Patent GB-1187623-A (GB)
Title: Improvements in or relating to Information Storage Arrangements
Inventor: BOBECK ANDREW HENRY
IPC: G11C19/08
Filed: 1967-08-10
Abstract: 1,187,623. Magnetic storage devices. WESTERN ELECTRIC CO. Inc. 10 Aug., 1967 [16 Sept., 1966 (2)], No. 36777/67. Heading H3B. [Also in Division G4] A shift register comprises a sheet of magnetic storage material in which single wall domains, i.e. domains not bounded by an edge of the sheet, are established by input information and are propagated along the sheet. In one arrangement, Fig. 1, an yttrium orthoferrite sheet 11 is isotropic in its surface plane and has a preferred direction of magnetization normal to the sheet. Initially the whole sheet is magnetized in the downward direction except for a peripheral zone which is oppositely magnetized by a conductor C, as denoted by the minus and plus symbols in the Figures. An input pulse in a looped input conductor 16 causes the peripheral magnetization to extend to bit location BL11 as shown in Fig. 4, and a propagation pulse in a looped conductor P1 then separates a single wall domain from the extended peripheral magnetization in this bit location (see Fig. 5). The isolated single domain wall is then propagated along the sheet by 3-phase pulses applied to conductors P1, P2 and P3 until a read location B21n is reached. Interrogation is effected by pulsing a looped conductor 18 so as to eliminate the domain and produce an induced output in a conductor 19. Alternatively non-destructive readout may be effected optically by using the Kerr or Faraday effects. In a modification, Fig. 6 (not shown), a plurality of such shift registers are arranged in parallel on a single sheet and have both row and column propagation conductors P1-P3. The information stored may then be advanced in parallel in columns or serially in rows. An alternative arrangement, Fig. 7, uses a sheet 11 of magnetic material having hard h and easy e directions of magnetization in the surface plane, the sheet 11 and a conducting film 12 being supported on an insulating substrate 13, e.g. of glass. Current from a source B through the conducting film 12 biases the sheet 11 in the hard direction. A single wall domain is established in the sheet by simultaneous application of a positive input pulse to an input conductor 17 and a positive pulse from a bi-polar source 16 to a conductor 14. This domain is moved along the hard direction by alternately applying negative and positive pulses to conductor 14, the movement probably being caused by domain distortion alternately away from and towards the easy axis. At the read out position the domain is detected by a sense conductor 20 and is then erased by a bias field Me. The arrangement is extended in Fig. 13 to provide parallel shift registers defined by respective conductors 14 1 , 14 3 , 14 5 , each being operated independently if required. Stored domains D 1  may not only be moved upwards and downwards serially, but may also be transferred from one register to another (unoccupied) register by a left or right movement, conductors 14 2 , 14 4  being provided for this purpose. Thus information in the register defined by conductor 14 1  may be transferred to the unoccupied register defined by conductor 142 by applying a negative pulse to 14 1 , followed by overlapping positive pulses firstly on conductor 14 2  and then on 14 1 . A modification is described, Fig. 16, in which the bias circuit is divided into parallel strips 52 so that the bias can be removed in a corresponding domain position in each of the registers. Absence of the bias then prevents movement of a domain from a chosen position in each of the registers, the remain domains being moved by the bi-polar pulses from source 56.