Spin-Lattice Relaxation and Superposition Model Calculation in Gd$\text{}^{3+}$-Doped LiErF$\text{}_{4}$ and LiDyF$\text{}_{4}$ Crystals

The X-band EPR measurements were performed on Gd$\text{}^{3+}$-doped LiErF$\text{}_{4}$ and LiDyF$\text{}_{4}$ single crystals at room temperature. The spin-lattice relaxation times were evaluated to be 2.7 × 10$\text{}^{-15}$ s, 1.0 × 10$\text{}^{-15}$ s and 2.2 × 10$\text{}^{-15}$ s for LiDyF$\text{}_{4}$ , LiErF$\text{}_{4}$ and LiYbF$\text{}_{4}$, respectively. Spin-Hamiltonian parameters are determined and discussed in the light of the superposition model in order to determine the distortion of Gd$\text{}^{3+}$ ion environment in LiREF$\text{}_{4}$ host lattices (RE = Yb, Y, Er, Dy, and Gd).