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AssigneeKnogo Corporation
InventorsY. Peter Zhou, Michael N. Cooper, Kyung-Ho Shin, Thomas P. Solaski, Jeffrey Taegue
Estimating the term…
A novel sensor element having low magnetic coercivity and an asymmetric hysteresis characteristic is formed by heating a strip of cobalt alloy in an exidizing atmosphere to form an oxide coating thereon and then the strip is cooled in the presence of a magnetic field of about 0.3 oersteds along its length. The strip is detected by subjecting it to an alternating magnetic interrogation field and passing the resulting magnetic disturbances through signal processing circuits which select pulses produced only once in each interrogation field cycle. The element is deactivated by subjecting it to a magnetic field which eliminates its asymmetry.
A sensor element having unique magnetic properties, said element comprising a first layer of a cobalt-iron alloy containing a metalloid element and a second layer of a complex metal-metalloid compound formed from the first layer, said layers being exchange coupled.
A sensor element having unique magnetic properties, said element comprising a first layer of a ferromagnetic material and a second layer of an antiferromagnetic material, said layers being exchange coupled.
A sensor element comprising an elongated strip of magnetic material having a magnetic coercivity of less than three oersteds and a magnetic hysteresis characteristic having a different slope in one direction of magnetization than in the opposite direction of magnetization.
A sensor element comprising an elongated strip of a cobalt-iron alloy containing a metalloid element which has been subjected to an oxidizing atmosphere at a temperature and for a time sufficient to form a film thereon.
An article surveillance system comprising an alternating magnetic field generator, a sensor element in the form of an elongated strip of a soft magnetic material and characterized by a magnetic hysteresis curve having a different slope in one direction of magnetization than in the opposite direction of magnetization, said sensor element being attachable to articles of merchandise to be protected, and a receiver responsive to magnetic waves generated by said generator, said receiver including a signal processor constructed and arranged to produce electrical signals corresponding to received magnetic waves which have been disturbed by said sensor element and to produce an alarm in response thereto.
A method of making a sensor element, said method comprising the steps of forming a first layer of an alloy of ferromagnetic material characterized by a magnetic coercivity less than three oersteds and subjecting said first layer to oxidation to form thereon a second layer of antiferromagnetic material which is exchange coupled with said first layer.
A method of detecting the presence, of an interrogation region, of a sensor element which has a magnetic hysteresis characterized by slopes of different steepness, said method comprising the steps of generating in said interrogation region an alternating magnetic field, detecting pulses produced by the effect of said sensor element on said magnetic field and producing an alarm in response to the occurrence of one pulse in each cycle of said alternating magnetic field.
Dependencies are inferred from the claim text.