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 3D lattice in the intermediate coupling regime. The ferromagnetic transition temperature $T_c$ shows an optimization behavior, first increases and then decreases, with respect to the absolute carrier density $p_{abs}$ for a given magnetic impurity concentration $x$, as seen in the experiment. 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 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.