High-Tc ferromagnetism in p-type ZnO diluted magnetic semiconductors

Using effective field theory, with a Honmura–Kaneyoshi differential operator technique, the transition temperature as a function of the carrier (hole) nc and impurity ni concentrations has been obtained for p-type ZnO diluted magnetic semiconductors. The Hamiltonian we used contains a damped and undamped Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction model to describe the exchange coupling constants Jij between the local moments Mni and Mnj. We use a higher value of l (undamped RKKY) in order to study the long-range RKKY coupling, and a small value of l (damped RKKY) in order to study the short-range RKKY coupling. By band structure calculation we include the finite band splitting, Δ, in our calculation, and we have calculated the exchange constants N0β for different impurity ni and hole nc concentrations. We calculated the band gap of Zn1−xMnxO (0≤x≤0.5) and Zn0.8Mn0.2O1−yNy(0≤y≤0.2), which mimics an optical transmission measurement. The magnetization variation as a function of temperaturefor different hole concentrations and nc/ni ratios is also investigated.