Abstract
Two quasi-one-dimensional oxides, Ca 3 CoPtO 6 and Sr 3 CoPtO 6 , were synthesized and characterized. A combination of X-ray absorption spectroscopy at the Co-K-, Co-L 2,3 -, and Pt-L 3 -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 Co 3+ and mixed Pt 2+ /Pt 4+ valence states. Magnetization measurements reveal the paramagnetic behavior down to 2 K with strong evidence for an unquenched orbital moment of the high-spin Co 2+ . The simple paramagnetic behavior of A 3 CoPtO 6 contrasts with the magnetic transitions observed in Ca 3 CoRhO 6 , Sr 3 CoIrO 6 , and other isostructural materials. This difference is ascribed to the nonmagnetic 5d 6 state of Pt 4+ that prevents magnetic couplings between the Co 2+ ions. © 2014 American Chemical Society.