Crystalline properties of Ne+‐implanted garnet films with varying implantation energies and dosages have been studied by means of the double‐crystal x‐ray‐diffraction method, and it was found that when implantation‐induced damage was low, Pendello¨sung interference was observed which is directly related to crystal perfection, and a layer with large microscopic strain was found to become amorphous. The damage profiles were determined by measuring changes in x‐ray rocking curves after etching the implanted layers. Based on these experimental results, an implanted layer model was derived. The influences of the crystalline properties on the magnetic properties were also investigated from the viewpoints of the flux keeper and hard‐bubble‐suppression effects. For high implantation dosage the amorphous layer becomes magnetically inactive. This phenomenon is ascribed to randomly oriented micro‐magnetic‐domains with zero net magnetization caused by large microscopic strain in the amorphous layer. The effect of annealing is also discussed.