Strain-coupled, crystalline polymer-inorganic interfaces for efficient magnetoelectric sensing.

Magnetoelectric sensing holds promise for flexible sensors, offering precise detection of both electric and magnetic fields with minimal power consumption. However, its practical use has been constrained by weak magnetoelectric effects and limited overall performance, particularly under mechanical strain. Herein, we fabricated robust magnetoelectric polymer-inorganic nanocomposites through an interfacial cocrystallization strategy. By leveraging diazonium chemistry on vanadium diselenide (VSe) monolayers, we created a submolecular-flat interface between ferromagnetic VSe and ferroelectric poly(vinylidene fluoride) (PVDF) nanocrystals. This highly crystalline interface has few mobile polymer chains and thus limits energy dissipation and enhances interfacial energy transfer. The scalable composite films show exceptional magnetoelectric performance, with a magnetocapacitive coefficient of 23.6%. These films enable ultrafast magnetoelectric detection, approaching a 10-fold increase in speed compared with conventional sensors, and offer opportunities for integrating multifunctional materials such as thermoelectric coolers into wearable devices.