[1] Tohoku Univ, WPI Adv Inst Mat Res, Sendai, Miyagi 9808577, Japan
[2] Univ Sci & Technol Beijing, Dept Mat Phys & Chem, Beijing 100083, Peoples R China
[3] E China Normal Univ, Key Lab Polar Mat & Devices, Shanghai 200062, Peoples R China
[4] Chinese Acad Sci, Inst Phys, Beijing 100080, Peoples R China
[5] Tohoku Univ, Inst Mat Res, Sendai, Miyagi 9808577, Japan
[6] USA, Res Lab, Aberdeen Proving Ground, MD 21005 USA