Valence band structure and magnetic properties of Co-doped Fe_3O_4(100) films

摘要

Structural and magnetic properties, and the valence band structure of pure and Co-doped (up to 33%) Fe_3O_4(100) films were investigated. Reconstruction of the Fe_3O_4(100) surface is found to be blocked by Co doping. Doped Co ions in Fe_3O_4 are in a charge state of 2 + and substitute the Fe~(2+) in the B site of Fe_3O_4. All the films exhibit room temperature ferromagnetism. Co doping changes the coercivity and reduces saturation magnetization. The density of states near the Fermi level is reduced by Co doping due to the decrease of Fe~(2+) in the B site, which might responsible for the decrease in conductivity and magnetoresistance of Co-doped Fe_3O_4. The Verwey transition in the range of 100-120 K is observed for the pure Fe3O_4 film, while no transition could be detected for Co-doped Fe_3O_4 films.