Investigation of optical and magnetic properties of Mn-doped tetragonal ZrO2 nanocrystals

Pure and Mn-doped ZrO2 nanocrystals (Zr1-xMnxO2) with varying Mn concentrations (x ​= ​0.02, 0.04, 0.06, and 0.08) have been synthesized using sol-gel method. The effect of Mn doping concentration on structural, optical and magnetic properties has been investigated. X-ray diffraction data and SAED analysis revealed that all Zr1-xMnxO2 nanocrystals have a tetragonal structure without any secondary phase. The average crystallite size obtained from XRD decreases (within the experimental uncertainty) with increased Mn concentration. Magnetic measurements have revealed that Zr0.98Mn0.02O2 nanocrystalline sample exhibits both low and room temperature ferromagnetism. The origin of ferromagnetism is attributed to the anionic vacancies created due to Mn doping in ZrO2. Higher Mn concentrations shows superparamagnetism whereas pure ZrO2 displayed diamagnetic behavior. The UV–Vis absorption spectra showed a wide absorption peak at 200–330 ​nm, and a redshift was observed in the bandgap with an increase in the concentration of Mn2+.