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In the present work, pure CeO2, neodymium-doped CeO2, and neodymium and transition metal element (Cu, Zn, Cr)-codoped CeO2 nanoparticles were synthesized by an auto-combustion method and annealed at 700 ∘C. The X-ray diffraction (XRD) studies revealed that all the samples exhibited a single-phase cubic fluorite structure with the incorporation of respective dopant ions into the CeO2 lattice. The scanning electron microscopy (SEM) images displayed the prepared nanoparticles which had an irregular flaky structure with large agglomerations. The Fourier transform Raman (FT-Raman) spectroscopy analysis revealed the increased oxygen vacancy defects in CeO2 host after doping and codoping with neodymium and transition metal elements. Ultraviolet-diffuse reflectance spectroscopy (UV-DRS) studies revealed the decrease in bandgap values in doped and codoped samples compared to pure CeO2 sample. The Fourier transform infrared spectroscopy (FTIR) studies revealed the presence of functional groups in the prepared samples. Photoluminescence (PL) spectroscopy analysis reported the decreased luminescence intensities of Nd-doped and neodymium and transition metal-codoped CeO2 nanoparticles. The vibrating sample magnetometer (VSM) results depicted that all the samples exhibited room-temperature ferromagnetism. [ABSTRACT FROM AUTHOR]

The effects of Fe ion vacancy on structural and magnetic properties of NiFeO4 nanoparticles are investigated using X-ray diffraction, Fourier transform infrared, morphological, and magnetic measurements. The introduction of Fe ion vacancy leads to the increase of the lattice parameter and decrease of the particle size. Moreover, vibrating sample magnetometer measurement results revealed that the values of the magnetization decreased and that coercivity had no regular behavior with increasing Fe ion vacancy content. These behaviors could be explained by considering cation distribution in the spinel structure. The estimated cation distribution results show that the Fe ion vacancy mostly occurred at the B sites which is in good agreement with the theoretical calculations. [ABSTRACT FROM AUTHOR]