Fei Zaiyao, Huang Bevin, Malinowski Paul, Wang Wenbo, Song Tiancheng, Sanchez Joshua, Yao Wang, Xiao Di, Zhu Xiaoyang, May Andrew F, Wu Weida, Cobden David H, Chu Jiun-Haw, Xu Xiaodong
Department of Physics, University of Washington, Seattle, WA, USA.
Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, USA.
Nat Mater. 2018 Sep;17(9):778-782. doi: 10.1038/s41563-018-0149-7. Epub 2018 Aug 13.
Discoveries of intrinsic two-dimensional (2D) ferromagnetism in van der Waals (vdW) crystals provide an interesting arena for studying fundamental 2D magnetism and devices that employ localized spins. However, an exfoliable vdW material that exhibits intrinsic 2D itinerant magnetism remains elusive. Here we demonstrate that FeGeTe (FGT), an exfoliable vdW magnet, exhibits robust 2D ferromagnetism with strong perpendicular anisotropy when thinned down to a monolayer. Layer-number-dependent studies reveal a crossover from 3D to 2D Ising ferromagnetism for thicknesses less than 4 nm (five layers), accompanied by a fast drop of the Curie temperature (T) from 207 K to 130 K in the monolayer. For FGT flakes thicker than ~15 nm, a distinct magnetic behaviour emerges in an intermediate temperature range, which we show is due to the formation of labyrinthine domain patterns. Our work introduces an atomically thin ferromagnetic metal that could be useful for the study of controllable 2D itinerant ferromagnetism and for engineering spintronic vdW heterostructures.
在范德华（vdW）晶体中发现本征二维（2D）铁磁性，为研究基本的二维磁性以及采用局域自旋的器件提供了一个有趣的领域。然而，一种表现出本征二维巡游磁性的可剥离vdW材料仍然难以捉摸。在此，我们证明了可剥离的vdW磁体FeGeTe（FGT）在减薄至单层时表现出具有强垂直各向异性的稳健二维铁磁性。层数相关研究表明，对于厚度小于4纳米（五层）的情况，从三维到二维伊辛铁磁性发生转变，同时单层中的居里温度（T）从207 K快速降至130 K。对于厚度大于约15纳米的FGT薄片，在中间温度范围内出现了独特的磁行为，我们表明这是由于迷宫状畴图案的形成所致。我们的工作引入了一种原子级薄的铁磁金属，这对于可控二维巡游铁磁性的研究以及自旋电子vdW异质结构的工程应用可能是有用的。
