Conductivity without spin-signal, spin signal without conductivity-switchable radical ion salts of deuterated Cu(DCNQI)2

Cu(DCNQI)2 can be switched from a metallic state to an insulating one by external pressure or internal (chemical) pressure in a very abrupt manner. We have used the pronounced anticoincidence of the ESR-intensity and the conductivity to study the processes at the phase transitions in detail by measuring simultaneously the ESR and conductivity as a function of T and under pressure. We have a break down of the conductivity if 20 % of the total volume is switched into ESR-active areas. This is interpreted by a percolation limit between the still conducting (ESR-silent) domains. Including individual internal pressure values for differently deuterated Cu(DCNQI)2 salts and alloys between deuterated and undeuterated DCNQl, a general phase diagram can be given.