FR2573895

An electronic surveillance system marker comprises an active component responsive to incident magnetic energy for causing an associated article surveillance system to render an output alarm and deactivatable, through change in the molecular organization of the active component, without requirement for disruption of the unitary character of the component or change in its chemical composition. The marker component is selected to be of molecularly unorganized, e.g., amorphous, matter and the deactivation step involves molecularly organizing such matter, e.g., by rendering crystalline at least a portion of the component. The amorphous matter is preferably selected to be a metal composition. The deactivation step is desirably practiced by maintaining such portion of the marker component at a temperature above the crystallization temperature of the component and thereby to crystallize a coercive force in the portion different from the coercive force in the remainder of the component. Alternatively, the marker component is selected to have retained stress which is mechanically constrained therein, the deactivation step involving the relieving of such retained mechanical stress.