Giant moment and magnetic anisotropy in Co-doped ZnO films grown by pulse-injection metal organic chemical vapor deposition

We report on large magnetic moments of up to 18.9 mu(B)/Co in Co-doped ZnO films grown by pulse-injection metal organic chemical vapor deposition. The magnetic moment saturates easily in perpendicular magnetic fields and is considerably reduced when the magnetic field is applied parallel to the film plane. The saturation moment is largest for a small Co doping concentration of 1% and persists up to a temperature well above 900 K. These extraordinary magnetic attributes cannot be explained by the spin-only moment of Co2+ ions or Co cluster, but suggest the formation of orbital states in a defect-related impurity band. (c) 2006 American Institute of Physics.