2008 Volume 49 Issue 11 Pages 2469-2473
Extensive calculations based on density functional theory have been carried out to understand the dependence of magnetic coupling on the concentration and distribution of V dopants in bulk ZnO. We considered three different doping concentration of V, namely 5.6%, 8.3% and 12.5%. At low doping concentration, ferromagnetic, anti-ferromagnetic and ferrimagnetic couplings are energetically nearly degenerate. Consequently, thermal fluctuation in samples may cause diverse magnetic behaviors. However, the ferromagnetic state becomes stable as the concentration of V increases to 12.5%. At low concentrations (5.6% and 8.3%) V atoms substitute Zn atoms uniformly in bulk ZnO, while they tend to cluster when their concentration reaches 12.5%. The present study provides an understanding of the conflicting experimental observations in V-doped bulk ZnO.