  All-optical pump-probe detection of magnetization precession has been
performed for ferromagnetic EuO thin films at 10 K. We demonstrate that the
circularly-polarized light can be used to control the magnetization precession
on an ultrafast time scale. This takes place within the 100 fs duration of a
single laser pulse, through combined contribution from two nonthermal
photomagnetic effects, i.e., enhancement of the magnetization and an inverse
Faraday effect. From the magnetic field dependences of the frequency and the
Gilbert damping parameter, the intrinsic Gilbert damping coefficient is
evaluated to be {\alpha} \approx 3\times10^-3.
