Abstract: A harmonic-type electronic article surveillance marker includes a thin, elongated active element and flux concentrators provided at the ends of the active element. The flux concentrators have magnetic anisotropies that are oriented perpendicular to the length of the active element. The orientation of the magnetic anisotropies and the anisotropy field of the flux concentrators stabilize the switching threshold of the marker. The switching threshold level can be controlled by varying parameters such as the angle of the magnetic anisotropies relative to the length of the active element, the strength of the anisotropy field of the magnetic anisotropies, and the geometry of the active element and the flux concentrators.

Abstract: A single deactivation device is used to deactivate both harmonic type EAS markers and magnetomechanical type EAS markers. The deactivation device includes a housing, and a permanent magnet and a coil disposed within the housing. The coil is circular and is arranged concentrically with, and outside of, the permanent magnet. The permanent magnet forms a DC magnetic field for deactivating the harmonic type marker by magnetizing control elements thereof. The coil is driven to generate an AC magnetic field that deactivates the magnetomechanical type marker by degaussing a control element thereof. The maximum amplitude of the AC magnetic field is lower than the level of the DC magnetic field, and is substantially below the coercivity of the control elements of the harmonic type marker. The coercivity of the control element of the magnetomechanical type marker is low enough to be degaussed by the AC magnetic field.

Abstract: A bias element for use in a magnetomechanical EAS marker is magnetized to saturation. Then the magnetic charge in the bias element is redistributed by applying to the bias element a magnetic field having an AC ringdown characteristic. The redistribution of magnetic charge improves the stability of the bias element, so that the marker incorporating the bias element is less likely to have its resonant frequency shifted by exposure to a stray magnetic field.

Abstract: A coil array for an EAS marker deactivation device is formed of three co-planar "pancake" coils energized by an a.c. drive signal and arranged to provide significant alternating magnetic fields in each of two orthogonal, horizontal directions. The coil geometry and arrangement are selected to provide smooth field distribution to minimize the possibility of harm to video and audio tapes and other magnetic medium products.

Abstract: A device for deactivating a magnetomechanical electronic article surveillance marker includes first, second, third and fourth rectangular coils arranged in a two-by-two array in a common plane. Drive circuitry energizes the coils according to an operating cycle which includes three modes. In the first mode, all four coils are driven with respective alternating currents in phase with each other. In the second mode, the first and second coils are driven in phase with each other and the third and fourth coils are driven substantially in phase with each other and substantially 180.degree. out of phase with the first and second coils. In the third mode, the first and third coils are driven in phase with each other and the second and fourth coils are driven in phase with each other and 180.degree. out of phase with the first and third coils.

Abstract: A material used to form a biasing element for a magnetomechanical EAS marker has a coercivity that is lower than the coercivity of biasing elements used in conventional magnetomechanical markers. The marker formed with the low coercivity material can be deactivated by applying an AC magnetic field at a level that is lower than is required for deactivation of conventional markers. The marker with the low coercivity bias element can also be deactivated when at a greater distance from a deactivation device than was previously practical.

Abstract: A magnetic recording system uses an improved spin valve magnetoresistive (SVMR) sensor. The SVMR sensor has a self-pinned laminated layer as the pinned ferromagnetic layer in place of the conventional single-layer pinned layer. Because this laminated layer is "self-pinned", a hard bias or exchange bias layer is not needed. The self-pinned laminated layer has at least two ferromagnetic films antiferromagnetically coupled to one another across a thin antiferromagnetically (AF) coupling film. Since the two ferromagnetic films in this laminated layer have their magnetic moments aligned antiparallel, their two magnetic moments can be made to essentially cancel by making the two ferromagnetic films of substantially the same thickness. The magnetic field energy generated by the signal field acting on this laminated layer will be significantly less than the effective anisotropy energy of the laminated layer.

Abstract: A magnetoresistive read sensor incorporates a granular multilayer sensing element comprising a plurality of layers of generally flat particles of a ferromagnetic material embedded in a nonmagnetic electrically conductive material. A bias layer separated from the magnetoresistive sensing element by a spacer layer provides a magnetic field to bias the magnetoresistive sensing element at a desired non-signal point. The ferromagnetic and the nonmagnetic materials are mutually immiscible, or may be miscible or partially miscible and processed in a manner to control interdiffusion. The magnetoresistive sensing element is formed by alternatively despositing layers of ferromagnetic material and layers of nonmagnetic conductive material on a substrate and then annealing the structure.

Abstract: A magnetoresistive read sensor incorporates a multilayer sensing element formed of one or more magnetoresistive elements in a planar array, each magnetoresistive element having a multilayer structure of at least two ferromagnetic layers separated by a nonmagnetic layer. The ferromagnetic layers are coupled antiferromagnetically by magnetostatic coupling at opposing edges of the ferromagnetic layers. A bias layer separated from the magnetoresistive sensing element by a spacer layer provides a magnetic field to bias the magnetoresistive sensing element at a desired non-signal point for linear response. The magnetoresistive sensing element is formed by alternatively depositing layers of ferromagnetic material and layers of nonmagnetic material on a substrate and then patterning the resulting structure using photolithographic techniques to provide a planar array of magnetoresistive elements.