* Corresponding authors

^a National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
E-mail: ryu@tsinghua.edu.cn

^b Department of Physics, Beijing Engineering Research Center of Detection and Application for Weak Magnetic Field, University of Science and Technology Beijing, Beijing 100083, China
E-mail: meng7707@sas.ustb.edu.cn

^c State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China