1. Dpto. Física de Materiales, Facultad de Química, UPV/EHU, 1072, San Sebastián 20080, Spain
2. IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
3. Dpto. Física Aplicada I, EUPDS, UPV/EHU, Plaza Europa 1, San Sebastián 20018, Spain
4. Laboratory of Magnetism, Faculty of Physics, University of Bialystok, 15-424, Bialystok, Poland