کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1331383 1500118 2013 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The synthesis and characterisation of LaCa2Fe2GaO8
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
The synthesis and characterisation of LaCa2Fe2GaO8
چکیده انگلیسی

The synthesis and characterisation of LaCa2Fe2GaO8 is described. Neutron powder diffraction data reveal LaCa2Fe2GaO8 adopts an anion-vacancy ordered, ‘triple layer’ structure consisting of an OOTLOOTR stacking sequence of layers of (Fe/Ga)O6 octahedra (O) and (Fe/Ga)O4 tetrahedra (T), related to that of the 4-layer brownmillerite structures (a=5.4784(1) Å, b=22.6780(4) Å, c=5.6007(1) Å, space group Pbma). The apex-linked chains of tetrahedra within structure of LaCa2Fe2GaO8 exhibit a cooperative twisting distortion which alternates in direction between adjacent layers of tetrahedra, the first time such an arrangement has been seen in a triple-layer phase. Magnetisation and neutron diffraction data reveal that LaCa2Fe2GaO8 exhibits two magnetic ordering transitions. On cooling below 550 K the phase adopts a state with short range antiferromagnetic coupling within each double layer of (Fe/Ga)O6 octahedra, but only weak coupling between layers. On cooling below 470 K full three-dimensional, G-type antiferromagnetic order is observed.

LaCa2Fe2GaO8 adopts an anion-vacancy ordered, ‘triple layer’ structure consisting of an OOTLOOTR stacking sequence of layers of FeO6 octahedra (O) and GaO4 tetrahedra (T), in which the chains of apex-linked tetrahedra exhibit a cooperative twisting distortion which alternates in direction between adjacent layers of tetrahedra. On cooling below 550 K, LaCa2Fe2GaO8 adopts a state with strong two-dimensional antiferromagnetic order within each double layer of FeO6 octahedra, but only weak coupling between layers. On cooling below 470 K full three-dimensional antiferromagnetic order is observed.Figure optionsDownload as PowerPoint slideHighlights
► LaCa2Fe2GaO8 exhibits a novel anion-vacancy ordered triple-layer structure type.
► New structure variant rationalised on the basis of strucutral parameters.
► Multiple magnetic transitions: paramagnetic–two-dimensional–three-dimensional.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Solid State Chemistry - Volume 198, February 2013, Pages 203–209
نویسندگان
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