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

We have investigated the magnetic properties (ESR, static susceptibility and magnetization experiments) of the new organic superconductor κ-(MDTTTF) 2AuI2 above and below the SC phase transition temperature (Tc ≽ 4 K). At ambient pressure the electronic structures of this salt and of two related compounds [κ-(BEDT)2Cu(SCN) 2 and κ-(BEDT) 2Ag(CN)2, H2O have been calculated using an extended Huckel method. The analysis of both experimental results and calculated data has led us to propose a unified picture independently of the present molecular blocks. Finally the problem of the competition between the SC and AF low-temperature states which is based on the experimental evidences of electronic correlations has been examined. However, in the absence of any experimental evidence of an AF state, the origin of the electron pairing is still unclear in these quasi 2d materials.