Anderson localization enhanced ferromagnetism in Zn0.95Co0.05O

We report an enhancement in the ferromagnetic characteristics of Zn0.95CO0.05O thin films due to the localization of charge carriers. Epitaxial thin films of Zn0.95-xCo0.05GaxO (x=0-0.05) were grown on single-crystal sapphire (0001) substrates by pulsed laser deposition technique. The role of charge carrier localization on the electrical and magnetic properties of ZnO:Co was studied by introducing Ga into the system. It was observed that Ga plays a significant role in affecting both the electrical transport mechanism as well as the magnetization of the material. Electrical resistivity of Zn0.95Co0.05O at room temperature was similar to 96 m Omega cm and exhibited metal-like temperature dependence, although strongly influenced by electron-electron (e-e) interactions. Strong e-e interaction was understood to arise because of the randomness introduced in the crystal potential of ZnO by the cobalt dopants. As the Ga dopants are introduced, randomness in crystal potential and hence the disorder further increases resulting in the Anderson localization of the carriers. The increase in localization was accompanied by a significant enhancement in the magnetic moment from 0.75 mu(B)/Co in Zn0.95Co0.05O films to 1.6 mu B/Co in Zn0.90Co0.05Ga0.05O. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3197138]