Spin-orbit interaction and two-dimensional weak localization in a carbon matrix with cobalt nanoclusters

The magnetic-field dependence of the magnetoresistive effect in carbon fibers that contain cobalt nanoclusters and exhibit effects of weak localization at low temperatures (T < 45 K) is investigated on the metal side of the dielectric-metal transition. The carbon fibers are prepared by heat treatment of carboxylated cellulose after the substitution of cobalt cations for protons of COOH groups. It is found that, under conditions of two-dimensional weak localization at temperatures below 10 K, the carbon fibers possess an alternating magnetoresistance due to spin-orbit scattering of electrons by cobalt nanoclusters. The time of phase breaking of the wave function and the time of spin-orbit scattering are determined from a comparison of the experimental and theoretical magnetic-field dependences of the electrical resistance.