1. Department
of Materials Science and Engineering, University of California, Berkeley, California 94720, United States
2. Spin
Convergence Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea
3. Department
of Electronics Engineering, National Changhua University of Education, Changhua 50007, Taiwan
4. Department
of Materials Sciences and Engineering, Stanford University, Stanford, California 94305, United States
5. Energy
and Environmental Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
6. Materials
Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States