Glass - Back to the Future!

Presenting Author:
Raluca Iordanescu

article posted 4 April 2016

Raluca Iordanescu is a Research Scientist at National Institute R&D for Optoelectronics INOE 2000, Optospintronics Department; doctor in Physics. The authors main activities: Thin films obtaining by PLD (Pulsed Laser Deposition) technique, sol-gel films obtaining by spin-coating method; advanced materials characterization by FTIR, Raman, UV-Vis and fluorescence spectroscopy.

Structural, morphological and magnetic properties of Ce3+ and Tb3+-doped silico-phosphate sol-gel thin films

C. R. Iordanescu*1, M. Elisa1, I. C. Vasiliu1, B. A. Sava2, L. Boroica2, M. Valeanu3, V. Kuncser3, A. Beldiceanu4, A. Volceanov5, M. Eftimie5

Ce3+ and Tb3+-doped silico-phosphate films were obtained by sol-gel method, deposited by spin-coating technique on silicon substrate at different rotation rates. The homogeneity of the films was investigated by conoscopy method. It was observed that the analyzed films are isotropic but relative inhomogeneous due to the deposition technique. FTIR and Raman spectroscopy put in evidence vibration modes specific to silico-phosphate structural units from the deposited films. The morphology of the sol-gel films was investigated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) and the elemental composition was determined by Energy Dispersive X-ray (EDX) analysis. The thicknesses of the films were measured by SEM analysis in transversal section. The magnetic and magneto-optical properties were registered and analyzed using SQUID and MOKE equipment, respectively. The magnetization curves were fitted for two different temperatures (150 K and 300 K) at different magnetic fields (up to 5 T). Ce3+-doped film presents a ferromagnetic behavior up to 23 kOe but at higher fields, the diamagnetic contribution of the substrate becomes dominant. In the case of the Tb3+-doped film, the magnetic measurements reveal only the substrate diamagnetic contribution. According to the Faraday effect, a rotation of the polarization vector is observed for a light passing through specific transparent materials, if a magnetic field is applied along the wave-vector. The rotation is proportional to the passing length, the intensity of the magnetic field and the intrinsic electric properties of the material as taken into account by the so-called Verdet constant. Consequently, the magneto-optical measurements prove an important negative Faraday rotation for Ce3+-doped sol-gel film (Figure 1(a)) and almost zero Faraday rotation for the that Tb3+-doped film (Figure 1(b)).

Figure 1. Faraday rotation versus magnetic field for (a) Ce3+ and (b) Tb3+-doped silico-phosphate films

Taking into account that the thickness of Ce3+ and Tb3+-doped silico-phosphate films is 18 m and 27 m, respectively, the Verdet constant deduced from the relationships from Figure 1 is 33710-2 min/Oe/cm and 210-4 min/Oe/cm, respectively, at the wavelength of 635 nm

1 National Institute of R & D for Optoelectronics INOE 2000, 409 Atomistilor Str., Magurele, Jud. Ilfov, 077125, Romania
2 National Institute for Laser, Plasma and Radiation Physics, POB MG-7, 77125 Bucharest-Magurele, Romania
3 National Institute of Materials Physics, POB MG-7, 77125 Bucharest-Magurele, Romania
4 S.C. ProOptica S.A., 67 Gheorghe Petrascu Str., Bucharest, Romania
5 University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 1 Polizu Str., Bucharest, Romania