Evidence of Ferromagnetism and Ultrafast Dynamics of Demagnetization in an Epitaxial FeCl<sub>2</sub> Monolayer.

Zhou, Xuhan; Jiang, Tianran; Tao, Ye; Ji, Yi; Wang, Jingying; Lai, Tianshu; Zhong, Dingyong · ACS Nano · 2024

basic_science · Level V

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Abstract

The development of two-dimensional (2D) magnetism is driven not only by the interest of low-dimensional physics but also by potential applications in high-density miniaturized spintronic devices. However, 2D materials possessing a ferromagnetic order with a relatively high Curie temperature (<i>T</i><sub>c</sub>) are rare. In this paper, the evidence of ferromagnetism in monolayer FeCl<sub>2</sub> on Au(111) surfaces, as well as the interlayer antiferromagnetic coupling of bilayer FeCl<sub>2</sub>, is characterized by using spin-polarized scanning tunneling microscopy. A Curie temperature (<i>T</i><sub>c</sub>) of ∼147 K is revealed for monolayer FeCl<sub>2</sub>, based on our static magneto-optical Kerr effect measurements. Furthermore, temperature-dependent magnetization dynamics is investigated by the time-resolved magneto-optical Kerr effect. A transition from one- to two-step demagnetization occurs as the lattice temperature approaches <i>T</i><sub>c</sub>, which supports the Elliott-Yafet spin relaxation mechanism. The findings contribute to a deeper understanding of the underlying mechanisms governing ultrafast magnetization in 2D ferromagnetic materials.