1. Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, USA
2. Department of Physics and Institute of Materials Science and Engineering, Washington University, St. Louis, Missouri 63130, USA
3. Department of Physics, Nanchang University, Nanchang 330031, China
4. Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
5. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
6. Department of Physics, University of California, Berkeley, California 94720, USA
7. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA