Mixed samarium valences effect in Faraday rotation glasses: Structure, optical, magnetic and magneto-optical properties

Sm2+ ions are attractive in high density memory applications due to its spectral hole burning property. In this study, for the first time, the influence of mixed valence states of Sm ions to magnetic and magneto optical property of diamagnetic glasses were studied. The chemical valence states of Sm and their modification on glass structure, optical absorption, luminescence, magnetic and Faraday rotation performances were characterized using X-ray Photoelectron Spectroscopy (XPS), X-Ray diffraction, Ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), Raman spectra and vibrating-sample magnetization (VSM) measurements, respectively. Characteristic emission peaks due to D-5(0)-> F-7(0) and D-5(0)-> F-7(1) transitions of Sm2+ and (5)G(5/2)-> H-6(7/2), (5)G(5/2)-> H-6(9/2) transitions of Sm3+ ions were detected in luminescence spectra, indicating the reduction of Sm3+ to Sm2+. XPS analysis on Sm3d core-level spectra demonstrated the co-existence of Sm2+ and Sm3+ and their evolution was Sm2O3 content-dependent. Optical absorption of H-6(5/2)->(4)G(5/2), F-6(11/2), F-6(9/2), F-6(7/2), F-6(5/2) transitions of Sm3+ ions were observed in UV-VIS spectra, however, the absorption peaks of Sm2+ were covered by the stronger absorption of Pb2+ and Bi3+ ions in the UV region. The refractive index, optical cutoff wavelength and band gap of glasses were changed by the incorporation of highly polarizable Sm ions. Due to the different magnetic ordering of Sm2+ and Sm3+ ions, glass doped with 1%Sm2O3 presented diamagnetic nature while glasses doped with higher Sm2O3 exhibited paramagnetic behavior, and the Faraday rotation property also was greatly influenced by magnetization susceptibility. 1%Sm2O3 doped glasses presented the strongest magnetization and biggest Verdet constant of 0.1886 min/G.cm at 633 nm. Several influence factors to Verdet constant such as non-bridging oxygen structure, wavelength, refractive index, magnetic susceptibility and temperature were discussed.