RESONANCE FIELDS OF THE ELECTRON-PARAMAGNETIC RESONANCE LINES IN KCUF3 - THE EFFECT OF THE DZYALOSHINSKY-MORIYA EXCHANGE INTERACTION AND THE INEQUIVALENT G-TENSORS

The authors report that the electron paramagnetic resonance field H res measured at a fixed microwave frequency in KCuF3, a compound having one-dimensional Heisenberg antiferromagnetic properties in spite of its pseudocubic crystal structure, is temperature independent for the external field H parallel to the chain axis, while Hres for H perpendicular to the chain axis shows a very weak decreasing tendency with decreasing temperature to TN=39 K over the wide region of short-range order. Considering the recent discovery that this compound has a Dzyaloshinsky-Moriya (DM) antisymmetric exchange interaction the authors suggest that Hres is governed by the DM interaction and the antisymmetric spin-correlation functions (SnalphaSn beta+1-SnbetaSn alpha+1) with alpha not= beta ( alpha , beta =x, y, z), resulting in the temperature independence of Hres. They also point out that the two inequivalent g-tensors in this compound can be the origin of the very weak decreasing tendency of Hres observed for H perpendicular to the chain axis.