Defect‐Mediated Coupling of Physical Properties in Nickel Doped Titanium Dioxide Semiconductor for Multifunctional Materials and Device Applications

In this work, Ni – doped Titanium dioxide (Ni–TiO ₂ ) were synthesized using a solid‐state route with varying Ni concentrations (0, 1, 3, and 5 wt.%) to investigate the influence of Ni‐induced defects on their structural, optical, electrical, dielectric, and magnetic properties. X‐ray diffraction and Raman spectroscopy confirmed single‐phase TiO ₂ without detectable secondary phases, while X‐ray photoelectron spectroscopy verified substitutional Ni ²⁺ incorporation and oxygen‐vacancy‐ related defects. Hall measurements revealed that carrier concentration and electrical conductivity increased with increasing Ni concentration, while carrier mobility decreased due to defect induced scattering. Dielectric and impedance analyses further revealed non‐Debye relaxation behavior and defect assisted charge transport. UV–Vis spectroscopy demonstrated progressive band‐gap narrowing with increasing Ni incorporation. Magnetic measurements by SQUID is indicated a transition from diamagnetism in undoped TiO ₂ to weak ferromagnetism in Ni – doped samples at 300 K, with enhanced magnetization at 5 K, consistent with a defect‐mediated bound magnetic polaron mechanism. PE measurements showed increased remanent polarization with Ni incorporation. Overall, the results demonstrate that Ni‐induced V _o simultaneously enhance physical properties, establishing defect engineering as a potential approach to the multifunctional properties of TiO ₂ for sensing, spintronic, and energy‐related applications.