DFT modeling of Mn charged states in Ga1 − xMnxAs diluted ferromagnetic semiconductors: The cluster approach

Quantum chemical cluster modeling of the high-symmetry nanoclusters Ga15MnAs16H36 and Ga12MnAs16H36 simulating the bulk of a GaAs crystal with Mn paramagnetic impurity center is carried out within the Density Functional Theory. A Generalized Gradient Approximation method PBEPBE/LanL2DZ is used to study the neutral Mn0 and ionized Mn− states of a Mn atom in the nanoclusters under consideration. The change of the charge state of the impurity center from Mn0 to Mn− leads to a considerable relaxation of Mn-As bonds in the immediate surroundings of the Mn atom and to the “p-hole” recombination. It also affects the spin density localization. The components of the g-tensor for both the neutral Mn0 and the ionized Mnstates are calculated by the Gauge-Independent Atomic Orbital (GIAO) method with the hybrid density-functional mPW1PW91. The resulting values of the g-factor are in good agreement with the experimental Electron Paramagnetic Resonance data. The results obtained confirm the applicability of the cluster approach for describing charge effects in dilute ferromagnetic semiconductors.