Structure and magnetism of rare-earth-substituted Ca3Co2O6 |
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Authors: | Charles H Hervoches Helmer Fjellvåg Vivian Miksch Fredenborg |
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Institution: | a Institute for Energy Technology, P.O. Box 40, N-2027 Kjeller, Norway b Centre for Materials Science and Nanotechnology; Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway |
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Abstract: | Yttrium- and rare-earth-substituted derivatives of Ca3−vRvCo2O6 (RY, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, and Lu) have been synthesized and structurally characterized by powder X-ray and neutron diffraction. All phases adopt the K4CdCl6-type structure with space group R3¯c), in which the trivalent R3+ substituents randomly occupy the Ca2+ site. The homogeneity range of Ca3−vRvCo2O6 extends to v≈0.90 for the substituents concerned. A significant increase in the Co2-O distances within the trigonal-prismatic Co2O6 co-ordination polyhedra upon introduction of R3+ confirms that extra electrons from the R3+-for-Ca2+ substitution exclusively enter the Co2 site of the quasi-one-dimensional Ca3−vRvCo2O6 structure, thereby formally reducing its oxidation state. This is furthermore supported by magnetic susceptibility and low-temperature neutron diffraction measurements. The long-range ferrimagnetic ordering temperature is reduced upon R substitution and appears to vanish for v>∼0.30. |
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Keywords: | Rare-earth substitution Ca3Co2O6 structure Low-dimensional material Magnetic properties |
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