Structure, Magnetism, and Valence States of Cobalt and Platinum in Quasi-One-Dimensional Oxides A3CoPtO6 with A = Ca, Sr

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• 作者：D. Mikhailova ; C. Y. Kuo ; P. Reichel ; A. A. Tsirlin ; A. Efimenko ; M. Rotter ; M. Schmidt ; Z. Hu ; T. W. Pi ; L. Y. Jang ; Y. L. Soo ; S. Oswald ; L. H. Tjeng
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 13, 2014
• 年：2014
• 卷：118
• 期：10
• 页码：5463-5469
• 全文大小：452K
• 年卷期：v.118,no.10(March 13, 2014)
• ISSN：1932-7455

文摘

Two quasi-one-dimensional oxides, Ca₃CoPtO₆ and Sr₃CoPtO₆, were synthesized and characterized. A combination of X-ray absorption spectroscopy at the Co-K-, Co-L_2,3-, and Pt-L₃-edges and X-ray photoelectron spectroscopy establishes unambiguously the divalent state of Co and the tetravalent state of Pt in both compounds, in contrast to the earlier assumption of the Co³⁺ and mixed Pt²⁺/Pt⁴⁺ valence states. Magnetization measurements reveal the paramagnetic behavior down to 2 K with strong evidence for an unquenched orbital moment of the high-spin Co²⁺. The simple paramagnetic behavior of A₃CoPtO₆ contrasts with the magnetic transitions observed in Ca₃CoRhO₆, Sr₃CoIrO₆, and other isostructural materials. This difference is ascribed to the nonmagnetic 5d⁶ state of Pt⁴⁺ that prevents magnetic couplings between the Co²⁺ ions.