Patent GB-1016173-A (GB)
Title: Magnetic storage device
IPC: G11C11/06
Filed: 1962-10-10
Abstract: 1,016,173. Magnetic thin film matrix stores. HUGHES AIRCRAFT CO. Oct. 10, 1962 [Oct. 30, 1961], No. 38363/62. Heading G4C. [Also in Divisions H1 and H3] A magnetic storage element comprises a circularly-polarized magnetic thin film formed on a flat substrate. Construction of elements. A thin magnetic film 106, Fig. 6, of 80% Ni, 20% Fe is formed by evaporation or electro-chemical deposition on a substrate 108 having non-magnetic properties such as glass, anodized aluminium, plastics or ceramic, the film having a central aperture 110 in alignment with a similar aperture in the substrate. During the formation of the film, a current is passed through a wire extending through the substrate aperture to establish a circular path of easy magnetization. The film and substrate is sandwiched between two conductors 120, 120a which are separated by insulation 114 and are insulated from the film. The conductors are shaped to provide partial loops adjacent each surface of the film, and are connected together at one end 149 to form a bias winding which magnetizes the film in a radial sense when energized. A sensing and writing conductor 138 is passed through the aligned substrate and film apertures, and when energized establishes a circumferential field acting along the circular path of easy magnetization. Several separate thin film storage elements may be formed on a common substrate, and a suitable vacuum deposition process is described, Fig. 2 (not shown). The several films formed on a common substrate may be coated with insulation and overlaid by copper biasing windings formed in the shape shown in Fig. 6, by vacuum deposition through a mask, Fig. 3 (not shown). Alternatively, the film storage elements may be formed by electrochemical deposition in a plating bath 71, Fig. 4, in which a glass substrate 82 carries a plurality of copper discs joined together to form the cathode. A continuous current is passed through a wire 94 which threads apertures in the discs and the substrate, and so establishes a circular path of easy magnetization as the thin magnetic layer is deposited from the electrolyte on to the copper discs. Construction of storage array. Fig. 7 shows two stacks 162, 164 of magnetic thin films, each sandwiched between a biasing winding. Each layer of a stack stores a binary word, and the individual digits of the word are stored in respective columns of a stack such as columns 166, 168, 171 of stack 162. Groups of bias windings are connected at one end to single terminals X1-X4 and at the other end to terminals X 1 -X 4 , each Y terminal being connected to a different bias winding in each of the groups. Consequentially by applying a pulse between a selected X and a selected Y terminal, a single bias winding in one stack only is energized, each bias circuit including a rectifier such as 246. The writing and sense wires 138, 208, 209 are threaded through similar columns of both stacks, and include balancing transformers 220, 230, 232 providing connections to write conductors 226, 236, 238 and sense conductors 224, 233, 242. Selection of a bias winding for reading or writing a word. Bi-stable units 370, 373, 376, 378, Fig. 9, are set in accordance with signals in a control circuit 427 to selectively open an AND gate in each of two rectifiers gate groups 382, 398. Consequently a transistor 362-368 is conditioned to pass a pulse from a transformer 350 to an X terminal of the bias windings, and a transistor 410-416 is rendered conductive to complete the selected bias winding circuit through a Y terminal. Non-destructive read-out. A radial flux is produced in each thin film storing a selected word when the associated bias winding is energized; and partial switching of the films occurs which induces outputs in the sense wires 138, 208, 209, Fig. 7, appropriate to the direction of remanent magnetization. The sensed outputs pass through sense conductors 224, 233, 242 to respective amplifiers such as 516, Fig. 8. Sense amplifiers, each amplifier 516, 518, Fig. 8, has a PNP transistor controlled by the sense output in respective conductors 224, 234. An intermediate amplifying transistor 548 and an emitter-follower transistor 560 are also provided, the amplified output being applied to conductor 592 in one or the other polarity sense according to the digit read out. Each sense amplifier is gated by a strobe pulse applied through a transformer 530 to normallyconductive rectifiers 576, 582 so that the amplifiers are operative only during the read out period in a read-write cycle. Pulse source. A pulse 334 from a computer control system 335 is applied through an amplifier 332 to a delay line 330 which provides a bias winding pulse on conductor 344 effective for the duration of the read/write operation. In addition, the sense amplifier strobe pulse on conductor 514 and a write control pulse on conductor 434 is derived from the delay line. Writing. A signal on lead 453 sets a write control bi-stable unit 448 and sets a digit register bi-stable unit 450 according to the digit value. Other digits of the word are stored in digit registers such as 452. The two units 448 and 450 open one of two rectifier AND gates 456, 478 in a writing circuit 444, and when a write control pulse is applied from conductor 434 to a transformer 442, one side of a pulsepull transistor group 464, 486, 502, 508 becomes conductive and applies a pulse of appropriate polarity to a write conductor 226. At this phase of operation a bias winding and the sense conductors of one stack of thin films are coincidently energized, and the remanent magnetic states are switched in accordance with the polarity of the sense-winding pulses. The bias winding pulse is terminated before the sense winding pulses and the thin films take up remanent states along the easy path in correspondence with the word to be registered. If the original word is to be retained after non-destructive read out, the writing operation is suppressed. Modifications. In Fig. 11 (not shown), the use of balancing transformers in the sensing circuits is avoided by the use of separate conductors for sensing and writing, both conductors being threaded through each film aperture and arranged relatively so as to suppress spurious output pulses. The use of two bias conductors to form a winding may be avoided by insulating the films from a conductive substrate which serves as a common bias conductor for all the films in a plane; Fig. 12 (not shown).