GB1054751A - - Google Patents

Abstract

1,054,751. Magnetic information storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 27, 1964 [March 29, 1963], No. 8100/64. Heading H3B. [Also in Division H1] In a magnetic thin film store in which two conductors extend transversely to each other the area of film adjacent the conductors' intersections forms an individual storage cell and the width of each conductor is not greater than the " remaining domains " produced in the film by an incomplete switching process. If a gradually increasing external field H is applied in the direction # to an anisotropic thin film the magnetization of the latter is as shown in Figs. 5 a to 5 d, the vectors rotating until H = Hp, Fig. 4, when partial rotational switching occurs and stripshaped domains appear with the magnetization of alternate strips in different directions. Since a stray field energy with a strong local effect is linked with the suddenly formed domain walls and prevents further rotational switching, then if before wall moving occurs Fig. 5d, the external field is switched-off the stray field energy prevents the magnetization returning to its initial conditions and " remaining domains " of opposite magnetization directions are left, Fig. 5e. In the store of Fig. 11 (not shown), orthogonal sets of strip drive lines 12, 13 are arranged above a magnetic film 11. The areas 19 of the film 11 underlying the intersections of the drive lines form the storage cells and are of smaller area than the " remaining domains " which are formed by incomplete switching and reducing the external field to zero. Since the storage cells are smaller than the domains only the anisotropy of the film and the drive field are effective so that the magnetization of each cell can switch coherently. The memory cells may be rectangular, Fig. 13 (not shown), and the drive lines may be connected in parallel, Figs. 14, 15 (not shown).