Infrared optical conductivity of In1-xMnxAs

We have investigated the infrared optical absorption coefficient alpha(omega) of p-type diluted magnetic semiconductor In1-xMnxAs in the photon energy range up to 0.9 eV. alpha(omega) exhibits a quasi-Drude as well as interband transition components. It has been found that the quasi-Drude component of alpha(omega) increases with decreasing temperature, T, whereas the interband component decreases. Such a temperature dependent shift in the spectral weight strongly suggests that, in addition to the p-d exchange interaction, the double-exchange-like mechanism is participating in the ferromagnetic ordering process in III-V diluted magnetic semiconductors. From the far infrared data, it is concluded that the hopping range of the conducting holes is of the order of inter-Mn ion distance. (C) 2001 Elsevier Science B.V. All rights reserved.