Anomalous thickness dependence of Curie temperature in air-stable two-dimensional ferromagnetic 1T-CrTe2 grown by chemical vapor deposition

TLDR

Ferromagnetic two‑dimensional van der Waals materials offer exciting physics and spintronic opportunities, yet their controllable synthesis and ambient stability remain difficult. The study aims to grow air‑stable 1T‑CrTe₂ ultrathin crystals with tunable thickness via chemical vapor deposition. Chemical vapor deposition was used to produce thickness‑controlled 1T‑CrTe₂ films, and first‑principles calculations attribute the magnetic changes to reduced Coulomb screening in the two‑dimensional limit. The films exhibit robust anomalous Hall effect, a thickness‑dependent switch of the easy axis from in‑plane to out‑of‑plane, and a monotonic rise in Curie temperature as thickness decreases from ~130 nm to ~7.6 nm.

Abstract

Abstract The discovery of ferromagnetic two-dimensional van der Waals materials has opened up opportunities to explore intriguing physics and to develop innovative spintronic devices. However, controllable synthesis of these 2D ferromagnets and enhancing their stability under ambient conditions remain challenging. Here, we report chemical vapor deposition growth of air-stable 2D metallic 1T-CrTe 2 ultrathin crystals with controlled thickness. Their long-range ferromagnetic ordering is confirmed by a robust anomalous Hall effect, which has seldom been observed in other layered 2D materials grown by chemical vapor deposition. With reducing the thickness of 1T-CrTe 2 from tens of nanometers to several nanometers, the easy axis changes from in-plane to out-of-plane. Monotonic increase of Curie temperature with the thickness decreasing from ~130.0 to ~7.6 nm is observed. Theoretical calculations indicate that the weakening of the Coulomb screening in the two-dimensional limit plays a crucial role in the change of magnetic properties.