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MSE Seminar-Prof. Colin Broholm, Johns Hopkins University
Friday, April 25, 2008
1:00 p.m.
Rm. 2108, Chemical and Nuclear Engineering Bldg.
For More Information:
Annette Mateus
301 405 5207
amateus@umd.edu

"Ferroelectricity in Frustrated Magnets"

While electrostatics and magnetostatics are disparate phenomena in a vacuum, no symmetry forbids materials from responding magnetically to an electric field or vise versa. Materials with a strong magneto-electric response challenge our understanding of magnetic dielectrics and are of interest for applications. I discuss specific examples of magneto-electricity in transition metal oxides such as TbMnO3, Ni3V2O8, and RbFe(MoO4)2 where competing magnetic interactions frustrate conventional magnetic order for [1-3]. Our experiments show that when the eventual low T magnetic order breaks spatial inversion symmetry it is accompanied by ferroelectricity. Moreover, application of an electric field along the polar direction favors one of the two inversion symmetry related magnetic domains. We infer that inversion symmetry breaking magnetic order acts as an effective electric field through the magneto-elastic distortions that relieve frustration. The results presented are based on magnetic neutron diffraction experiments and theoretical work by A. B. Harris [4].

[1] M. Kenzelmann, A. B. Harris, S. Jonas, C. Broholm, J. Schefer, S. B. Kim, C. L. Zhang, S.-W. Cheong, O. P. Vajk, and J. W. Lynn, Phys. Rev. Lett. 95, 087206 (2005).

[2] G. Lawes, A. B. Harris, T. Kimura, N. Rogado, R. J. Cava, A. Aharony, O. Entin-Wohlman, T. Yildirim, M. Kenzelmann, C. Broholm, and A. P. Ramirez, Phys. Rev. Lett. 95, 087205 (2005).

[3] M. Kenzelmann, G. Lawes, A.B. Harris, G. Gasparovic, C. Broholm, A.P. Ramirez, G.A. Jorge, M. Jaime, S. Park, Q. Huang, A.Ya. Shapiro, and L.A. Demianets, cond-mat/0701426, to appear in Phys. Rev. Lett. (2007).

[4] A. B. Harris, cond-mat/0610241 (2006).

For more information, contact Annette Mateus at (301) 405-5207 or amateus@umd.edu.

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