CO₂ Stress-Driven Room Temperature Ferromagnetism of Ultrathin 2D Gallium Oxide

Spintronic devices work by manipulating the spin of electrons other than charge transfer, which is of revolutionary significance and can largely reduce energy consumption in the future. Herein, ultrathin two-dimensional (2D) non-van der Waals (non-vdW) γ-Ga₂O₃ with room temperature ferromagnetism is successfully obtained by using supercritical CO₂ (SC CO₂). The stress effect of SC CO₂ under different pressures selectively modulates the orientation and strength of covalent bonds, leading to the change of atomic structure including lattice expansion, introduction of O vacancy, and transition of Ga-O coordination (GaO₄ and GaO₆). Magnetic measurements show that pristine γ-Ga₂O₃ is nonferromagnetic, whereas the SC CO₂ treated γ-Ga₂O₃ exhibits obvious ferromagnetic behavior with an optimal magnetization of 0.025 emu g^-1 and a Curie temperature of 300 K.