Metamagnetic transition in a van der Waals antiferromagnet

The specificity of a metamagnetic transition in van der Waals antiferromagnets are considered for a CrI$_3$ bilayer, which is a two-dimensional antiferromagnet. Special attention is paid to the type of magnetoelectric effect that manifests itself as an electric-field-induced transition from the antiferromagnetic to the ferromagnetic state in a bias magnetic field close to the critical transition field. Its supposed mechanism is the linear magnetoelectric effect allowed by the crystal symmetry. Based on the group-theoretical approach, the structure of the magnetoelectric tensor in CrI$_3$ and similar crystals is obtained, suggesting that the transverse magnetoelectric effect is possible along with the longitudinal effect near the spin-flop transition, provided that the magnetic anisotropy decreases to values comparable with the interlayer exchange field. The presence of the transverse magnetoelectric effect is important in the context of detecting electrically induced gyromagnetic effects in van der Waals materials.