[1] Univ Puerto Rico, Dept Engn Sci & Mat, Mayaguez, PR 00681 USA
[2] Univ Sci & Technol Beijing, Dept Phys, Beijing 100083, Peoples R China
[3] Capital Normal Univ, Dept Phys, Beijing 100037, Peoples R China
[4] Univ Sci & Technol Beijing, Sch Mat Sci & Engn, Beijing 100083, Peoples R China
[5] Florida State Univ, Natl High Magnet Field Lab, Tallahassee, FL 32310 USA