Study of the amorphization of ion-irradiated yttrium iron garnet by high-resolution diffraction techniques

The amorphization process of yttrium iron garnet (YIG) epitaxial films, caused by irradiation with 235 MeV 84 Kr ions, has been studied by high-resolution diffraction techniques. For this purpose, the X-ray rocking curves of the (888) reflection, at a Bragg angle of around 60 degrees , were recorded at increasing ion fluences using a five-crystal diffractometer. It is shown that in-plane compression stresses were built up in the irradiated films and then relaxed at an amorphization yield around 40%. Moreover, high-resolution transmission electron microscopy showed that continuous latent ionization tracks were formed both in the YIG films and in the gallium garnet substrates. At very high fluence, when tracks fully overlap, both film and substrate were found by electron diffraction to be amorphous.