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|Type:||Artigo de periódico|
|Title:||Structure and magnetic properties of Li3Fe2(AsO4)(3-x)(PO4)(x) [x=0, 1, 1.5, 2]: two sublattice weak ferromagnets|
|Abstract:||The Li3Fe2(AsO4)(3 - x)(PO4)(x) (x = 0, 1, 1.5, 2) solid solution was prepared by the ceramic method. Li3Fe2(AsO4)(3) crystallizes in the monoclinic P112(1)/n space group with the cell parameters, a = 8.608(1), b = 12.215(1), c = 8.929(1) Angstrom and gamma = 90.76(1)degrees. The structure consists of a three-dimensional framework of vertex-sharing FeO6 octahedra and AsO4 tetrahedra with the lithium ions distributed in three four-coordinated crystal sites. There are two independent iron positions in the structure of this compound, Fe(1) and Fe(2). The cell parameters of the isostructural Li3Fe2(AsO4)(3 - x)(PO4)(x) (x = 0, 1, 1.5, 2) phases follow Vegard's law. The IR spectra show the evolution of the intensity for the bands corresponding to the AsO4 and PO4 tetrahedra in the solid solution. An isotropic signal with a g value of 2.0 is observed in the ESR spectra of all compounds, in good agreement with the presence of a high spin Fe(III) ion with slightly distorted octahedral symmetry. The magnetization measurements and the magnetic DC and AC susceptibility data show an antiferromagnetic behavior for these compounds, with the presence of a ferromagnetic component below the ordering temperature. T-N decreases from 35.5 to 31 K with decreasing the amount of arsenate. The magnetic results are explained by the existence of a phenomenon of ferrimagnetism in these compounds, due to the existence of two different magnetic sublattices, corresponding to the Fe(1) and Fe(2) sites. The presence of canting between the magnetic moments of these two sublattices has been also detected. This fact agrees with the relative orientation of the FeO6 magnetic octahedra in the Li3Fe2(AsO4)(3 - x)(PO4)(x) (x = 0, 1, 1.5, 2) compounds.|
|Editor:||Royal Soc Chemistry|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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