Supercritical CO2-modulated defect dynamic equilibrium for magnetic-proton dual-functional CaZrO3

Abstract

Fabrication of magnetic-proton dual-functional CaZrO₃ via supercritical CO₂ (SC CO₂)-modulated dynamic defect equilibrium and multiscale lattice strain engineering was achieved. By tuning SC CO₂ pressure, a critical synergy in which oxygen vacancies convert dynamically to hydroxyl groups (−OH) through proton-conductive pathways occurs, and simultaneously pressure-induced lattice compression enhances spin polarization of O-2p orbitals. High-resolution transmission electron microscopy and X-ray diffraction revealed that 16 MPa of SC CO₂ triggered defect-strain coupling, stabilizing room-temperature ferromagnetism with a saturation magnetization of 0.0865 emu g⁻¹ and coercivity of 130.5 Oe, and simultaneously obtained proton-conductive properties. Therefore, this green, dopant-free approach establishes SC CO₂ as a versatile tool to regulate defect dynamics and lattice strain, bridging the gap between theoretical predictions and experimental realization of ferromagnetism in d⁰ oxides.