1. School of Physics, Engineering and Technology, University of York, York, U.K
2. Advanced Spintronics Medical Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
3. Institute for Materials Research, Tohoku University, Sendai, Japan
4. Center for Science and Innovation in Spintronics, Core Research Cluster, Tohoku University, Sendai, Japan
5. Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan