Contribution of s-d exchange interaction to magnetoresistance of ZnO-based heterostructures with a magnetic barrier

We report the origin of the positive magnetoresistance (MR) occurring in the ZnO conduction layer underneath of the Zn0.88Mn0.12O magnetic barrier layer. First, n-type Zn0.88Mn0.12O/ZnO modulation-doped heterostructures were fabricated on ZnO (000 (1) over bar) single-crystal substrates using pulsed laser deposition. The MR characteristics of two heterostructures with different low-temperature electron mobility (mu), corresponding to the magnitude of interface broadening generated by intermixing or interdiffusion of Mn ions during deposition, were evaluated to investigate the mechanism of spin-related transport phenomena occurring at the heterointerface. The Zn0.88Mn0.12O/ZnO heterostructure with high mu shows the Brillouin-function-like MR behavior, while that with low mu shows typical two-dimensional diluted magnetic semiconductor (2D DMS) MR behavior originating from the existence of Mn ions in the ZnO conduction layer. On the other hand, for a heterostructure with high mu, 2D DMS MR is eliminated from the MR due to suppress the interface broadening, and the spin splitting of the subband in ZnO channel is induced through the difference of the penetration probability of wave function of up-spin carriers and down-spin carriers into the Zn0.88Mn0.12O barrier layer.