COMPETING SPIN-EXCHANGE INTERACTIONS IN ZN1-XMNXSE ZN1-YFEYSE MULTIPLE-QUANTUM-WELL STRUCTURES/

We report the study of a mixed-spin multiple-quantum-well system consi sting of alternating Zn1-xMnxSe and Zn1-yFeySe layers, grown by molecu lar-beam epitaxy. The two spin components of the heavy-hole exciton ar e each dominated by different exchange interactions as revealed by the ir temperature and magnetic-field dependence. We find that the energy of the spin-down sigma(+) component (-3/2, - 1/2) is well described by exchange interactions of the electron and holes with Mn2+ ions (Brill ouin paramagnet), while the energy of the spin-up sigma(-) component ( +3/2, +1/2) is determined by the interactions of carriers with Fe2+ io ns (Van Vleck paramagnet). Thus, these tailored heterostructures permi t simultaneous study of Brillouin and Van Vleck paramagnetism as well as associated carrier dynamics in a single structure.