Eur. Phys. J. B (2015) 88: 85
https://doi.org/10.1140/epjb/e2015-50774-5

Regular Article

Electronic instabilities and irradiation effects in the (TMTTF)₂X series

¹ Université Bordeaux, Centre de Recherches Paul Pascal, CNRS, UPR CNRS 8641, 115 Avenue Dr. A. Schweitzer, 33600 Pessac, France
² Laboratoire de Physique des Solides, Université Paris Sud, CNRS, UMR 8502, 91405 Orsay, France
³ Architectures Moléculaires Matériaux Nanostructurés, Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM12-ENSCM-UM1, 8 rue de l’école normale, 34296 Montpellier Cedex 5, France

^a e-mail: pascale.foury@u-psud.fr

Received: 4 November 2014
Received in final form: 13 February 2015
Published online: 6 April 2015

Abstract

The paper presents a single-crystal ESR study of a series of pristine and X-ray irradiated (TMTTF)₂X salts, where TMTTF is tetramethyltetrathiafulvalene and X is either a centro-symmetrical (SbF₆ and Br) or a non-centro-symmetrical (ReO₄, ClO₄, BF₄, SCN and NO₃) monovalent anion. Besides standard line-width and spin-susceptibility measurements, the analysis of the asymmetry of the ESR line shape allows to obtain simultaneous information on the electrical conductivity. This whole set of data is used to determine the charge and spin gaps related to the charge ordering (CO) and anion ordering (AO) ground states and their evolution as a function of X-ray irradiation damages. We show in particular that the sensibility of (TMTTF)₂X salts to irradiation depends upon the nature of the anion X and that the CO ground state is drastically affected by irradiation damages at the difference of the AO ground state. We also present evidence of a CO transition and of a decoupling between the AO transition and the opening of a spin gap in (TMTTF)₂NO₃.