Microstructure And Magnetic And Optical Properties Of Mn²⁺-doped Mg_xZn_1-xO Powders

In this paper, Mn-doped Mg_xZn_1-xO samples were prepared through sol-gel method. Then X-ray diffraction, Raman spectroscopy, superconducting quantum interference magnetometers and cathode-ray luminescence spectrometer were used to characterize the morphology, structure, magnetic, optical properties of the samples. We dedicated to research the impact of Mn2+ to their optical and magnetic properties.Through the analysis of XRD patterns, samples present good hexagonal wurtzite structure. For the samples didn't reduce, in addition to ZnO diffraction peaks, two more diffraction peaks at the 2θ=29.95°and 2θ=43.17°location were found. After anlysis we concluded that the former diffraction peaks belonged to ZnMn₂O₄ while the latter came from MgO. However, the samples did not appear redandently peaks after reduction but still maintained the wurtzite structure of ZnO. We thought this was involved with O vacancies (Vo) which introduced through reduction. After calculation we found the lattice constant of doped samples became larger which indicated Mn2+ had successful replaced Zn2+ into the lattice.Mn-doped state usually introduced defects, but could not characterize by XRD, so we did Raman test. In the Raman spectrum of the sample did not reduce showed ZnMn₂O₄ Raman peak at the 680 cm-1, and this peak disappeared after reduction processing, the result was consistent with XRD. In addition, a strong Raman peak appeared at 526 cm^-1 which was caused by defects such as oxygen vacancies or zinc interstitial particles in ZnO bulk. And this Raman peaks enhanced after reduction indicating reduction process will indeed increase the oxygen vacancies of samples.In absorption spectrum, there was a clear diffraction peak at band tail (410nm) besides the absorption edge of ZnO, and it became stronger after reduction. This was consistent with other literature which concluded this was due to the impurity level of Mn. This indicated that Mn ions had come into the lattice, which was consistent with the XRD results.Significant UV and visible light were observed in PL spectra. Relative to the samples did not reduced, the green emission of reduced sample was distinct stronger, which was due to the Mn ions came into the lattice.Through magnetic measurements we found that the sample that did not reduce didn't show magnetic while the sample after reduction appeared relatively weak magnetic properties. We also thought this was due to the introduction of O vacancies and forming Mn²⁺-Vo-Mn²⁺ super-exchange interaction.