Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Department of Physics Institute of Solid Solid State Physics Nanjing University Nanjing 210093;
Institute for Materials Research Tohoku University Sendai 980 Japan;
Institute for Materials Research Tohoku University Sendai 980 Japan;