Interplay between Jahn-Teller instability, uniaxial magnetism and ferroelectricity in Ca3CoMnO6

摘要

Ca3CoMnO6 is composed of CoMnO6 chains made up of face-sharing CoO6 trigonalprisms and MnO6 octahedra. The structural, magnetic, and ferroelectricproperties of this compound were investigated on the basis of densityfunctional theory calculations. Ca3CoMnO6 is found to undergo a Jahn-Tellerdistortion associated with the CoO6 trigonal prisms containing high-spin Co2+(d7) ions, which removes the C3 rotational symmetry and hence uniaxialmagnetism. However, the Jahn-Teller distortion is not strong enough to fullyquench the orbital moment of the high-spin Co2+ ions thereby leading to anelectronic state with substantial magnetic anisotropy. The Jahn-Tellerdistorted Ca3CoMnO6 in the magnetic ground state with up-up-down-down spinarrangement is predicted to have electric polarizations much greater thanexperimentally observed. Implications of the discrepancy between theory andexperiment were discussed.