Raman spectroscopic and magnetic properties of Europium doped nickel oxide nanoparticles prepared by microwave-assisted hydrothermal method

Pure and 5 mol% Eu doped nickel oxide (NiO) nanoparticles were synthesized by microwave-assisted hydrothermal method. X-ray diffraction and Rietveld refinement analysis confirmed the phase and purity of prepared nanoparticles. Scanning electron microscopy analysis revealed that the undoped nanoparticles are porous flake-like structures while the doped samples were aggregated. X-ray photoelectron spectroscopy analysis disclosed that Eu doping increases hole concentration, Ni2+ vacancies, and defective oxygen concentration in the nanoparticles. The magnetic analysis shows the presence of weak ferromagnetism in lower fields of the undoped nanoparticles. On doping with Eu, the ferromagnetic behaviour increases due to increased oxygen defects and uncompensated surface spins. Raman spectroscopy investigation shows the absence of 2 M vibrational mode and reduced antiferromagnetic coupling in the prepared samples. It also substantiated the presence of defects in the prepared samples. Eu doping produced local vibrations that overlap with SO mode of NiO and shifting of 1 M band due to its higher mass. Eu dopant can modify the magnetic property of NiO nanoparticles that can be used in sp intro nic applications. (C) 2020 Published by Elsevier B.V.