Ultrahigh field electron cyclotron resonance absorption in In_1-xMn_xAs films

We have carried out an ultrahigh-field cyclotron resonance study of n-type In_1-xMn_xAs films, with Mn composition x ranging from 0% to 12%, grown on GaAs by low-temperature molecular-beam epitaxy. We observe that the electron cyclotron resonance peak shifts to lower field with increasing x. A detailed comparison of experimental results with calculations based on a modified Pidgeon-Brown model allows us to estimate the s-d and p-d exchange-coupling constants, α and β, for this important III-V dilute magnetic semiconductor system.