1. Institute of Materials Science, Vietnam Academy of Science and Technology, 100000 Hanoi, Vietnam
2. Thai Nguyen University of Science, 250000 Thai Nguyen, Vietnam
3. Department of Electrical Engineering, TELEMIC group, KU Leuven, 3001 Leuven, Belgium
4. Laboratory of Solid State Physics and Magnetism, KU Leuven, 3001 Leuven, Belgium