1. Division of Materials Physics and Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
2. Spintronics Research Network Division, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Suita, Osaka, 565-0871, Japan
3. Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
4. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
5. Department of Physics, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan