Atomically Thin CrCl3: An in-Plane Layered Antiferromagnetic Insulator

TL;DR

This paper reports that atomically thin CrCl3 is an in-plane layered antiferromagnetic insulator with potential for 2D magnetic studies and spintronic applications, confirmed through optical and tunneling magnetoresistance measurements.

Contribution

It demonstrates that CrCl3 has an easy-plane magnetic anisotropy and antiferromagnetic interlayer coupling down to the bilayer, expanding understanding of 2D magnetic materials.

Findings

CrCl3 is an in-plane layered antiferromagnetic insulator.

Ligand field photoluminescence observed down to monolayer.

Interlayer coupling remains antiferromagnetic in bilayer.

Abstract

The recent discovery of magnetism in atomically thin layers of van der Waals (vdW) crystals has created new opportunities for exploring magnetic phenomena in the two-dimensional (2D) limit. In most 2D magnets studied to date the c-axis is an easy axis, so that at zero applied field the polarization of each layer is perpendicular to the plane. Here, we demonstrate that atomically thin CrCl3 is a layered antiferromagnetic insulator with an easy-plane normal to the c-axis, that is the polarization is in the plane of each layer and has no preferred direction within it. Ligand field photoluminescence at 870 nm is observed down to the monolayer limit, demonstrating its insulating properties. We investigate the in-plane magnetic order using tunneling magnetoresistance in graphene/CrCl3/graphene tunnel junctions, establishing that the interlayer coupling is antiferromagnetic down to the bilayer. From the temperature dependence of the magnetoresistance we obtain an effective magnetic phase diagram for the bilayer. Our result shows that CrCl3 should be useful for studying the physics of 2D phase transitions and for making new kinds of vdW spintronic devices.