A spin- model for CsCuCl in an external magnetic field

Abstract

CsCuCl3 is a ferromagnetically stacked triangular spin-1/2 antiferromagnet. We discuss models for its zero-temperature magnetization process. The models range from three antiferromagnetically coupled ferromagnetic chains to the full three-dimensional situation. The situation with spin-1/2 is treated by expansions around the Ising limit and exact diagonalization. Further, weak-coupling perturbation theory is used mainly for three coupled chains which are also investigated numerically using the density-matrix renormalization group technique. We find that already the three-chain model gives rise to the plateau-like feature at one third of the saturation magnetization which is observed in magnetization experiments on CsCuCl3 for a magnetic field perpendicular to the crystal axis. For a magnetic field parallel to the crystal axis, a jump is observed in the experimental magnetization curve in the region of again about one third of the saturation magnetization. In contrast to earlier spinwave computations, we do not find any evidence for such a jump with the model in the appropriate parameter region. PACS. 75.10.Jm Quantized spin models -75.45.+j Macroscopic quantum phenomena in magnetic systems -75.50.Ee Antiferromagnetics A. Honecker et al.: A Spin-1 2 Model for CsCuCl3 in an External Magnetic FieldThe purpose of the present paper is to gain some qualitative insight and demonstrate that new theoretical approaches to CsCuCl 3 are viable. It should be possible to develop all these approaches further to improve the accuracy of the results, to obtain a more realistic modeling or to compute other quantities. The modelNow we proceed to give a more accurate description of our model and the parameter region we are interested in. We model CsCuCl 3 by a stacked triangular lattice antiferromagnet as sketched in Fig. 2.1.