A New Storage Element Suitable for Large-Sized Memory Arrays- The Twistor

A century ago Wiedemann 1 observed that if a suitable magnetic rod which carries a current is magnetized by an external axial field, a twist 1319 1320 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , N O V E M B E R 1 9 5 7 of the rod will result. The effect is a consequence of the resultant helical flux field causing a change in length of the rod in a helical sense. Conversely, it was also observed that a rod under torsion will produce a voltage between its ends when the rod is magnetized (see Fig. 1). Recently, during an investigation of the magnetic properties of nickel wire, it was observed that a voltage was developed across the ends of a nickel wire as its magnetization state was changed. Both the amplitude and the polarity of the observed signal could be varied by movements of the nickel wire. Most surprising, the amplitude of the observed voltage i 2 of Fig. 2, was many times that which would be expected if a con> ventional pickup loop were used. After determining experimentally that the observed voltage was generated solely in the nickel wire and was not a result of air flux coupling the sensing loop (nickel wire plus unavoidable copper return wire), it was concluded that the flux in the nickel wire must follow a helical path. This suggested that torsion was the cause of the observed effect, a conclusion verified experimentally. The direction of the applied twist de-