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Acta Metall Sin  2018, Vol. 54 Issue (9): 1281-1288    DOI: 10.11900/0412.1961.2017.00492
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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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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 words:  CoFeB thin film      stripe magnetic domain      ferromagnetic resonance      oblique sputtering      rotational magnetic anisotropy     
Received:  27 November 2017     
ZTFLH:  O469  
Fund: Supported by National Natural Science Foundation of China (Nos.11674336, 51522105, 51525103 and 11627801), National Key Research and Development Program of China (No.2016YFA0201102) and Ningbo Science and Technology Innovation Team (No.2015B11001)

Cite this article: 

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.

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Fig.1  Schematic of fabricating amorphous CoFeB magnetic films at oblique incidence (β is the oblique sputtering angle; HA and EA represent the hard and easy axes caused by oblique sputtering, respectively)
Fig.2  XRD spectra for CoFeB thin films fabricated at different oblique angles (β)
Fig.3  Cross-section TEM image (a) and SAED pattern (b) of CoFeB thin films grown at β=0°
Fig.4  Normalized hysteresis loops of CoFeB films grown at β=0° (a), β=30° (b), β=45°(c), β=60° (d), and the corresponding magnetic domains in a scanning area of 10 μm×10 μm (insets) (M/Ms—normalized magnetization, H—magnetic field intensity)
Fig.5  Angular dependence of the remanence ratio for CoFeB films grown at different oblique angles (Mr/Ms—remanence ratio, θ—angle between the magnetic field and the in-plane static magnetic anisotropy)
Fig.6  Schematic of ferromagnetic resonance measurement in different orientations of magnetic field (Hp—microwave magnetic field)
Fig.7  Angular dependence of the ferromagnetic resonance fields for CoFeB films grown at β=0o (a), β=30o (b), β=45o (c) and β=60o (d) (Hr—ferromagnetic resonance field intensity)
Fig.8  Angular dependence of the ferromagnetic resonance field intensity for CoFeB films grown at different oblique angles (M—magnetization, θH—angle between the magnetic field and the normal direction of film surface, θM—angle between the magnetization and the normal direction of the film surface) (a) and cross-section SEM image of the CoFeB film prepared at β=60o (b)
Fig.9  Stripe magnetic domains of CoFeB thin films with different thicknesses of 180 nm (a), 200 nm (b), 240 nm (c) and 300 nm (d) grown at β=45o
[1] Phuoc N N, Ong C K.Anomalous temperature dependence of magnetic anisotropy in gradient-composition sputterred thin films[J]. Adv. Mater., 2013, 25: 980
[2] Wei J W, Wang J B, Liu Q F, et al.An induction method to calculate the complex permeability of soft magnetic films without a reference sample[J]. Rev. Sci. Instrum., 2014, 85: 054705
[3] Phuoc N N, Ong C K.Tailoring thermal stability behaviour of magnetic thin films by hybrid oblique gradient-composition sputtering[J]. J. Phys., 2013, 46D: 485002
[4] Kittel C.Interpretation of anomalous larmor frequencies in ferromagnetic resonance experiment[J]. Phys. Rev., 1947, 71: 270
[5] Ziberi B, Frost F, H?che T, et al.Ripple pattern formation on silicon surfaces by low-energy ion-beam erosion: Experiment and theory[J]. Phys. Rev., 2005, 72B: 235310
[6] Lisfi A, Lodder J C, Wormeester H, et al.Reorientation of magnetic anisotropy in obliquely sputtered metallic thin films[J]. Phys. Rev., 2002, 66B: 174420
[7] Fan X L, Xue D S, Lin M, et al.In situ fabrication of Co90Nb10 soft magnetic thin films with adjustable resonance frequency from 1.3 to 4.9 GHz[J]. Appl. Phys. Lett., 2008, 92: 222505
[8] Yang Y, Liu B L, Tang D M, et al.Influence of the magnetic field annealing on the extrinsic damping of FeCoB soft magnetic films[J]. J. Appl. Phys., 2010, 108: 073902
[9] Viala B, Inturi V R, Barnard J A.Effect of magnetic annealing on the behavior of FeTaN films[J]. J. Appl. Phys., 1997, 81: 4498
