1. Departamento de Física, Universidade Federal de São Carlos (UFSCAR) 13560-905, São Carlos, SP, Brazil
2. Departamento de Engenharia Elétrica, Universidade Federal de São Carlos 13560-905, São Carlos, SP, Brazil
3. Institute of Physics Gleb Wataghin, UNICAMP, Campinas, Brazil
4. School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, Nottingham NG7 2RD, United Kingdom