Room temperature optical and magnetic properties of polyvinylpyrrolidone capped ZnO nanoparticles

Defect induced room temperature ferromagnetic properties of polyvinylpyrrolidone (PVP) capped nanocrystalline ZnO samples have been studied. Crystal phase and the lattice parameter of the synthesized nanocrystalline samples have been determined from X-ray diffraction spectra (XRD) and high-resolution transmission electron micrographs (HR-TEM). Room temperature photoluminescence (PL) spectrum for the bare ZnO sample shows a strong band at ~ 379 nm and another band at ~ 525 nm. The PL spectra also revealed that the number of oxygen vacancies in the uncapped sample is more than the PVP capped sample. Both sample exhibit ferromagnetic property at room temperature when annealed at 500 °C for 3 h, due to the formation of adequate oxygen vacancy related defects. The saturation magnetization for the annealed PVP capped sample is found to be larger compared to that for the uncapped sample.