The use of magnetron sputtering film as a diffusion source was recently achieved in the industrial production of important grain-boundary-diffusion magnets. In this paper, the multicomponent diffusion source film is explored to optimize the microstructure of NdFeB magnets and improve their magnetic properties. Multicomponent Tb₆₀Pr₁₀Cu₁₀Al₁₀Zn₁₀ films of 10 μm in thickness and single Tb films of 10 μm in thickness were deposited on commercial NdFeB magnets’ surfaces by magnetron sputtering as diffusion sources for grain boundary diffusion. The effects of diffusion on the microstructure and magnetic properties of the magnets were investigated. The coercivity of multicomponent diffusion magnets and single Tb diffusion magnets increased from 11.54 kOe to 18.89 kOe and 17.80 kOe, respectively. The microstructure and element distribution of diffusion magnets were characterized by scanning electron microscope and transmission electron microscopy. The multicomponent diffusion facilitates the infiltration of Tb along grain boundaries, rather than entering the main phase, thereby improving the Tb diffusion utilization. Furthermore, compared to the Tb diffusion magnet, the thicker thin-grain boundary was observed in multicomponent diffusion magnets. This thicker thin-grain boundary can effectively serve as the impetus for the magnetic exchange/coupling between grains. Therefore, the multicomponent diffusion magnets have higher coercivity and remanence. The multicomponent diffusion source has an increased mixing entropy and decreased Gibbs free energy, and it therefore does not easily enter the main phase but is retained in the grain boundary, thus optimizing the microstructure of the diffusion magnet. Our results show that the multicomponent diffusion source is an effective route for fabricating diffusion magnets with high performance.

(Dy_0.7Y_0.25La_0.05)₂O₃ magneto-optical transparent ceramics were successfully fabricated by pressureless sintering in reductive H₂ atmosphere (PLSH). The raw powder of (Dy_0.7Y_0.25La_0.05)₂O₃ was synthesized by a modified self-propagating high-temperature synthesis (SHS) and sintered to transparent ceramics at 1400–1600 °C in a flowing H₂ atmosphere, showing good sinterability of the as-synthesized raw powder. The magneto-optical Verdet constant of (Dy_0.7Y_0.25La_0.05)₂O₃ transparent ceramics was measured to be −191.57 rad/(T·m) at a wavelength of 632.8 nm. In this magneto-optical material of (Dy_0.7Y_0.25La_0.05)₂O₃, relative cheaper Dy and Y were used to replace Tb, and the low cost and good magneto-optical property showed the advantage of application on Faraday isolators (FIs) and Faraday rotators (FRs).