Supercritical CO2 synthesis of LaAlO3/SrTiO3 heterostructures with tunable room-temperature ferromagnetism

Introduction: Two-dimensional magnets hold great promise for spintronic applications, and LaAlO3/SrTiO3 heterostructures provide an important platform for exploring emergent interfacial magnetic phenomena. Traditional fabrication methods such as pulsed laser deposition suffer from high vacuum requirements, high cost, and operational complexity, which limit their widespread use. Materials and methods: A supercritical CO2-assisted strategy was developed to fabricate 2D LaAlO3/SrTiO3 heterostructures. This method enables the simultaneous exfoliation of nanosheets, heterostructure assembly, and amorphization of LaAlO3. The structure, composition, and morphology were characterized by Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS,) and Raman spectroscopy. The magnetic properties were measured using a vibrating sample magnetometer at room temperature. Results: CO2 pressure critically controls the lattice expansion, amorphization of LaAlO3, and interfacial defect formation. The saturation magnetization is strongly pressure-dependent, reaching 0.13 emu/g at 300 K under 14 MPa. The enhanced ferromagnetism mainly originates from B-site cation defects and TiAl antisite defects, while oxygen vacancies dominate the magnetism at higher pressures. Conclusions: The supercritical CO2 route provides a green, efficient, and scalable way to construct 2D magnetic oxide heterostructures with tunable room-temperature ferromagnetism. This method offers a new strategy for interface engineering and promotes the development of oxide-based spintronic devices.