1. Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
2. Center for Science and Innovation in Spintronics, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
3. Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
4. Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India
5. NanOsc AB, Kista 16440, Sweden