Effect of Crystalline Quality on Magnetic Properties of Mn-Doped ZnO Nanowires

Mn-doped ZnO nanowires are synthesized by a vapor phase deposition method in air and in a vacuum, respectively. X-ray diffraction results show that all the diffraction peaks correspond to the hexagonal wurtzite structure. X-ray absorption fine structure spectra suggest that a single Mn²⁺-containing phase exists and Mn²⁺ions occupy Zn²⁺ ions in the ZnO lattice. Photoluminescence spectra show that many defects exist in the doped nanowires as the samples grown in air, and the crystalline quality decreases with the increase of Mn. These samples exhibit obvious room-temperature ferromagnetic characteristics, and the magnetization increases with the increase of Mn. The sample with higher crystal quality grown in a vacuum exhibits the paramagnetic behavior at room temperature. As the as-grown samples are annealed, the crystalline quality improves, while the magnetization of the samples grown under the air condition translates from room-temperature ferromagnetism to the paramagnetism behavior. The above results indicate that the magnetic property of the Mn-doped ZnO nanowires can be controlled by the crystalline quality.