Cross-tie shift register

Abstract

The principle, design, fabrication and operating conditions of a shift register memory device using cross-tie wall structure in polycrystalline magnetic films will be described. This device is nonvolatile, silicon compatible and can be fabricated in a three mask level process. Each data track of this device consists of a stripline conductor, a 25 μm wide magnetic film data strip and single level data generator/propagator/detector circuitry. This is the first such device to incorporate a functioning generator, propagate circuit, and detector on a single level, thus greatly simplifying fabrication and increasing reliability and yield. A spatially varying magnetic field produced by the periodic wide/narrow propagate bias stripline is used in conjunction with the magnetic field produced by a uniform stripline to achieve propagation. Propagation is accomplished by generating cross-tie/Bloch line pairs and subsequently annihilating trailing pairs. Cross-tie shift registers have been fabricated on both glass and silicon substrates and have been tested.

Micromagnetic study of the double-layered MR elements

“…Therefore, a trial and error method was developed to discover the geometries which support the stable operations of the creation, annihilation and propagation of the Bloch lines in the crosstie wall. As a result, special structures such as serrated stripes [17] and snake shaped geometry [18] were suggested. It is not likely that this approach will lead to a successful commercial memory system because of the small output signal level and the lack of proper analysis model.…”