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

• Published in: Journal of physical chemistry. C Vol. 118; no. 10; pp. 5463 - 5469
• Main Authors: Mikhailova, D, Kuo, C. Y, Reichel, P, Tsirlin, A. A, Efimenko, A, Rotter, M, Schmidt, M, Hu, Z, Pi, T. W, Jang, L. Y, Soo, Y. L, Oswald, S, Tjeng, L. H
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.03.2014
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp411503s

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.