BOUND MAGNETIC POLARON IN CR-BASED DILUTED MAGNETIC SEMICONDUCTORS

The theory of a donor bound magnetic polaron (BMP) in Cr-based diluted magnetic semiconductors is presented. The Cr BMP generalizes the phys ical 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 devel oped Cr BMP model recovers characteristic behavior of both Mn BMP and Fe BMP: zero-field spin-flip energy (a fingerprint of Mn BMP) and anti crossings of BMP states (typical for Fe BMP). The model provides a per fect description of the BMP energy structure recently observed in a sp in-flip Raman scattering experiment of Cd1-xCrxS. Additionally, from t his analysis the Cd1-xCrxS conduction band exchange integral is evalua ted as N(0)alpha= + 0.22 eV.