[1] Univ Halle Wittenberg, Inst Phys, D-06120 Halle, Germany
[2] Tbilisi State Univ, Dept Phys, GE-0128 Tbilisi, Georgia
[3] Ctr Invest Mat Avanzados CIMAV SC, Chihuahua Monterrey 31109, Chihuahua, Mexico
[4] Rzeszow Univ Technol, Dept Phys, PL-35959 Rzeszow, Poland
[5] Univ Lisbon, Dept Phys, P-1049001 Lisbon, Portugal
[6] Univ Lisbon, Inst Super Tecn, CFIF, P-1049001 Lisbon, Portugal