GB989749A - Improvements in or relating to magnetic circuits - Google Patents

Abstract

989,749. Circuits employing thin magnetic films. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 3, 1962 [July 20, 1961], No. 25394/62. Heading H3B. A shift register comprising a chain of magnetic cells is adapted to invert information by introducing a domain wall between two cells intermediate its length. Shift register.-A shift register comprises a chain of anisotropic thin magnetic cells, consecutive cells being taken to contain the same information if no domain wall exists between them (see for example cells 50-54, Fig. 6a). If now the conductor associated with cell 53 is pulsed, with a current less than the nucleation current but greater than the critical current for domain movement, so as to set it to its opposite state, the domain wall 62 is transferred to the right-hand side of cell 53 and the information in cell 52 is transferred to cell 53. Thus, by pulsing each cell alternately with positive and negative pulses information may be transferred through the register. To prevent backward transfer the cell 54 following the one to which information is to be transferred must be in the same state as its predecessor 53. Thus, information must be passed through consecutive groups of at least three cells. Fig. 1 shows an embodiment having three pulsing conductors, whereas the embodiment of Fig. 6a uses only two conductors to transfer information through groups of four cells. The first pulse applied to a cell may be considered to be a resetting pulse and the second pulse a transfer pulse. Inverting shift register.-For applications in which it is necessary to invert information with respect to the reset directions so that mere change of convention may not be used (such as when the outputs of two similar circuits are combined in a gate) a pair of cells 54, 55 are provided, the second one being provided with a winding which allows it to be set to the " 0 " position so as to produce a domain wall between it and cell 54 whatever the state of cell 56. Owing to the change in convention of the state corresponding to binary information at the junction of the cells information is reversed on being fed through the register although all the cells are still reset to the " 0 " state. An added conductor is supplied to cell 54 as unless a resetting pulse is applied immediately after a transfer pulse the domain 61 may be transferred backwards through the register. Such a winding is not required for the embodiment of Fig. 1. Logical circuits.-Logical circuits employing inverting devices of the type described are described with reference to Figs. 9 to 11 (not shown). Cells having circular anisotropy or linear anisotropy may be used either separately or in combination (Fig. 8, not shown).