High Frequency EPR Spectroscopy of Germanium Cuprate. I. The Case of Doping with Cobalt

TL;DR

This study uses high-frequency EPR spectroscopy to analyze the effects of cobalt doping on CuGeO3, revealing new insights into impurity-induced resonance lines and deviations from universal doping behavior.

Contribution

It provides detailed spectroscopic data for Co-doped CuGeO3, highlighting deviations from expected doping models and comparing experimental results with theoretical predictions.

Findings

Discovery of a new Co2+ related resonance line

Deviations from universal doping scenarios

Comparison with Oshikawa and Affleck theory

Abstract

Resonant magnetoabsorption spectra for CuGeO3 single crystals containing 2% of Co impurity are studied in the frequency range 60-360 GHz in magnetic field up to 16 T at temperatures 2-60 K. It is found that together with the resonance on Cu2+ chains a new absorption line related with Co2+ ions appears in EPR spectrum. The full set of spectroscopic data (g-factors, linewidths, integrated intensities) have been determined for both resonances. The obtained results exhibit considerable deviations from the universal scenario of doping for CuGeO3 and discussed in the frames of the models of the quantum critical behavior and the three-dimensional antiferromagnet with the reduced by disorder Neel temperature. The Oshikawa and Affleck theory for EPR in 1D S=1/2 AF spin chain is compared with experiment.