1. Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
2. Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
3. Laboratoire de Chimie Théorique, Namur Institute of Structured Matter (NISM), University of Namur, rue de Bruxelles, 61, B-5000 Namur, Belgium