VI₃—a New Layered Ferromagnetic Semiconductor

TLDR

Two‑dimensional materials are promising for next‑generation electronics, and insulating 2D ferromagnets—rare yet crucial for new device architectures—are a key focus. The study aims to investigate insulating 2D ferromagnets as a route to novel device architectures. VI3, a layered van der Waals semiconductor with a BiI3‑type structure, exhibits ferromagnetism below 49 K, shows a subtle structural transition at 78 K, hosts magneto‑optical Kerr effect–visible domains, and has a 0.6 eV optical bandgap while remaining highly resistive.

Abstract

2D materials are promising candidates for next-generation electronic devices. In this regime, insulating 2D ferromagnets, which remain rare, are of special importance due to their potential for enabling new device architectures. Here the discovery of ferromagnetism is reported in a layered van der Waals semiconductor, VI3 , which is based on honeycomb vanadium layers separated by an iodine-iodine van der Waals gap. It has a BiI3 -type structure ( R3¯ , No.148) at room temperature, and the experimental evidence suggests that it may undergo a subtle structural phase transition at 78 K. VI3 becomes ferromagnetic at 49 K, below which magneto-optical Kerr effect imaging clearly shows ferromagnetic domains, which can be manipulated by the applied external magnetic field. The optical bandgap determined by reflectance measurements is 0.6 eV, and the material is highly resistive.