[1] Univ Pais Vasco UPV EHU, Leioa 48940, Spain
[2] BCMaterials, Dept Elect & Elect, Leioa 48940, Spain
[3] Ural Fed Univ, Lab Magnet Sensors, Ekaterinburg 620002, Russia
[4] Inst Electrophys, Amundsen Str 106, Ekaterinburg 620016, Russia
[5] Univ Maryland, Dept Phys, College Pk, MD 20742 USA
[6] CSIC, Inst Ciencia Mat, Madrid 28049, Spain