Two Fe/Gd/Fe/Gd multilayers with different layer thicknesses were grown on Si (100) by magnetron sputtering. The as-deposited samples were vacuum-annealed at 100°C, 200°C, and 300°C. They were studied by grazing incidence x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), vibrating sample magnetometer (VSM) and magneto-optical Kerr effect (MOKE). The deposition rates for Fe and for Gd are (1-2) and 4 Å s−1, respectively. The XRD and SIMS data show that interdiffusion occurs between Fe and Gd layers, and between Gd and Si layers. The thicker multilayers show strong in-plane uniaxial anisotropy.