1. Quantum Spin Team Korea Research Institute of Standards and Science Daejeon 34113 Republic of Korea
2. Center for Spintronics Korea Institute of Science and Technology Seoul 02792 Republic of Korea
3. Institute for Chemical Research Kyoto University Kyoto Japan
4. Nanoscale Semiconductor Engineering Hanyang University Seoul 02792 Republic of Korea
5. Department of Physics Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea