1. PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
2. Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
3. Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
4. Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
5. Physics Institute, University of Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
6. Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan