On physical properties of the organic metal (BEDT-TTF)4Hg 3 _ δCl8

Abstract

2014 Nous présentons des études de résonance paramagnétique sur les électrons de conduction du (BEDT-TfF)4Hg3-03B4Cl8, complétées par des mesures de susceptibilité paramagnétique statique, de force thermoélectrique et d'absorption IR. Nous avons montré que les interactions d'échange fortes conduisent à un spectre RPE simple, élargi par le couplage spin-orbite. La bidimensionalité du système de spin a été également confirmée. Des anomalies ont été observées près de 80 K pour certaines propriétés physiques ; nous supposons qu'elles sont provoquées par une déformation du réseau des ions Hg. Nous avons démontré que l'anisotropie spectrale (RPE, IR) n'est pas toujours comparable à l'anisotropie de transport électrique du métal organique. Abstract. 2014 Conduction electron spin résonance study is presented together with static susceptibility, thermopower and IR absorption measurements for (BEDT-TTF)4Hg3-03B4Cl8. It is shown that the strong exchange interactions lead to a single ESR line broadened by the spin-orbit coupling ; the role of twodimensionality of the salt is emphasized. The two-dimensionality of the spin ordering is also stated. The anomalies of the ESR parameters near 80 K may be associated with a phase transition caused probably by the deformation of the incommensurate Hg sublattice. Our study confirms that the anisotropy of the spectral (IR, ESR) properties does not necessarily agree with that of the transport properties of the organic metal.

Magnetic properties of κ-(MDTTTF)2AuI2 salt in the normal and superconducting states

“…this is in contrast with the classical temperature decrease in RIS which are one-chain compounds. This result has also been observed in other K salts, [1,4,9]. As we will explain in the next part, this effect is associated with the intermediate values observed for these g-factor components because they result from the back and forth spin motion between the two kinds of dimers.…”

Organic Conductors with Unusual Band Fillings

“…The optical reflectance spectra of the Cl and the Br salts are similar to those of other κ-phase (ET) 2 X salts . The electron spin resonance (ESR) and the static susceptibility measurements show Bonner−Fischer-type susceptibility ( J = −74 K for the Cl salt) . The temperature dependence of thermoelectric power is linear at high temperatures but changes sign, and it is not linear at low temperatures .…”

“…The electron spin resonance (ESR) and the static susceptibility measurements show Bonner−Fischer-type susceptibility ( J = −74 K for the Cl salt) . The temperature dependence of thermoelectric power is linear at high temperatures but changes sign, and it is not linear at low temperatures . The 1 H NMR T 1 -1 is reported to be anomalously frequency dependent for the Br salt, probably due to cross-relaxation via quadrupolar Br, and does not follow the simple Korringa relation both for the Cl and for the Br salts .…”

Electron Spin Resonance: A Major Probe for Molecular Conductors

“…From the electronic point of view, their structures can be considered as two-dimensional and the large electrical conductivity in the molecular plane leads to Dysonian EPR lines. EPR studies were made for different series, as κ-(BEDT-TTF) 2 Ag(CN) 2 (H 2 O), , κ-(BEDT-TTF) 2 Cu(NCS) 2 , ,− the κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]X, − κ-(BEDT-TTF) 4 Hg 3 - δ X 8 , − and κ-(BEDT-TTF) 2 Cu 2 (CN) 3 - δ X δ salts (where X is an halogen atom). , As already mentioned, a generic phase diagram has been proposed for the κ-phases, taking the example of κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl, explained in the frame of the 2D Hubbard model . Indeed, EPR data of these different materials present some recurrent features.…”