Ferrimagnetism of the Heisenberg Models on the Quasi-One-Dimensional Kagome Strip Lattices

Abstract

We study the ground-state properties of the S =1/2 Heisenberg models on the quasi-one-dimensional kagome strip lattices by the exact diagonalization and density matrix renormalization group methods. The models with two different strip widths share the same lattice structure in their inner part with the spatially anisotropic two-dimensional kagome lattice. When there is no magnetic frustration, the well-known Lieb–Mattis ferrimagnetic state is realized in both models. When the strength of magnetic frustration is increased, on the other hand, the Lieb–Mattis-type ferrimagnetism is collapsed. We find that there exists a non-Lieb–Mattis ferrimagnetic state between the Lieb–Mattis ferrimagnetic state and the nonmagnetic ground state. The local magnetization clearly shows an incommensurate modulation with long-distance periodicity in the non-Lieb–Mattis ferrimagnetic state. The intermediate non-Lieb–Mattis ferrimagnetic state occurs irrespective of strip width, which suggests that the intermediate phase of the two-dimensional kagome lattice is also the non-Lieb–Mattis-type ferrimagnetism.