A 3D Oxalate-Based Network as a Precursor for the CoMn2O4 Spinel: Synthesis and Structural and Magnetic Studies

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• 作者：Jelena Habjani膷 ; Marijana Juri膰 ; Jasminka Popovi膰 ; Kre拧imir Mol膷anov ; Damir Paji膰
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：September 15, 2014
• 年：2014
• 卷：53
• 期：18
• 页码：9633-9643
• 全文大小：720K
• ISSN：1520-510X

文摘

A novel heterometallic oxalate-based compound of the formula {[Co(bpy)₃][Mn₂(C₂O₄)₃]路H₂O}_n (1; bpy = 2,2鈥?bipyridine) was synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), and magnetization measurement. The molecular structure of 1 is made of a three-dimensional (3D) anionic network, [Mn₂(C₂O₄)₃]_n^{2n鈥?/sup>, and tris-chelated cations [Co(bpy)₃]2+ occupying the vacancies of the framework. Splitting between the zero-field-cooled (ZFC) and field-cooled (FC) branches of susceptibility below the small peak at 13 K indicates magnetic ordering. Compound 1 was used as a single-source precursor for the formation of the mixed-metal oxide CoMn₂O₄. This conversion via thermal decomposition was explored by thermal analysis (TGA and DTA), IR spectroscopy, powder XRD, and magnetic susceptibility measurement. From refined structural parameters, it could be seen that the spinel obtained by the thermal treatment of 1 at 800 掳C is characterized by the inversion parameter 未 = 21%, and therefore the structural formula at room temperature can be written as tet[Co_0.79Mn_0.21]oct[Co_0.105Mn_0.895]₂O₄. The temperature dependence of magnetization for CoMn₂O₄ points to at least three magnetic phases: the ferrimagnetic state is observed below 83 K, and up to 180 K blocking of the magnetic moments of nanocrystallites of 31 nm appears, transforming to paramagnetic-like behavior above 180 K. Microstructural characterization of the CoMn₂O₄ sample was carried out by means of XRD line-broadening analysis.}