Magnetization plateaux of Cs2CuBr4

Cs2CuBr4 is a new two-dimensional spin-1/2 system, where 1/3-plateau has been observed in external magnetic fields for H parallel to b and H parallel to c. It is expected that magnetic behaviors of the material are well explained by a two-dimensional antiferromagnetic Heisenberg model on a distorted triangular lattice. In the model, there are two types of interactions. J(1) and J(2), where J(1) chains are coupled with interchain interactions J(2). Using an exact diagonalization method, we investigate magnetic properties, especially magnetization curve. In the magnetization, 1/3-plateau appears for 0.7 less than or similar to J(2)/J(1) less than or similar to 1.3. In the plateau phase. three-fold degenerate translational symmetry broken ground state is realized. Our results indicate that the material has a more frustrated character than what has been expected from a classical theory. (c) 2006 Elsevier B.V. All rights reserved.