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arXiv · 0806.1607

Ising magnetism and ferroelectricity in Ca$_3$CoMnO$_6$

Hua Wu·T. Burnus·Z. Hu·C. Martin·A. Maignan·J. C. Cezar·A. Tanaka·N. B. Brookes·D. I. Khomskii·L. H. Tjeng
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Abstract

The origin of both the Ising chain magnetism and ferroelectricity in Ca$_3$CoMnO$_6$ is studied by $ab$ $initio$ electronic structure calculations and x-ray absorption spectroscopy. We find that Ca$_3$CoMnO$_6$ has the alternate trigonal prismatic Co$^{2+}$ and octahedral Mn$^{4+}$ sites in the spin chain. Both the Co$^{2+}$ and Mn$^{4+}$ are in the high spin state. In addition, the Co$^{2+}$ has a huge orbital moment of 1.7 $μ_B$ which is responsible for the significant Ising magnetism. The centrosymmetric crystal structure known so far is calculated to be unstable with respect to exchange striction in the experimentally observed $\uparrow\uparrow\downarrow\downarrow$ antiferromagnetic structure for the Ising chain. The calculated inequivalence of the Co-Mn distances accounts for the ferroelectricity.

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Hua Wu, T. Burnus, Z. Hu, C. Martin, A. Maignan, J. C. Cezar, A. Tanaka, N. B. Brookes, D. I. Khomskii, L. H. Tjeng. 2008-12-04. Ising magnetism and ferroelectricity in Ca$_3$CoMnO$_6$. https://doi.org/10.1103/physrevlett.102.026404

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