A. Moradpour

Pressure Induced Magnetic State in (TMTTF)2PF6

Abstract We present 1H NMR relaxation data on (TMTTF)2PF6. The low temperature insulating state is shown to be non magnetic at ambient pressure and antiferromagnetic (SDW) at 13kbar.

Low Temperature Properties of (TMTSF)2CIO4, under Pressure

Abstract To examine the role of anion ordering for superconductivity we studied the low temperature properties of rapidly cooled (Q-state) and slowly cooled (R-state) states of (TMTSF)2ClO4 through resistivity measurements under pressure. In the R-state the anion ordering remained at 25 K up to 8 kb (maximum studied pressure), while the superconductivity disappeared above 3 kb. In the Q-state, below 4.2 K, we observed resistance upturn below 2 kb and metallic behaviour without superconductivity above 3 kb. The superconductivity was suppressed either by anion disorder or by pressures higher than 3 kb.

Anion Ordering and Atomic Vibrations in (TMTSF)2ClO4

Abstract We report the first observation of the specific heat anomaly associated with anion ordering in (TMTSF)2ClO4. The phase transition analyse reveals a configuration entropy R Log (2) which can be reduced by 20% on fast cooled sample. The low temperature lattice specific-heat deviate strongly from the prediction of a 3D debye model.

The Role of TMTSF Synthesis on the Superconducting Properties of (TMTSF)2.ClO4

Abstract The superconducting properties of (TMTSF)2ClO4 were found to be highly dependent on the origin of the TMTSF obtained by different synthetic procedures. These differences were assigned to the presence of low amounts of sulfur (up to 0.3%), introduced, in place of selenium, in the course of the synthesis avoiding the use of CSe2. The latter method was improved so the superconducting transition of (TMTSF)2 ClO4 therefrom was found to be the same as for samples prepared with TMTSF synthesized from CSe2.

Cooperative Phenomena in (TMTSF)2ClO4 NMR Relaxation

Abstract 1H and77 Se NMR relaxation data on relaxed (TMTSF)2ClO4 are presented and an interpretation is proposed for the non-Korringa behaviour which is based on the existence of one-dimensional 2kF spin correlations.

The effect of pressure on anion ordering in (TMTSF)2BF4

We have measured, via electrical transport measurements, the effect of pressure on the anion ordering (AO) transition in (TMTSF)2BF4. The effect of low pressures (<3.5 kbar) is to lower the metal-insulator (MI) transition temperature associated with the AO of the BF4− anions. In the intermediate pressure range (4–7 kbar) the resistivity exhibits anomalous behaviour, peaking at 20 K, the detailed behaviour depending on both the pressure and thermal treatment. In the same pressure/temperature range, the thermoelectric power remains metallic, indicating that the resistive anomalies result from a change in the carrier mobility. Above 7 kbar, the resistivity is metallic down to low temperatures, and incomplete superconductivity is observed in several samples.