Observation of intrinsic crystal phase in bare CrI3 ferromagnetism

TL;DR

This paper reveals the intrinsic monoclinic crystal structure of few-layer CrI3, demonstrating its correlation with magnetic order and the effects of hBN encapsulation, advancing understanding of 2D ferromagnetic materials.

Contribution

It provides the first experimental evidence of the intrinsic monoclinic stacking in bare few-layer CrI3, linking structure to magnetic properties.

Findings

Intrinsic monoclinic stacking confirmed in bare CrI3 layers.

hBN encapsulation induces spring damping, affecting interlayer sliding.

Monoclinic phase persists across a wide temperature range from 300 to 10 K.

Abstract

Intrinsic structural phase is a crucial foundation for the fundamental physical properties, and for creating innovative devices with unprecedented performances and unique functionalities. Long-range ferromagnetic orders of van der Waals CrI3 are strongly tied with interlayer stacking orders. However, the intrinsic structure of few-layer CrI3 still remains elusive; the predicted monoclinic phase has not yet been experimentally detected in bare few-layer CrI3. Here we uncover the intrinsic structure of few-layer CrI3 with interlayer antiferromagnetic coupling, which unambiguously show monoclinic stacking in both bare and hBN-encapsulated bilayer and tri-five-layer CrI3 throughout an entire temperature range from 300 to 10 K. An exotic spring damping effect from hBN encapsulation layers is experimentally observed in hBN/CrI3/hBN heterostructures, which partly hinders interlayer sliding of CrI3. This work demonstrates the intrinsic monoclinic crystal phase of few-layer CrI3 and associated correlation with magnetic orders, opening up numerous opportunities for creating magnetic texture by stacking design.