Effects of temperature and atomic disorder on the magnetic phase transitions in ZnO nanoparticles obtained by sol-gel method

In this work, we have studied the effects of temperature and atomic disorder on the magnetic phase transitions in ZnO nanoparticles obtained by sol-gel method. The samples were sintered at temperatures of 600 degrees C, 800 degrees C 1000 degrees C and 1200 degrees C for 2 h. The X-ray diffraction (XRD) analysis have shown a single phase, belonging to the hexagonal structure of ZnO and the Rietveld refinement showed an increase in the lattice parameters a and c with increasing sintering temperature. The crystallite mean size (D) increases from 61 nm to 70 nm, while the lattices strain decreases from 0.181% to 0.169% when the sintering temperature varies from 600 degrees C to 1200 degrees C. The magnetic measurements at 300 K, exhibit a ferromagnetic contribution in combination with a paramagnetic component for samples obtained at 600 degrees C, 800 degrees C and 1000 degrees C. A magnetic transition was verified for the sample obtained at 1200 degrees C, now with diamagnetic behavior. The sol-gel method is presented as an alternative to study the evolution of the different magnetic phases as a function of the degree of atomic disorder in ZnO nanoparticles. (C) 2018 Elsevier B.V. All rights reserved.