1. Department
of Physics, Philipps University Marburg, Marburg, Germany
2. Department
of Physics, University at Buffalo, Buffalo, New York 14260, United States
3. SGIker Medidas
Magneticas,
F. Ciencia y Tecnologia, Sarriena s/n, 48940 Leioa, Spain
4. CIC biomaGUNE, Paseo Miramón no. 182, 20009 San Sebastian, Spain