The Preparation of High Saturation Magnetization and Low Coercivity Feco Soft Magnetic Thin Films via Controlling the Thickness and Deposition Temperature

Wenjie Yang; Junjie Liu; Xiangfeng Yu; Gang Wang; Zhigang Zheng; Jianping Guo; Deyang Chen; Zhaoguo Qiu; Dechang Zeng

doi:10.3390/ma15207191

The Preparation of High Saturation Magnetization and Low Coercivity Feco Soft Magnetic Thin Films via Controlling the Thickness and Deposition Temperature

Materials (Basel). 2022 Oct 15;15(20):7191. doi: 10.3390/ma15207191.

Authors

Wenjie Yang^{1

2}, Junjie Liu^{1

2}, Xiangfeng Yu^{1

2}, Gang Wang^{1

2

3}, Zhigang Zheng^{1

2

3}, Jianping Guo⁴, Deyang Chen⁴, Zhaoguo Qiu^{1

2

3}, Dechang Zeng^{1

2

3}

Affiliations

¹ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.
² Zhongshan R&D Center for Materials Surface and Thin Films Technology of the South China University of Technology, Gent Materials Surface Technology (Guangdong) Co., Ltd., Zhongshan 528437, China.
³ Yangjiang Branch, Guangdong Laboratory Materials Science and Technology Yangjiang Advanced Alloys Laboratory, Yangjiang 529500, China.
⁴ Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China.

Abstract

FeCo thin films with high saturation magnetization (4 πM_s) can be applied in high-frequency electronic devices such as thin film inductors and microwave noise suppressors. However, due to its large magnetocrystalline anisotropy constant and magnetostrictive coefficient of FeCo, the coercivity (H_c) of FeCo films is generally high, which is detrimental to the soft magnetic properties. Meanwhile, the thickness and deposition temperature have significant effects on the coercivity and saturation magnetization of FeCo films. In this paper, FeCo thin films with different thicknesses were prepared by magnetron sputtering at different temperatures. The effects of thickness and deposition temperature on the microstructure and magnetic properties of FeCo thin films were systematically studied. When the film thickness increases from 50 nm to 800 nm, the coercivity would decrease from 309 Oe to 160 Oe. However, the saturation magnetization decreases from 22.1 kG to 15.3 kG. After that, we try to further increase the deposition temperature from room temperature (RT) to 475 °C. It is intriguing to find that the coercivity greatly decreased from 160 Oe to 3 Oe (decreased by 98%), and the saturation magnetization increased from 15.3 kG to 23.5 kG (increased by 53%) for the film with thickness of 800 nm. For the film with thickness of 50 nm, the coercivity also greatly decreased from 309 Oe to 10 Oe (decreased by 96%), but the saturation magnetization did not change significantly. It is contributed to the increase of deposition temperature, which will lead to the increase of grain size and the decrease of the number of grain boundaries. And the coercivity decreases as the number of grain boundaries decreases. Meanwhile, for the thicker films, when increasing the deposition temperature the thermal stress increases, which changes the appearance of (200) texture, and the saturation magnetization increases. Whereas, it has a negligible effect on the orientation of thin films with small thickness (50 nm). This indicates that high-temperature deposition is beneficial to the soft magnetic properties of FeCo thin films, particularly for the films with larger thickness. This FeCo thin film with high saturation magnetization and low coercivity could be an ideal candidate for high-frequency electronic devices.

Keywords: FeCo thin film; coercivity; deposition temperature; saturation magnetization; thickness.

Grants and funding

This work was supported by National Natural Science Foundation of China (51901079), Guangdong Basic and Applied Basic Research Foundation (2019A1515010857, 2020A1515010736), Guangzhou Municipal Science and Technology Program (202007020008, 202102020596), Zhongshan Collaborative Innovation Fund (2018C1001), and the Opening Project of National Engineering Research Center for Powder Metallurgy of Titanium & Rare Metals.