Structure refinement and magnetic properties of C-Fe(PO3)(3) studied by neutron diffraction and Mossbauer techniques

C-Fe(PO3)(3) has been synthesized using H3PO4 and Fe(NO3)(3). 9H(2)O as sta rting compounds. Single crystals were grown under vacuum with a trace of Fe Cl2. Fe(PO3)(3) crystallizes in the monoclinic space group Cc, with a = 13. 148(4) Angstrom, b = 19.076(2) Angstrom, c 9.410(3) Angstrom, beta = 127.00 (2)degrees, and Z = 12. Its structure has been determined through direct me thods and difference Fourier synthesis and has been refined to R = 0.0405 ( R-W = 0.047). Fe(PO3)(3) belongs to a series of isotypic M(PO3)(3) trimetap hosphates (M = Al, V, Sc, In, Ti, Mo, Rh, Cr) which are characterized by a tridimensional network of isolated MO6 octahedra connected through PO4 tetr ahedra. Fe(PO3)(3) is antiferromagnetic below T-N = 10 K. The magnetic stru cture has been determinated by means of powder neutron diffraction: each ir on atom is linked to six iron nearest neighbors of opposite spin, through s ix single Fe-O-P-O-Fe superexchange pathways. The moment direction lies in the (010) plane, making an angle of similar to 32 degrees with the a axis ( mu similar to 4.4 mu(B)). Mossbauer spectra are fitted with two doublets an d three sextuplets in the paramagnetic and the antiferromagnetic states, re spectively. Their rather high isomer shifts are explained by the inductive effect. (C) 1999 Academic Press.