Laboratoire Leon Brillouin;
UMR12 CEA-CNRS;
C.E.Saclay;
91191 Gif sur Yvette Cedex;
France;
Laboratoire de Physique des Solides;
CNRS UMR 8502;
Universite Paris-Sud;
Batiment 510;
91405 Orsay CEDEX;
France;
Institut Curie;
Centre de Recherche;
CNRS UMR168;
Universite Pierre et Marie Curie;
26 rue d'Ulm;
75248 Paris CEDEX 05;
France;
Department of Chemical Engineering;
School of Materials Science and Engineering;
Tsinghua University;
Beijing 100084;
China;