The Role of Oxygen Stoichiometry on Phase Stability, Structure, and Magnetic Properties of Sr2CoIrO6−δ

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• 作者：D. Mikhailova ; N. Narayanan ; W. Gruner ; A. Voss ; A. Senyshyn ; D. M. Trots ; H. Fuess ; H. Ehrenberg
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：November 15, 2010
• 年：2010
• 卷：49
• 期：22
• 页码：10348-10356
• 全文大小：1072K
• 年卷期：v.49,no.22(November 15, 2010)
• ISSN：1520-510X

文摘

The phase stability, crystal structure, and magnetic properties of perovskite-like nonstoichiometric Sr₂CoIrO_6−δ were studied. Oxygen deficiency can be well controlled and reversibly varied up to δ = 0.33. A single phase exists at least for partial oxygen pressures between 10⁻⁵ and 1 bar at 1273 K, followed by phase decomposition at higher temperature with the elimination of metallic Ir and the formation of a new phase with approximately Sr₃CoIrO₆ composition crystallizing in K₄CdCl₆ structure type. The structural features of Sr₂CoIrO_6−δ are dependent on both temperature and oxygen content and were determined by synchrotron and neutron powder diffraction. Both the increasing amount of oxygen vacancies at constant temperature and increasing temperature at constant oxygen content result in the same higher crystal symmetry of Sr₂CoIrO_6−δ: (1) The oxygen-stoichiometric phase Sr₂CoIrO_6.00 is monoclinic (I2/m or P2₁/n) at room temperature but cubic (Fm-3m) for Sr₂CoIrO_5.67. (2) A sequence of phase transitions was observed for Sr₂CoIrO_6.00 in air. All Sr₂CoIrO_6−δ compositions show weak ferromagnetism at low temperature with a canted but predominantly antiferromagnetic ground state. The magnetic ordering temperature decreases monotonously with increasing oxygen deficiency, while pronounced extrema are observed for the paramagnetic moment and the Curie−Weiss temperature at an oxygen deficiency δ ≈ 0.10, which corresponds to the P2₁/n ↔ I2/m phase transformation.