Ni-doped ZnO: Studies on structural and magnetic properties

The Zn1-xNixO (0 >= x >= 0.1) systems were synthesized by a solid-state reaction technique at 700 degrees C for 7 h. The X-ray diffraction (XRD) pattern reveals the presence of secondary peaks due to NiO in Ni overdoped (>0.03) ZnO matrix. The compositional mapping on 5% Ni-doped ZnO on an electron probe microstructural analyzer (EPMA) indicates the segregation of oxides of Ni on the bulk surface. The ZnO samples doped with 3 and 5% Ni exhibit room-temperature ferromagnetism (RTFM). But, 7 and 10% Ni-doped ZnO samples do not exhibit ferromagnetism. Possibly, the enhanced antiferromagnetic interaction between neighboring Ni-Ni ions suppresses the ferromagnetic ordering, at higher doping concentrations of Ni, resulting in a rapid decrease in magnetic moments. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim