  We present a magneto-optical study of the carrier dynamics in compressively
strained Ge(1-x)Sn(x) films having Sn compositions up to 10% epitaxially grown
on blanket Ge on Si (001) virtual substrates. We leverage the Hanle effect
under steady-state excitation to study the spin-dependent optical transitions
in presence of an external magnetic field. This allowed us to obtain direct
access to the dynamics of the optically-induced carrier population. Our
approach singled out that at cryogenic temperatures the effective lifetime of
the photogenerated carriers in coherent Ge(1-x)Sn(x) occurs in the sub-ns time
scale. Supported by a model estimate of the radiative lifetime, our
measurements indicate that carrier recombination is dominated by non-radiative
processes. Our results thus provide central information to advance the
fundamental understanding of carrier kinetics in this novel direct-gap group-IV
material system. Such knowledge can be a stepping stone in the quest for the
implementation of Ge(1-x)Sn(x)-based functional devices.
