Strain profiles in ion-implanted bubble devices investigated by transmission electron diffraction

Abstract

Selected area electron diffraction has been used to obtain strain profiles around unimplanted disks in thin (<2000 Å) films of (111) oriented garnets. Measurements of in-plane lattice constant were made as a function of position in (SmYGdTm)3Ga0.4Fe4.6O12 films implanted with oxygen (120 KeV, 1×1014/cm2) and helium (80 KeV, 4×1015/cm2). In most cases the data show a relaxation of stress normal to and near to the implanted boundary. These results are consistent with models suggesting that stress relaxation normal to an implanted boundary is critical to the formation of charged walls. In addition, effects of the nonuniform stress field on the local anisotropy in the underlying bubble layer of an ion-implanted contiguous disk device are considered. It is shown that under the edge of an implanted region, there is a tensile stress perpendicular to the film plane which reduces the perpendicular anisotropy, causing reduced bubble-nucleation thresholds in bubble materials with large negative values of λ111.