Investigation of exchange bias effect of fine cobalt particles with oxidized surface

Phase characteristics of the partially oxidized cobalt particles were investigated. It is shown that the studied system consists of Co, CoO, and Co3O4 phases. The paper presents results for the magnetic characteristics of Co particles covered by a CoO shell. Magnetic measurements were performed at 77 K. It is shown that the shapes of the hysteresis loop of the investigated system are different for different cases of cooling, with and without applications of external magnetic field. Structural investigations were performed on single particles.