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ヤマガミ ヒロシ
YAMAGAMI HIROSHI
山上 浩志 所属 京都産業大学 理学部 物理科学科 職種 教授 |
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| 言語種別 | 英語 |
| 発行・発表の年月 | 2017/09/11 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | Electronic structure and magnetic properties of magnetically dead layers in epitaxial CoFe2O4/Al2O3/Si(111) films studied by x-ray magnetic circular dichroism |
| 執筆形態 | その他 |
| 掲載誌名 | PHYSICAL REVIEW B |
| 出版社・発行元 | AMER PHYSICAL SOC |
| 巻・号・頁 | 96(10) |
| 著者・共著者 | Yuki K. Wakabayashi,Yosuke Nonaka,Yukiharu Takeda,Shoya Sakamoto,Keisuke Ikeda,Zhendong Chi,Goro Shibata,Arata Tanaka,Yuji Saitoh,Hiroshi Yamagami,Masaaki Tanaka,Atsushi Fujimori,Ryosho Nakane |
| 概要 | Epitaxial CoFe2O4/Al2O3 bilayers are expected to be highly efficient spin injectors into Si owing to the spin filter effect of CoFe2O4. To exploit the full potential of this system, understanding the microscopic origin of magnetically dead layers at the CoFe2O4/Al2O3 interface is necessary. In this paper, we study the cation distribution, electronic structures, and the magnetic properties of CoFe2O4(111) layers with various thicknesses (thickness d = 1.4, 2.3, 4, and 11 nm) in the epitaxial CoFe2O4(111)/Al2O3(111)/Si(111) structures using soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) combined with cluster-model calculation. The magnetization of CoFe2O4 measured by XMCD gradually decreases with decreasing thickness d, and finally, a magnetically dead layer is clearly detected at d = 1.4 nm. The magnetically dead layer has frustration of magnetic interactions, which is revealed from comparison between the magnetizations at 300 and 6 K. From analysis using configuration-interaction cluster-model calculation, the decrease of d leads to a decrease in the inverse-to-normal spinel structure ratio and also a decrease in the average valence of Fe at the octahedral sites. These results strongly indicate that the magnetically dead layer at the CoFe2O4/Al2O3 interface originates from various complex networks of superexchange interactions through the change in the cation distribution and electronic structure. Furthermore, from comparison of the magnetic properties between d = 1.4 and 2.3 nm, it is found that the ferrimagnetic order of the magnetically dead layer at the CoFe2O4/Al2O3 interface is partially restored by increasing the thickness from d = 1.4 to 2.3 nm. |
| DOI | 10.1103/PhysRevB.96.104410 |
| ISSN | 2469-9950/2469-9969 |
| PermalinkURL | https://link.aps.org/article/10.1103/PhysRevB.96.104410 |
| researchmap用URL | http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.96.104410/fulltext |