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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 | 2018/10/30 |
| 形態種別 | 研究論文 |
| 査読 | 査読あり |
| 標題 | Cation distribution and magnetic properties in ultrathin (Ni1-xCox)Fe2O4 (x=0-1) layers on Si(111) studied by soft x-ray magnetic circular dichroism |
| 執筆形態 | その他 |
| 掲載誌名 | PHYSICAL REVIEW MATERIALS |
| 出版社・発行元 | AMER PHYSICAL SOC |
| 巻・号・頁 | 2(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 | We study the electronic structure and the magnetic properties of epitaxial (Ni1-xCox)Fe2O4(111) layers (x = 0 - 1) with thicknesses d = 1.7 - 5.2 nm grown on Al2O3(111)/Si(111) structures, to achieve a high value of inversion parameter y, which is the inverse-to-normal spinel-structure ratio, and hence to obtain good magnetic properties even when the thickness is thin enough for electron tunneling as a spin filter. We revealed the crystallographic (octahedral O-h or tetrahedral T-d) sites and the valences of the Fe, Co, and Ni cations using experimental soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism spectra and configuration-interaction cluster-model calculation. In all the (Ni1-xCox)Fe2O4 layers with d = about similar to 4 nm, all Ni cations occupy the Ni2+ (O-h) site, whereas Co cations occupy the three different Co2+ (O-h), Co2+ (T-d), and Co3+ (O-h) sites with constant occupancies. According to these features, the occupancy of the Fe3+ (O-h) cations decreases and that of the Fe3+ (T-d) cations increases with decreasing x. Consequently, we obtained a systematic increase of y with decreasing x and achieved the highest y value of 0.91 for the NiFe2O4 layer with d = 3.5 nm. From the d dependences of y and magnetization in the d range of 1.7 - 5.2 nm, a magnetically dead layer is present near the NiFe2O4/Al2O3 interface, but its influence on the magnetization was significantly suppressed compared with the case of CoFe2O4 layers reported previously [Y. K. Wakabayasi et al., Phys. Rev. B 96, 104410 (2017)], due to the high site selectivity of the Ni cations. Since our epitaxial NiFe2O4 layer with d = 3.5 nm has a high y values (0.91) and a reasonably large magnetization (180 emu/cc), it is expected to exhibit a strong spin filter effect, which can be used for efficient spin injection into Si. |
| DOI | 10.1103/PhysRevMaterials.2.104416 |
| ISSN | 2475-9953/2475-9953 |
| PermalinkURL | https://link.aps.org/accepted/10.1103/PhysRevMaterials.2.104416 |
| researchmap用URL | https://link.aps.org/article/10.1103/PhysRevMaterials.2.104416 |