1. Department of Physics, University of California, Berkeley, CA 94720, USA.
2. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
3. Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.
4. Fakultät für Physik, Ludwig-Maximilians-Universität München, 80799 Munich, Germany.
5. Department of Aerospace Engineering, Iowa State University, Ames, IA 50011, USA.
6. Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.
7. Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA.
8. Ames Laboratory, Division of Materials Science and Engineering, Ames, IA 50011, USA.