課題番号 ：S-16-MS-2032
利用形態 ：機器利用
利用課題名（日本語） ：原子層物質-磁性薄膜複合体のX線磁気円二色性分光
Program Title (English) ：XMCD spectroscopy of atomic layer material-magnetic thin film hybrid structures
利用者名（日本語） ：境　誠司1), 渡邉　貴弘1,2), 山田 洋一2)
Username (English) ：S. Sakai1), T. Watanabe1,2), Y. Yamada2)
所属名（日本語） ：1) 量子科学技術開発機構, 2) 筑波大学数理物質科学研究科
Affiliation (English) ：1) National Institutes for Quantum and Radiological Science and Technology,
2) Institute of Applied Physics, University of Tsukuba

１．概要（Summary ）
Tailoring magnetic properties of nanomagnets are essentially important in developing magnetic and spintronic memory devices. Recent studies have demonstrated graphene-induced perpendicular magnetic anisotropy in a ultra-thin cobalt film on graphene [1, 2] and at the interface region of graphene/Ni(111) [3]. In addition, single layer graphene and hexagonal boron nitride on Rh(111) and Ru(0001) (so-called graphene and h-BN nanomesh) have been shown to be useful as a template for fabricating regularly-arranged nanoparticles of magnetic metals [4-6] relevant to the nanoscale periodicity of the Moiré pattern.

２．実験（Experimental）
In this study, we investigated the magnetic property of Fe nanoparticles (~20 nm dimeter) deposited on h-BN nanomesh (h-BN/Ru(0001)) with X-ray magnetic dichroism (XMCD) spectroscopy. Total-electron-yield X-ray absorption (XAS) and XMCD measurements were performed at BL-4B of UVSOR III using an ultra-high-vacuum XMCD apparatus. The sample was prepared in-situ by depositing Fe on the surface of h-BN/Ru(0001). The Fe L2,3 edge XAS and XMCD were measured at low temperatures (6.8 K and 140 K) under the magnetic field up to 5 T.

３．結果と考察（Results and Discussion）
Figure 1 show (a) the Fe L2,3 edge XAS spectra of the Fe/h-BN/Ru(0001) sample measured at 6.8 K under the grazing incidence (30º) and applying the magnetic fields of ±5 T (the red and blue lines represent the spectra under the conditions of the circular x-ray vector parallel and antiparallel to the magnetic field) and the magnetic hysteresis loops at 6.8 K and 140 K under the (b) normal and (c) grazing incidence as a function of the magnetic field. A clear XMCD signals from the Fe nanoparticles were detected as shown in Fig. 1a. The Fe nanoparticles are found to be ferromagnetic and have an in-plane easy axis of magnetization as can be judged from the good coincidence between the hysteresis at 6.8 K and 140 K and the change of the curve shape depending on the incidence

direction as in Fig. 1b and 1c. The magnetic anisotropy field is roughly estimated to be 0.6 T from the intercept of the normal and grazing incidence curve, which is reasonably attributed to the shape anisotropy of the planer Fe nanoparticles (Fig. 1).

Fig. 2. (a) Fe L2,3 edge XAS spectra of 1.4 nm Fe/h-BN/Ru(0001) at 6.8 K under the grazing incidence and the hysteresis at 6.8 K and 140 K of the Fe L3 intensity under the (b) normal and (c) grazing incidence

４．その他・特記事項（Others）
[1] C. Vo-Van et al., New J. Phys. 12 (2010) 103040.
[2] J. Coraux et al., J. Phys. Chem. Lett. 3 (2012) 2059.
[3] Y. Matsumoto et al., J. Mater. Chem. C 1 (2013) 5533.
[4] F. Donati et al., Phys. Rev. Lett.113 (2014) 177201.
[5] R. Zhang et al., Phys. Rev. B 78 (2008) 165430.
[6] I. Bihuega et al., Surf. Sci. 602 (2008) L95.
[7] B. Wang et al., J. Phys. Chem. Lett. 2 (2011) 2341.

５．論文・学会発表（Publication/Presentation）
なし

６．関連特許（Patent）
なし