ENHANCED CHARGE LOCALIZATION IN THE ORGANIC ALLOYS [(TMTSF)1-X(TMTTF)X]2REO4

Structural, electrical and magnetic studies of [(TMTSF)1-x (TMTTF)x]2R eO4 alloys are reported. They exhibit around x approximately 0.5 an en hanced charge localization and a strong decrease of the (1/2, 1/2, 1/2 ) anion-ordering (AO) transition temperature. The localization enhance ment is attributed to a 4k(F) order of charge on the sites due to the alternate order of TMTSF and TMTTF molecules. This heteropolar charge distribution is suggested to weaken the 2k(F) bond response and thus t o depress the AO transition. These properties contrast with those exhi bited by the hybrid salt (TMDTDSF)2ReO4.