J. Phys. IV France
Volume 114, April 2004
Page(s) 119 - 121

J. Phys. IV France
114 (2004) 119
DOI: 10.1051/jp4:2004114025

Pressure effect on the charge ordering phase transition in the quasi-one-dimensional conductor (TMTTF) 2SbF 6

M. Nagasawa1, 2, 1, F. Nad3, 2, P. Monceau4, 2 and J.M. Fabre5

1  Dept. Natural Sciences and Dept. Material Science, Tokyo Denki University, Nishikicyo 2-2, Kanda, Chiyoda, Tokyo, 101-8457, Japan
2  Centre de Recherches sur les Très Basses Températures, associée à l'Université Joseph Fourier, CNRS, BP. 166, 38042 Grenoble Cedex 9, France
3  Institute of Radioengineering and Electronics, Russia Academy of Sciences, Mokhovaya 11, 103907 Moscow, Russia
4  Laboratoire Léon Brillouin, Unité Mixte de Recherche, CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
5  Laboratoire de Chimie Structurale Organique, Université de Montpellier, 34095 Montpellier Cedex 5, France

Conductivity and permittivity of the quasi-one-dimensional conductor (TMTTF) 2SbF 6 have been measured at low frequencies ( $f =
10^{2} \sim 10^{7}$  Hz) under several pressures ( $P= 0 \sim 0.5$GPa). The real part of the conductivity has a maximum at  $T_{\rm m}$ due to charge localization of Mott-Hubbard type. Below  $T_{\rm m}$, the real part of the permittivity ( $\varepsilon $ $\prime )$ shows a sharp peak with the magnitude in the order of  $10^{5} \sim10^{6}$. It has been suggested that the anomaly of  $\varepsilon $ $\prime $ is due to a charge ordering (CO) phase transition. We found that the CO transition temperature decreases with pressure. Above 0.25GPa, the temperature dependence of  $\varepsilon $ $\prime $ is strongly dependent on frequency in the frequency range of measurements. We will discuss the pressure effect on the CO phase transition in (TMTTF) 2X family. Key words. organic compounds - charge ordering - permittivity.

© EDP Sciences 2004