  In order to study a possible magnetic proximity effect in magnetite-carbon
structures, we have performed magnetization measurements of graphite-magnetite
composites with different mass ratios as well as the measurement of the
magnetoresistance of one of them and of the magnetization of a magnetite-carbon
bilayer. The overall results do not indicate the induction of bulk
ferromagnetism in graphite and disordered carbon structures through their
contact with magnetite.
