• • Direct observation of out-of-plane ferroelectric polarization in trilayer NiI2 via non-collinear spiral spin configuration, with magnetic domains and hysteresis loops confirming multiferroic order at the 2D limit; this eliminates the need for bulk single crystals and enables atomically thin memory elements.
• • Coexistence of ferroelectricity and antiferroelectricity in a single-phase trilayer NiI2, with magnetic control of ferroelectric domain switching dynamics; this provides a pathway for magnetoelectric coupling with independent and synergistic manipulation of order parameters, critical for energy-efficient logic devices.
• • Advanced micro-nano magneto-optical-electric joint measurement scanning imaging with linear/non-linear tandem capacitance significantly enhances the area-to-distance ratio in the capacitance plane, enabling precise identification of low-dimensional multiferroics where optical techniques fail.
• • The demonstration of magnetoelectric coupling in trilayer NiI2 at the 2D limit opens avenues for ultra-compact spintronic devices with all-electric-field switching, potentially reducing energy consumption per switching event by leveraging coupled electric and magnetic orders.