A new route to enhance the ferromagnetic transition temperature in diluted magnetic semiconductors

We investigate the magnetic and the transport properties of diluted magnetic semiconductors using a spin-fermion Monte-Carlo method on a simple cubic lattice in the intermediate coupling regime. The ferromagnetic transition temperature T (c) shows an optimization behavior with respect to the absolute carrier density p (abs) and the magnetic impurity concentration x as seen in the experiments. Our calculations also show an insulator-metal-insulator transition across the optimum p (abs) where the T (c) is maximum. Remarkably, the optimum p (abs) values lie in a narrow range around 0.11 (holes/site) for all x values and the ferromagnetic T (c) increases with x. We explain our results using the polaron percolation mechanism and outline a new route to enhance the ferromagnetic transition temperature in experiments.