1. Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, Japan
2. Department of Physics, Graduate School of Science, Kobe University, Kobe 675-0013, Japan
3. Center for Spintronics Research Network, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
4. Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
5. JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan