Increased Curie temperature and enhanced perpendicular magneto anisotropy of Cr2Ge2Te6/NiO heterostructure

TL;DR

This study demonstrates that forming heterostructures of Cr2Ge2Te6 with NiO significantly increases its Curie temperature and perpendicular magnetic anisotropy, showing potential for engineering 2D magnetic materials.

Contribution

The paper reports the first observation of increased Curie temperature and magnetic anisotropy in Cr2Ge2Te6 when combined with NiO heterostructures, advancing 2D magnetism control.

Findings

Curie temperature nearly doubles to ~120 K in heterostructures.

Hysteresis loops become square with larger coercive fields.

Magnetic properties are tunable via heterostructure interface.

Abstract

Magnetism in two-dimensional van der Waals materials has received significant attention recently. The Curie temperature reported for those materials, however, has been so far remained relatively low. Here, we measure magneto-optical Kerr effects (MOKE) under perpendicular magnetic field for van der Waals ferromagnet Cr2Ge2Te6 as well as its heterostructure with antiferromagnetic insulator NiO. We observe a notable increase in both Curie temperature and magnetic perpendicular anisotropy in Cr2Ge2Te6/NiO heterostructures compared to those in Cr2Ge2Te6. Measurements on the same exfoliated Cr2Ge2Te6 flake (on a SiO2/Si substrate) before and after depositing NiO show that the hysteresis loop can change into a square shape with larger coercive field for Cr2Ge2Te6/NiO. The maximum Curie temperature (TC) observed for Cr2Ge2Te6/NiO reaches ~120 K, is nearly twice the maximum TC ~ 60 K reported for Cr2Ge2Te6 alone. Both enhanced perpendicular anisotropy and increased Curie temperature are observed for Cr2Ge2Te6 flakes with a variety of thicknesses ranging from ~5 nm to ~200 nm. The results indicate that magnetic properties of two-dimensional van der Waals magnets can be engineered and controlled by using the heterostructure interface with other materials.