Crystal Structure Refinement and Magnetic Properties of Fe4(P2O7)3 Studied by Neutron Diffraction and Mössbauer Techniques

✍ Scribed by L.K Elbouaanani; B Malaman; R Gérardin; M Ijjaali

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 421 KB
• Volume: 163
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9415

✦ Synopsis

Fe4(P2O7)3 was prepared from Fe(PO3)3 and FePO4 at 9403C under oxygen. The unit cell is monoclinic, space group P21"n, with a ‫؍‬ 7.389(2) A > , b ‫؍‬ 21.337(1) A > , c ‫؍‬ 9.517(2) A > , ‫؍‬ 90(1)3, and Z ‫؍‬ 4. The crystallographic structure has been determined from a single crystal through direct methods and di4erence Fourier synthesis and re5ned to R ‫؍‬ 0.10 (Rw ‫؍‬ 0.09). The threedimensional framework is built up from Fe2O9 clusters of two face-sharing octahedra, linked by bent diphosphates P2O7 (P+O+P&1563). Fe4(P2O7)3 is antiferromagnetic below TN ‫؍‬ 50 K. The magnetic structure has been determinated by means of powder neutron di4raction. There are four antiferromagnetic iron sublattices corresponding to the four crystallographically distinct iron atoms. The magnetic moments are antiferromagnetically coupled inside the Fe2O9 dimers, in agreement with the Goodenough rules. They are parallel to the c axis and have 4.55(5) B value at 1.7 K. The magnetic interactions are discussed. MoK ssbauer spectra are 5tted with four doublets and sextuplets in the paramagnetic and antiferromagnetic states, respectively. Their rather high isomer shifts are explained by the inductive e4ect.

2002 Elsevier Science (USA)