Exchange energies, bound magnetic polarons, and magnetization in CdSe:Co and CdS:Co

The sp-d exchange energies, bound magnetic polarons, and magnetization have been studied in Cd_1-x{Co}ₓ$Se and ${Cd}_{1{{-}}x}CoₓS. For x=0.02--0.05, magnetization measurements of the Co²⁺ ions at liquid-helium temperatures are adequately described by a modified Brillouin function for pure spin S=3/2 ions. In spin-flip Raman-scattering (SFRS) measurements from donor-bound electrons we observe a large Zeeman splitting of {~}4--10 meV at high magnetic fields, and bound magnetic polaron energies of 0.2--0.4 meV at B=0. The s-d exchange energy between conduction electrons and Co²⁺ ions, obtained by combining the SFRS and magnetization results, is found to be {α}N₀=274±{}6 meV for CdSe, and {α}N₀=179±{}4 meV for CdS. For Cd_1-x{Co}ₓSe, from reflectivity measurements and the α{N}₀value we obtain β{N}₀$=-2120±{}50 meV.