Recent development in magnetic-bubble memory

The magnetic-bubble memory-the new solid-state nonvolatile memory-has taken a prominent place in today´s memory market. It is widely used in industrial and information area, because it is reliable, maintenance-free, and durable. Improvements on bubble materials, processing, and chip design, especially Permalloy tracks, led magnetic-bubble memory to 4-Mbit devices which are now commercially available. Conventional Permalloy tracks are, however, not suitable for higher bit density devices because they require a large driving field. To overcome this problem, ion-implanted tracks have been developed. Physics of ion-implantation to garnets and the ion-implanted tracks have been studied and understood. The ion-implanted devices have been developed as 16-Mbit hybrid devices. The ion-implanted bubble technology is promising for 64-Mbit devices in the near future. In packaging, the innovative development has been done. The PFC (Picture Frame Core) packages reduce the device size drastically. In the future, the Bloch line memory-an ultra-high density memory-will be developed, based on bubble memory technology. This paper reviews these technologies in detail.