[1] Beihang Univ, Ctr Condensed Matter & Mat Phys, Key Lab Micronaro Measurement Manipulat & Phys, Beijing 100191, Peoples R China
[2] Univ Minnesota, Ctr Micromagnet & Informat Technol, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA
[3] Chinese Acad Sci, Inst Phys, Beijing 100191, Peoples R China