We report on the magnetic and structural properties of Y3Fe5O12 (YIG) thin films deposited on a thermally oxidized silicon substrate. The broadband ferromagnetic measurements allowed to distinguish between intrinsic and extrinsic linewidth contributions revealing relatively low values of Gilbert damping parameter that is in the range of 10-20x10^-4 for film thicknesses below 100 nm. However, the inhomogeneous linewidth broadening remained larger than 30 mT as a result of structural defects. This could guide further development of YIG films integrated with silicon that exhibit low magnetic losses.
