MAGNETIC-PROPERTIES OF ADSORBED OXYGEN IN MICROPOROUS CARBON

Microporous activated carbon fibers consisting of a disordered network of micrographites provide a micropore random network available for th e adsorption of a large amount of gaseous materials. We investigate ma gnetic properties of oxygen molecules condensed in the micropore as a molecule-based random magnet. Magnetic susceptibility shows Curie-Weis s temperature dependence with the Weiss temperature of about -20K at l ow oxygen concentrations below 1% of the saturation concentration. The increase in the oxygen concentration makes the development of the sec ond contribution to the susceptibility that has a broad hump around 60 K. The magnetic behavior is explained in term of the formation of anti ferromagnetic oxygen clusters on micrographitic domains, where the int ernal and marginal oxygen molecules in the cluster contribute to the s usceptibility with a short range order hump and the Curie-Weiss suscep tibility, respectively.