Disturb Thresholds in Cylindrical Film Memory Wire

The magnetization of the circularly anisotropic magnetic wire developed for cylindrical film memories can be disturbed by a combination of two fields parallel to the hard and easy anisotropy axes, respectively. The measured threshold levels of the fields needed to disturb the wire are smaller than predicted by the rotational switching model. Under the specific conditions encountered in the memory, the reduction in the threshold levels is considerable and must be taken into account in the design of the memory. The threshold levels are very dependent on the way that the disturbing fields are applied. A pulsed field applied many times in a direction normal to the magnetization is considerably more effective in reducing the threshold levels than is a dc field of the same amplitude. The threshold relationships for different combinations of pulsed and dc fields in both easy and hard anisotropy directions are presented. The effect of reduced threshold levels on the design of a memory is discussed. They can result in inter-bit interaction. The amplitude of the readout signal may also change following particular writing sequences.