1. Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai 980-8577, Japan
2. WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
3. Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
4. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
5. Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan