Temperature dependence of the mode-amplitudes refined in the $P 2_{1} / n, I 2 / m$ and $I 4 / m$ space groups for the $\mathrm{Sr}_{2} \mathrm{Ni}_{1-x} \mathrm{Mg}_{x} \mathrm{TeO}_{6}$ series ( $\mathrm{x}=0.3$ and 0.5)
Temperature dependence of the mode-amplitudes refined in the P 2_{1} / n, I 2 / m and I 4 / m space groups for the \mathrm{Sr}_{2} \mathrm{Ni}_{1-x} \mathrm{Mg}_{x} \mathrm{TeO}_{6} series ( \mathrm{x}=0.3 and 0.5)