All-Magnetic Logic Elements Using Strained Permalloy Wire

Abstract

An element for performing digital logic which employs Permalloy wire, solenoids, and resistors and utilizes a two-phase current pulse source has been studied experimentally. The reentrant hysteresis loop exhibited by a torsionally strained Permalloy wire provides the mechanism for power gain. A balanced input circuit assures unidirectional information flow and provides means for obtaining logic functions. Each element consists of two 0.6-in. bifilar-wound solenoids for bias and reset pulse currents, one or several 0.025-in. solenoids to which logic inputs are applied, an output resistor and a Permalloy wire core. The application of a bias current pulse to the logic element will cause the magnetization to change from the zero to the one state provided a signal is present simultaneously at the input to nucleate the magnetization reversal. The reset current pulse switches the magnetization back again and produces an output across the bias coil which is used to control one or several following elements. A buffer zone, the magnetization of which is controlled by the reset pulse, separates adjacent logic elements to minimize element interaction. Measurements on elements employing a 1.5-mil, 5-79 Permalloy core show that a switching time of 15 μsec and a power gain of 10 can be achieved. Preliminary tests indicate satisfactory operation over the temperature range of −55° to +185°C. These elements have been used to construct flip-flops, binary counters and a serial adder which employs majority logic. The circuits operated successfully when the pulse currents from the power supply were varied by ±20%. Because an open flux structure is used, it is believed that similar techniques will have application in circuits employing deposited magnetic films.