Conduction electron spin resonance measurements on TTF-TNNQ and (TMTTF)2BF4 under hydrostatic pressure

Abstract

Conduction electron spin resonance (CESR) measurements under hydrostatic pressure on two chain organic conductor tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ) and single chain organic conductor bis tetramethyl-tetrathiofulvalene borontetrafluorid ((TMTTF)2BF4) are presented. In both cases the CESR linewidth increases strongly with pressure in contradiction with the Elliott-mechanism for spin relaxation. The g-factor is pressure independent for both compounds while the spin susceptibility decreases by - 8 ± 1 %/kbar for TTF-TCNQ and - 3 ± 1 %/kbar for (TMTTF) 2BF4 at room temperature

Structure and electronic properties of potassium-doped single-wall carbon nanotubes

“…Also, comparison of the temperature ͑T͒ and doping dependences of the CESR linewidth ͑proportional to the spin relaxation rate͒ with the momentum relaxation rate ͑proportional to resistivity͒ can reveal non-Fermi-liquid and/or reduced dimensionality effects. 10 CESR was observed in undoped SWNT by Petit et al 11 but not by Bandow et al; 12 and was recently reported in K-doped SWNT at fixed concentration. 13 Electrochemistry is a powerful doping method because it affords precise control of guest concentration, facilitates in situ experiments on air-sensitive materials, and provides a controlled method to test reversibility.…”

Electron Spin Resonance: A Major Probe for Molecular Conductors

“…Table summarizes the principal values of the g tensor obtained with different anion and cation radicals. Some EPR studies under pressure have also been reported for these charge-transfer salts. ,, …”

“…Then, some departure from strict one-dimensionality is necessary to obtain a finite EPR line width and the role of interchain electron tunneling is crucial. Several empirical generalizations of the Elliot relation have been suggested, ,, but the quantitative analysis of the EPR line width of organic conductors remains difficult. The effect of low dimensionality has been extensively studied for magnetic insulators.…”

“…Some EPR studies under pressure have also been reported for these charge-transfer salts. 24,109,110 Finally, it should be noted that other chargetransfer salts were synthesized in this period, using different donor molecules. Typical examples are TTT-TCNQ and TTT-TCNQ 2 (where TTT stands for tetrathiatetracene) 111,112 and the decomposition technique was also used to separate the susceptibility of each stack and discuss the observed Peierls instability.…”

Electron spin resonance in alkali doped SWCNTs

“…In other words, the T 1 and the momentum relaxation time, τ are proportional, the two being inversely proportional to the ESR line-width and the resistivity, respectively. The EY relation has been established for all elemental metals [16,18] and for a number of correlated metals where CESR has been observed [19]. The EY relation originates in the fact that conduction electron wave functions are not pure Zeeman states but are admixtures of the spin up and down states due to spinorbit coupling.…”