Signature of Electromagnons and Multiferroic Domains in NiI₂ through Raman Spectrum

Multiferroic van der Waals materials, in which coexistence of ferromagnetism (FM) and ferroelectricity (FE) within a single phase is observed, offer a promising avenue for achieving electric control of magnetism in the two-dimensional (2D) regime. This capability holds significant implications for the advancement of spintronic devices, including magnetic storage and magnetic random-access memory. To comprehend the intricate interplay between magnetism and ferroelectricity, it is imperative to scrutinize the response of their fundamental excitations to external stimuli, including magnetic fields, electrical doping, and temperature variations. Recently, type-II multiferroic Nickle Diiodide (NiI₂) was evident to exhibit an inversion symmetry breaking by spiral magnetism down to the atomic limit through the utilization of second harmonic generation (SHG) and birefringence measurement. In this talk, we present an investigation into the magneto-Raman spectrum of the type-II multiferroic order manifest in layered NiI₂, which is characterized by a proper-screw magnetic order with given handedness. By symmetry analysis, we use both linear and circular cross polarization to identify various multiferroic domains characterized by distinctive electromagnon modes. Our studies also uncover the significant magnetoelectric effect arising from the spin-phonon coupling in NiI₂. These observations establish NiI₂ as an intriguing platform for the exploration of emergent multiferroic effects and associated magnetic textures in the two-dimensional limit.