Abstract
Electron spin resonance (ESR) measurements on CuGeO 3 doped with Zn 2+ ions have been performed in the temperature range of 3–300 K. The ESR spectra of Cu 2+ ions have been observed to be strongly temperature dependent for both pure and doped samples. The ESR line intensity exponentially vanishes below a critical temperature, T c=14 K, for pure CuGeO 3. However, the replacement of magnetic Cu 2+ by non-magnetic Zn 2+ ion causes a drastic shift of T c to lower values, as well as significant increase in ESR signal intensity as the temperature is further decreased. The one-dimensional antiferromagnetic spin chain formed by Cu 2+ ions is broken by Zn 2+ ion, giving uncoupled spins at the end of the chains which result in an extra contribution to the spectra at lower temperatures. It is shown that the ground state of dimerized spins is singlet.
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