In rhombohedral CaMn7O12, an improper ferroelectric polarization of magnitude 2870 {\mu}C m-2 is induced by an incommensurate helical magnetic structure that evolves below TN1 = 90 K. The electric polarization was found to be constrained to the high symmetry three-fold rotation axis of the crystal structure, perpendicular to the in-plane rotation of the magnetic moments. The multiferroicity is explained by the ferroaxial coupling mechanism, which in CaMn7O12 gives rise to the largest magnetically induced, electric polarization measured to date.
@article{arxiv.1110.4585,
title = {Giant improper ferroelectricity in the ferroaxial magnet CaMn7O12},
author = {R. D. Johnson and L. C. Chapon and D. D. Khalyavin and P. Manuel and P. G. Radaelli and C. Martin},
journal= {arXiv preprint arXiv:1110.4585},
year = {2015}
}
Comments
10 pages, 4 figures, and 1 table. Submitted to Physical Review Letters