1. Department of Physics and Astronomy, Clemson University 1 , Clemson, South Carolina 29634, USA
2. NASA Goddard Space Flight Center 2 , Greenbelt, Maryland 20771, USA
3. IBM T.J. Watson Research Center 3 , Yorktown Heights, New York 10598, USA
4. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory 4 , Oak Ridge, Tennessee 37830, USA
5. Department of Physics and Astronomy, Rutgers University 5 , Newark, New Jersey 08901, USA
6. Department of Materials Science and Engineering, University of Texas in Dallas 6 , Richardson, Texas 75080, USA
7. Department of Physics, University of Maryland 7 , College Park, Maryland 20740, USA