Eur. Phys. J. B 71, 339-344 (2009)
https://doi.org/10.1140/epjb/e2009-00225-1

Double-exchange model study of multiferroic RMnO₃ perovskites

¹ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
² Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 32831, USA
³ Nanjing National Laboratory of Microstructures, Nanjing University, 210093, Nanjing, P.R. China
⁴ Computational Condensed Matter Physics Laboratory, RIKEN, Wako, 351-0198, Saitama, Japan
⁵ CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012, Japan
⁶ International Center for Materials Physics, Chinese Academy of Sciences, 110016, Shenyang, P.R. China

Corresponding author: ^a saintdosnju@gmail.com

Received: 27 February 2009
Revised: 26 March 2009
Published online: 15 July 2009

Abstract

In this proceeding, recent theoretical investigations by the authors on the multiferroic RMnO₃ perovskites are briefly reviewed at first. Using the double-exchange model, the realistic spiral spin order in undoped manganites such as TbMnO₃ and DyMnO₃ is well reproduced by incorporating a weak next-nearest neighbor superexchange (~10% of nearest neighbor superexchange) and moderate Jahn-Teller distortion. The phase transitions from the A-type antiferromagnet (as in LaMnO₃), to the spiral phase (as in TbMnO₃), and finally to the E-type antiferromagnet (as in HoMnO₃), with decreasing size of the R ions, were also explained. Moreover, new results of phase diagram of the three-dimensional lattice are also included. The ferromagnetic tendency recently discovered in the LaMnO₃ and TbMnO₃ thin films is explained by considering the substrate stress. Finally, the relationship between our double-exchange model and a previously used J₁-J₂-J₃ model is further discussed from the perspective of spin wave excitations.