Ni-Doped SnO₂ Dilute Magnetic Semiconductors: Morphological Characteristics and Optical and Magnetic Properties

Ni-doped SnO₂ dilute magnetic semiconductors were prepared by precipitation method. The obtained spherical nanoparticles are pure tetragonal rutile phase, and Ni ions promote the growth of SnO₂ nanoparticles. The optical band gap energy of the SnO₂ nanoparticles decreases from 3.14 to 2.84 eV when input x% Ni. The room-temperature photoluminescence (PL) spectra and X-ray photoelectron spectroscopy (XPS) confirm the existence of surface oxygen vacancies caused by the large specific surface area and the introduction of Ni ions. All the synthesized Ni-doped SnO₂ nanoparticles achieve room-temperature ferromagnetism, with a saturation magnetization of up to 2.95 × 10⁻³ emu/g at a dopant concentration of 2%. The interaction between oxygen vacancies and Ni²⁺ realizes the magnetic transition of nanoparticles from diamagnetic to ferromagnetic.