Giant effective excitonic g factors of Mn-doped ZnO/MgxZn1−xO core–shell nanowires

•The theory is extended to calculate the band structure of core–shell nanowire.•The band structure of Mn-doped ZnO/ZnMgO nanowires has been calculated.•The degenerate hole states are split by the applied magnetic field.•The effective excitonic g   factors gexgex has been calculated.

The electronic structure of Mn-doped ZnO/MgxZn1−xO core–shell nanowires are calculated based on the six-band k→·p→ effective-mass theory. According to the transition rules in nanowires, the lowest optical transition is split to two individual transitions with different circular polarized properties when the sp-d exchange interaction is considered. Through the calculation, a giant negative effective excitonic g   factors gexgex are found in Mn-doped ZnO/MgxZn1−xO core–shell nanowires, gexgex is affected greatly by the radius of ZnO core and the concentration of Mn2+ in ZnO core, while ∣gex∣∣gex∣ is influenced slightly by the total radius and the content of Mg2+ in MgxZn1−xO shell. In addition, gexgex increases slightly with the increase of the magnetic field. Our calculations can promote the potential applications of ZnO/MgxZn1−xO core–shell nanowires in the field of spintronics.