Study of room temperature ferromagnetism for cobalt and manganese doped ZnO diluted magnetic semiconductor

We report the results of electronic and magnetic properties of poly-crystalline Zn_1-xM_xO (M = Co and Mn) pellets studied by XRD, VSM and XPS. The specimens were synthesized by solid state reaction method using high purity oxides. Samples exhibit Wurtzite hexagonal symmetry and show interesting magnetic properties. The Co (5%) doped sample prepared by heating in air shows a paramagnetic state in agreement with several claims. But the sample prepared by heating in Ar atmosphere depicts ferromagnetic ordering. Addition of 2% Mn in it further enhances its magnetic moment. The specimens ZnCoO (Ar heated) and ZnCoMnO were hydrogenated at 550°C that caused a significant change in their magnetization. The Co doped ZnO shows a robust increment in the magnetic moment but the Mn doping does not seem to respond to hydrogenation. O 1s XPS results show clear evidence of oxygen depletion for the samples prepared by heating in Ar atmosphere and a further depletion upon hydrogenation. Results suggest oxygen vacancies as the basic origin for room temperature ferromagnetism in doped ZnO.