1. Physics Department Federal University of Sergipe São Cristóvão Sergipe 49100‐000 Brazil
2. Department of Materials Science and Engineering and Department of Physics University of California Berkeley CA 94720 USA
3. Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
4. Department of Materials Science and Engineering NTNU Norwegian University of Science and Technology Norway
5. Department of Materials Science and Engineering Cornell University Ithaca NY 15805 USA
6. Department of Materials Science and Engineering Pennsylvania State University University Park PA 16802 USA