NI-2+ IONS IN RBCDF3 - AN EPR STUDY IN THE CUBIC AND TETRAGONAL PHASES

The EPR spectra of Ni2+ ions in RbCdF3 occupying a Cd2+ substitutional site have been studied both in the cubic (T>124 K) and in the tetragonal (T<124 K) phase. In the cubic phase they are characterized by an isotropic g factor (g=2.34±0.01). In the tetragonal phase the EPR spectra of Ni2+ are described by an axial spin Hamiltonian with S=1. The g tensor does not change with temperature. The principal values are g?=2.321±0.005 and g=2.295±0.005. The crystal-field parameter D has a value of 12.23±0.03 GHz at 77 K and decreases as the temperature increases. Below the transition temperature (124 K) it varies according to D(T)=D0--T-T0--22 with D0=1.75 GHz, T0=124 K, and 2=0.25. This 2value compares well with those obtained by other techniques. © 1990 The American Physical Society.