Electrical conductivity and X-ray diffuse scattering study of the family of organic conductors (perylene)2M(mnt)2, (M=Pt, Pd, Au)

Reports resistivity measurements along the high-conductivity axis of Per 2 Pt(mnt) 2 , Per 2 Pd(mnt) 2 and Per 2 -Au(mnt) 2 . At low temperatures a clear metal-insulator phase transition is observed at 6.5K and 28K, respectively for the first two salts, while it appears very gradually for the Au salt. The X-ray study shows above these critical temperatures one-dimensional structural fluctuations for Per 2 Pt(mnt) 2 and Per 2 Pd(mnt) 2 , which are attributed to the M(mnt) 2 stacks, and no such scattering for Per 2 Au(mnt) 2 , down to 12K. The diffuse scattering 'condenses' in superstructure reflections below 28K in Per 2 Pd(mnt) 2 , which thus might undergo a spin-Peierls phase transition. The nature of these various phase transitions is discussed.