuation, kondo lattice, and heavy-fermion phenomena
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2006.10.119

A new mixed-valence iron phosphate Na1.25Mg1.10Fe1.90(PO4)3 has been synthesized as single crystals by a flux technique and its structure has been refined from X-ray data to a residual R1=0.032. The compound crystallizes in the monoclinic space group C2/c with the parameters: a=11.7831(3)A, b=12.4740(3)A, c=6.3761(2)A, beta=113.643(2) deg and Z=4. The structure belongs to the alluaudite structural type, and thus it obeys to the X(2)X(1)M(1)M(2)2(PO4)3 general formula. The X(2) and X(1) sites are occupied by sodium while the M(1) and M(2) sites feature a statistical distribution of iron and magnesium. Additional information about the cation distribution has been extracted from a Mossbauer spectroscopy study which confirmed the mixed valency of the compound. A magnetic susceptibility study has also been undertaken and has shown the compound to be antiferromagnetic with a Neel temperature of about 35K.