For years the desideratum of flat-film fabricators has been a simply constructed high-density random-access NDRO bit organized memory with word and digit current levels low enough for high-density integrated electronics. This paper describes a new direction in flat-film memories that achieves that goal and a projected cost/bit an order-of-magnitude less than that of integrated circuit wire or core memories. Permalloy films only 100-Å thick, continuous in at least one direction to avoid registration problems, are deposited on glass or metal substrates; overlays having densities up to 40 000 bits/in.2 requiring word and digit currents as low as 25-mA peak are attached. The low-signal problem is solved by using rf alternating current in the word-line overlay and a sense amplifier tuned to double the word-current frequency. Switching is by magnetization creep, which allows bit organization and sharing of sense amplifiers similar to that of plated wire. Functional performance, uniformity, and reproducibility of four types of array geometries (10 000–30 000 bits/in.2) are described. Electron micrographs of domains in a 100-Å NiFe mirror being written, disturbed, and erased with 2-mil word and digit lines are shown. Also described are: a word driver and selection system which provides a constant word current of 35-mA rms at 35 MHz applicable to an array of 4096 word lines, and a sense gating system capable of sensing a 20-μ volt-induced sense signal at a frequency of 70 MHz with a 5:1 ``1'' to ``0'' ratio before discrimination; the sense amplifier has a 12-MHz bandwidth which allows 50-nsec changes in sense signal to be followed, but rejects word and digit noise. The access and cycle times of a prototype module under construction are 2 μsec.
An observation technique utilizing the longitudinal Kerr magneto-optic effect was used in various studies of thin film recording. The semitransparent nature of the recording media allowed simultaneous observation of recorded domains and the write and read head gaps. Thin film heads were used to record in iron films having coercivities ranging from 60 to 160 Oe. The apparatus allowed quick determinations of maximum linear densities which were as high as 1550 flux reversals/cm. Recorded domain orientation with respect to the gap of a thin film read head was easily observed, and the corresponding output signals on an oscilloscope were photographed. The write-read-observe apparatus with a thin film read head was also helpful in detecting the magnetic field from Néel walls.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.