1. Materials Science & Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
2. Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing, China.
3. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
4. Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel.
5. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore.
6. Suzhou Research Institute, National University of Singapore, Suzhou 215123, China.