Crystallographic and Magnetic Structure of the Perovskite-Type Compound BaFeO2.5: Unrivaled Complexity in Oxygen Vacancy Ordering

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• 作者：Oliver Clemens ; Melanie Gr枚ting ; Ralf Witte ; J. Manuel Perez-Mato ; Christoph Loho ; Frank J. Berry ; Robert Kruk ; Kevin S. Knight ; Adrian J. Wright ; Horst Hahn ; Peter R. Slater
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：June 16, 2014
• 年：2014
• 卷：53
• 期：12
• 页码：5911-5921
• 全文大小：574K
• 年卷期：v.53,no.12(June 16, 2014)
• ISSN：1520-510X

文摘

We report here on the characterization of the vacancy-ordered perovskite-type structure of BaFeO_2.5 by means of combined Rietveld analysis of powder X-ray and neutron diffraction data. The compound crystallizes in the monoclinic space group P2₁/c [a = 6.9753(1) 脜, b = 11.7281(2) 脜, c = 23.4507(4) 脜, 尾 = 98.813(1)掳, and Z = 28] containing seven crystallographically different iron atoms. The coordination scheme is determined to be Ba₇(FeO_4/2)₁(FeO_3/2O_1/1)₃(FeO_5/2)₂(FeO_6/2)₁ = Ba₇Fe^[6]₁Fe^[5]₂Fe^[4]₄O_17.5 and is in agreement with the ⁵⁷Fe M枚ssbauer spectra and density functional theory based calculations. To our knowledge, the structure of BaFeO_2.5 is the most complicated perovskite-type superstructure reported so far (largest primitive cell, number of ABX_2.5 units per unit cell, and number of different crystallographic sites). The magnetic structure was determined from the powder neutron diffraction data and can be understood in terms of 鈥淕-type鈥?antiferromagnetic ordering between connected iron-containing polyhedra, in agreement with field-sweep and zero-field-cooled/field-cooled measurements.