Three different sputtering approaches are described for the synthesis of garnet films in the thickness range of 0-4 μ. The experimental requirements for producing single-phase, polycrystalline GdIG films are described in some detail, especially in the rf sputtering mode. Unexpectedly large systematic variations in the unit lattice parameter of the garnet structure as a function of film thickness are reported. Possible causes for these systematic structural changes are discussed. © 1968 The American Institute of Physics.