Patent GB-1235929-A (GB)
Title: Improvements in or relating to information storage arrangements
Inventor: BOBECK ANDREW HENRY
IPC: G11C19/04
Filed: 1968-10-09
Abstract: 1,235,929. Magnetic storage apparatus. WESTERN ELECTRIC CO. Inc. 9 Oct., 1968 [12 Oct., 1967], No. 47869/68. Heading H3B. In an information storage apparatus in which a single wall domain is moved from one position to the other position in a two-position bit location in a sheet of magnetic material in accordance with information to be stored in the location on impedance additional to that of sheet 11 to domain movements from one position to the other position is provided. The store of Fig. 1 includes a sheet 11 of a rare earth orthoferrite in which single wall domains can be moved in response to offset magnetic propagation fields and a contiguous glass sheet 21 apertured to provide figure of eight configurations constituted by a plurality of apertures filled with magnetic material A12, A21, A22 &c. The magnetic material is magnetized in a direction opposite to that of the single wall domains, Fig. 2B (not shown), and hence repel a single wall domain. A domain D, Fig. 2A, occupies the position shown in this Figure in a bit location if a "1" is stored and the other position in the figure of eight if a "0" is stored Fig. 3 (not shown) repulsive forces from the portions b1, b2 of the figure of eight constituting an impedance to domain movements. The repulsive field is superimposed on a bias magnetic field generated by magnet M. In order to store a "0" currents i are applied to the selected X, Y conductors in the direction shown so that at the selected bit location fields which attract the domain D are set up sufficient to overcome the threshold provided by the magnetic material of regions b1, b2 and the domain D moves to the "0" position. At the partially selected bit locations at which only one conductor is energized the attractive force is insufficient to overcome the threshold and the domains do not move to the "0" position. In order to store a "1" the currents i are reversed in polarity Read out.-In order to read out of a required bit location pulses of the polarity shown in Fig. 2A are applied to the X,Y lines corresponding to the required bit location which cause a domain D to move to the zero position thereby inducing a voltage in sense conductor 15 indicating that a domain was in the "1" position. In the absence of a domain in the "1" position no output is induced in the conductor 15 when pulses are applied to the X, Y lines. The sense conductor 15 includes a return conductor to ground running parallel with the conductor 15, the two conductors being arranged for noise suppression Fig. 5 (not shown). Read out may alternatively be optical using the Kerr and Faraday effects. 3-position per bit location.-In the embodiment of Fig. 6 each bit location includes three positions arranged in line encompassed by an oval shaped boundary impedance. The central position, occupied by domain D, corresponds to the "1" position of Fig. 2A, the lower position to the "0" position and the upper position to a read position. A permanent positive pole of a dipole is fixed centrally in each position of the bit location to provide an additional impedance to domain movement by using three regions of positively magnetized material in sheet 21, Fig. 1. Information is written into a bit location in the same manner as described above by applying pulses to the X, Y write conductors. Read out is by applying pulses to the additional X, Y read conductors so that the presence of a domain in the central position is detected as that domain moves to the upper position. Opposite polarity read pulses return any domain so moved. In the arrangement of Fig. 7 (not shown) the pulses necessary to return a domain to the central position are made unnecessary by including a negative pole distribution in the upper position which repulses domains and renders that position unstable. Instead of using a non-magnetic sheet 21 an apertured magnetic sheet may be used to distort a uniform bias field to provide domain movement impedance.