We present a theory for electronic and magneto-optical properties of n-typeIn(1-x)Mn(x)As magnetic alloy semiconductors in a high magnetic field, B. Weuse an 8-band Pidgeon-Brown model generalized to include the wavevector (Kz)dependence of the electronic states as well as s-d and p-d exchangeinteractions with localized Mn d-electrons. Calculated conduction-band Landaulevels exhibit effective masses and g factors that are strongly dependent ontemperature, magnetic field, Mn concentration (x), and Kz. Cyclotron resonance(CR) spectra are computed using Fermi's golden rule and compared withultrahigh-magnetic-field (> 50 T) CR experiments, which show that the electronCR peak position is sensitive to x. Detailed comparison between theory andexperiment allowed us to extract s-d and p-d exchange parameters, alpha andbeta. we find that not only alpha but also beta affects the electron massbecause of the strong interband coupling in this narrow gap semiconductor. Inaddition, we derive analytical expressions for the effective masses and gfacors within the 8-band model. Results indicate that (alpha - beta) is thecrucial parameter that determines the exchange interaction correction to thecyclotron masses. These findings sould be useful for designing novel devicesbased on ferromagnetic semiconductors.
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