Europhys. Lett.
Volume 63, Number 3, August 2003
Page(s) 446 - 452
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00530-3
Europhys. Lett., 63 (3) , pp. 446-452 (2003)

Anomalous temperature dependence of the ESR linewidth in $\chem{CuGeO_3}$ doped with magnetic impurities and the universal relations in the Oshikawa-Affleck theory

S. V. Demishev1, Y. Inagaki2, H. Ohta2, S. Okubo2, Y. Oshima2, A. A. Pronin1, N. A. Samarin1, A. V. Semeno1 and N. E. Sluchanko1

1  General Physics Institute of RAS - Vavilov str., 38, 119991 Moscow, Russia
2  Kobe University - 1-1 Rokkodai, Nada, Kobe 657-8501, Japan

(Received 16 August 2002; accepted in final form 23 May 2003)

Studying the ESR line in $\chem{CuGeO_3}$ doped with $\chem{Ti}$, $\chem{Fe}$, and $\chem{Co}$ impurities we find that magnetic impurities cause the anomalous low-temperature increase of the linewidth $w(T)\sim(B_{\ab{res}}/T)^{2}$ (where $B_{\ab{res}}$ denotes the resonant field) accompanied by the temperature-dependent g-factor shift $\Delta g(T)$. For T<20 $\un{K}$, these parameters are strongly correlated and the ratio $w(T)/\Delta g(T)$ follows the general relation $w(T)/\Delta g(T)\sim
k_{\ab{B}}T/\mu_{\ab{B}}$ . The observed effects agree with the predictions of the theory of ESR developed by Oshikawa and Affleck for 1D $S=\frac{1}{2}$ antiferromagnetic chains.

76.30.-v - Electron paramagnetic resonance and relaxation.
76.30.Fc - Iron group ( 3d) ions and impurities ( $\chem{Ti}$- $\chem{Cu}$).

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