1. i3N and Department of Physics, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
2. i3N/CENIMAT, Physics Department, NOVA School of Science and Technology, Campus de Caparica, NOVA University Lisbon, 2829-516 Caparica, Portugal
3. i3N/CENIMAT, Science Materials Department, Faculty of Sciences and Technology, Nova University of Lisbon, 2829-516 Caparica, Portugal