1. Department of Electronic Engineering, University of York, York YO10 5DD, UK
2. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
3. Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
4. Department of Physics, University of York, York YO10 5DD, UK
5. Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research, Singapore 138632, Singapore
6. Center for Science and Innovation in Spintronics Core Research Cluster, Tohoku University, Sendai 980-8577, Japan