Abstract
The origin of both the Ising chain magnetism and ferroelectricity in is studied by ab initio electronic structure calculations and x-ray absorption spectroscopy. We find that has alternate trigonal prismatic and octahedral sites in the spin chain. Both the and are in the high-spin state. In addition, the has a huge orbital moment of 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 antiferromagnetic structure for the Ising chain. The calculated inequivalence of the Co-Mn distances accounts for the ferroelectricity.
- Received 9 June 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.026404
©2009 American Physical Society