Deactivatable/reactivatable magnetic marker having a step change in magnetic flux

Claim 2

A marker for use in an article surveillance system in which an applied alternating magnetic field is established in a surveillance zone and an alarm is activated when a predetermined perturbation to said field is detected, said marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard or semi-hard magnetic material; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to the applied alternating magnetic field such that the magnetic flux of said marker element undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said marker element having a deactivated state wherein said marker element exhibits a different hysteresis characteristic from the hysteresis characteristic exhibited by said marker element in the active state; d) said second component of said marker element having an activating state which places said marker element in said active state and a deactivating state which places said marker element in said deactivated state; whereby the marker element is switched between said active state and said deactivated state by switching said second component between said activating state and said deactivating state, respectively.

Claim 3

A marker in accordance with claim 1 wherein: said marker element when in said deactivated state exhibits a hysteresis characteristic with step changes in flux which are less than the step changes exhibited by said marker element when in the active state, or exhibits a hysteresis characteristic with only gradual changes in flux.

Claim 4

A marker in accordance with claim 2 wherein: said activating state of said second component corresponds to a first magnetic state of said second component; and said deactivating state of said second component corresponds to a second magnetic state of said second component.

Claim 5

A marker in accordance with claim 3 wherein: said first magnetic state is one where the second component is magnetized substantially to saturation; and said second magnetic state is one where the second component is substantially demagnetized.

Claim 6

A marker in accordance with claim 1 wherein: said hard or semi-hard magnetic material of said second component comprises a layer which surrounds said first component.

Claim 7

A marker in accordance with claim 1 wherein: said second component has a thickness which is less than about 1 um.

Claim 8

A marker in accordance with claim 1 wherein: said preselected offset field value is substantially zero and said hysteresis characteristic of said marker element in said active state: A) exhibits a negligible flux change for a first direction of said applied field having a value which is up to said predetermined threshold value; B) exhibits a first-direction step change in flux at the first direction value of the applied field equal to said predetermined threshold value; C) exhibits a gradual decrease in flux for a decrease in the first direction value of the applied field from beyond said predetermined threshold value; D) exhibits a negligible flux change for a second direction of said applied field having a value which is up to said predetermined threshold value, said second direction being opposite said first direction; E) exhibits a second-direction step change in flux at the second direction value of the applied field equal to said predetermined threshold value; and F) exhibits a gradual decrease in flux for a decrease in the second direction value of said applied field from beyond said predetermined threshold value.

Claim 9

A marker in accordance with claim 1 wherein: said soft magnetic material comprises a soft amorphous magnetic material; and said second component comprises a crystallized region of said soft amorphous magnetic material.

Claim 10

A marker in accordance with claim 8 wherein: said soft amorphous magnetic material comprises a transition metal-metalloid composition.

Claim 11

A marker in accordance with claim 9 wherein: said transition metal-metalloid composition comprises a transition metal which represents 60%-90% of said composition.

Claim 12

A marker in accordance with claim 10 wherein: said transition metal-metalloid composition comprises one or more transition metals selected from the group comprising Fe, Co, and Ni.

Claim 13

A marker in accordance with claim 11 wherein: said transition metal-metalloid composition is essentially given by the formula Co 74 .26 Fe 4 .74 Si 2 .1 B 18 .9.

Claim 14

A marker in accordance with claim 9 wherein: said transition metal-metalloid composition is essentially given by the formula Co 39 .5 Fe 39 .5 Si 2 .1 B 18 .9.

Claim 15

A marker in accordance with claim 1 wherein: said soft magnetic material comprises a transition metal-metal composition.

Claim 16

A marker in accordance with claim 14 wherein: said transition metal-metal composition comprises Co in an amount that is about 75-95% of said composition.

Claim 17

A marker in accordance with claim 15 wherein: said transition metal-metal composition is selected from the following group of compositions: Co 90 Zr 10 Co 90 Zr 8 Nb 2 Co 90 Zr 5 Nb 5

Claim 18

A marker in accordance with claim 1 wherein: said soft magnetic material is amorphous; and said semi-hard or hard magnetic material is a deposit on said soft amorphous magnetic material.

Claim 19

A marker in accordance with claim 1 wherein: said marker element when in said active state has domains whose walls are in a pinned state and remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until applied field reaches the predetermined threshold value at which the walls are released from the pinned state causing said regenerative step change in magnetic flux, the walls returning to the pinned state at the time when the applied field reaches the preselected offset field value after passing through the predetermined threshold value and said marker element when in said deactivated state has domains whose walls are inhibited from assuming the pinned state.

Claim 20

A marker for use in an article surveillance system in which an applied alternating magnetic field is established in a surveillance zone and an alarm is activated when a predetermined perturbation to said field is detected, said marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard or semi-hard magnetic material made from the first component; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to the applied alternating magnetic field such that the magnetic flux of said marker undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said second component being substantially magnetized to place the marker element in its active state.

Claim 21

A marker for use in an article surveillance system in which an applied alternating magnetic field is established in a surveillance zone and an alarm is activated when a predetermined perturbation to said field is detected, said marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard or semi-hard magnetic material made from the first component; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to the applied alternating magnetic field such that the magnetic flux of said marker undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said second component being substantially magnetized to place the marker element in its active state.

Claim 22

A marker in accordance with claim 19 wherein said predetermined threshold value depends upon the composition selected for the material of the first component.

Claim 23

An electronic article surveillance system for detecting the presence of an article in an interrogation zone comprising: means for generating an applied alternating magnetic interrogation field in the interrogation zone, the magnitude of said interrogation field in said interrogation zone exceeding a predetermined threshold value; and a marker secured to the article, the marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard a semi-hard magnetic material; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to said applied alternating magnetic field such that the magnetic flux of said marker element undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said marker element having a deactivated state wherein said marker element exhibits a different hysteresis characteristic from the hysteresis characteristic exhibited by said marker element in the active state; d) said second component of said marker element having an activating state which places said marker element in said active state and a deactivating state which places said marker element in said deactivated state; whereby the marker element is switched between said active state and said deactivated state by switching said second component between said activating state and said deactivating state, respectively; and receiver means for detecting the presence of the marker when the marker element is in the interrogation zone and while the marker element is in the active state by detecting perturbations of the interrogation field.

Claim 24

An electronic article surveillance system for detecting the presence of an article in an interrogation zone comprising: means for generating an applied alternating magnetic interrogation field in the interrogation zone, the magnitude of said interrogation field in said interrogation zone exceeding a predetermined threshold value; and a marker secured to the article, the marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard a semi-hard magnetic material; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to said applied alternating magnetic field such that the magnetic flux of said marker element undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said marker element having a deactivated state wherein said marker element exhibits a different hysteresis characteristic from the hysteresis characteristic exhibited by said marker element in the active state; d) said second component of said marker element having an activating state which places said marker element in said active state and a deactivating state which places said marker element in said deactivated state; whereby the marker element is switched between said active state and said deactivated state by switching said second component between said activating state and said deactivating state, respectively; and receiver means for detecting the presence of the marker when the marker element is in the interrogation zone and while the marker element is in the active state by detecting perturbations of the interrogation field.

Claim 25

A system in accordance with claim 21 wherein: said activating state of said second component corresponds to a first magnetic state of said second component; and said deactivating state of said second component corresponds to a second magnetic state of said second component.

Claim 26

A system in accordance with claim 22 further comprising: first means for changing the magnetic state of said second component from said first magnetic state to said second magnetic state.

Claim 27

A system in accordance with claim 23 wherein: said first magnetic state of said second component is one in which said second component is substantially magnetized by applying a DC magnetic field to said marker; and said first means includes means for substantially demagnetizing said second component to place said second component in said second magnetic state.

Claim 28

A system in accordance with claim 24 wherein: said demagnetizing means applies one of an AC degaussing field and a field from a multipole magnet to said marker.

Claim 29

A system in accordance with claim 25 wherein: said AC degaussing field has an initial amplitude equal to or greater than 500 Oe.

Claim 30

A system in accordance with claim 23 wherein: said first magnetic state of said second component is a magnetic state developed by bringing a multipole magnet adjacent to said marker; and said first means comprises means for applying one of an AC degaussing field and a DC field to said marker.

Claim 31

A system in accordance with claim 23 further comprising: second means for changing the magnetic state of said second component from said second magnetic state to said first magnetic state.

Claim 32

A system in accordance with claim 28 wherein: said second means comprises means for applying a DC field to said marker.

Claim 33

A system in accordance with claim 29 wherein: said DC field is equal to or greater than 200 Oe.

Claim 34

A system in accordance with claim 21 wherein: said marker element when in said active state has domains whose walls are in a pinned state and remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches the predetermined threshold value at which the walls are released from the pinned state causing said regenerative step change in magnetic flux, the walls returning to the pinned state at the time when the applied field reaches the preselected offset field value after passing through the predetermined threshold value; and said marker element when in said deactivated state having domains whose walls are inhibited from assuming the pinned state.

Claim 37

A method of making a marker in accordance with claim 32 wherein: said first processing step comprises: forming said first and second components from said one or more materials; and establishing in said second component said activating state; and said establishing step occurs concurrently with or subsequent to said forming step.

Claim 38

A method of making a marker in accordance with claim 33 wherein: said soft magnetic material comprises an amorphous transition metal-metal composition.

Claim 39

A method of making a marker in accordance with claim 34 wherein: said transition metal-metal composition comprises Co in an amount that is about 75-90% of said composition.

Claim 40

A method of making a marker in accordance with claim 35 wherein: said transition metal-metal composition is selected from the following group of compositions: Co 90 Zr 10 Co 90 Zr 8 Nb 2 Co 90 Zr 5 Nb 5 .

Claim 41

A method of making a marker in accordance with claim 32 wherein: said second processing step occurs subsequent to said first processing step and includes establishing domain walls in said marker element which remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until said applied field reaches said predetermined threshold value.

Claim 42

A method of making a marker in accordance with claim 32 wherein: said one or more materials comprise a soft amorphous magnetic material; and said first processing step comprises annealing said soft amorphous magnetic material in a first annealing state at a temperature and for a time sufficient to at least substantially crystallize a region of said soft amorphous magnetic material, whereby said crystallized region forms said second component of said marker element, and an uncrystallized bulk region of said soft amorphous magnetic material forms said first component of said marker element.

Claim 43

A method of making a marker in accordance with claim 38 wherein: said soft amorphous magnetic material comprises a transition metal-metalloid composition.

Claim 44

A method of making a marker in accordance with claim 39 wherein: said soft amorphous transition metal-metalloid composition is essentially given by the formula Co 39 .5 Fe 39 .5 Si 2 .1 B 18 .9.

Claim 45

A method of making a marker in accordance with claim 39 wherein: said transition metal-metalloid composition comprises a transition metal which represents 60%-90% of said composition.

Claim 46

A method of making a marker in accordance with claim 41 wherein: said transition metal-metalloid composition comprises one or more transition metals selected form the group comprising Fe, Co, and Ni.

Claim 47

A method of making a marker in accordance with claim 42 wherein: said transition metal-metalloid composition is essentially given by the formula Co 74 .26 Fe 4 .74 Si 2 .1 B 18 .9.

Claim 48

A method of making a marker in accordance with claim 43 wherein: said time over which said first annealing stage is conducted is within a range of about 15 min. to about 60 min.; and said temperature at which said first annealing stage is conducted is about 380° C.

Claim 49

A method of making a marker in accordance with claim 44 wherein: said second processing step comprises: annealing of said soft amorphous magnetic material in a second annealing stage to establish domain walls in said marker element, said domain walls remaining in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches said predetermined threshold value, said second annealing stage being conducted at a temperature of about 400° C. and for a time of about 5 minutes.

Claim 50

A method of making a marker in accordance with claim 45 wherein: said first processing step includes one of applying a DC field of about 60 Oe to said amorphous magnetic material and contacting said amorphous magnetic material with a multipole magnet.

Claim 51

A method of making a marker in accordance with claim 46 wherein: said first and second annealing stage are each carried out in an environment consisting essentially of one of air, nitrogen and mixtures thereof.

Claim 52

A method of making a marker in accordance with claim 38 wherein: said time over which said first annealing stage is conducted is within a range of about 2 minutes to 120 minutes and the temperature at which said first annealing stage is conducted is within a range of about 350° C. to 450° C.; and said second processing step comprises: annealing of said soft amorphous magnetic material in a second annealing stage, said second annealing stage being conducted for a time within a range of about 1 minute to 5 minutes and at a temperature within a range of about 400° C. to 420° C.

Claim 53

A method of making a marker in accordance with claim 38 wherein: said second processing step comprises: annealing said soft amorphous magnetic material in a second annealing stage at a temperature and for a time so as to establish domain walls in said marker, said domain walls remaining in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches said predetermined threshold value.

Claim 54

A method of making a marker in accordance with claim 38 wherein: said first processing step includes applying a DC magnetic field along the length of said soft amorphous magnetic material.

Claim 55

A method of making a marker in accordance with claim 38 wherein: said first processing step contacting said soft amorphous magnetic material with a multipole magnet.

Claim 56

A method of making a marker in accordance with claim 32 wherein: a first one of said materials comprises a soft amorphous magnetic material; a second one of said materials comprises a semi-hard or hard magnetic material; and said first processing step comprises integrally depositing said second one of said materials on said first one of said materials.

Claim 57

A method of making a marker in accordance with claim 32 wherein: the thickness of said second component is less than about 1 um.

Claim 58

A method of making a marker in accordance with claim 32 wherein: said marker element when in said active state has domains whose walls are in a pinned state and remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches the predetermined threshold value at which the walls are released from the pinned state causing said regenerative step change in magnetic flux, the walls returning to the pinned state at the time when the applied field reaches the preselected offset field value after passing through the predetermined threshold value; and said marker element when in said deactivated state has domains whose walls are inhibited from assuming the pinned state.

Claim 63

A method of making a marker in accordance with claim 56 wherein: said step of applying a DC field occurs concurrently with or subsequent to said step of heating said marker element to form a part of said soft amorphous magnetic material into said hard or semi-hard component.

Claim 64

A method of making a marker in accordance with claim 57 wherein: said step of heating said marker element to cause said marker element to exhibit said hysteresis characteristic occurs subsequent to said step of applying said DC field to said marker element and includes establishing domain walls in said marker element which remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches said predetermined threshold value.

Claim 65

A method of making a marker in accordance with claim 58 wherein: said step of heating said marker element to form a portion of said soft amorphous magnetic material into said hard or semi-hard component occurs for a time sufficient to at least substantially crystallize a region of said soft amorphous magnetic material, said crystallized region forming said hard or semi-hard component.

Claim 66

A method of making a marker in accordance with claim 59 wherein: said soft amorphous magnetic material comprises a transition metal-metalloid composition.

Claim 67

A method of making a marker in accordance with claim 60 wherein: said step of heating said marker element to form a part of said soft amorphous magnetic material into said hard or semi-hard component is conducted for a time within a range of 15 minutes to 60 minutes and at a temperature of about 380° C.; said step of heating said marker element to cause said marker element to exhibit said hysteresis characteristic is conducted at a temperature of about 400° C. and for a time of about 5 minutes; and said step of applying a DC field to said marker element includes one of applying a DC field of about 60 Oe to said amorphous magnetic material and contacting said amorphous magnetic material with a multipole magnet.

