Magnetic evolution of Cr$_2$Te$_3$ epitaxially grown on graphene with post-growth annealing

TL;DR

This study explores how annealing affects the composition, structure, and magnetic properties of Cr$_{2}$Te$_{3}$ films grown on graphene, revealing phase transitions and magnetic anisotropy changes with temperature.

Contribution

It provides new insights into the thermal evolution and magnetic behavior of Cr$_{1+x}$Te$_2$ thin films on graphene, highlighting phase stability and magnetic property tuning.

Findings

Phase transition from perpendicular to in-plane magnetic anisotropy above 450°C.

Curie temperature increases from 180 K to 240-250 K after annealing.

Cr film formation occurs above 650°C.

Abstract

Two-dimensional and van der Waals ferromagnets are ideal platform to study low dimensional magnetism and proximity effects in van der Waals heterostructures. Their ultimate two dimensional character offers also the opportunity to easily adjust their magnetic properties using strain or electric fields. Among 2D ferromagnets, the Cr$_{1+x}$Te$_2$ compounds with $x$=0-1 are very promising because their magnetic properties depend on the amount of self-intercalated Cr atoms between pure CrTe$_2$ layers and the Curie temperature (T$_C$) can reach room temperature for certain compositions. Here, we investigate the evolution of the composition, structural and magnetic properties of thin Cr$_{1.33}$Te$_2$ (Cr$_2$Te$_3$) films epitaxially grown on graphene upon annealing. We observe a transition above 450{\deg}C from the Cr$_{1.33}$Te$_2$ phase with perpendicular magnetic anisotropy and a T$_C$ of 180 K to a composition close to Cr$_{1.39}$Te$_2$ with in-plane magnetic anisotropy and a T$_C$ of 240-250 K. This phase remains stable up to 650{\deg}C above which a pure Cr film starts to form. This work demonstrates the complex interplay between intercalated Cr, lattice parameters and magnetic properties in Cr$_{1+x}$Te$_2$ compounds.