Effect of Ni Substitution on Optical Transitions and Magnetic Behavior of Mesoporous NixCo3-xO4 (0 ≤ x ≤ 1) Thin Films Prepared by Electrophoretic Deposition

High-quality nickel cobaltite (NixCo3-xO4, 0 <= x <= 1) nanopowders with various nickel contents have been prepared by a facile hydrothermal method, calcined in air at 300 degrees C for 2 h, then coated on the surface of indium tin oxide sheets by electrophoretic deposition. The optical, microstructural, and magnetic properties were characterized by x-ray diffraction (XRD) analysis, ultraviolet-visible (UV-Vis) spectrophotometry, field emission-scanning electron microscopy (FE-SEM), and vibrating-sample magnetometry. The XRD patterns of the pure and Ni-doped Co3O4 powders revealed the formation of single-phase spinel structure, without any impurity phases for all samples. The position and intensity of various absorption bands in the UV-Vis spectra were influenced by the distribution of Co2+ and Ni2+ ions at tetrahedral sites of the spinel structure, revealing that O2- -> Co2+ and O2- -> Ni2+ transition sites were affected by increasing the Ni2+ content, thereby changing the optical properties of NixCo3-xO4. Vibrating-sample magnetometry analysis revealed that the magnetic nature of the prepared nanopowders changed from anti-ferromagnetic to very weak ferrimagnetic.