Claim 68

A method of making a marker in accordance with claim 60, wherein: said step of heating said marker element to form a part of said soft amorphous magnetic material into said hard or semi-hard component is conducted for a time within a range of about 2 minutes to 120 minutes and at a temperature within a range of about 350° C. to 450° C.; and said step of heating said marker element to cause said marker element to exhibit said hysteresis characteristic is conducted at a time within a range of about 1 minute to 5 minutes and at a temperature in a range of about 400° C. to 420° C.

Claim 69

A method of making a marker in accordance with claim 61 wherein: said transition metal-metalloid composition is essentially given by the formula CO 39 .5 Fe 39 .5 Si 2 .1 B 18 .9.

Claim 70

A method in accordance with claim 56 wherein: soft amorphous magnetic material is selected from the following group of compositions: Co 90 Zr 10 Co 90 Zr 8 Nb 2 Co 90 Zr 5 Nb 5 .

Claim 71

A method of making a marker in accordance with claim 56 wherein: said marker element when said hard or semi-hard component is in the first magnetic state, has domains whose walls are in a pinned state and remain in a pinned state during the time from when the applied field passes through the preselected offset field value toward and until the applied field reaches the predetermined threshold value at which the walls are released from the pinned state causing said regenerative step change in magnetic flux, the walls returning to the pinned state at the time when the applied field reaches the preselected offset field value after passing through the predetermined threshold value; and said marker element, when said hard or semi-hard component is in the second magnetic state, has domains whose walls are inhibited from assuming the pinned state.

Claim 72

A marker for use in an electronic article surveillance system in which an applied alternating magnetic field is established in a surveillance zone and an alarm is activated when a predetermined perturbation to the field is detected, said marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard or semi-hard magnetic material; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to an applied alternating magnetic field such that the magnetic flux of said marker element undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said marker element having a deactivated state wherein said marker element exhibits a different hysteresis characteristic from the hysteresis characteristic exhibited by said marker element in the active state; d) said second component of said marker element having an activating state wherein said second component is substantially demagnetized which places said marker element in said active state and a deactivating state wherein said second component is substantially magnetized which places said marker element in said deactivated state; whereby said marker element is switched from said active state to said deactivated state by switching said second component from said activating state to said deactivating state.

Claim 73

A marker for use in an electronic article surveillance system in which an applied alternating magnetic field is established in a surveillance zone and an alarm is activated when a predetermined perturbation to the field is detected, said marker comprising: a) a marker element including first and second integral components, said first component comprising a soft magnetic material and said second component comprising a hard or semi-hard magnetic material; b) said marker element having an active state wherein said marker element exhibits a hysteresis characteristic upon being subjected to an applied alternating magnetic field such that the magnetic flux of said marker element undergoes substantially no change during the time from when the applied field passes through a preselected offset field value toward and until the applied field reaches a predetermined threshold value, undergoes a regenerative step change at the time when the applied field reaches the predetermined threshold value and undergoes a gradual change during the time from when the applied field passes through the predetermined threshold value toward and until the applied field reaches the preselected offset field value; c) said marker element having a deactivated state wherein said marker element exhibits a different hysteresis characteristic from the hysteresis characteristic exhibited by said marker element in the active state; d) said second component of said marker element having an activating state wherein said second component is substantially demagnetized which places said marker element in said active state and a deactivating state wherein said second component is substantially magnetized which places said marker element in said deactivated state; whereby said marker element is switched from said active state to said deactivated state by switching said second component from said activating state to said deactivating state.

Claim 76

A method of making a marker in accordance with claim 67 in which the predetermined threshold value depends upon the coercivity of the crystallized layer.

Claim 77

A method of making a marker in accordance with claim 67 in which the predetermined threshold value depends upon the magnitude of the DC magnetic field applied to the crystallized layer.