1. IPIT & Department of Physics, Chonbuk National University, Jeonju 54896, Korea
2. Peter Grünberg Institute (PGI-7), Research Centre Juelich, Juelich 52425, Germany
3. Pohang Accelerator Laboratory, Pohang 37673, Korea
4. Institute for Materials in Electrical Engineering II, RWTH Aachen University, Aachen 52074, Germany