Europium-Induced Ferromagnetism on Bismuth Germanium Oxide Nanoparticles toward Spintronics Applications

Phosphors of Bi₄Ge₃O₁₂:Eu³⁺ were obtained by using the polymeric precursor route. After confirming the Eu incorporated into the Bi₄Ge₃O₁₂ lattice, we analyzed the magnetic behavior in the systems with 0%, 2%, 5%, and 10%. The magnetization vs magnetic field measurements evidenced ferromagnetism in all the samples, with different magnetization saturation values. In the pristine structure, the magnetic behavior is directly related to Bi vacancies, where the neighbor O atoms induce spin polarization. The ferromagnetic characteristics are enhanced in the 2% Eu content because Eu atoms take on the Bi vacancy sites. In contrast, the ferromagnetic character diminishes as the Eu content is increased to 5%, which is directly correlated with site competence as Eu can occupy either Bi or Ge sites. Upon raising the Eu percentage to 10%, the ferromagnetic character gets strengthened. In this case, we hypothesize that zones of the material with a high concentration of Eu may appear with ferromagnetic alignment, confirmed by our ab initio computations. The evidence generated in this paper lays the foundations for considering rare-earth-doped Bi₄Ge₃O₁₂ for applications in the spintronics industry.