Ferromagnetism of Graphite Nanopowders with Cobalt Oxide Impurity and Its Evolution at Moderate Annealing

A study of the influence of a small impurity of cobalt oxide CoO on the magnetic properties of graphite nanopowder is presented in this article. It is shown that such an impurity is responsible for the weak ferromagnetism of a sample freshly prepared and annealed at 670 K in air, which substantially increases after vacuum annealing. The effect of an exchange bias caused by the partial reduction of antiferromagnetic CoO particles to metallic cobalt, which is a ferromagnet, is discovered.