Remarkable red-shift of upconversion luminescence and anti-ferromagnetic coupling in NaLuF₄:Yb³⁺/Tm³⁺/Gd³⁺/Sm³⁺ bifunctional microcrystals

胡仕刚¹，刘云新²，吴笑峰¹，唐志军¹，李志明³，颜焕元⁴，陈增辉²，胡盼¹，余意¹

1. School of Information and Electrical Engineering, Hunan University of Science and Technology2. Department of Physics and Electronic Science, Hunan University of Science and Technology3. School of Information Science and Engineering, University of Jinan4. College of Mechanical and Electrical Engineering, Hunan University of Science and Technology

摘 要：Lanthanide doped bifunctional materials are potentially important for developing multifunctional devices. Here, NaLuF₄:Yb³⁺/Tm³⁺/Gd³⁺/Sm³⁺ optical-magnetic bifunctional microcrystals were successfully synthesized by hydrothermal method, which could emit ⁴80 nm blue light from the ¹G₄→³H₆ electronic transition and ⁸00 nm infrared light from the ³H₄→³H₆ electronic transition of Tm³⁺ ion, under the excitation of 980 nm infrared light. By doping Sm³⁺ ion into Na Lu F4:Yb³⁺/Tm³⁺/Gd³⁺, the infrared emission peak centered at 800 nm would shift obviously to longer wavelength. This indicated that Sm³⁺ ion could efficiently tune the energy level gaps of Tm³⁺ ions in Na Lu F4 host which was demonstrated based on the crystal field theory. In addition, these NaLuF₄:Yb³⁺/Tm³⁺/Gd³⁺/Sm³⁺ microcrystals presented unique ferromagnetic property instead of usually reported paramagnetic property. Importantly, the ferromagnetic property decreased with increasing the concentration of Gd³⁺ ion. This was in good agreement with Swift’s theoretical investigation that the coexistence of light rare earth(Gd³⁺) and heavy rare earth(Yb³⁺/Tm³⁺) would lead to the anti-ferromagnetic coupling in the sub-lattices.

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