Transverse field annealing process to form e.a.s. marker having a step change inmagnetic flux

摘要

A marker to be used in an article surveillance system is formed by processing a continuous ribbon of magnetic material having a longitudinal axis. Domains are developed in the magnetic material to produce a wall configuration which includes a plurality of substantially parallel domain walls extending in a wall direction that is canted at least 15 DEG from the longitudinal axis of the continuous ribbon. The continuous ribbon is then further processed to cause the wall configuration of substantially parallel domain walls to remain in a pinned state for values of applied field below a threshold value. The processed continuous ribbon can be cut to produce discrete magnetic elements which exhibit a step change in magnetic flux when the applied field crosses a threshold value.