1. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501, USA
2. Department of Applied Physics, Stanford University, Stanford, California 94305, USA
3. Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, (GREYC-UMR 6072), CNRS-ENSICAEN—Université de Caen Basse-Normandie, 6 Boulevard Maréchal Juin, 14050 Caen Cedex, France
4. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
5. Laboratoire de Sciences des Procédés et des Matériaux, UPR3407, CNRS, Institut Galilee, Universite Paris-Nord, Villetaneuse, France
6. Peter Grünberg Institute (PGI9-IT), JARA-Fundamentals of Future Information Technology, Research Centre Jülich, Jülich D-52425, Germany
7. Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
8. Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
9. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853-1501, USA