Ferromagnetic stability optimization via oxygen-vacancy control in single-atom Co/TiO2 nanostructures.

Oxygen vacancies and their correlation with the nanomagnetism and electronic structure are crucial for applications in dilute magnetic semiconductors design applications. Here, we report on cobalt single atom-incorporated titanium dioxide (TiO₂) monodispersed nanoparticles synthesized using a thermodynamic redistribution strategy. Using advanced synchrotron-based X-ray techniques and simulations, we find trivalent titanium is absent, indicating trivalent cations do not influence ferromagnetic (FM) stability. Density functional theory calculations show that the FM stability between Co²⁺ ions is very weak. However, electron doping from additional oxygen vacancies can significantly enhance this FM stability, which explains the observed room-temperature ferromagnetism. Moreover, our calculations illustrate enhanced FM interactions between Co_Ti + V_O complexes with additional oxygen vacancies. This study explores the electronic structure and room-temperature ferromagnetism using monodispersed nanocrystallites with single-atom-incorporated TiO₂ nanostructures. The strategies described herein offer promise in revealing magnetism in other single-atom-incorporated nanostructures.