[1] Korea Univ, KU KIST Grad Sch Converging Sci & Technol, Seoul 02841, South Korea
[2] Korea Inst Sci & Technol, Ctr Spintron, Seoul 02792, South Korea
[3] Korea Univ, Dept Mat Sci & Engn, Seoul 02841, South Korea
[4] NIST, Phys Measurement Lab, Gaithersburg, MD 20899 USA
[5] Univ Alabama Birmingham, Dept Phys, Birmingham, AL 35294 USA
[6] Korea Adv Inst Sci & Technol KAIST, Dept Phys, Daejeon 34141, South Korea