Volume 85, Number 5, March 2009
Article Number 57004
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 20 March 2009
EPL, 85 (2009) 57004
DOI: 10.1209/0295-5075/85/57004

Dynamical magnetoelectric effects induced by the Dzyaloshinskii-Moriya interaction in multiferroics

Chenglong Jia and Jamal Berakdar

Institut für Physik, Martin-Luther Universität Halle-Wittenberg - Heinrich-Damerow-Str.4 06120 Halle (Saale), Germany, EU

received 12 November 2008; accepted in final form 13 February 2009; published March 2009
published online 20 March 2009

We study the dynamical interplay between ferroelectricity and magnetism in a multiferroic with a helical magnetic order. We show that the dynamical exchange-striction induces a biquadratic interaction between the spins and transverse phonons resulting in quantum fluctuations of the spontaneous ferroelectric polarization ${\bf P}$ in the ferroelectric phase. The hybridization between the spin wave and the fluctuation of the electric polarization leads to low-lying transverse phonon modes. Those are perpendicular to ${\bf P}$ and to the helical spins at small wave vector but then turn parallel to ${\bf P}$ at a wave vector close to the magnetic modulation vector. For helical magnetic structure, the spin chirality which determines the direction of ${\bf P}$, also possesses a long-range order. Due to the dynamical Dzyaloshiskii-Moriya interaction, the spin chirality is strongly coupled to the spin fluctuation which implies an on-site inversion of the spin chirality in the ordered spin-(1/2) system and results in a finite scattering intensity of polarized neutrons from a cycloidal helimagnet.

75.80.+q - Magnetomechanical and magnetoelectric effects, magnetostriction.
71.70.Ej - Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect.
77.80.-e - Ferroelectricity and antiferroelectricity.

© EPLA 2009