SPECIFIC PROPERTIES OF ION-IMPLANTED BUBBLE CIRCUITS

Stress measurements using the beam cantilever method have been performed on ion implanted garnet films for bubble applications. A maximum average stress of 6.109 ergs/cc is obtained for a nuclear energy loss density of about 1ev/Å3. A very fast decrease occurs for higher dosages. Ion implanted circuits for bubble propagation are shown to be formed by alternated portions of convex and concave squares. A bubble rotates in one period of the external drive field around a concave square and in three periods around a convex square. The latter has strongly anisotropic properties as determined by bubble collapse field measurements. Consequently the propagation on ion implanted patterns is also anisotropic and occurs with different velocities. The magnetocrystalline anisotropy is revealed by measuring the collapse and run out fields of free bubbles, and the nucleation field of bubbles on the edge of a disk. The conjunction of these two anisotropies leads to bias field margins which are dependent on the loop orientation with respect to the crystallographic axis. The comparison between ion implanted and permalloy coated garnets suggests the importance for successful propagation of the three following properties: adherence of bubbles along the propagation patterns, sample homogeneity and three fold symmetry.