1. Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
2. National Institute of Advance Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Ibaraki 305-8568, Japan
3. Institute of Materials Science (IMS), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam