Capping walls and self-bias in small-bubble materials

The self-biasing principle was demonstrated as early as 1971. In spite of its obvious advantages in replacing the bulky bias magnets, it is not in use in current bubble products. There are new cogent reasons for its further pursuit. (1) Together with coilless devices such as perforated sheets, self-biasing structures can make bubble packages as simple as those for semiconductor IC´s. (2) Absence of bias field in contiguous-disk devices will prevent drive-layer magnetization from tilting out of plane, thus removing the cause of anisotropic propagation behavior and extra drive-field requirement. (3) The bias layer is also effective in suppressing hard bubbles. Nevertheless, if we accept the above arguments and pursue self-bias structures for future applications, we must make sure that their efficacy can indeed be maintained in miniaturized devices.