Multiferroic nanoparticles of Ni doped CoCr2O4: An XPS study

Three spinel compounds, namely CoCr2O4, (Co0.75Ni0.25)Cr2O4, and (Co0.5Ni0.5)Cr2O4 were investigated using x-ray photoelectron spectroscopy techniques. These compounds were synthesized using sol-gel techniques. The gel was dried and subsequently calcined at 600 °C to achieve crystallinity and the correct cubic phase. The survey scans of the analyzed samples with detailed spectra of the Co 2p, Ni 2p, Cr 2p, O 1s, and the valence band were collected. The core levels are found to be asymmetric and have multiple components. Ni and Co have 2+/3+ oxidation states, whereas Cr prefers 3+ oxidation state. The O 1s core level demonstrates three components. The low binding energy component refers to the lattice oxygen atoms, whereas the two high binding energy components correspond to the surface adsorbed hydroxyl groups resulting from water and the alcohol used for the synthesis of these nanoparticles. The data emanating from this study are reported.