Magnetism in polycrystalline cobalt-substituted zinc oxide

We present results of the preparation (by precursor decomposition), characterization (with x-ray diffraction, transmission electron microscopy, and dc magnetization measurements), and detailed computation (using density functional theory) of polycrystalline ZnO with up to 15% substitution of the zinc sites by divalent cobalt. The experimental results indicate the dominant magnetic interaction in well-characterized stoichiometric phases ${\mathrm{Zn}}_{1-x}{\mathrm{Co}}_x\mathrm{O},$ $x=0.05,$ 0.10, 0.15, is nearest-neighbor antiferromagnetic. Our computations suggest robust ferromagnetism will only occur in the presence of additional hole doping.