The Dispersion Locked Memory Mode for Magnetic Films

In the usual thin film magnetic memory, that which utilizes the two stable easy direction magnetization states for storage, inverted films (H
c
>H
k
) are often used to reduce disturb sensitivity. In general, inverted films exhibit a high angular dispersion and an open hard direction hysteresis loop with considerable remanence. Middelhoek has attributed this high remanence to the large number of Néel walls formed after the application of a hard direction field exceeding the anisotropy field. The stable state resulting from this “dispersion locking” finds utility as a storage state and is the subject treated here. This paper describes an orthogonal storage mode which could form the basis for a word-organized high-speed memory using unipolar drivers. Test programs and the results obtained therefrom are illustrated to show the useful operating range in a typical film. The total absence of “creep” and the unipolar digit current input to the device are seen to be features of this dispersion locked mode.