SE7412483L - - Google Patents

Abstract

1474703 Magnetic storage devices PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 3 Oct 1974 [6 Oct 1973] 42930/74 Heading H3B Magnetic bubble domains of two distinct and stable sizes, and which may represent the binary digits zero and one respectively, are present simultaneously in a layer of magnetic material, the area of the larger bubbles being at least 15% and at most 125% greater than the area of the smaller bubbles. The bubble size is determined by a domain guiding structure consisting of an overlay of two or three permalloy strips, a two permalloy strip arrangement 2, 3 for small and large bubbles 5, 6 being shown in Fig. 1, while Fig. 2 shows a three strip arrangement 12, 13, 14 for small and large bubbles 16, 17. By representing binary data with bubbles of two different sizes all possible bubble positions in the magnetic layer 1, 11 may be occupied. A small bubble 35 coupled with a single permalloy strip 32, Fig. 4a, may be expanded to a large bubble 36, Fig. 4b, by a current pulse in a conductor loop 34. Similarly a current pulse of reverse polarity in a conductor loop 44, Figs. 5a and 5b, may be used to contract a large bubble 45 coupled with two permalloy strips 42, 43 into a small bubble 46. The bubbles may be propagated along the length of the permalloy strips by a varying magnetic field, propagation being effected by a T and I bar permalloy pattern 4, Fig. 1, or as permalloy angel fish pattern 15, Fig. 2. Alternatively the domain guiding structure and propagation pattern may be combined as shown in Fig. 3, propagation being effected by current in a convoluted conductor 24 while the direction of propagation is determined by the spatial positions of projections 25 on the permalloy strip 22. For reading a bubble with discrimination as to size a permalloy strip 56, Fig. 6, connected to gold conductors 57, 58 is sufficiently adjacent to one strip 53 of the domain quide structure to detect a large bubble by induction but not a small bubble.