Soniscan: A ferroacoustic thin-film memory

The Soniscan ferroacoustic memory is a new all-electronic mass storage system which utilizes a propagating sonic pulse to access a batch-fabricated film storage medium. The storage element consists of two magnetostrictive film layers with a conductor sandwiched between them. They are deposited on a thin glass substrate and etched into a suitable pattern. A piezoelectric transducer is bonded to one edge of the substrate. The switching behavior of the magnetic storage element is described by a modified Stoner-Wohlfarth model and the sonic wave generation and propagation by a one-dimensional transmission-line analog. The fabrication and operation of the storage elements are discussed. The design of a 10⁷bit memory system is presented. A 2048-bit experimental model of a Soniscan memory has been constructed. It has an access time of less than 2μs, a data rate of 7 Mbit/s/line, and a storage density of 4000 bit/in²A Soniscan bulk store will be relatively inexpensive, since memory planes are batch fabricated; a single electronic unit, the transducer driver switch, half-selects tens of thousands of bits during reading and writing; and sense and recording electronics are shared among many planes by the series stringing of write-sense lines. It is expected that Soniscan will present an attractive alternative to electromechanical units in many applications.