In a structure with two tunnel-coupled quantum wells of different widths, the spin Kerr effect resulting from pulsed optical pumping at the narrow-well exciton resonance reveals the wide-well electron magnetization dynamics. Our analysis shows that the effect is driven by electron exchange between narrow-well excitons and spin-polarized electrons in the wide well. A theoretical model of the spin Kerr effect has been developed accounting for the interwell electron spin exchange. In the studied double-well structure with CdTe and ${\mathrm{Cd}}_{0.98}{\mathrm{Mn}}_{0.02}\mathrm{Te}$ quantum wells separated by a ${\mathrm{Cd}}_{0.88}{\mathrm{Mg}}_{0.12}\mathrm{Te}$ barrier with a thickness of 1.6 nm (5 monolayers), the model accurately describes the experimental results and allows us to estimate the interwell electron exchange constant as ${\delta }_e\approx 1.1\times {10}^{-15}\text{eV}{\text{cm}}^2$.

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• Exchange interaction
• Magneto-optical Kerr effect
• Spin dynamics
• Spin polarization
• Dilute magnetic semiconductors
• Quantum wells
• Photoluminescence
• Reflectivity