Electric-Field Control of Ferromagnetism in Mn-Doped ZnO Nanowires

In this Letter, the electric-field control of ferromagnetism was demonstrated in a back-gated Mn-doped ZnO (Mn-ZnO) nanowire (NW) field-effect transistor (PET). The ZnO NWs were synthesized by a thermal evaporation method, and the Mn doping of 1 atom % was subsequently carried out in a MBE system using a gas-phase surface diffusion process. Detailed structural analysis confirmed the single crystallinity of Mn-ZnO NWs and excluded the presence of any precipitates or secondary phases. For the transistor, the field-effect mobility and n-type carrier concentration were estimated to be 0.65 cm(2)/V-s and 6.82 X 10(18) cm(-3), respectively. The magnetic hysteresis curves measured under different temperatures (T = 10-350 K) clearly demonstrate the presence of ferromagnetism above room temperature. It suggests that the effect of quantum confinements in NWs improves T-c, and meanwhile minimizes crystalline defects. The magnetoresistace (MR) of a single Mn-ZnO NW was observed up to 50 K. Most importantly, the gate modulation of the MR ratio was up to 2.5 % at 1.9 K, which implies the electric-field control of ferromagnetism in a single Mn-ZnO NW.