Coupled spin-charge order in frustrated itinerant triangular magnets

Abstract

We uncover four spin-charge ordered ground states in the strong coupling limit of the Kondo lattice model on triangular geometry. The results are obtained using Monte Carlo simulations, with a classical treatment of localized moments. Two of the states at one-third electronic filling (n = 1/3) consist of decorated ferromagnetic chains coupled antiferromagnetically with the neighboring chains. The third magnetic ground state is noncollinear, consisting of antiferromagnetic chains separated by a pair of canted ferromagnetic chains. An even more unusual magnetic ground state, a variant of the 120° Yafet-Kittel phase, is discovered at n = 2/3. These magnetic orders are stabilized by opening a gap in the electronic spectrum: a "band effect." All the phases support modulations in the electronic charge density due to the presence of magnetically inequivalent sites. In particular, the charge ordering pattern found at n = 2/3 is observed in various triangular lattice systems, such as 2H-AgNiO2, 3R-AgNiO2, and NaxCoO2