Structural phase transitions and Raman identifications of the layered van der Waals magnet CrI2

Understanding the phase-transition processes of van der Waals (vdW) materials plays a vital role in their performance control and application development. Here, we investigate the structural transitions and Raman identifications of the monoclinic and orthorhombic phases of the layered vdW magnet CrI2. At present, the characterization of these two phases remains a challenge, and our first-principles calculations show that they each have a specific Raman spectrum, which proposes a reliable method to identify them. Moreover, we discover that CrI2 with orthorhombic phase exhibits both ferroelectricity and magnetism simultaneously due to its unique interlayer stacking order, indicating that it will provide a platform for the popular sliding ferroelectricity and multiferroicity.

Automated summary

Understanding the phase-transition processes of van der Waals (vdW) materials is crucial for controlling their performance and developing their applications. In this study, we investigate the structural transitions and Raman identifications of the monoclinic and orthorhombic phases of the layered vdW magnet CrI2. Our first-principles calculations reveal that each phase has a specific Raman spectrum, providing a reliable method to identify them. Additionally, the orthorhombic phase of CrI2 exhibits both ferroelectricity and magnetism simultaneously due to its unique interlayer stacking order, indicating its potential as a platform for sliding ferroelectricity and multiferroicity.