On the control of optical spin injection by tuning the band gap offset in magnetic/non-magnetic hybrid structure

•We demonstrate control over spin injection efficiency in all-semiconductor hybrid magnetic/non-magnetic structure.•Our idea is to tune the band gap offset between magnetic and non-magnetic materials using 1.1 T magnetic field.•Magneto-optical luminescence measurements show resonance between excitons' spin states in the magnetic with that of the non-magnetic layers.•These results stimulate wider tunability of spin injection efficiency using small magnetic fields suitable for spin-based devices.

We investigate, using a heterostructure consisting of Cd0.97Mn0.03Te/Cd0.98Mg0.02Te layers the optical spin injection process from the Cd0.97Mn0.03Te spin aligner into the non-magnetic Cd0.98Mg0.02Te neighboring layer. We find that the spin injection process can be controlled by an external magnetic field (~0.5 T). Utilizing the circular polarization of the photoluminescence emitted from the Cd0.98Mg0.02Te layer, we monitor the injected spins of the carriers. As the magnetic field is increased, the degree of the circular polarization changes its sign from positive (with the σ+ intensity dominating), indicating occurrence of the spin injection, to a negative value (with the σ− intensity dominating), indicating the inhibition of the spin injection. We study also the temperature dependence of the degree of the circular polarization of Cd0.98Mg0.02Te emissions at a fixed magnetic field, and thus of the injection efficiency.