Local moment scattering in the one-dimensional molecular conductors Cu_xNi_1-x (Phthalocyaninato) I

Cu_xNi_1-x (pc)I (pc=phthalocyaninato) are molecular metals whose conducting stacks incorporate a one-dimensional chain of local moments (Cu²⁺, 1 2) strongly coupled to the conduction electrons. We report here the thermoelectric power and the microwave conductivity (17 GHz) of these solid solutions as a function of temperature. The microwave conductivity being metallic at room temperature suddenly drops and shows a large positive magnetoconductivity down to low temperature. These effects are discussed in terms of magnetic scattering of the free carriers by the local moments Cu²⁺ (S = 1 2. At lower temperatures (T<8 K), the conductivity becomes practically constant and frequency dependent; this behavior is rather ascribed to a new type of relaxation mechanism associated to the chain of local moments.