Magnetic tuning in excitonic Bragg structures of (Cd,Mn)Te/(Cd,Zn,Mg)Te

We demonstrate that giant spin splitting specific to diluted magnetic semiconductors offers a tool to tune the light wavelength (corresponding to the exciton energy) across the Bragg or anti-Bragg resonances in appropriately designed long-period multiple-quantum-well structures. In particular, an unusually strong influence of the magnetic field upon the shape, magnitude, and spectral position of polariton reflectivity is observed in the case of high-quality periodic structures, in which thick barriers of Cd0.93Mg0.04Zn0.03Te separate 20 thin equidistant quantum wells of nonmagnetic CdTe and magnetic Cd0.96Mn0.04Te placed alternatively. The spectra obtained experimentally are well reproduced by theoretical calculations which incorporate effects of the sp-d exchange interaction into the formalism of transfer matrices.