Low-temperature positive magnetoresistance in ZnO-based heterostructures

Abstract

The positive magnetoresistance (MR) usually appears at cryogenic temperature in ZnO-based transport systems, the origin of which is reported to be related to the localized magnetic moment. Here we find a different origin of the positive MR in Zn1−x Mg x O/ZnO heterostructures prepared by magnetron sputtering. The large positive MR is observed in all samples at 2 K. On increasing temperature, the observed positive MR is gradually suppressed and transformed into the negative MR at higher temperature. Similarly, the suppression of the positive MR also occurs in the samples with the higher electron density. The experimental data can be well described by applying a two-band model combined with the weak localization (WL) theory. This indicates that the observed positive MR originates from the impurity-band-related two-band transport, while the observed negative MR arises from the WL.