Stacking-Engineered Ferroelectricity and Multiferroic Order in van der Waals Magnets

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Two-dimensional (2D) materials with ferroic properties (ferromagnetism, ferroelectricity, ferroelasticity) are key for advanced nanotechnology.
• Achieving multiferroic order, which combines multiple ferroic properties, is challenging due to complex electron and spin interactions.

Purpose of the Study:

• To propose a universal strategy for engineering multiferroic 2D materials.
• To demonstrate this strategy using van der Waals magnets and first-principles calculations.
• To discover novel magnetoelectric coupling mechanisms in engineered 2D systems.

Main Methods:

• Utilizing van der Waals magnets and manipulating layer stacking to break inversion symmetry.
• Employing first-principles calculations to investigate bilayer Nickel Iodide (NiI2).
• Analyzing the relationship between interlayer spin order and interfacial electronic polarization.

Main Results:

• Demonstrated that rotating adjacent layers in bilayer NiI2 by 180° induces ferroelectricity.
• Discovered a strong magnetoelectric coupling between interlayer spin order and interfacial polarization.
• Validated a general and systematic approach for designing 2D multiferroics.

Conclusions:

• The proposed stacking-engineering method offers a viable route to realize 2D multiferroics.
• This approach facilitates the discovery of novel 2D materials with significant magnetoelectric coupling.
• The findings hold promise for the development of multifunctional nanoscale electronic devices.