1. KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
2. Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Korea
3. Department of Electrical Engineering, Korea University, Seoul 02841, Korea
4. Spin Engineering Physics Team, Korea Basic Science Institute, Daejeon 34133, Korea
5. Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
6. Division of Nano and Information Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea