  The intricate interplay between spin and lattice degrees of freedom in
two-dimensional magnetic materials plays a pivotal role in modifying their
magnetic characteristics, engendering hybrid quasiparticles, and implementing
functional devices. Herein, we present our comprehensive and in-depth
investigations on magnetic and lattice excitations of MnPSe3-xSx (x = 0, 0.5,
and 1.5) alloys, utilizing temperature- and polarization-dependent Raman
scattering. Our experimental results reveal the occurrence of multiple phase
transitions, evidenced by notable changes in phonon self-energy and the
appearance or splitting of phonon modes. These emergent phases are tied to the
development of long and short-range spin-spin correlations, as well as to spin
reorientations or magnetic instabilities. Our analysis of two-magnon
excitations as a function of temperature and composition showcases their
hybridization with phonons whose degree weakens with increasing x. Moreover,
the suppression of spin-dependent phonon intensity in chemically
most-disordered MnPSe3-xSx (x = 1.5) suggests that chalcogen substitution
offers a control knob of tuning spin and phonon dynamics by modulating
concurrently superexchange pathways and a degree of trigonal distortions.
