Enhancement of Domain Wall Pinning in High-Temperature Resistant Sm₂Co₁₇ Type Magnets by Addition of Y₂O₃

In this study, the effects of Y₂O₃ addition on the magnetic properties, microstructure and magnetization reversal behavior of Sm(Co_0.79Fe_0.09Cu_0.09Zr_0.03)_7.68 magnet were investigated. By addition of Y₂O₃, the coercivity was increased from 21.34 kOe to 27.42 kOe at 300 K and from 5.14 kOe to 6.27 kOe at 823 K. A magnet with a maximum magnetic energy product of 9.86 MGOe at 823 K was obtained. With the interdiffusion of Y and Sm after appropriate addition, the Cu content within the cell boundary phase close to the oxide was detected to be nearly twice as high as that away from the oxide. We report for the first time that a collection of lamellar phases were formed on both sides of the inserted oxide, providing a strong pinning field against magnetic domain wall motion based on in-situ Lorentz TEM observation. Furthermore, the ordering process of the original magnet was delayed after Y₂O₃ addition, resulting in the refinement of cellular structure, which can also enhance the domain wall pinning ability of cellular structures based on micromagnetic simulation. However, excessive addition of Y₂O₃ led to large Cu-rich phase and Zr-rich impurity phase precipitated at the edge of the oxide, resulting in the destruction of cellular structures and a significant reduction in coercivity. This study provides a new technical approach to regulate the microstructure of Sm₂Co₁₇ type magnets. Addition of Y₂O₃ is expected to play a significant role in improvement of high temperature magnetic properties.