Coexistence of Magnetic Orders in Two-Dimensional Magnet CrI$_3$

TL;DR

This study reveals that in intermediate-thickness CrI3 flakes, ferromagnetic and antiferromagnetic orders can coexist within the same material, with surface layers exhibiting AFM order and the bulk maintaining FM order, highlighting complex magnetic behavior.

Contribution

The paper demonstrates the coexistence of different magnetic orders in a single CrI3 flake, providing new insights into magnetic heterostructures in 2D materials.

Findings

Surface layers (~13 nm) show antiferromagnetic order similar to few-layer CrI3.

Bulk of the flake remains ferromagnetic with a remnant magnetic state.

Weak interlayer coupling allows formation of c-axis magnetic domains.

Abstract

The magnetic properties in two-dimensional van der Waals materials depend sensitively on structure. CrI3, as an example, has been recently demonstrated to exhibit distinct magnetic properties depending on the layer thickness and stacking order. Bulk CrI3 is ferromagnetic (FM) with a Curie temperature of 61 K and a rhombohedral layer stacking, while few-layer CrI3 has a layered antiferromagnetic (AFM) phase with a lower ordering temperature of 45 K and a monoclinic stacking. In this work, we use cryogenic magnetic force microscopy to investigate CrI3 flakes in the intermediate thickness range (25 - 200 nm) and find that the two types of magnetic orders hence the stacking orders can coexist in the same flake, with a layer of ~13 nm at each surface being in the layered AFM phase similar to few-layer CrI3 and the rest in the bulk FM phase. The switching of the bulk moment proceeds through a remnant state with nearly compensated magnetic moment along the c-axis, indicating formation of c-axis domains allowed by a weak interlayer coupling strength in the rhombohedral phase. Our results provide a comprehensive picture on the magnetism in CrI3 and point to the possibility of engineering magnetic heterostructures within the same material.