Dresden 2009 – scientific programme

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MA: Fachverband Magnetismus

MA 24: Magnetic Semiconductors

MA 24.6: Talk

Wednesday, March 25, 2009, 16:00–16:15, HSZ 401

Magnetic phase of cobalt doped zinc oxide from first-principles and Monte Carlo methods — •Sanjeev kumar Nayak, Alfred Hucht, and Peter Entel — Physics Department, University of Duisburg-Essen, 47048 Duisburg, Germany

Understanding the magnetic properties of transition metal doped II-VI semiconductors, such as zinc oxide, is one of the active problems in materials science. Theoretically various mechanisms are sought to explain any underlying magnetic phenomena. Experimentally the situation is not yet conclusive. Hence, the need for thorough studies of this material is a priority. We studied the cobalt doped zinc oxide from a combination of different theoretical methods. The exchange interactions of cobalt spins in zinc oxide were calculated at various distances and for different compositions by the ab-initio technique. Treating the exchange interactions in a classical Heisenberg model, Monte Carlo simulations were done to study the phase diagram. Our results show no magnetization for doping concentrations below 20% cobalt. Intermediate concentrations of cobalt doping sustain stable ferromagnetic phase, however, for large concentrations of cobalt, the system acquires a complicated phase with antiferromagnetically coupled ferromagnetic bi-layers. The Neél temperature of cobalt oxide from our calculations match very well with that of the experimental value for fcc lattice.