Investigations of DC-magnetization behavior of nanocrystalline ZnO:Ni

Ferromagnetic character observed in chemically synthesized nanocrystalline ZnO:Ni (upto 10 at% Ni) powder samples has been tracked vis-à-vis the processing conditions. The DC-magnetization behavior is found to be strongly dependent upon the employed sample processing conditions. While the as-calcined samples are strongly ferromagnetic due to the presence of nickel clusters; sintering of the samples to higher temperature in air ambient oxidizes Ni clusters and the magnetic behavior of the samples undergo significant changes. The samples are no longer completely ferromagnetic and are a mixture of ferromagnetic, antiferromagnetic, paramagnetic and diamagnetic fractions, depending upon the temperature dependent solubility limit of Ni in ZnO. This work further clearly suggests that the weak room temperature ferromagnetism observed in the ZnO:Ni samples (upto 10 at% Ni), sintered in air at 900 °C/12 h, is an intrinsic effect.

Research highlights▶ The DC-magnetization behavior in Zn1−xNixO is found to be strongly dependent upon the employed sample processing conditions. The as-calcined samples are strongly ferromagnetic due to the presence of nickel clusters; the sintering of the samples to higher temperature in air ambient oxidizes Ni clusters. However, in all the sintered samples, this ferromagnetism originates definitely due in part to the partial substitution of Ni2+ ions at Zn-sites. ▶ The Zn1−xNixO samples are a mixture of ferromagnetic, antiferromagnetic, paramagnetic and diamagnetic fractions. The fraction of all these changes with change in sintering temperature. ▶ This work further clearly suggests that the weak room temperature ferromagnetism observed in the ZnO:Ni samples (upto 10 at% Ni), sintered in air at 900 °C/12 h, is an intrinsic effect.