International Business Machines Corporation

Emerson W Pugh

Mitchell S Cohen

George E Keefe

Guard rails are described for particular use with magnetic bubble domain chips using contiguous propagation elements. These guard rails generally surround the active device area (storage area) of the chip and are used to move stray bubble domains from the storage area to the edge of the chip, or to a collapser etc., and also to prevent stray bubbles from entering the active device area. These guard rail structures are comprised of contiguous propagation elements characterized by an undulating edge and a smooth edge, both of which generally move bubble domains away from the active device area in response to the reorientation of the same magnetic drive field. In one embodiment, the guard rail is a spiral structure surrounding the active device area, having one end in the interior of the magnetic bubble chip adjacent to the active device area, and another end near the edge of the chip, or near a bubble annihilator, etc. In another embodiment, the guard rail is comprised of a plurality of structures generally defining a broken-spiral which surround the active device area. One end of each of structure is located near the active device area, while the other end is disposed toward the edge of the magnetic bubble chip.

Guard rail for contiguous element bubble chips

These improved current controlled transfer switches are particularly useful for changing the propagation path of very small bubble domains without requiring large amounts of transfer current. The underlying principle is that the transfer operation occurs when the magnitude of the magnetic drive field used to move bubble domains has diminished to a small value, or is zero. This means that the magnetic field due to current in the switch does not have to overcome the effect of the drive field and therefore can be very small while still being effective. This is termed a 'start/stop' operation and in one embodiment, current-assisted transfer is achieved by utilizing a change in the sequence of the magnetic drive field (generally an in-plane rotating field) at the time of transfer. In another embodiment, a continuous 'three-quadrant' magnetic drive field is used instead of the customary 360.degree. rotating drive field. This three-quadrant field cycle is also the normal cycle for bubble storage operations and bubble motion elsewhere in the magnetic circuit is not disturbed by the switching operation because all devices are designed to operate with only one type of drive field cycle, which is the three-quadrant cycle. Switches operating in accordance with these principles do not have to have a particular design; in fact, several different designs are illustrated.

Bubble domain transfer switches

Gapless, single-sided propagation structures are provided for implementing the continuous movement of magnetic bubble domains in both straight lines and around reverse direction turns under the control of a reorienting in-plane field. One embodiment comprises a closed loop of open-sided, joined hexagonal patterns having traps and dead end legs at the joined corners to cause transfer from one hexagonal pattern to the next, thus implementing continuous circulation around the loop and preventing backtracking. Another embodiment employs straight, parallel strips joined at their ends to form a loop. Bubble movement is promoted by a series of angled strip legs intersecting the main strips to provide sequentially advancing magnetic poles as the field vector rotates.

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Mount Kisco, NY, United States of America

Emerson W Pugh