Room temperature ferromagnetism in undoped and Mn doped t-ZrO2 nanostructures originated due to oxygen vacancy and effect of Mn doping on its optical properties

Abstract

In the present report, we have synthesized undoped and Mn doped (1, 5, and 10 at.%) t-ZrO2 nanostructures by sol–gel method and their magnetic and optical properties have been investigated. UV–VIS. spectroscopy revealed the increase in band gap energy with Mn doping in ZrO2 matrix. The increase of optical band gap is attributed to Moss–Burstein effect. Photoluminescence (PL) spectroscopy revealed the presence of oxygen vacancies in undoped and Mn doped ZrO2 nanostructures. The shifting of peak position of the emission band to higher wavelength region for Mn doped ZrO2 nanostructures is attributed to the quantum size effects. The possible PL mechanism in undoped and Mn doped ZrO2 nanostructures is also discussed. In the present report, we have observed room temperature ferromagnetism (RTFM) for undoped and Mn doped t-ZrO2 nanostructures. The value of saturation magnetization (Ms) is decreased with the increase of Mn content into t-ZrO2 matrix. Oxygen vacancies are found responsible for RTFM in undoped ZrO2. The paramagnetic nature of Mn doped (10 at.%) t-ZrO2 nanostructures is explained in terms of anti-ferromagnetic coupling of Mn–Mn at high doping concentration.