A Spin-1/2 Model for CsCuCl_3 in an External Magnetic Field

TL;DR

This paper models the magnetization process of CsCuCl_3 using various spin-1/2 models, revealing a plateau at one-third saturation magnetization consistent with experiments, but no jump predicted by earlier theories.

Contribution

It introduces a comprehensive spin-1/2 modeling approach for CsCuCl_3, combining expansions, exact diagonalization, and DMRG to explain experimental magnetization features.

Findings

The three-chain model reproduces the one-third magnetization plateau.

No evidence of a jump in magnetization was found in the model, contrary to earlier spinwave predictions.

The models align with experimental observations for perpendicular magnetic fields.

Abstract

CsCuCl_3 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 CsCuCl_3 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.