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

摘要

We study the ground-state properties of the S=1/2 Heisenberg models on thequasi-onedimensional kagome strip lattices by the exact diagonalization anddensity matrix renormalization group methods. The models with two differentstrip widths share the same lattice structure in their inner part with thespatially anisotropic two-dimensional kagome lattice. When there is no magneticfrustration, the well-known Lieb-Mattis ferrimagnetic state is realized in bothmodels. When the strength of magnetic frustration is increased, on the otherhand, the Lieb-Mattis-type ferrimagnetism is collapsed. We find that thereexists a non-Lieb-Mattis ferrimagnetic state between the Lieb-Mattisferrimagnetic state and the nonmagnetic ground state. The local magnetizationclearly shows an incommensurate modulation with long-distance periodicity inthe non-Lieb-Mattis ferrimagnetic state. The intermediate non-Lieb-Mattisferrimagnetic state occurs irrespective of strip width, which suggests that theintermediate phase of the two-dimensional kagome lattice is also thenon-Lieb-Mattis-type ferrimagnetism.