Garpul O. Structural and magnetic disordering of surface layers of Yttrium Iron Garnet films implanted with silicon ions.

This thesis is devoted to the study of changes of crystalline and magnetic structure as well as physical and chemical properties of subsurface layers of Y3Fe5O12 YIG films in consequence of Si+ ion implantation with different energies and fluencies. Physical laws of the crystal lattice transformation have been established, and subsequently the mechanisms of the process of defects creation and change of electronic structure have been studied in dependence on implantation conditions. It has been shown that increasing Si+ ion energy from 100 to 150 keV causes the maximum level of defect creation, which takes place mainly due to nuclear energy losses, and the depth of bedding of radiation defects drows linearly, while the concentration of defects decreases. Implantation of YIG films with a dose of 5·1013 Si+/cm2 in the chosen energy range causes the creation of monotonously decreasing strain profiles which in basic lines reproduce the shape of the theoretically calculated distributions of elastically induced radiation defects. The similarity of the dependence of relative content of the duplicate component of the M?ssbauer spectrum on implanted ion energy for a subsurface layer (65 nm) and the dependence of integrated value of the strain profile obtained from the results of the X-ray diffractometry has been established, and also their correlation with the changes of the integral disordering value of the subsurface layer structure has been found. The decrease of the effective magnetic-field value on the iron ion nucleus with the increase of implantation dose up to 6 1013 cm-2 as well as the symbate character of change of this field value in both magnetic sublattices has been established.