  Spin-1/2 Heisenberg model on kagome lattice is a typical frustrated quantum
spin system. A basic structure of kagome lattice is also present in
kagome-strip lattice in one dimension, where a similar type of frustration is
expected. We thus study the magnetization plateaus of the spin-1/2 Heisenberg
model on a kagome-strip chain with three-independent antiferromagnetic exchange
interactions by the density-matrix renormalization group method. In a certain
range of exchange parameters, we find twelve kinds of magnetization plateaus,
nine of which have magnetic structures breaking either translational or
reflection symmetry spontaneously. The structures are classified by an array of
five-site unit cells with specific bond-spin correlations. In a case with
nontrivial plateau, 3/10 plateau, we find long-period magnetic structure with a
period of four unit cells.
