Magnetic Bubble Memories. Solid State File Utilizing Micro Magnetic Domains

Abstract

Magnetic bubbles are cylindrical magnetic domains which exist in single crystalline magnetic garnet and orthoferrite films or amorphous Gd-Co films. These domains behave just like bubbles when observed in a microscope, leadng to the name of magnetic bubbles. In 1967, Bobeck [11.1] of Bell Laboratories announced the idea of sequential memory devices using the propagation of magnetic bubbles. In these devices, binary codes ‘1’ and ‘0’ are stored as the presence and absence of magnetic bubbles respectively. In 1969, Bobeck et al. [11.2] and Perneski [11.3] experimentally demonstrated the possibility of these devices by generating, propagating and annihilating magnetic bubbles in a controlled way. The very new idea and high potentiality of these devices attracted many scientists and engineers who were involved in applied magnetics. Since then research on magnetic bubble memories from materials and physics, to devices and systems has been carried out extensively. As a result magnetic memories have been developed as practical solid state files which are now used commercially for electronic switching systems, numerical control machines, robotics, terminals and so on.