Structure, morphology, optical and magnetic response of ZnO, Mn₃O₄ and doped Zn_0.5Mn_0.5O nanoparticles as-synthesized using a chemical co-precipitation method

Nano-polycrystalline samples of pristine and Mn-doped ZnO were synthesized using the feasible chemical co-precipitation method to investigate structural, vibrational and magnetic properties. From the x-ray diffraction pattern, ZnO was indexed and fitted in a single-phase wurtzite structure (hexagonal phase, P63mc). The simulation of Mn₃O₄ was performed according to the initial parameter of tetragonal symmetry (I4₁/amd space group). For the Zn_0.5Mn_0.5O sample, fitting was undertaken with both P6₃mc and I4₁/amd structural models, and showed that the diffraction profile is a result of the superposition of both spectral contributions. The average grain size obtained for different compositions of ZnO, Mn₃O₄, and Zn_0.5Mn_0.5O are 84.79, 72.26 and 68.24 nm, respectively. The optical band gap was obtained as 3.41 and 4.17 eV for the ZnO and Zn_0.5Mn_0.5O samples, respectively. The Raman spectrum of Zn_0.5Mn_0.5O also verified a mixed behaviour of ZnO and Mn₃O₄ lattice vibration and presents two broad bands around 657 and 537 cm⁻¹. Room temperature magnetization–magnetic (M–H) field measurements showed the diamagnetic nature of ZnO, and the paramagnetic behaviour of Mn₃O₄, and Zn_0.5Mn_0.5O nanocrystalline samples. (paper)