1. Research Institute for Magnetoelectronics and Nano-Magnetic Field Detection and College of Science, China Three Gorges University, Yichang 443002, People's Republic of China
2. Department of Physics, Chungbuk National University, Cheongju, Chungbuk 28644, South Korea
3. Spin Engineering Physics Team, Korea Basic Science Institute, Daejeon 34133, South Korea
4. Research Institute for Nanoscale Science and Technology, Chungbuk National University, Cheongju, Chungbuk 28644, South Korea