1. State Key Laboratory of Material Processing and Die & Mould TechnologySchool of Materials Science and EngineeringHuazhong University of Science and Technology Wuhan Hubei 430074 China
2. Center for Functional NanomaterialsBrookhaven National Laboratory Upton NY 11973 USA
3. Frontier Institute of ChemistryFrontier Institute of Science and Technology jointly with College of ScienceXi'an Jiaotong University Xi'an Shanxi 710054 China
4. Department of Physics and AstronomyCalifornia State University Northridge CA 91330 USA
5. Current address: School of Physical Science and TechnologyInner Mongolia University Hohhot Inner Mongolia 010021 China
6. Faculty of Materials Science and ChemistryChina University of Geosciences Wuhan Hubei 430074 China
7. College of Materials Science and EngineeringChangsha University of Science and Technology Changsha 410114 China
8. School of Materials Science and Engineering & National Institute for Advanced MaterialsNankai University Tianjin 300350 China
9. Current address: Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences Beijing 100190 China