Giant enhancement of interlayer exchange in an ultrathin 2D magnet

TL;DR

This study reveals a ten-fold enhancement of interlayer exchange in ultrathin CrCl3 crystals, linked to stacking order differences, offering new insights into 2D magnetic interactions relevant for spintronics.

Contribution

It demonstrates a significant increase in interlayer exchange in exfoliated CrCl3 and links it to changes in stacking order, advancing understanding of 2D magnetic properties.

Findings

Ten-fold increase in interlayer exchange in ultrathin CrCl3

Exfoliated films do not undergo bulk crystallographic phase transition

Stacking order influences interlayer magnetic interactions

Abstract

Following the recent isolation of monolayer CrI3, there has been a surge of new two-dimensional van der Waals magnetic materials, whose incorporation in van der Waals heterostructures offers a new platform for spintronics, proximity magnetism, and quantum spin liquids. A primary question in this burgeoning field is how exfoliating crystals to the few-layer limit influences their magnetism. Studies on CrI3 have shown a different magnetic ground state for ultrathin exfoliated films but the origin is not yet understood. Here, we use electron tunneling through few-layer crystals of the layered antiferromagnetic insulator CrCl3 to probe its magnetic order, finding a ten-fold enhancement in the interlayer exchange compared to bulk crystals. Moreover, temperature- and polarization-dependent Raman spectroscopy reveal that the crystallographic phase transition of bulk crystals does not occur in exfoliated films. This results in a different low temperature stacking order and, we hypothesize, increased interlayer exchange. Our study provides new insight into the connection between stacking order and interlayer interactions in novel two-dimensional magnets, which may be relevant for correlating stacking faults and mechanical deformations with the magnetic ground states of other more exotic layered magnets, such as RuCl3.