Magnetic phase transitions in bechgaard salts and related compounds: Electronic localisation and interchain couplings

Abstract The physical properties of Bechgaard salts and related compounds are quickly described when an electronic localisation is present. In this case, the low-temperature ground state results in a competition between two instabilities: a Spin-Peierls distortion and an antiferromagnetic ordering. 1D theory results are compared with experimental data to show that the electronic localisation is not the only relevant parameter which drives this competition. The need for a quasi-1D theory is demonstrated with the introduction of relevant interchain couplings. The nature of these couplings is discussed to show that the Spin-Peierls ground state does not appear frequently, in agreement with experiment.