  We report the first observation of Rabi oscillations in the spin-7/2 ensemble
of trivalent gadolinium ions hosted in CaWO$_4$ single crystal. A number of
transitions within the lowest electronic multiplet $^8S_{7/2}$ of Gd$^{3+}$ ion
are studied using a combination of continuous-wave and pulsed electron
paramagnetic resonance spectroscopy. The corresponding Rabi damping curves and
the spin coherence times are detected at varying strengths of the microwave
field. These data are well reproduced by a theoretical model which accounts for
the intrinsic inhomogeneity of the microwave field within the microwave
resonator and the magnetic dipole interactions in the diluted spin ensemble.
The results indicate that the studied 8-level ground manifold of Gd$^{3+}$ ion
can represent an effective three qubit quantum system.
