Comparative study of the organic conductor (H/sub 8/-ET)/sub 2/Hg(SCN)/sub 2/Br and its deuterated analogue

Summary form only given. Structural resistivity and EPR study of the single crystal (Hg-ET)/sub 2/Hg(SCN)/sub 2/Br and its deuterated analog (D/sub 8-ET)/sub 2/Hg(SNC)/sub 2/ Br are presented. These salts belong to the -type structure class of organic conductors. Temperature dependence of ESR linewidth for these salts are very similar to that of conductivity. The first-order phase transition with localization of the electrons on ET dimers at 100K are found for hydrogen-containing salt, wheras two phase transition of semiconductor-semiconductor tye and possible magnetic ordering at low temperatures (near 10K) are found for deuterium containing compound. The drastic isotope effect in these compound is considered to be associate with hydrogen bond between terminal CH-groups of cationic sheet and Br-atom in anionic sheet in hydrogen containing compound.