Resonance fields of the electron paramagnetic resonance lines in KCuF: the effect of the Dzyaloshinsky-Moriya exchange interaction and the inequivalent g-tensors

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Abstract
The authors report that the electron paramagnetic resonance field Hres 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 (Snalpha Snbeta +1-Snbeta Snalpha +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.