Effect of natural ferrite oxide nanoparticles on structural and magneto optic properties of erbium doped tellurite glass

Two series of erbium doped magnesium tellurite glasses embedded with Fe3O4 nanoparticles (NPs) with composition (89-x) TeO2 - 10MgO - 1Er2O3 - (x) Fe3O4, where (x = 0, 0.2, 0.4, 0.6 and 0.8 mol%) and (89.6-y) TeO2-10MgO-(y) Er2O3-0.4Fe3O4, where (y = 0.2, 0.4, 0.6, 0.8 and 1.0 mol%) were prepared using melt quenching technique. Thorough characterizations of these glasses were made using X-ray diffraction (XRD), differential thermal analyzer (DTA), ultraviolet-visible-near-infrared (UV-Vis-NIR), Fourier transform infrared (FTIR), Raman spectroscopy, photoluminescence (PL) spectroscopy, energy dispersive X-ray (EDX), high resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) spectroscopy. The presence of a broad hump in the X-ray diffraction (XRD) pattern confirms the amorphous nature of glass. HRTEM images verified the existence of Fe NPs with average diameter of 4.8 nm (TMEF3 sample) and 4.5 nm (TMFE3 sample) corresponding to d311 spacing. The glass density and molar volume were found to be in the range of 4.03-5.27 gcm-3 and 37.20-28.54 cm3 mol-1, respectively. It was also found that as the amount of Fe3O4 NPs was increased, the glass stability increased. DTA analysis demonstrated an increase in the glass transition temperature from 321 oC to 363 oC with the increase of Fe3O4 NPs. The UV-Vis-NIR absorption spectra revealed seven absorption bands centered at 452 nm, 522 nm, 571 nm, 656 nm, 795 nm, 978 nm and 1528 nm which are assigned to the transition from ground state 4I15/2 to the various excited levels 4F7/2, 2H11/2, 4S3/2, 4F9/2, 4I9/2, 4I11/2, 4I13/2, respectively. Surface plasmon resonance (SPR) peaks of Fe3O4 NPs were observed at 408 nm. The FTIR and Raman spectra revealed modification in network structures which is evident from wavenumber of [TeO4] and [TeO3] structural units located around 600 cm-1 and 700 cm-1, respectively. The luminescence of Er3+ ion under 375 nm excitation revealed four peaks centered at 420 nm, 460 nm, 490 nm and 516 nm which correspond to light green (4F3/2 ? 4I15/2), light green (4F7/2 ? 4I15/2), green (2H11/2 ? 4I15/2) and red (4S3/2 ? 4I15/2) emissions, respectively. The Judd-Ofelt intensity parameter, spontaneous emission probabilities, radiative lifetime and branching ratios of all transitions were calculated based on Judd-Ofelt theory. The glass magnetization in magnetic field up to 10 kOe at room temperature was found to be in the range of 0.012 – 0.052 emu g-1. The g-factor values of 1.99 to 3.06 indicate that the glass samples are paramagnetic. The result of the present work revealed that the investigated glass can be a potential material for magneto-optic devices and solid-state lasers