Abstract
We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly interrelated the magnetisation and magnetoresistance by invoking the polaron percolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (similar to 40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non- interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/ un-doped ZnO. (c) 2016 Author(s).