Spin-dependent transport in a ZnMnO/ZnO heterostructure

We report a spin-dependent transport property in modulation-doped ZnMnO:Al/ZnMnO/ZnO heterostructures. Using ZnO (0001) single crystal substrates, the heterostructures with atomically smooth surface and interface were prepared. For the sample with the Mn concentration of 12 at. %, the electron confinement at the ZnMnO/ZnO interface was recognized, indicating that ZnMnO layer acted as a barrier layer. In this paper, we investigated if an s-d exchange interaction exists between s electron conducting in the ZnO channel layer and Mn d spin in the ZnMnO barrier layer at the interface. To eliminate the Lorentz force and weak localization effects from the magnetoresistance (MR), the MR was measured under the magnetic field parallel to the sample surface. For a ZnMnO/ZnO heterostructure with the sheet carrier concentration of 5.46x10(12) cm(-2), at 1.85 K, the parallel-field MR revealed that a positive MR was dominant below 0.8 T, while a negative MR was recognized above 0.8 T. The positive MR was well fitted to a Brillouin function, suggesting the existence of an s-d exchange interaction at the ZnMnO/ZnO interface. The effect of the sheet carrier concentration on the MR behavior was also discussed. (c) 2008 American Institute of Physics.