%0 Journal Article
%T Systematic Variations in the Charge-Glass-Forming Ability of Geometrically Frustrated $¦È$-(BEDT-TTF)$_2X$ Organic Conductors
%A T. Sato
%A F. Kagawa
%A K. Kobayashi
%A A. Ueda
%A H. Mori
%A K. Miyagawa
%A K. Kanoda
%A R. Kumai
%A Y. Murakami
%A Y. Tokura
%J Physics
%D 2014
%I arXiv
%R 10.7566/JPSJ.83.083602
%X The critical cooling rate $R_{\rm c}$ above which charge ordering is kinetically avoided upon cooling, which results in charge-glass formation, was investigated for the geometrically frustrated system $\theta$-(BEDT-TTF)$_2X$. X-ray diffraction experiments revealed that $\theta$-(BEDT-TTF)$_2$TlCo(SCN)$_4$ exhibits a horizontally charge-ordered state, and kinetic avoidance of this state requires rapid cooling of faster than 150 K/min. This value is markedly higher than that reported for two other isostructural $\theta$-type compounds, thus demonstrating the lower charge-glass-forming ability of $X$ $=$ TlCo(SCN)$_4$. In accounting for the systematic variations of $R_{\rm c}$ among the three $\theta$-(BEDT-TTF)$_2X$, we found that stronger charge frustration leads to superior charge-glass former. Our results suggest that charge frustration tends to slow the kinetics of charge ordering.
%U http://arxiv.org/abs/1408.2913v1