Pylypiv V. Defects, strains, and magnetic structure of modified garnet ferrite films.

This thesis is devoted to the study of relationships between structural defects, parameters of strain profiles, and magnetic microstructure of subsurface layers in yttrium iron garnet (YIG) films, as well as to establishing physical laws of the magnetic microstructure transformation of YIG films under influence of ion implantion with different ion masses (F+, O+, P+, Si +) and subsequent heat treatment. The creation of defects in subsurface layers at the implantation of light F+ and O+ ions has been found to occur mainly due to electron energy losses, whereas for P+ and Si+ ions with intermediate masses the nuclear energy losses are predominant. In the first case, the energy losses of implanted ion at the retardation in garnet structure are spent mainly on the track formation with Frenkel pairs, and in the second one the energy losses are sufficient to develop secondary collision cascades with the formation of extended defects. The main types of structural defects (spherical clusters and dislocation loops) in substrate and film volumes have been established, and their characteristics (radius and concentration) and the parameters of strain profiles in the substrate-film and film-air transition layers have been determined. The dependences of structural defect characteristics and strain profile parameters in the subsurface layers of YIG films on the ion implantation modes and implanted ion species have been obtained.