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Observation of spin freezing and relaxation at microwave frequencies in the spin ladder compound $Sr_{14-x}Ca_{x}Cu_{24}O_{41}$

Z. Zhai·P. V. Patanjali·N. Hakim·J. B. Sokoloff·S. Sridhar·U. Ammerahl·A. Vietkine·A. Revcolevschi
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Abstract

We report the observation of a frequency ($ω$) and temperature (T) -dependent loss peak in $χ''$ and accompanying dispersion in $χ'$ from microwave (2-18GHz) measurements of the complex susceptibility $\tildeχ(ω, T)=χ'+iχ''$ of $Sr_{14-x}Ca_{x}Cu_{24}O_{41}$. We associate this phenomenon with a rapid decrease of spin disorder and corresponding spin relaxation rate, representing a ``spin freezing transition'' accompanying charge ordering which occurs at temperatures $\sim 250K$. Our results enable direct quantitative measurements of the spin relaxation rate, and yield information on spin dynamics in these materials and the related compounds $SrCuO_{2}$ and $Sr_{2}CuO_{3}$.

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Z. Zhai, P. V. Patanjali, N. Hakim, J. B. Sokoloff, S. Sridhar, U. Ammerahl, A. Vietkine, A. Revcolevschi. 1999-03-12. Observation of spin freezing and relaxation at microwave frequencies in the spin ladder compound $Sr_{14-x}Ca_{x}Cu_{24}O_{41}$. https://arxiv.org/abs/cond-mat/9903198

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