Controlling the magnetic properties of layered Cr₂Te₃ thin films via ex-situ annealing

We present a post-growth ex-situ annealing method to control the Curie temperature and magnetic anisotropy of Cr₂Te₃ van der Waals ferromagnetic thin films. The as-grown Cr₂Te₃ films exhibit a Curie temperature ∼ 170 K with an out-of-plane magnetic easy axis. Upon high temperature (300 – 400 °C) ex-situ annealing, the magnetic phase of the film changes: the Curie temperature is significantly increased to ∼ 300 K and the magnetic easy axis is reoriented to the in-plane direction. Electronic, chemical, and structural analyses suggest that the c-axis lattice constant expansion, accompanying the annealing process, is the origin of the ex-situ-annealing-induced modulation of the Cr₂Te₃ film magnetic properties. These results demonstrate that a practical ex-situ annealing process can be effectively used to control the magnetic properties of van der Waals ferromagnetic thin films. Furthermore, the room temperature ferromagnetic ordering emerging upon annealing, along with its robustness against post-growth thermal processes, suggests that the Cr₂Te₃ thin film is a promising magnetic material candidate for potential application in van-der-Waals-material-based spintronic devices.