Effect of zinc substitution on magneto-optical properties of Mn1-xZnxFe2O4/SiO2 nanocomposites

Abstract

Zn doped manganese ferrites (MZF)/SiO2 (Mn1-xZnxFe2O4/SiO2 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0)) nanocomposites with different Mn contents were successfully synthesized by a modified sol-gel autocombustion route using citric acid as a chelating agent and tetraethyl orthosilicate (TEOS) as a source of silica matrix. Silica coatings were done via a modified Stober method. Optical properties of MnZn-ferrites were improved by coating them with silica. The nitrate-citrate-silica gel exhibited self-propagating combustion behavior, and it is directly transformed into nanosized MnZn-ferrite nanoparticles with spinel cubic crystal structure. MZF/SiO2 nanocomposites show superparamagnetic behavior at room temperature (RT). The highest M-s value is about 73 Oe for Mn0.6Zn0.4Fe2O4 sample. This value is slightly less than that of the bulk Mn-ferrite, which is about 80 emu/g. The higher M-s value was attributed to cation distribution change from normal spinel to mixed structure. The diffuse reflectance (DR) measurements were applied to determine the band gap (E-g) of samples. The estimated E-g value of SiO2 coated ZnFe2O4 samples (1.95 eV) is in accordance with the literature values. Silica coating has a positive impact on the optical band gap (E-g) of MZF/SiO2 nanocomposite. In addition, the raising optical E-g values by increasing Mn content were observed for MZF/SiO2 nanocomposites. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.