EN
Temperature dependence of the b^{0}_{2} spin-hamiltonian parameter for Gd^{3+} in RbCdF_{3} single crystals is described. The dependence is interpreted in terms of the 4f^{7} electrons coupling to the whole phonon spectrum of the crystal. The presented data give also an insight into the dynamics of charge compensators causing a tetragonal distortion of the crystal field.