Carrier induced ferromagnetism in Mn-doped ZnO: Monte Carlo simulations

Ferromagnetism in Mn-doped ZnO is investigated by Monte Carlo simulations assuming indirect exchange interaction via two different competing mechanisms: (i) antiferromagnetic superexchange and (ii) an oscillating carrier mediated interaction. The calculations are performed for p- and n-type samples. The Mn ion is taken as a substitutional impurity and its concentrations varied from 3% to 20%. The carrier concentrations (holes or electrons) were tested in the range of 1x10(16)-1x10(20) cm(-3). These simulations showed paramagnetic, ferromagnetic, and spin-glass behaviors for the p-type samples depending on the Mn and hole concentrations. On the other hand, no phase transition was observed for the n-type samples, whatever the Mn and electron concentrations used in the simulations. (c) 2008 American Institute of Physics.