1. School of Materials Science and Energy Engineering Foshan University Foshan 528000 P. R. China
2. Materials Science and Engineering Program and Texas Materials Institute The University of Texas at Austin Austin TX 78712 USA
3. Department of Chemistry and Biochemistry Florida State University Tallahassee FL 32306 USA
4. National High Magnetic Field Laboratory Tallahassee FL 32310 USA
5. Neutron Scattering Division Oak Ridge National Laboratory Tallahassee FL 37830 USA
6. State Key Lab of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 P. R. China