GB1436709A - Data storage - Google Patents

Abstract

1436709 Magnetic storage arrangements POST OFFICE 1 Aug 1973 [8 Aug 1972] 36895/72 Heading H3B Binary information is propagated in a cylindrical magnetic domain shift register in a form equivalent to a travelling wave, propagation being effected by the interacting movement of a series of domains each constrained by a high permeability overlay pattern to move only between two stable and adjacent positions. In Fig. 4 the two permitted positions for a domain are defined by a pair of facing C-shaped overlays such as 15A, 15B, while in Fig. 5 a domain can exist at either end of an overlay bar such as 32. A series-parallel array of six overlay dots such as 54 is used in Fig. 6 to define two permitted domain locations each formed by a square of four dots, the overlay pattern in this embodiment including bar overlays 53-61 as used in Fig. 5. Each arrangement operates on the same principle which involves triplet grouping of the individual two-position domain overlays such as 31, 32, 33 and 32, 34, 35, Fig. 5, and the provision of domain shift conductors 42, 43, 44. Domains in the normal or zero positions are represented in the figures by hatched circles and are initially formed by superimposing, on the transverse bias field normally required, a smaller field pulsed with microsecond pulses at a repetition rate of about 1 kHz. Superfluous domains are then removed by a small increase in the bias field. Operation of the register involves pulsing conductor 42, Fig. 5, so that a domain is displaced to the opposite end of overlay bar 31. Conductor 44 is then pulsed by a positive pulse which displaces the domain in bar 33 and is then negatively pulsed to restore the bar 33 domain to its initial position. As the domains of overlay bars 31, 32, 33 are immediately adjacent during the positive pulse period, mutual repulsion causes the domains of bars 31 and 32 to be transferred to the opposite bar ends. Conductor 43 is then pulsed in the same manner as conductor 44 with the result that the domain of bar 35 is moved into proximity with the domains of bars 32 and 34. Mutual repulsion again takes place, and this time the domain of bar 34 is transferred to the opposite end of the bar. Subsequent interaction of the domains as the conductors 44 and 43 are alternately pulsed, steps the input signal from conductor 42 as a travelling wave of domain displacement from left to right through the register. A suitable magnetic material for supporting the domains is stated to be a layer of magnetic garnet such as Eu 1 Er 2 Ga 0À7 Fe 4À3 O 12 on a non-magnetic substrate.