Wiley, Acta Crystallographica Section a Foundations of Crystallography, a1(68), p. s95-s95, 2012
DOI: 10.1107/s0108767312098157
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In rhombohedral CaMn7O12, an improper ferroelectric polarization of magnitude 2870 {μ}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. ; Comment: 10 pages, 4 figures, and 1 table. Submitted to Physical Review Letters