High-field magnetic circular dichroism in ferromagnetic InMnSb and InMnAs: Spin-orbit-split hole bands and g factors

Carrier-induced ferromagnetism in magnetic III-V semiconductors has opened up several opportunities for spintronic device applications as well as for fundamental studies of a material system in which itinerant carriers interact with the localized spins of magnetic impurities. In order to understand the hole mediated ferromagnetism, probing the band structure in these material systems is crucial. Here we present magnetic circular dichroism (MCD) studies on MOVPE grown InMnSb and InMnAs, both with the Curie temperatures above 300 K. The measurements were performed on samples with different Mn contents with the excitation energy tuned from 0.92-1.42 eV and external magnetic fields up to 31 T. The large g factors in these systems allow us to measure the MCD at relatively high temperatures (190 K). These measurements are compared with MCD calculations based on an eight-band Pidgeon-Brown model, which is generalized to include the coupling between the electron/hole and the Mn spin in a ferromagnetic state. Comparison of the observed MCD with the theoretical calculations provides a direct method to probe the band structure including the temperature dependence of the spin-orbit split-off gap and g factors, and to estimate the sp-d coupling constants.