Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions

Measurements of Faraday and Mossbauer effects have been performed at room temperature for alkali silicate glasses containing a large amount of Eu2+ ions to examine the relation between local structure and magnitude of Verdet constant. The Mossbauer spectra indicate that about 80% of europium ions are present as a divalent state. The effective transition wavelength and effective transition probability for the 4f(7) --> 4f(6)5d transition of Eu2+, which causes the Faraday effect, are derived from the wavelength dependence of Verdet constant. Both effective transition wavelength and effective transition probability are large compared with borate glasses; leading to the large magnitude of Verdet constant of the alkali silicate glasses. The variation of effective transition wavelength with glass composition is connected with the change of 6s-electron density of Eu2+ evaluated from the Mossbauer spectroscopy.