Ni-Doped ZnO nanoparticles prepared by sol–gel: enhanced electrical conductivity and transition from non-magnetic to magnetic behavior

Zinc oxide (ZnO) is a widely investigated semiconductor owing to its versatility in electronic and optoelectronic applications. However, its intrinsic diamagnetism and relatively low electrical conductivity limit its performance in advanced electronic and spintronic systems. In this work, we investigate the effect of nickel-induced hybridization in ZnO nanoparticles with a nominal Ni concentration of 20%, focusing on the resulting structural, electrical, dielectric, and magnetic properties. The incorporation of Ni ions into the ZnO lattice promotes hybridization between Ni 3 d and O 2p orbitals, leading to modifications in the electronic structure and defect landscape. This effect results in a significant enhancement of electrical conductivity, with a thermally activated conduction mechanism characterized by a low activation energy of approximately 84 meV, indicating facilitated charge transport via defect-related states. Magnetic measurements reveal a transition from diamagnetic to superparamagnetic behavior, with a saturation magnetization of 6 emu/g at 5 K, decreasing to 1.5 emu/g at 300 K. Overall, the observed hybridization-driven tuning of electrical and magnetic properties highlights the potential of Ni-doped ZnO nanoparticles for applications in electronic devices, spintronics, gas sensing, photocatalysis, and magnetic hyperthermia.