Reinvestigation of the GdP₅O₁₄ crystal structure at room temperature and magnetic properties

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• 作者：H. Ettis ; H. Naï ; li ; T. Mhiri
• 关键词：Gadolinium ultraphosphate ; Crystal structure ; Twin ; Magnetic properties
• 刊名：Materials Chemistry and Physics
• 出版年：2007
• 期刊代码：58_02540584
• 类别：ms
• 出版时间：15 April 2007
• 卷：102
• 期：2-3
• 页码：275-280
• 文件大小：993 K

摘要

Gadolinium ultraphosphate, GdP₅O₁₄ has been synthesized by a flux method. The room temperature structure of the title compound was solved from twinned single-crystal X-ray diffraction data in the monoclinic space group P2₁/c with a = 8.7411(3); b = 8.8997(2); c = 12.9308(5) Å; β = 90.07(2)°; V = 1005.93(6) ų and Z = 4. Crystals of the title compound exhibit twinning by pseudomerohedry. The apparent symmetry is caused by twinning and by the pseudo-orthorhombic symmetry of the lattice. Due to the pseudosymmetry the space group Pnmb has been assigned and after a complete structure refinement applied to a twinned crystal, the correct space group is P2₁/c. The atomic arrangement in the present structure is very close to the previously reported one of GdP₅O₁₄ at T = 145 K (type I) [J.M. Cole, M.R. Lees, J.A.K. Howard, R.J. Newport, G.A. Saunders, E. Schönherr, J. Solid State Chem. 150 (2000) 377], but a small deviation in the unit cell has been notified. The refinement gave R₁ = 2.1%and wR₂=8.4% based on 4138 independent reflections and 3619 observed, I > 2σ(I). The result of structural analysis establishes that the structure is built up with discrete anionic ribbons linked by the cations in a complex way. Magnetic susceptibility studies show paramagnetic behavior, following Curie's law with a magnetic moment of 7.96μ_B per formula unit.