EPR Study of Ni²⁺-Vacancy Dipoles in LiCl Crystals

抄録

The paramagnetic resonance spectra of Ni²⁺ in LiCl have been studied at 9 GHz. Two kinds of Ni²⁺ centers associated with positive ion vacancy in their nearest or next nearest neighbour position are observed. Their spin Hamiltonian parameters are determined to be g_x=2.27±0.04, g_y=2.26±0.02, g_z=2.31±0.01, |D|=0.564±0.002 cm⁻¹, |E|=0.080±0.002 cm⁻¹, and g_⁄⁄=2.360±0.005, g_⊥=2.30±0.05, |D|=3.1±0.3 cm⁻¹ and |E|\simeq0.0 cm⁻¹.
The Ni²⁺-vacancy dipoles aggregated to form clusters and the isolated dipoles decayed in number. The decay constant of third order rate process is about 1.2×10⁵ h⁻¹ (mole fraction)⁻² at room temperature.
The EPR line width depends upon the crystal orientation. Interaction between near neighbour dipoles contributed to this anisotropic line width.