Multiferroic metals are materials that exhibit both electric polarization and magnetic order in the same crystal—a state known as multiferroicity. Because these properties coexist, they can interact through magnetoelectric (ME) coupling, allowing electric fields to influence magnetism.
Unfortunately, bulk multiferroic materials face limitations, including relatively small spontaneous polarization, weak ME coupling coefficients, and limited operational stability under ambient conditions due to oxygen-vacancy-induced leakage currents, which restrict their practical applications.
Now, however, researchers from the Institute of Physics of the Chinese Academy of Sciences, along with their collaborators from Zhejiang University, have realized electric-field control of magnetic states using a two-dimensional (2D) van der Waals material, while demonstrating intrinsic room-temperature (RT) multiferroicity with strong ME coupling.
The study is published in the journal Nature Materials.
Specifically, the team developed a novel alternating antiferromagnetic (AFM)/ferromagnetic (FM) layered configuration in bilayer CrTe2, in which the interlayer electrostatic potential difference intrinsically breaks inversion symmetry, thus giving rise to reversible out-of-plane polarization. They then realized high-quality bilayer CrTe2 films via molecular beam epitaxy, demonstrating an RT-stable 2D multiferroic phase.
First-principles calculations combined with scanning tunneling microscopy, piezoresponse force microscopy, and magnetic force microscopy confirmed that the electrostatic potential difference between the AFM and FM layers induced spontaneous inversion symmetry breaking and generated robust ferroelectric polarization. In contrast to spin-orbit-coupling-driven mechanisms in typical type-II multiferroics, this interlayer charge-asymmetry mechanism enabled strong ME coupling that persisted up to RT.
The proposed FM/AFM superlattice structure establishes a universal design principle for engineering 2D single-phase multiferroics. The RT and air-stable “electrical writing and magnetic reading” demonstrated in bilayer CrTe2 bridges the gap between fundamental multiferroic physics and scalable applications, thereby positioning 2D multiferroics as a viable platform for CMOS-compatible, energy-efficient spintronic memory, accelerating their integration into post-Moore nanoelectronics.