An effective model of magnetoelectricity in multiferroics RMn₂O₅

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

Corresponding author: hu4@purdue.edu

Received: 15 January 2008
Accepted: 8 April 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.