Résumé
The theory of a donor bound magnetic polaron (BMP) in Cr-based diluted magnetic semiconductors is presented. The Cr BMP generalizes the physical situation for Mn-based and Fe-based BMP due to particular energy structure of Cr2+ ions, exhibiting features typical for both Mn2+ and Fe2+ ions. The ground state of the Cr2+ ion is a semidoublet, yielding a permanent magnetic moment of the ion, similarly as for Mn2+ or Co2+ ions. On the other hand the ground state is followed by closely lying excited states, analogously to the situation for Fe2+ ions. The developed Cr BMP model recovers characteristic behavior of both Mn BMP and Fe BMP: zero-field spin-flip energy (a fingerprint of Mn BMP) and anticrossings of BMP states (typical for Fe BMP). The model provides a perfect description of the BMP energy structure recently observed in a spin-flip Raman scattering experiment of Cd1-xCrxS. Additionally, from this analysis the Cd1-xCrxS conduction band exchange integral is evaluated as N(0)alpha= + 0.22 eV.