Tailored strain–octahedral–defect interplay for giant multiferroicity in BiFeO3 via scandium implantation

The escalating demand for high-performance nonvolatile memories, driven by the rapid evolution of artificial intelligence hardware, highlights the urgent need for breakthroughs in multiferroic thin-film engineering. While environmentally benign bismuth ferrite (BFO) thin films exhibit intrinsic ferroelectric-ferromagnetic duality, their performance suffers considerable degradation because of dimensional scaling effects and stochastic percolation of oxygen vacancies (${\mathrm{V}}_{\mathrm{O}}^{••}$${\mathrm{V}}_{\mathrm{O}}^{••}$). Herein, we introduce a quantum-engineered implantation strategy utilizing scandium ions (Sc³⁺) as metastable interstitial dopants to systematically establish self-adaptive lattice-oxygen vacancy equilibria through quantum-confined interactions. Atomic-resolution electron microscopy and multiferroicity scaling behavior analysis reveal that precise Sc³⁺ implantation (dose: 10¹⁵ ions·cm⁻²) induces a quantum-confined strain field and vacancy dipole ordering, synergistically enhancing ferroelectric polarization to 158.6 μC/cm² while suppressing leakage currents to 10⁻⁸ A/cm². Concurrently, strain-mediated magnetoelectric coupling elevates saturation magnetization to 0.82 emu/cm³ via the modulation of the spin–lattice interaction, accompanied by electronic structure reconfiguration (bandgap narrowing ΔE_g = 2.09 eV). Crucially, Sc³⁺–${\mathrm{V}}_{\mathrm{O}}^{••}$${\mathrm{V}}_{\mathrm{O}}^{••}$ pairs exhibit policy network-like characteristics, wherein each dopant autonomously optimizes local multiferroic responses through strain-oxygen chemical potential feedback loops. This study provides a Materials Genome blueprint for the design of multiferroic systems, bridging the gap between quantum-scale manipulation and device-level operational stability in oxide electronics.