Control of magnetic transitions via interlayer engineering in ferroelectric H2O–OH systems

Controlling magnetic phase transitions in two-dimensional (2D) multiferroics is crucial for both fundamental scientific knowledge and practical applications. Here, we present a general strategy for inducing magnetic transitions in 2D ferroelectrics based on the electron pairing principle. First-principles calculations revealed the coupled ferroelectric and ferromagnetic behavior in water-hydroxyl (H2O–OH) monolayer, with ferromagnetism arising from unpaired electrons in 2p bonding orbitals of the OH groups. A ferromagnetic-to-nonmagnetic phase transition occurs via interlayer coupling, forming H2O2 molecules where electrons pair up. Conversely, the nonmagnetic-to-ferromagnetic transition can be triggered by stacking rearrangements that prevent H2O2 formation and restore unpaired electrons. Importantly, such magnetic transitions can be efficiently controlled by external electric fields. Notably, low-energy-electron-assisted synthesis method and high-resolution scanning tunneling microscopy confirm the successful creation of H2O–OH overlayer on Ag(111). These findings provide an approach for magnetism control in 2D ferroelectrics and offer insights for future spintronic and multiferroic devices.