Preparation and electrical properties of cobalt-containing carbon fibers

Carbon fibers with inclusions of cobalt nanoclusters are prepared by heat treatment of carboxylated cellulose containing cobalt cations. The influence of the heat treatment conditions on the structuring of the carbon matrix and cobalt clusters, the magnetization hysteresis loop, the temperature dependence of the conductivity, and the magnetoresistance is investigated. It is established that the cobalt-containing carbon fibers heat treated at T _M =700 and 900°C possess superparamagnetic and ferromagnetic properties, respectively. It is shown that fibers heat treated under different conditions are characterized by different conduction mechanisms and can exhibit anisotropic and giant magnetoresistances and also the effects associated with the influence of magnetic field on the processes of weak localization and spin-orbit scattering.