High-<i>T</i><sub><i>c</i></sub> Ferromagnetic Semiconductor in Thinned 3D Ising Ferromagnetic Metal Fe<sub>3</sub>GaTe<sub>2</sub>.

Chen, Zhaoxu; Yang, Yuxin; Ying, Tianping; Guo, Jian-Gang · Nano Lett · 2024

basic_science · Level V

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Abstract

Emergent phenomena in exfoliated layered transition metal compounds have attracted much attention in the past several years. Especially, pursuing a ferromagnetic insulator is one of the exciting goals for stimulating a high-performance magnetoelectrical device. Here, we report the transition from a metallic to high-<i>T</i><sub><i>c</i></sub> semiconductor-like ferromagnet in thinned Fe<sub>3</sub>GaTe<sub>2</sub>, accompanied with competition among various magnetic interactions. As evidenced by critical exponents, Fe<sub>3</sub>GaTe<sub>2</sub> is the first layered ferromagnet described by a 3D Ising model coupled with long-range interactions. An extra magnetic phase from competition between ferromagnetism and antiferromagnetism emerges at a low field below <i>T</i><sub><i>c</i></sub>. Upon reducing thickness, the Curie temperature (<i>T</i><sub><i>c</i></sub>) monotonically decreases from 342 K for bulk to 200 K for 1-3 nm flakes, which is the highest <i>T</i><sub><i>c</i></sub> reported as far as we know. Furthermore, a semiconductor-like behavior has been observed in such 1-3 nm flakes. Our results highlight the importance of Fe<sub>3</sub>GaTe<sub>2</sub> in searching for ferromagnetic insulators, which may benefit spintronic device fabrication.