  Alloyed MnxZn1_xPS3 samples have been grown covering the whole compositional
range and studied by means of Raman spectroscopy at temperatures covering from
4K up to 850K. Our results, supported by SQUID magnetic measurements, allowed,
from one hand, to complete the magnetic phase diagram of MnxZn1_xPS3 and
establish x>0.3 as the composition at which the alloy retains
antiferromagnetism and, from the other hand, to identify the Raman signatures
indicative of a magnetic transition. The origin of these Raman signatures is
discussed in terms of spin-phonon coupling resulting in the appearance of low-
and high-frequency zone-folded phonon modes. For the alloy, an assignment of
the 1st and 2nd order modes is provided with the aid of first-principle
lattice-dynamical calculations. The compositional dependence of all phonon
modes is described and the presence of zone-folded modes is shown to take place
for both, the alloy and MnPS3. Finally, a comparison of the Raman spectra of
ZnPS3 to other compounds of the transition-metal phosphorous trisulfide family
allowed shows that low-frequency phonon peaks exhibit an abnormally large
broadening. This is consistent with previous claims on the occurrence of a
second-order Jahn-Teller effect that takes place for ZnPS3 and Zn-rich
MnxZn1_xPS3.
