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Structure, Magnetism, and Valence States of Cobalt and Platinum in Quasi-One-Dimensional Oxides A 3 CoPtO 6 with A = Ca, Sr

2014; American Chemical Society; Volume: 118; Issue: 10 Linguagem: Inglês

10.1021/jp411503s

1932-7455

Daria Mikhailova, Chang‐Yang Kuo, P. Reichel, Alexander A. Tsirlin, Anastasia Efimenko, M. Rotter, Marcus Schmidt, Zhiwei Hu, T. W. Pi, Ling‐Yun Jang, Y. L. Soo, Steffen Oswald, L. H. Tjeng,

Multiferroics and related materials

Two quasi-one-dimensional oxides, Ca3CoPtO6 and Sr3CoPtO6, were synthesized and characterized. A combination of X-ray absorption spectroscopy at the Co-K-, Co-L2,3-, 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.