Direct observation of high spin polarization in Co2FeAl thin films

Xiaoqian Zhang; Huanfeng Xu; Bolin Lai; Qiangsheng Lu; Xianyang Lu; Yequan Chen; Wei Niu; Chenyi Gu; Wenqing Liu; Xuefeng Wang; Chang Liu; Yuefeng Nie; Liang He; Yongbing Xu

doi:10.1038/s41598-018-26285-9

Direct observation of high spin polarization in Co₂FeAl thin films

Sci Rep. 2018 May 23;8(1):8074. doi: 10.1038/s41598-018-26285-9.

Authors

Xiaoqian Zhang¹, Huanfeng Xu¹, Bolin Lai¹, Qiangsheng Lu^{2

3}, Xianyang Lu⁴, Yequan Chen¹, Wei Niu¹, Chenyi Gu⁵, Wenqing Liu^{1

4}, Xuefeng Wang¹, Chang Liu², Yuefeng Nie⁵, Liang He⁶, Yongbing Xu^{7

8}

Affiliations

¹ Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China.
² Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China.
³ Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA.
⁴ York-Nanjing Joint Centre (YNJC) for spintronics and nano engineering, Department of Electronics, The University of York, York, YO10 3DD, United Kingdom.
⁵ National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
⁶ Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China. heliang@nju.edu.cn.
⁷ Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China. ybxu@nju.edu.cn.
⁸ York-Nanjing Joint Centre (YNJC) for spintronics and nano engineering, Department of Electronics, The University of York, York, YO10 3DD, United Kingdom. ybxu@nju.edu.cn.

Abstract

We have studied the Co₂FeAl thin films with different thicknesses epitaxially grown on GaAs (001) by molecular beam epitaxy. The magnetic properties and spin polarization of the films were investigated by in-situ magneto-optic Kerr effect (MOKE) measurement and spin-resolved angle-resolved photoemission spectroscopy (spin-ARPES) at 300 K, respectively. High spin polarization of 58% (±7%) was observed for the film with thickness of 21 unit cells (uc), for the first time. However, when the thickness decreases to 2.5 uc, the spin polarization falls to 29% (±2%) only. This change is also accompanied by a magnetic transition at 4 uc characterized by the MOKE intensity. Above it, the film's magnetization reaches the bulk value of 1000 emu/cm³. Our findings set a lower limit on the thickness of Co₂FeAl films, which possesses both high spin polarization and large magnetization.