Crystal structures and magnetic properties of iron (III)-based phosphates: Na4NiFe(PO4)3 and Na2Ni 2Fe(PO4)3

Rachid Essehli, Brahim El Bali, Said Benmokhtar, Khalid Bouziane, Bouchaib Manoun, Mouner Ahmed Abdalslam, Helmut Ehrenberg

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17 Citations (Scopus)

Abstract

Crystal structures from two new phosphates Na4NiFe(PO 4)3 (I) and Na2Ni2Fe(PO 4)3 (II) have been determined by single crystal X-ray diffraction analysis. Compound (I) crystallizes in a rhombohedral system (S. G: R-3c, Z = 6, a = 8.7350(9) , c = 21.643(4) , R1 = 0.041, wR2=0.120). Compound (II) crystallizes in a monoclinic system (S. G: C2/c, Z = 4, a = 11.729(7) , b = 12.433(5) , c = 6.431(2) , β = 113.66(4)°, R 1 = 0.043, wR2=0.111). The three-dimensional structure of (I) is closely related to the Nasicon structural type, consisting of corner sharing [(Ni/Fe)O6] octahedra and [PO4] tetrahedra forming [NiFe(PO4)3]4+ units which align in chains along the c-axis. The Na+ cations fill up trigonal antiprismatic sites within these chains. The crystal structure of (II) belongs to the alluaudite type. Its open framework results from [Ni2O10] units of edge-sharing [NiO6] octahedra, which alternate with [FeO6] octahedra that form infinite chains. Coordination of these chains yields two distinct tunnels in which site Na+. The magnetization data of compound (I) reveal antiferromagnetic (AFM) interactions by the onset of deviations from a Curie-Weiss behaviour at low temperature as confirmed by Mössbauer measurements performed at 4.2 K. The corresponding temperature dependence of the reciprocal susceptibility χ-1 follows a typical Curie-Weiss behaviour for T > 105 K. A canted AFM state is proposed for compound (II) below 46 K with a field-induced magnetic transition at H ≈ 19 kOe, revealed in the hysteresis loop measured at 5 K. This transition is most probably associated with a spin-flop transition.

Original languageEnglish
Pages (from-to)1163-1171
Number of pages9
JournalJournal of Alloys and Compounds
Volume509
Issue number4
DOIs
Publication statusPublished - 28 Jan 2011

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Keywords

  • Alluaudite
  • Crystal structure
  • Hyperfine interaction
  • Magnetism
  • Nasicon
  • Synthesis

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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