1. Laboratoire CRISMAT UMR 6508 CNRS ENSICAEN, 6 boulevard du Maréchal Juin, 14050 Cedex 04 Caen, France
2. Department
of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, United States
3. Institute
of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium