Magnetic properties of (Ni, Co)-doped tin oxide thin films

Metal-doped tin oxide (SnO${}_2$) is an auspicious material for oxide-based diluted magnetic semiconductors, exhibiting remarkable optical and conductive properties. This study focuses on SnO${}_2$ thin films, both undoped and doped with Cobalt (Co) or Nickel (Ni), synthesized via spray pyrolysis — a simple, cost-effective, and versatile technique widely utilized in the fabrication of sensors and photovoltaic devices. The samples have been characterized in terms of their composition, morphology, crystallinity, optical properties, electrical conductivity, and magnetic behavior. The undoped SnO${}_2$ films demonstrated a resistivity of approximately 10⁻² $\Omega$cm and exhibited soft ferromagnetic behavior attributed to oxygen vacancies. In contrast, the Ni- and Co-doped samples showed significant alterations in their crystalline structure and electrical properties, displaying n-type carrier behavior. The incorporation of dopants enhanced the room-temperature soft ferromagnetism and led to a reduction in optical transmittance, accompanied by shifts in the bandgap energy. Density Functional Theory calculations provided a theoretical foundation for interpreting the experimental results, including the influence of unavoidable impurities like Chlorine. These findings underscore the potential of metal-doped SnO${}_2$ thin films for advanced applications in spintronics and optoelectronics.