Kurovets V. Crystalline and magnetic microstructures of epitaxial ferrite-garnet films implanted by helium ions.

In the thesis, the crystalline and magnetic microstructures of epitaxial ferrite-garnet films implanted by helium ions with an energy of 100 keV in the doses 1?1015-1?1016 сm-2 were investigated.The possibility of radiation-disordered areas generation was analyzed using mathematical modeling of radiation defects formation process. The main characteristics of such areas were established. For the first time it was theoretically proved that during the implantation of helium ions with the energy of 100 keV in the near-surface region ? 200 nm of Yttrium Iron Garnet (YIG) the effectiveness of defect formations due to electronic target subsystem excitations is comparable with efficiency of defects creation at nuclear braking.It was established that in the ion-implanted surface layers of ferrite-garnet films the main types of radiation defects are dislocation loops (with the average radius of 2-5 nm), disordered regions of ellipsoid form with maximum linear size of 10 nm and point defects with the effective radius of 0.11 nm. The minimum on the dose dependence of the measured microhardness values of ferrite-garnet film surface layers is observed at 2·1015 cm-2. The dependence of maximum strain on the YIG from their thickness has a maximum at the film thickness of 3 µm, which is due to varying impact degree of growth defects and mechanical stress in the processes of radiation defect formation at various film thicknesses.According to the study results of the ion implantation changes in the surface layers of the La,Ga:YIG films it has been found that the strain profiles, in comparison with the corresponding profiles of unsubstituted YIG films, are offset in depth. Increase of defect formation intensity and decrease of microhardness value are associated with less covalence degree of chemical bonds.