[1] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China
[2] Chinese Acad Sci, Int Ctr Mat Phys, Shenyang 110016, Peoples R China
[3] Univ Nebraska, Dept Phys & Astron, Lincoln, NE 68588 USA
[4] Univ Nebraska, Nebraska Ctr Mat & Nanosci, Lincoln, NE 68588 USA