Patent GB-1433901-A (GB)
Title: Magnetic devices
IPC: G11C19/08
Filed: 1973-08-23
Abstract: 1433901 Magnetic storage devices WESTERN ELECTRIC CO Inc 23 Aug 1973 [24 Nov 1972 29 Aug 1972] 40022/73 Heading H3B A single wall magnetic domain generator or replicator comprises a layer of magnetic material in which domains may be propagated by an in-plane rotating magnetic field along paths defined by first and second overlays of magnetically soft material, a domain at a position in the first overlay path where the two overlays are adjacent being caused to elongate between the overlays when the rotating magnetic field is in a particular orientation and a first pulse is applied to a conductor coupling the two overlays, a domain so elongated being divided by a second pulse in the conductor to provide both the original domain and its replicate. For domain generation the first overlay is a magnetically soft disc about which a permanent domain is rotated by the in-plane field, while for domain replication both overlays define propagation paths extending primarily in a linear direction. Domain generation.-In Fig. 1 a domain S is rotated about an overlay disc 16 by an inplane field source 14, and each time it reaches the spatial position shown in Fig. 2 and a current pulse i is passed between the limbs 20 and 21 of a T-shaped conductor 17, the domain elongates to couple with the first element of a second overlay 13, If a current pulse is then passed between limbs 20 and 22 the domain divides as shown in Fig. 3. An alternative arrangement, Fig. 10, uses a curved conductor formed with a slot N. A first current pulse P1 between 20 and 21 elongates the domain S rotating about disc 16 to S1, but the extended domain can extend over the slot to S 2  only when the pulse terminates. If a second pulse P2 of the same polarity is then applied between 20 and 21 the domain is divided. Domain replication.-Fig. 11 shows a storage system in which domains in a major loop path 112 may be transferred by replication into a storage minor loop path 113, or vice versa. Each loop path is defined by an overlay pattern of chevron-shaped magnetically soft elements as shown in Fig. 12 and a propagated domain DO is in strip form. Such a domain in loop 113 is elongated, Fig. 13, to couple with loop 112 when located between the limbs of a conductor loop 128 carrying a current pulse IS. When this current is replaced by a short current pulse I c  of reverse polarity, Fig. 14, the ends of the domain have been propagated in opposite directions along the two loops 112, 113 by the rotating field so that the tilted domain becomes severed into two parts as shown in Fig. 15. The overlay pattern may be modified so that it serves as the current loop, Fig. 18, the current path comprising overlay limbs 160, 161 and bridged chevrons in minor loop 113. A storage system including a major loop coupled to a plurality of minor loops for domain replication, and including a read-out arrangement in which domains are elongated and magnetoresistively detected is outlined, Fig. 17 (not shown). The overlays may be permalloy, and the magnetic layer Y 1 Gd 1 Tm 1 Ga 0À8 Fe 4À2 O 12  formed by deposition from the liquid phase on a substrate of Y 1 Gd 1À3 Tm 0À9 Ga 0À9 Fe 4 O 12 .