We have studied by x-ray diffraction the deformations of thin smectic films induced by antagonistic anchorings, as a function of thickness and temperature. The structure of the cores is revealed for thicknesses of the order of 0.15 μm when the deformations are dominated by the presence of the focal conics cores. In a cylindrical geometry imposed by the unidirectional anchoring on the substrate, the cores are tube-shaped rotating grain boundaries (RGB). The spatial extension is of the order of 0.14 × 0.22 μm2, larger than the ones usually proposed in the literature. A drastic evolution of the x-ray scans with temperature is also revealed. It corresponds to a variation of the location of the RGB and is analyzed as the result of a weak variation of the 8CB/air surface tension with temperature.