1. Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR8580, Ecole Centrale Paris, Grande voie des vignes, 92290 Châtenay-Malabry, France
2. Physics Department, University of Arkansas, Fayetteville, Arkansas 72701
3. Department of Physics, University of South Florida, Tampa, Florida, 33620
4. Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland