GB1367474A - Magnetic device - Google Patents

Abstract

1367474 Magnetic storage arrangements INTERNATIONAL BUSINESS MACHINES CORP 6 March 1972 [12 April 1971] 10270/72 Heading H3B Bubble domains are propagated in a magnetic sheet 10, Fig. 2, by current pulses in straight conductors 12-1 to 12-N. The magnetic field associated with a conductor such as 12-1 opposes the domain stabilizing field Hz on one side of the conductor and enhances it on the other; this effective variation of bias field causes a domain to move, and if alternate conductors are pulsed 180 degrees out of phase the domain will move along the sheet, following the region of least bias field. The stable domain positions are to one side or the other of the conductors as shown by numbers 1-8 on Fig. 2. Because the conductors pass to and fro across the sheet bipolar propagation pulses are used, the motion from positions 1-8 being as shown in Fig. 3; propagation in the opposite direction occurs if the currents I 1 or I 2 are reversed. In Fig. 2, a domain generator 16 has four current hoops 16L, 16S, 16R and 18. Initially 16S is pulsed to create a domain, then 16L and 16R are pulsed with loop 18 and the domain splits into two portions which move under loops 16L and 16R. The latter portion is offset by permalloy dots 20 and can be propagated by currents I 1 and I 2 . The portion under loop 16L may be returned to loop 16S and split to form another domain for propagation, the process being repeated as required. At the other end of the sheet a bubble busting loop 32 is provided. Readout is by a magnetosensitive resistor 26 connected to constant current source 28 and voltmeter 30 as described in Specifications 1,334,603 and 1,358,546. Parallel propagation paths may be used along the sheet with an appropriate number of generators, detectors and busters. The one set of propagation conductors remain sufficient however, though permalloy keeper regions are applied to them to prevent the domains drifting sideways, Figs. 4 and 5 (not shown). The keepers also raise propagation efficiency. The conductors may be arranged to give a closed recirculating path. A looped conductor may be provided adjacent the input of each path to collapse a domain when it is desired to write a binary 0.