Mixed valence effects in Pr:YbF3 nanocrystals and influence to EPR, magnetic and Faraday rotation properties of diamagnetic glasses

Abstract The co-existence of light and heavy rare earth ions will arouse interesting optical, magnetic and magneto optical properties to matrix due to energy transfer between various rare earth ions and spin-orbit interactions of electric dipoles and magnetic dipoles. Pr and Yb co-doped orthorhombic Pr:YbF3 nano-crystals have been prepared by hydrothermal method, the structure and properties of Pr:YbF3 were characterized using X-ray diffraction, scanning electron microscopy, electron paramagnetic resonance, Raman & Infrared spectra and superconducting quantum interference device. The introduction of Pr into YbF3 induced changes on morphology, structure and properties due to different ionic radius, electronegativity and bond strength. The fabricated Pr:YbF3 nanocrystal doped glasses show good transparency and morphology. Pr:YbF3 nanocrystals were well dispersed in glass with slightly increased size (25 nm). X-ray photoelectron spectra confirmed the co-existence of Yb2+, Yb3+ and Pr3+ in 1% and 2% doped glasses, and additional Pr4+ in 4% doped one. Optical absorption edge red-shifted and emission intensity increased with the doping amount. Energy transfer between Pr3+ and Yb3+ ions was observed around 1000 nm. Due to the electron transition and energy transfer, the magnetization changed from diamagnetic to ferromagnetic and showed temperature-dependent behaviors. The Faraday rotation was significantly reinforced by Pr:YbF3 and a giant Verdet constant of -0.32 min/G.cm was obtained at 533 nm wavelength for 4% Pr:YbF3 doped glass which is promising for magneto optical devices.