G. P. Zhang, Jian Zhang, Qi-Li Zhang, Jiang-Tao Zhou, M. H. Shangguan
The effect of antiferromagnetic (AF) superexchange (SE) interaction on double exchange model in two-dimensional triangular lattice is investigated in this Letter. The long-range ferromagnetic (FM) spin-spin correlation and strong electron-spin correlation in triangular lattice are two important factors for truncation error of FM-like spin-spin correlation near quarter filling by truncated polynomial expansion, which can be overcome by high expansion moment M. Near quarter filling, non-coplanar spin configuration is induced by competition between FM parallel alignment mediated by itinerant electrons and AF SE interaction between localized spins. A phase transition from FM to non-coplanar phase is characterized by both spin structure factor and the change of the slope of energy in term of AF SE interaction, which is accompanied by a phase separation in electronic density. At strong AF SE interaction, there is also another phase separation accompanying the phase transition from non-coplanar spin phase to 120-degree spin phase. Finally we discuss the effect of temperature on magnetic structure.
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http://arxiv.org/abs/1206.6944
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