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

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 ${\mu }_B$ 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.

4 pages, 3 figures, PRL in press (changes made upon referees comments)

References in corpus (3)

• Local electronic structure and magnetic properties of LaMn0.5Co0.5O3 studied by x-ray absorption and magnetic circular dichroism spectroscopy
• Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3
• Insulating state and the importance of the spin-orbit coupling in Ca${}_3$CoRhO${}_6$