1. Department of Electrical and Computer Engineering, University of Texas at San Antonio, San Antonio, Texas 78249, USA
2. Department of Physics, State University of Maringá, Maringá – PR 87020-900, Brazil
3. Department of Physics, Universidade Estadual do Centro-Oeste, Guarapuava – PR 85040-080, Brazil
4. Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas – SP 13083-859, Brazil
5. Department of Physics, Federal University of São Carlos, São Carlos – SP 13565-905, Brazil