Issue
EPL
Volume 82, Number 5, June 2008
Article Number 57005
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/82/57005
Published online 26 May 2008
EPL, 82 (2008) 57005
DOI: 10.1209/0295-5075/82/57005

An effective model of magnetoelectricity in multiferroics RMn2O5

Chen Fang and Jangping Hu

Department of Physics, Purdue University - West Lafayette, IN 47907, USA

hu4@purdue.edu

received 15 January 2008; accepted in final form 8 April 2008; published June 2008
published online 26 May 2008

Abstract
An effective model is developed to explain the phase diagram and the mechanism of magnetoelectric coupling in multiferroics, RMn2O5. We show that the nature of magnetoelectric coupling in RMn2O5 is a coupling between two Ising-type orders, namely, the ferroelectric order in the b-axis, and the.coupled magnetic order between two frustrated antiferromagnetic chains. The frustrated magnetic structure drives the system to a commensurate-incommensurate phase transition, which can be understood as a competition between a collinear order stemming from the "order by disorder" mechanism and a chiral symmetry order. The low-energy excitation is calculated and it quantitatively matches experimental results. Distinct features and the effects of external magnetic field in the electromagnon spectra in the incommensurate phase are predicted.

PACS
75.25.+z - Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.).
75.47.Lx - Manganites.
77.80.-e - Ferroelectricity and antiferroelectricity.

© EPLA 2008