Fast Nondestructive Read, Slow Write Memory Device Using Thick Magnetic Films

A device is proposed for providing an ultra high speed read, but comparatively slow write, memory device. The device has certain similarities to other proposed devices, but the mode of operation and performance is quite new and makes use of effects which are normally avoided or minimized in usual memory devices. The storage element is a thick-film bias magnet with a coercive force smaller than its self-demagnetizing field and is tightly coupled to a second anisotropic thick film which serves as the sensing or reading device. The array conductors are all external to the coupled structure (i.e., no conductors lie between the films) thereby simplifying fabrication. A modified coincident current technique is used to write the information into the bias film. A stored ``1´´ is obtained by setting the bias film and hence the read film into a demagnetized state. A read current applied to the word line will cause rotation of the magnetic moments of the read film toward its hard axis, thus inducing a signal in the sense line. A stored ``0´´ is obtained by saturating the bias film, which in turn saturates the read film in its hard direction and thus prevents any signal from being induced in the sense line during reading. The modes of operation and design parameters are presented as well as a number of measurements. The results thus far have shown that there are no fundamental barriers to overcome.