Short-range ferromagnetic interaction in a monolayer VSe film revealed by element-specific X-ray magnetic circular dichroism

元素選択的磁気円二色性による単層VSe薄膜の短距離強磁性相互作用の観測

角田 一樹   ; 竹田 幸治   ; 日下 翔太郎*; 小林 功佳*; 平原 徹*

Sumida, Kazuki; Takeda, Yukiharu; Kusaka, Shotaro*; Kobayashi, Katsuyoshi*; Hirahara, Toru*

Since the discovery of graphene, atomically thin two-dimensional van der Waals (2D vDW) materials have attracted a great deal of attention due to their rich properties. In 2018, the presence of the long-range ferromagnetic ordering in the monolayer VSe was reported. Remarkably, the recorded Curie temperature of the monolayer VSe film exceeded the room temperature. However, soon after the discovery of strong ferromagnetism, a number of controversial results emerged. In this work, we investigated the intrinsic magnetic properties and electronic structures of the monolayer and multilayer VSe films by means of ARPES, first-principles calculations, and XMCD measurements. We succeeded in detecting a clear XMCD signal from the atomically thin VSe films under a magnetic field. By manipulating the incidence angle of the X-ray, we were able to disentangle the in-plane and out-of-plane magnetic properties and found a strong magnetic anisotropy. Moreover, temperature-dependent XMCD revealed that there is no long-range ferromagnetic ordering even at 6 K, but short-range ferromagnetic interactions between vanadium ions exist in the two-dimensional plane.