Determination of charge-compensated C3v (Ⅱ) centers for Er3+ ions in CdF2 and CaF2 crystals  

作　　者：Rui-Peng Chai Dan-Hui Hao Dang-Li Gao Qing Pang 柴瑞鹏;郝丹辉;高当丽;庞庆(College of Science,Xi’an University of Architecture and Technology,Xi’an 710055,China;Xi’an University of Architecture and Technology Huaqing College,Xi’an 710043,China)

机构地区：[1]College of Science,Xi’an University of Architecture and Technology,Xi’an 710055,China [2]Xi’an University of Architecture and Technology Huaqing College,Xi’an 710043,China

出　　处：《Chinese Physics B》2021年第3期466-472,共7页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.1170513);the Natural Science Foundation of Shaanxi Province,China(Grant No.Z20200051);the Foundation of the Education Department of Shaanxi Provincial Government,China(Grant No.16JK1461);the Scientific Research Foundation of Xi’an University of Architecture and Technology,China(Grant No.QN1729).

摘　　要：A unified theoretical method is established to determine the charge-compensated C3v(Ⅱ)centers of Er3+ions in CdF2 and CaF2 crystals by simulating the electron paramagnetic resonance(EPR)parameters and Stark energy levels.The potential(Er^(3+)–F^(−)–O_(4)^(2−))and(Er^(3+)-F_(7)^(−)-O_(4)^(2−))structures for theC3v(Ⅱ)centers of Er3+ions in CdF2 and CaF2 crystals are checked by diagonalizing 364×364 complete energy matrices in the scheme of superposition model.Our studies indicate that the C3v(Ⅱ)centers of Er3+ions in CdF2 and CaF2 may be ascribed to the local(Er^(3+)-F^(−)-O_(4)^(2−))structure,where the upper ligand ion F−undergoes an off-center displacement by∆Z≈0.3˚A for CdF2 and∆Z≈0.29˚A for the CaF2 along the C3 axis.Meanwhile,a local compressed distortion of the(ErFO4)6−cluster is expected to be∆R≈0.07˚A for CdF2:Er3+and∆R≈0.079˚A for CaF2:Er3+.The considerable g-factor anisotropy for Er3+ions in each of both crystals is explained reasonably by the obtained local parameters.Furthermore,our studies show that a stronger covalent effect exists in the C3v(Ⅱ)center for Er3+in CaF2 or CaF2,which may be due to the stronger electrostatic interaction and closer distance between the central Er3+ion and ligand O2−with the(Er^(3+)-F^(−)-O_(4)^(2−))structure.

关 键 词：EPR parameters distorted local structure covalent effect optical properties 

分 类 号：O469[理学—凝聚态物理]