Sol-gel synthesis, structure and magnetic properties of Mn-doped ZnO diluted magnetic semiconductors

2.5, 5, 10 and 15% Mn-doped ZnO diluted magnetic semiconductors (DMSs) were prepared via an ethyl acetoacetate-aided sol-gel process. The 5% Mn-doped ZnO consists of 20-50 nm spheroid-like particles and has a wurtzite phase. Existence of nanoscale ZnMnO₃ clusters in this sample is confirmed by HRTEM analysis. Vegard's law calculation reveals that about 2.6% Mn atoms have been incorporated into ZnO lattice. Besides major wurtzite phase, ZnMnO₃ secondary phase is observed in the 10% and 15% Mn-doped samples. The Mn-doped ZnO shows red shift of photoluminescence (PL), which arises from defects caused by Mn incorporation. The magnetic measurements confirm that the 2.5% and 5% Mn-doped ZnO samples display room-temperature ferromagnetism as well as paramagnetism, while the 10% and 15% samples exhibit paramagnetic effects. The as-observed ferromagnetic behaviors likely originate from cooperative effect of intrinsic and extrinsic magnetisms.