Double-exchange model study of multiferroic RMnO₃ perovskites

الأصل · EN

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.