[1] Bayerische Akad Wissensch, Walther Meissner Inst, D-85748 Garching, Germany
[2] Tech Univ Munich, Phys Dept, D-85748 Garching, Germany
[3] Norwegian Univ Sci & Technol, Ctr Quantum Spintron, Dept Phys, N-7491 Trondheim, Norway
[4] Tech Univ Dresden, Inst Festkorper & Mat Phys, D-01062 Dresden, Germany
[5] Nanosyst Initiat Munich, D-80799 Munich, Germany
[6] MCQST, D-80799 Munich, Germany
[7] Univ Konstanz, Dept Phys, D-78457 Constance, Germany