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金属学报  2018, Vol. 54 Issue (9): 1281-1288    DOI: 10.11900/0412.1961.2017.00492
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倾斜溅射对CoFeB薄膜条纹磁畴结构与磁各向异性的影响
马晓琴1,2, 詹清峰2,3(), 李金财2, 刘青芳1, 王保敏2, 李润伟2
1 兰州大学物理科学与技术学院磁学与磁性材料教育部重点实验室 兰州 730000
2 中国科学院宁波材料技术与工程研究所浙江省磁性材料及其应用技术重点实验室 中国科学院磁性材料与器件重点实验室 宁波 315201
3 华东师范大学物理与材料科学学院精密光谱科学与技术国家重点实验室 上海 200241
Influence of Oblique Sputtering on Stripe Magnetic Domain Structure and Magnetic Anisotropy of CoFeB Thin Films
Xiaoqin MA1,2, Qingfeng ZHAN2,3(), Jincai LI2, Qingfang LIU1, Baomin WANG2, Runwei LI2
1 Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, School of Physical Sciences and Technology, Lanzhou University, Lanzhou 730000, China
2 Key Laboratory of Magnetic Materials and Devices, Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
3 State Key Laboratory of Precision Spectroscopy, School of Physics and Materials Science, East China Normal University, Shanghai 200241, China
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摘要: 

利用倾斜溅射的方法制备了非晶CoFeB磁性薄膜,研究了倾斜溅射对非晶CoFeB磁性薄膜条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律。结果表明,倾斜溅射可以有效地降低CoFeB非晶薄膜条纹磁畴结构出现的临界厚度,无倾斜溅射时,CoFeB薄膜出现条纹磁畴结构的临界厚度大于240 nm,倾斜溅射时,出现条纹磁畴结构的临界厚度小于240 nm。磁性测试结果表明,对于具有条纹磁畴结构的CoFeB薄膜,倾斜溅射不仅可以提高磁性薄膜的面内静态磁各向异性的强度,同时还可以增强面内转动磁各向异性与垂直磁各向异性的强度。随着倾斜溅射角度的逐渐增大,磁各向异性的强度均呈现增大的趋势。XRD和TEM观测结果证明,CoFeB薄膜趋于非晶结构,同时,SEM观察结果表明,CoFeB薄膜虽然不存在长程有序的晶体结构,但依然可以形成柱状结构,由于倾斜溅射技术,形成的柱状结构呈倾斜状态,从而增强了薄膜的垂直磁各向异性,导致条纹磁畴结构的出现。

关键词 CoFeB薄膜条纹磁畴铁磁共振倾斜溅射转动磁各向异性    
Abstract

Magnetic anisotropy is one of the most important fundamental properties of magnetic thin film. The strength of magnetic anisotropy determines the ferromagnetic resonance frequency of magnetic films in the high-frequency applications. Because of the directionality of conventional static magnetic anisotropy in magnetic film, the high-frequency device usually shows an obvious directionality. When the microwave magnetic ?eld deviates from the perpendicular direction of magnetic anisotropy, the devices cannot reveal their best performance. The magnetic ?lm with a stripe magnetic domain structure displays an in-plane rotatable magnetic anisotropy, which can be an important strategy to solve the problem of magnetic ?eld orientation dependent performance in high-frequency device. Therefore, the magnetic domain, the magnetic anisotropy, and the high-frequency behaviors for magnetic ?lms with a stripe magnetic domain structure have received extensive attention. Previously, most of the studies focused on the stripe magnetic domain structure of polycrystalline thin films. However, less attention was paid on amorphous magnetic thin films. Since the amorphous magnetic films have no long-range ordered crystal structure, no magnetocrystalline anisotropy, no grain boundary defects resistance hindering the domain wall displacement, they usually show excellent soft magnetic properties and have been widely applied in high-frequency devices. CoFeB alloy is one of the most important amorphous magnetic materials and has been extensively applied in various spintronic devices. In this work, amorphous CoFeB magnetic thin films were prepared by using a method of oblique sputtering technique at room temperature. The influences of oblique sputtering on the stripe magnetic domain structure, the in-plane static magnetic anisotropy, the in-plane rotational magnetic anisotropy, and the perpendicular magnetic anisotropy of the amorphous CoFeB films were studied by scanning probe microscope, vibrating sample magnetometer, ferromagnetic resonance. It is found that the method of oblique sputtering could effectively reduce the critical thickness for the appearance of stripe magnetic domain in amorphous CoFeB films. For a non-oblique sputtered CoFeB film, the critical thickness for the appearance of the stripe magnetic domain is above 240 nm. In contrast, after been subjected to the oblique sputtering, the critical thickness becomes below 240 nm. The different magnetic characterizations indicate that for the growth of CoFeB films with stripe magnetic domain structure, the oblique sputtering could not only enhance the strength of in-plane static magnetic anisotropy, but also improve the in-plane rotational magnetic anisotropy and the perpendicular magnetic anisotropy. All of the magnetic anisotropies are increased with the angle of oblique sputtering. The observation results of XRD and TEM prove that the prepared CoFeB thin films tend to amorphous structure. The characterization of SEM observation indicates that although the amorphous CoFeB films do not possess long-range ordered crystalline structure, they still could form a kind of columnar structure. The slanted columnar structure of CoFeB films could significantly increase the perpendicular magnetic anisotropy, thus lead to the appearance of stripe magnetic domain structure.

Key wordsCoFeB thin film    stripe magnetic domain    ferromagnetic resonance    oblique sputtering    rotational magnetic anisotropy
收稿日期: 2017-11-27     
ZTFLH:  O469  
基金资助:国家自然科学基金项目 Nos.11674336、51522105、51525103和11627801,国家重点研发计划项目No.2016YFA0201102和宁波市科技创新团队项目No.2015B11001
作者简介: 作者简介 马晓琴,女,1990年生,硕士生

引用本文:

马晓琴, 詹清峰, 李金财, 刘青芳, 王保敏, 李润伟. 倾斜溅射对CoFeB薄膜条纹磁畴结构与磁各向异性的影响[J]. 金属学报, 2018, 54(9): 1281-1288.
Xiaoqin MA, Qingfeng ZHAN, Jincai LI, Qingfang LIU, Baomin WANG, Runwei LI. Influence of Oblique Sputtering on Stripe Magnetic Domain Structure and Magnetic Anisotropy of CoFeB Thin Films. Acta Metall Sin, 2018, 54(9): 1281-1288.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2017.00492      或      https://www.ams.org.cn/CN/Y2018/V54/I9/1281

图1  利用倾斜溅射制备CoFeB磁性薄膜的示意图
图2  不同倾斜溅射角度(β)下制备的CoFeB薄膜的XRD谱
图3  无倾斜溅射(β=0°)的CoFeB薄膜截面的TEM像和SAED花样
图4  不同倾斜溅射角度下生长的CoFeB薄膜的磁滞回线及相应的磁畴图
图5  不同倾斜溅射角度下生长的CoFeB薄膜的磁滞回线剩磁比(Mr/Ms)随磁场与面内静态磁各向异性方向的夹角(θ)的变化关系
图6  不同磁场方向下的铁磁共振测量示意图
图7  不同倾斜溅射角度下生长的CoFeB薄膜的铁磁共振场强度随磁场与θ的变化关系
图8  不同倾斜溅射角度下制备的CoFeB薄膜的铁磁共振场强度随磁场与膜面法线方向间的夹角(θH)的变化关系及倾斜溅射角度为60°时CoFeB薄膜的断面形貌像
图9  倾斜溅射角为45°时生长的不同厚度的CoFeB薄膜的条纹磁畴结构
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