Anomalous temperature dependence of the ESR linewidth in CuGeO3 doped with magnetic impurities and the universal relations in the Oshikawa-Affleck theory

Studying the ESR line in CuGeO3 doped with Ti, Fe, and Co impurities we find that magnetic impurities cause the anomalous low-temperature increase of the linewidth w(T) ~ (Bres/T)2 (where Bres denotes the resonant field) accompanied by the temperature-dependent g-factor shift Δg(T). For T < 20 K, these parameters are strongly correlated and the ratio w(T)/Δg(T) follows the general relation w(T)/Δg(T) ~ kBT/μB. The observed effects agree with the predictions of the theory of ESR developed by Oshikawa and Affleck for 1D S = ½ antiferromagnetic chains.