Influence of impurities on the structural and magnetic properties in ZnO

We investigated variations of physical properties in ZnO with doping impurities: K, Cr, and Cu ions. With K doping, we verified that K ions doped in ZnO have different stable positions bounded by the doping rate of 2 mol%. For the Cu- or Cr-doped ZnO, the characteristic 3d energy level would be contributed as carrier trap level due to the deep level in the ZnO and would change the magnetism via a shift of the Fermi level. We also report that ferromagnetism depends on the carrier density in Cr-doped ZnO and Cu-doped ZnO.