1. Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
2. Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan
3. Institute for Physics of Intelligence and Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
4. Center for Spintronics Research Network, Osaka University, Toyonaka, Osaka 560-8531, Japan