Supercritical CO ₂ ‐Enabled Exfoliation of SrSnO ₃ Nanocrystals With Ferromagnetism

With the rapid development of spintronics, ferromagnetic nanomaterials have shown critical unique advantages in the fields of information storage and quantum computation. The ABO ₃ ‐type perovskite oxide SrSnO ₃ is expected to realize room‐temperature ferromagnetism (RTFM) due to its tunable crystal structure and unique electron arrangement. However, developing stable RTFM in transition metal‐free SrSnO ₃ remains a long‐standing challenge—traditional strategies often cause lattice damage or impurity residues, failing to balance structural integrity and ferromagnetic performance. In this process, the precise supercritical CO ₂ (SC CO ₂ )‐induced strain effect can lead to stretching in the a‐axis direction while synchronously realizing repair of oxygen vacancies, forming a synergistic regulation of lattice structure and defect states. In addition, combining the systematic optimization of change in the crystal size to ultimately successfully realize the RTFM in SrSnO ₃ ( T _c = 400 K, M _s = 0.019 emu g ⁻¹ ) can be presented. Therefore, this study establishes a new strategy for the development of transition metal‐free ferromagnetic materials for the application of spintronic devices at room temperature, which not only enriches the technical toolbox for designing transition metal‐free ferromagnetic perovskites but also provides a feasible pathway for their practical application in next‐generation spintronic devices.