  The vibrational properties of ferrimagnetic $\mathrm{Mn_3Si_{2}Te_6}$ single
crystals are investigated using Raman spectroscopy and density functional
theory calculations. Eighteen Raman-active modes are identified, fourteen of
which are assigned according to with the trigonal symmetry. Four additional
peaks, obeying the $A_{1g}$ selection rules, are attributed to the overtones.
The unconventional temperature evolution of the $A_{1g}^5$ mode self-energy
suggests a competition between different short-range magnetic correlations that
significantly impact the spin-phonon interaction in $\mathrm{Mn_3Si_{2}Te_6}$.
The research provides a comprehensive insight to the lattice properties,
studies their temperature dependence and shows the arguments for existence of
competing short-range magnetic phases in $\mathrm{Mn_3Si_{2}Te_6}$.

Materials Science