Permalloy clad drawn wire for use in a semipermanent memory

Permalloy clad drawn wire, a new memory element for large-scale semipermanent memory, has been fabricated, and its pulse response measured. This wire is fabricated by a process in which a silver-copper alloy rod is put in a Permalloy tube, which is then drawn through dies. The Permalloy clad drawn wire described in this paper has a diameter of 0.1 mm and a Permalloy outer layer 3.5 microns thick. In the final annealing, which is the last step in fabrication of the wire, magnetic anisotropy caused by drawing in the longitudinal direction of the wire is erased. At the same time, a new anisotropy having its easy axis circumferential to the wire appears, if the Permalloy composition is chosen so that its magnetostriction is slightly negative. Permalloy clad drawn wire can be used in almost the same way as the magnet card twistor memory, except that the wire requires a small bias current. This bias current determines the direction of magnetization when the drive pulse is removed. For the wire described, a bias current of less than 30 mA is sufficient.