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arXiv · 1603.01470

Electronic and ionic conductivities in superionic Li$_4$C$_{60}$

D. Quintavalle·B. G. Márkus·A. Jánossy·F. Simon·G. Klupp·M. A. Győri·K. Kamarás·G. Magnani·D. Pontiroli·M. Riccò
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Abstract

The $10$ GHz microwave conductivity, $\sigma(T)$ and high field, $222$ GHz electron spin resonance (HF-ESR) of Li$_4$C$_{60}$ fulleride is measured in a wide temperature range. We suggest that the majority of ESR active sites and at least some of the charge carriers for $\sigma(T)$ are electrons bound to a small concentration of surplus or vacancy ions in the polymer phase. Both $\sigma(T)$ and the ESR line shape depend on ionic motion. A change of the activation energy of $\sigma(T)$ at $125$ K coincides with the onset of the ionic DC conductivity. The ESR line shape is determined mainly by Li ionic motion within octahedral voids below $150$ K. At higher temperatures, fluctuations due to ionic diffusion change the environment of defects from axial to effectively isotropic on the ESR time scale. $\sigma(T)$ data up to $700$ K through the depolymerization transition confirm that the monomeric phase of Li$_4$C$_{60}$ is a metal.

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D. Quintavalle, B. G. Márkus, A. Jánossy, F. Simon, G. Klupp, M. A. Győri, K. Kamarás, G. Magnani, D. Pontiroli, M. Riccò. 2016-03-04. Electronic and ionic conductivities in superionic Li$_4$C$_{60}$. https://doi.org/10.1103/physrevb.93.205103

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