Temperature-dependent ferromagnetic behavior in nanocrystalline ZnO synthesized by pyrophoric technique

Abstract Occurrence of room temperature ferromagnetism in nanocrystalline ZnO is confirmed through a series of studies conducted by calcining the samples at various temperatures. Magnetic measurements showed that room temperature ferromagnetic contribution decreases with the increase in calcination temperature up to 750 °C and again increases to a higher amount at 850 °C due to the change in stoichiometric ratio of Zn and O. Variation of defects in comparison to the wurtzite crystal structure has been observed from the micro-Raman studies. The broad shoulder peak appearing at 581 cm −1 becomes sharper for sample calcined up to 750 °C, indicating the decrease in oxygen vacancies and vacancy clusters.