Institution: | aPhysics School, Universidad Nacional de Colombia Sede Medellín A.A. 3840, Medellín, Colombia;bDepartment of Physics, Dalhousie University, Halifax, NS, Canada B3H 3J5;cCenter for Functional Nanomaterials Brookhaven National Laboratory, Upton, NY 11973, USA;dDepartment of Physics, University of Bologna V/le B. Pichat 6/2, I-40127 Bologna, Italy |