[10] Nogués J, Schuller I K.Exchange bias[J]. J. Magn. Magn. Mater., 1999, 192: 203
[11] Phuoc N N, Chai G Z, Ong C K.Enhancing exchange bias and tailoring microwave properties of FeCo/MnIr multilayers by oblique deposition[J]. J. Appl. Phys., 2012, 112: 113908
[12] Acher O, Dubourg S.Generalization of Snoek's law to ferromagnetic films and composites[J]. Phys. Rev., 2008, 77B: 104440
[13] Iakubov I T, Lagarkov A N, Maklakov S A, et al.Microwave permeability of composites filled with thin Fe films[J]. J. Magn. Magn. Mater., 2006, 300: e74
[14] Perrin G, Acher O, Peuzin J C, et al. Sum rules for gyromagnetic permeability of ferromagnetic thin films: Theoretical and experimental results [J]. J. Magn. Magn. Mater., 1996, 157-158: 289
[15] Chai G Z, Phuoc N N, Ong C K.Exchange coupling driven omnidirectional rotatable anisotropy in ferrite doped CoFe thin film[J]. Sci. Rep., 2012, 2: 832
[16] Wei J W, Zhu Z T, Feng H M, et al.Top-down control of dynamic anisotropy in permalloy thin films with stripe domains[J]. J. Phys., 2015, 48D: 465001
[17] Chai G Z, Phuoc N N, Ong C K.High thermal stability of zero-field ferromagnetic resonance above 5?GHz in ferrite-doped CoFe thin films[J]. Appl. Phys. Lett., 2013, 103: 042412
[18] Zhou C, Wei W W, Jiang C J.Regulated magnetic domains and high-frequency property in magnetic materials with columnar structure[J]. Appl. Phys., 2015, 121A: 39
[19] Singh G, Rout P K, Porwal R, et al.Strain induced magnetic domain evolution and spin reorientation transition in epitaxial manganite films[J]. Appl. Phys. Lett., 2012, 101: 022411
[20] Tee Soh W, Phuoc N N, Tan C Y, et al.Magnetization dynamics in permalloy films with stripe domains[J]. J. Appl. Phys., 2013, 114: 053908
[21] Fin S, Tomasello R, Bisero D, et al.In-plane rotation of magnetic stripe domains in Fe1-xGax thin films[J]. Phys. Rev., 2015, 92B: 224411
[22] Li C Y, Chai G Z, Yang C C, et al.Tunable zero-field ferromagnetic resonance frequency from S to X band in oblique deposited CoFeB thin films[J]. Sci. Rep., 2015, 5: 17023
[23] Yu J, Chang C, Karns D, et al.Thermal annealing effect on FeCoB soft underlayer for perpendicular magnetic recording[J]. J. Appl. Phys., 2002, 91: 8357
[24] Sharma P, Kimura H, Inoue A, et al.Temperature and thickness driven spin-reorientation transition in amorphous Co-Fe-Ta-B thin films[J]. Phys. Rev., 2006, 73B: 052401
[25] Co?sson M, Vinai F, Tiberto P, et al.Magnetic properties of FeSiB thin films displaying stripe domains[J]. J. Magn. Magn. Mater., 2009, 321: 806
[26] Zhan Q F, van Haesendonck C, Vandezande S, et al. Surface morphology and magnetic anisotropy of Fe/MgO(001) films deposited at oblique incidence[J]. Appl. Phys. Lett., 2009, 94: 042504
[27] Wang G X, Dong C H, Wang W X, et al.Observation of rotatable stripe domain in permalloy films with oblique sputtering[J]. J. Appl. Phys., 2012, 112: 093907
[28] Chen Y T, Xie S M.Magnetic and electric properties of amorphous Co40Fe40B20 thin films[J]. J. Nanomater., 2012, 2012: 486284
[29] Saravanan L, Raja M M, Prabhu D, et al.Effect of thickness on tuning the perpendicular coercivity of Ta/CoFeB/Ta trilayer[J]. J. Mater. Sci.: Mater. Electron., 2018, 29: 336
[30] Youssef J B, Vukadinovic N, Billet D, et al.Thickness-dependent magnetic excitations in Permalloy films with nonuniform magnetization[J]. Phys. Rev., 2004, 69B: 170002
[31] Zhou C, Jiang C J, Zhao Z.Enhancement of rotatable anisotropy in ferrite doped FeNi thin film with oblique sputtering[J]. J. Phys., 2015, 48D: 265001
[1] HE Zhengming;XU Fang;LUO Youquan;LU Guorong University of Science and Technology of China; Hefei. UNIAXIAL ANISOTROPY IN FeNiCuMnCosiP AMORPHOUS ALLOY RIBBON[J]. 金属学报, 1991, 27(2): 99-103.
[2] BI Siyun;MA Xiaoding;SONG Ruitian;MEI Liangmo;ZHAO Jiangao;GUO Yicheng Shandong University; Jinan. STRUCTURE AND FERROMAGNETIC RESONANCE OF METAL Fe/Cu SUPERLATTICES[J]. 金属学报, 1990, 26(5): 131-136.
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