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Accueil du site > Vie du Laboratoire > Archives > Archives 2012 "A la Une" >

22 mars 2012

Giant Improper Ferroelectricity in the Ferroaxial Magnet CaMn7O12

R. D. Johnson1,2,*, L. C. Chapon2,3, D. D. Khalyavin2, P. Manuel2, P. G. Radaelli1, and C. Martin4
1Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, United Kingdom
2ISIS Facility, Rutherford Appleton Laboratory-STFC, Chilton, Didcot, OX11 0QX, United Kingdom
3Institut Laue-Langevin, BP 156X, 38042 Grenoble, France
4Laboratoire CRISMAT, ENSICAEN, UMR F-6508 CNRS, 6 Boulevard du Marechal Juin, F-14050 Caen Cedex, France

Received 20 October 2011 ; published 6 February 2012

See accompanying Physics Viewpoint

In rhombohedral CaMn7O12, an improper ferroelectric polarization of magnitude 2870  μC 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 threefold 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.

© 2012 American Physical Society

DOI :10.1103/PhysRevLett.108.067201
PACS :75.85.+t,, 75.25.-j, 77.80.-e