Stripe Domains in Thin Magnetic Films and Their Application to Magneto-Optical Displays

A thin magnetic film display element is described which consists of a planar, hermetically sealed unit containing a RIS 1 magnetic film and an overlying colloidal suspension of iron oxide. The effect of the ``stripe'' domain structure of the magnetic film upon the colloid is such as to furnish an element which is capable of diffracting light incident upon the surface of the element in a manner similar to that of a diffraction grating. The interference phenomena are, however, controllable by a magnetic field applied so as to cause changes in the distribution of the magnetization within the film. Both the intensity and color of the diffracted light can be modified by the applied field and such modification, once produced, is permanent until subsequent alteration is required. Command of the element can be accomplished by coincident drive currents in matrix fashion as is common in the operation of planar magnetic memories. Measurements performed on experimental RIS 1 display panels indicate an element switching speed of less than 10 μsec, a brightness of over 30 ft·L and a contrast ratio of greater than 70:1. The feasibility of manual entry of information and electrical read of the latter has been demonstrated as well.