Magnetooptical Kerr rotation and magnetic circular dichroism (MCD) have been measured
in thin epitaxial layers of the narrow gap ferromagnetic semiconductors InMnSb and InMnAs grown
by low-temperature molecular beam epitaxy. The measurements were carried out in the wavelength
range from 400 to 7000 nm. The wavelength dependence of Kerr rotation and MCD were modelled using
the same set of parameters. To calculate the Landau level energies for the above systems we have
used a  -model developed by Trebin et al. [1, 2] combined with an exchange matrix, as described by
Rigaux [3]. Taking into account transition energies corresponding to the selection rules for
right and left circularly polarized light enabled us to calculate both Kerr rotation and MCD
using procedures described by Lang et al. [4] The fits yield values for the exchange parameters
N0α and N0β.
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