An excitonic representation of spin-exchange CM for samples Mn-1 and Mn-3 in the case of 3.1 eV excitation. This process occurs via activation of the Mn ion via exciton transfer from the CdSe shell (step 1 or 1') followed by Mn* relaxation, which creates a biexciton in the PbSe core (step 2 or 2'). In the case of 3.1 eV excitation, the energy of a photogenerated hot exciton is sufficiently high to excite both the 4 T 2 and 4 T 1 states of the Mn ion (the 4 T 1 state can also be excited via capture of a band-edge exciton following hot-exciton cooling). In sample Mn-1, spin-exchange CM can be driven by both the 4 T 2 − 6 A 1 and 4 T 1 − 6 A 1 spin-flip transitions. However, in sample Mn-3, which has a higher bandgap, spin-exchange CM can be driven only by the higher-energy 4 T 2 − 6 A 1 transition. Due to the larger number of spin-exchange CM pathways, sample Mn-1 shows a higher CM efficiency than sample Mn-3 ( a ).
