Magnetic-ion-pair interaction in (Cd,Mn)Te and (Cd,Mn)Se using spin-flip Raman scattering and magnetization

Isolated Mn ion pairs in dilute magnetic semiconductors exhibit steplike increases in the total spin alignment with increasing magnetic field. These steps in ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te and ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Se, with x≤0.05, are studied using spin-flip Raman scattering and magnetization measurements at 0.5≤T≤1.3 K. In dc fields to 30 T the optical spectra show three steps for (Cd,Mn)Te and two for (Cd,Mn)Se. Analysis of the field positions of the steps obtained by both methods gives the nearest-neighbor exchange constant $J_{\mathrm{NN}/k_B=\mathrm{-}6.1\pm 0.2}$ K for the telluride and -7.7±0.3 K for the selenide. By comparison of the optical and magnetization results, the s-d exchange parameter for (Cd,Mn)Te is found to be α$N_0$=211±10 meV.