1. Nanjing Tech University
2. College of Materials Science and Engineering
3. Nanjing 210009
4. China
5. East China Normal University
6. Key Laboratory of Polar Materials and Devices
7. Shanghai 200062
8. Toyota Physical and Chemical Research Institute
9. Nagakute 480-1192
10. Japan
11. Department of Physics
12. Northwest University
13. Xi'an 710069