Electron beam damage: Applications to bubble devices

The interaction between bubble domains and areas of deliberately introduced material damage is described. The damaged regions, of controlled extent and precise location, were introduced by exposing the material to a beam of electrons typically 8 micrometers in diameter. Using either samarium-terbium orthoferrite or epitaxial garnet, no domain interaction was apparent until the beam energy density was sufficient to cause visible surface damage to the specimen. In the latter case, the interaction between the damaged region and the domain wall was found to be of a repulsive nature, in contrast to the usual attractive interaction with naturally occurring defects. By producing continuous damage extending around the outline of a rectangle a large number of domains were constrained within the rectangle. Their symmetrical spacing from the lines of damage confirmed the repulsive nature of the interaction. The specimen temperature rise during exposure is calculated and possible mechanisms for the domain behavior considered. Some practical device applications using the damage technique are described. For instance, the motion of bubbles might be constrained to specific propagation channels, or the interaction used to perform logic functions.