کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1332759 | 979052 | 2008 | 12 صفحه PDF | دانلود رایگان |
Ca2Fe1−xMnxAlO5 (0⩽x⩽1) compounds were prepared by a self-combustion method under air (x=0, 0.1, 0.2 and 0.3) and nitrogen (x=0.5, 0.7 and 1.0). The samples prepared under nitrogen were successfully oxidized after short annealing under air. Both X-ray powder diffraction (XRD) Rietveld analysis and electron diffraction revealed that all compounds adopt the brownmillerite-type structure. All samples present an overall antiferromagnetic behaviour and data from magnetic measurements and Mössbauer spectroscopy allowed to conclude that the transition temperature decreases as Mn content increases for x⩽0.3 and increases in the case of the x⩾0.5 compounds. Except for x=1, chemical disorder due to the occupancy of both octahedral and tetrahedral sites by different metals as well as the competition between different moments’ orientation induce a complex magnetic behaviour characterized by magnetic frustration and canted antiferromagnetism. Mössbauer spectroscopy and chemical titrations also allowed to conclude about the preferential oxidation of Mn3+ over Fe3+, obtained by thermal treatment under air of the x=0.5 and 0.7 compositions.
Structure of the Ca2Fe1−xMnxAlO5 compound and electron diffraction pattern obtained along the [1¯01] zone axis (x=0.2), showing a brownmillerite structure.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 181, Issue 9, September 2008, Pages 2530–2541