Magnetically Switchable Ferroelastic Phase Transition in Two-Dimensional Multiferroics

Multiferroic coupling represents a major research frontier in condensed matter physics and materials science, given its importance for both fundamental studies and device applications. While current investigations predominantly focus on magnetoelectric effects, coupling with ferroelastic order remains an outstanding challenge, especially for controlling it. Here, we report a magnetically switchable ferroelasticity effect in a 2D antiferromagnetic multiferroic lattice, where magnetization reorientation is coupled to reversible switching of ferroelastic polarization. The underlying physics originates from an intriguing spin-lattice coupling induced by zigzag antiferromagnetic exchange, which produces an anisotropic exchange field and leads to lattice distortion. This spin-lattice coupling gives rise to 120° ferroelasticity, enabling robust magnetic control of ferroelastic order. Using first-principles calculations, we further validate this effect in multiferroic monolayer FePS₃. Our findings open a new pathway for the design of multiferroics with magnetically controllable properties.