1. Center for Magnetic Recording Research, University of California San Diego, La Jolla, California 92093-0401, USA
2. Faculty of Polytechnics, University of Donja Gorica, 81000 Podgorica, Montenegro
3. Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, BP 70239, F-54506 Vandoeuvre-les-Nancy, France