Dynamical Faraday rotation effects of sol–gel derived Al2O3–SiO2 glass containing Eu2+ ions

The optical and magnetic characterizations of Eu2+-doped Al2O3–SiO2 glass, which was synthesized by a sol–gel technique, were performed on the basis of absorption–fluorescence spectra, a dynamical Faraday rotation, a static magnetic susceptibility, and an electron paramagnetic resonance (EPR). The dynamics of Faraday rotation in pulsed magnetic fields revealed the formation of anti-coupled Eu2+–O–Eu2+ magnetic pairs at low temperature, as well as two contributions to the total rotation: a paramagnetic due to Eu2+ ions and an antimagnetic presumably due to Al-associated defect centers generated by H2-impregnation. The broad feature around g∼2.00 in the S-state EPR spectra implied a multi-site distribution of Eu2+ ions in Eu,Al-rich phase produced in the sol–gel transformation. The influence of Al2O3 on the aggregation of europium ions in a SiO2 network was discussed.