Evolution of Structure, Microstructure, Electrical and Magnetic Properties of Nickel Oxide (NiO) with Transition Metal ion Doping

We present a brief review on the evolution of structure, microstructure, electrical and magnetic properties of NiO with transition metal (TM) doping. The fcc structure of NiO is not affected with TM doping whereas the some of the TM ion influences the microstructure. The antiferromagnetic property of NiO is strongly modified with some of the TM (Fe, Mn, V) doping and the same is not much affected with some other TM (Co, Cr, Zn and Cu) doping. Not only the dopants but also the form of the material decides the magnetic order in the host matrix. Powder NiO exhibits room tem- perature ferromagnetism with Fe doping, superparamagnetism with Mn doping. NiO thin films on the other hand exhibit ferromagnetism with Fe, Mn and V doping. The ferromagnetic ordering in these cases was improved with Li co-doping. The increased ferromagnetism in these cases may be due to increase of hole concentration due to Li doping. Giant dielectric response has been observed for (Li, Fe) and (Li, V) doped NiO ceramics.