DepartmentofPhysicsandAstronomy;
UniversityofDelaware;
Newark;
DE19716;
USA;
BeijingLaboratoryofElectronMicroscopy;
InstituteofPhysics;
ChineseAcademyofSciences;
Beijing100080;
StateKeyLaboratoryforMagnetism;
InstituteofPhysics;
ChineseAcademyofSciences;
Beijing100080;
BeijingLaboratoryofElectronMicroscopy;
InstituteofPhysics;
ChineseAcademyofSciences;
Beijing100080//DepartmentofMaterialsSciencesandEngineering;
BeijingUniversityofTechnology;
Beijing100022;