Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

Abstract

We have studied the magneto-optic Faraday effect (FE) and electron paramagnetic resonance (EPR) in an aluminum potassium borate glass containing Fe oxides as an impurity in a concentration of 1.5 mass % and Mn impurity in variable concentration from 0 to 1.2 mass %. When manganese oxide is added to the glass composition, the paramagnetic contribution to the Faraday effect increases more slowly than the change in the total concentration of paramagnetic ions, which allows us to hypothesize the appearance of clusters in which the paramagnetic ions are coupled by antiferromagnetic interactions. Formation of clusters upon addition of manganese oxide is confirmed by the change in the nature of the EPR spectra, where we observe a manganese concentration dependence of the distribution of iron atoms with respect to the different positions in the glass matrix. Heat treatment leads to a strong increase in the Faraday effect and a change in the spectral dependences of the Faraday effect and the EPR, which is explained by enlargement of the clusters and appearance of nanoparticles.Introduction. The steady demand for technology in efficient media for controlling a light beam has stimulated the search for and investigation of new material having high magneto-optical quality, in particular in the IR region of the spectrum at wavelengths of 1.0-1.5 µm. Glass containing magnetic nanoparticles can be considered as such a material (see, for example, [1,2]). Creation of glasses with the required microstructure and specified physical properties requires detailed study of the processes of particle formation in all stages of glass manufacture. Usually nanoparticles having a crystalline structure are formed during additional heat treatments of the glass. However, inhomogeneities in the distribution of magnetic ions and the appearance of clusters which are nuclei for the magnetic phase occur even in the initial stages of glass manufacture, and to a significant extent determine the nature of the particles appearing as a result of additional heat treatments. In this work, we have studied a glass with the base composition 22.5K 2 O+ 22.5Al 2 O 3 +55B 2 O 3 , containing Fe 2 O 3 and MnO as impurities. In glasses of this group, magnetic nanoparticles are formed as a result of heat treatments even for low concentrations of paramagnetic additives (≈2.0 mass %) [1, 2]. Therefore, while remaining transparent in the spectral region 800-2500 nm, the glasses are characterized by a significant Faraday effect and a nonlinear field dependence for the Faraday effect. The need to optimize the indicated parameters explains why steady attention has been focused on the processes of nucleation and formation of magnetic inhomogeneities in glasses of this system. EPR is the method most often used for investigation of clusters of S transition metal ions in glasses, for example Fe 3+ (3d 5 , 6 S 5/2 ) [3-6]. The EPR spectra of Fe 3+ ions in glass matrices provide information about the immediate environment of the paramagnetic ion because different lines are obs...

Thermal properties of MnO2 and SiO2 containing phosphate glasses

“…Manganese ions have been frequently used for exploring the structure and properties of various kinds of glasses, not only phosphate but also borate [6] and silicate ones [7]. It is known that manganese ions exist in various valence states with a different local symmetry in the glass structure.…”

Effective Transition Probability for the Faraday Effect of Lanthanide(III) Ion Solutions

“…The Faraday effect has been studied mainly for ferromagnetic solids and thin films because the contribution of the magnetic domain to Faraday rotation is very large. [4][5][6][7] Only a few measurements have been reported for solutions. [8][9][10][11][12][13] The Faraday rotation of Ln(III) in phosphate glass has been measured by Berger et al 14 In their report, the magnitude of the Verdet constant varied periodically with the number of 4f electrons, and they tried to explain their results using the theory of van Vleck and Hebb, 15 in which the Verdet constant is proportional to the magnetic susceptibility.…”