  We uncovered for the first time the spin dynamics involved in the birth and
growth of giant spin polarons in a magnetic semiconductor. For this purpose, we
developed a new measurement technique, which for the first time provides direct
access to the spin dynamics, irrespective of phonons and carriers involved in
the process. Moreover, we solved for the first time the Landau-Liftshitz
equation in the specific scenario of spin polarons, which fits our data
excellently, and demonstrates for the first time that the spin polaron growth
slows down dramatically when the sample is cooled in the paramagnetic phase.
Finally, temperature dependent Monte Carlo simulations were performed, which
are in excellent agreement with the observed slowdown, which demonstrates for
the first time that fluctuations in the Weiss field play a decisive role in
spin coherence generation induced by light in magnetic materials. These results
offer a new tool and new insight for spin dynamics investigations.
