  The magneto-volume effect is a well-established yet frequently overlooked
phenomenon in magnetic materials that may affect a wide range of physical
properties. Our study explores the influence of the magneto-volume effect on
the transient reflectivity of MnSi, a well-known chiral magnet with strong
magnetoelastic coupling. We observe a unipolar reflectivity transient in the
paramagnetic phase, contrasting with a bipolar response in phases with magnetic
long-range order. Comparing our findings with thermal expansion from
literature, we establish that the bipolar response originates in the
magneto-volume effect which dominates the thermal expansion and influences the
optical reflectivity. Our results highlight not only that the magneto-volume
effect must be considered when discussing transient reflectivity measurements
of magnetic materials but also that such measurements permit to study the
characteristic time scales of the magneto-volume effect itself, contributing to
a deeper understanding of this often-neglected phenomenon.
