TRANSVERSE FIELD ANNEALING PROCESS TO FORM E.A.S. MARKER HAVING A STEP CHANGE IN MAGNETIC FLUX

摘要

A marker (20) to be used in an article surveillance system (51) is formed by processing a continuous ribbon (28) of magnetic material having a longitudinal axis. Domains (42) are developed in the magnetic material to produce a wall configuration which includes a plurality of substantially parallel domain walls (40) extending in a wall direction that is canted at least 15~ 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.