TRANSPORT-PROPERTIES OF STAGE-1 CUCCO1-CCL2 GRAPHITE-INTERCALATION COMPOUNDS

Stage-1 CucCo1-cCl2 graphite intercalation compounds approximate quasi -two-dimensional (2D) random spin systems with competing ferromagnetic and antiferromagnetic intraplanar exchange interactions. The temperat ure dependence of the in-plane electrical resistivity of these compoun ds has been measured near critical temperatures. The magnetic resistiv ity zeta(mag) consists of the long-range spin-order part zeta(LS) and the spin-fluctuation part zeta(SF). For 0 less than or equal to c less than or equal to 0.2 the long-range spin-order part zeta(LS) is domin ant: the temperature dependence of zeta(LS) is described by a smeared power law with an exponent 2 beta, where beta is the critical exponent of staggered magnetization. For 0.3 less than or equal to c less than or equal to 0.4 the spin-fluctuation part zeta(SF) becomes larger tha n zeta(LS). For 0.5 less than or equal to c less than or equal to 0.95 no appreciable magnetic resistivity is observed. For c = 1 the deriva tive -d zeta(mag)/dT shows a small peak at around 67 K due to the grow th of short-range spin order which is characteristic of the 2D Heisenb erg antiferromagnet. The critical behaviour of the in-plane resistivit y can be explained in terms of a model based on pi - d exchange intera ctions between pi-electrons in the graphite layers and magnetic spins in the intercalate layers. The pi-electrons are scattered by spins of a virtual antiferromagnetic in-plane spin configuration arising from t he superposition of two ferromagnetic in-plane structures with spin di rections antiparallel to each other. The pi - d exchange interactions of these compounds are also discussed.