Amorphous magnetostrictive alloy and an electronic article surveillance system employing same

A marker for use in a magnetomechanical electronic article surveillance system, said marker comprising:

• a bias element which produces a bias magnetic field of up to 10 Oe;
• a resonator disposed adjacent said bias element comprising an annealed amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, and a ranges from about 15 to about 30, b is at least about 12, c ranges from about 30 to about 50, and 79<a+b+c<85, said resonator having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least about 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• and
• a housing encapsulating said bias element and said resonator.

A marker for use in a magnetomechanical electronic article surveillance system, said marker comprising:

• a bias element which produces a bias magnetic field of up to 10 Oe;
• a resonator comprising an annealed amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, said alloy being selected from the group of alloy sets consisting of a first alloy set wherein a is at least about 15 and b is at least about 32, a second alloy set wherein a ranges between about 15 and about 40, and a third alloy set wherein a ranges between 15 and about 42, b ranges between about 18 and about 32, and c is at least about 10, and said resonator having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• and
• a housing encapsulating said bias element and said resonator.

A magnetomechanical electronic article surveillance system comprising:

• a marker comprising a bias element and a resonator, said resonator formed by an annealed amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, and a ranges from about 15 to about 30, b is at least about 12, c ranges from about 30 to about 50, and 79<a+b+c<85, said resonator having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least about 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• transmitter means for exciting said marker for causing said resonator to mechanically resonate and to emit said signal at a resonant frequency;
• receiver means for receiving and integrating said signal from said resonator at said resonant frequency;
• synchronization means connected to said transmitter means and to said receiver means for activating said receiver means for receiving and integrating said signal at said resonant frequency from said resonator in a first detection window beginning at approximately 0.4 ms after excitation of said resonator by said transmitter means and in a second detection window beginning at approximately 7 ms after excitation of said resonator by said transmitter means;
• and
• an alarm, said receiver means comprising means for triggering said alarm if said signal at said resonant frequency from said resonator integrated in said second detection window is substantially below said signal at said resonant frequency from said resonator integrated in said first detection window.

A magnetomechanical electronic article surveillance system comprising:

• a marker comprising a bias element and a resonator, said resonator formed by an annealed amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, said alloy being selected from the group of alloy sets consisting of a first alloy set wherein a is at least about 15 and b is at least about 32, a second alloy set wherein a ranges between about 15 and about 40, and a third alloy set wherein a ranges between 15 and about 42, b ranges between about 18 and about 32, and c is at least about 10, and said resonator having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• transmitter means for exciting said marker for causing said resonator to mechanically resonate and to emit said signal at a resonant frequency at said initial amplitude;
• receiver means for receiving and integrating said signal from said resonator at said resonant frequency;
• synchronization means connected to said transmitter means and to said receiver means for activating said receiver means for receiving and integrating said signal at said resonant frequency from said resonator in a first detection window beginning at approximately 0.4 ms after excitation of said resonator by said transmitter means and in a second detection window beginning at approximately 7 ms after excitation of said resonator by said transmitter means;
• and
• an alarm, said receiver means comprising means for triggering said alarm if said signal at said resonant frequency from said resonator integrated in said second detection window is substantially below said signal at said resonant frequency from said resonator integrated in said first detection window.

A method of making a resonator for use in a magnetomechanical electronic article surveillance system, comprising the steps of:

• providing an amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, said alloy being selected from the group of alloy sets consisting of a first alloy set wherein a is at least about 15 and b is at least about 32, a second alloy set wherein a ranges between about 15 and about 40, and a third alloy set wherein a ranges between 15 and about 42, b ranges between about 18 and about 32, and c is at least about 10, and;
• annealing said amorphous magnetostrictive alloy in a transverse magnetic field and at a temperature in a range between about 300.degree. C. and about 400.degree. C. for less than one minute for producing said annealed amorphous magnetostrictive alloy having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least about 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and having an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation.

A method of making a marker for use in a magnetomechanical electronic article surveillance system, comprising the steps of:

• providing an amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, and a ranges from about 15 to about 30, b is at least about 12, c ranges from about 30 to about 50, and 79<a+b+c<85;
• annealing said amorphous magnetostrictive alloy in a transverse magnetic field and at a temperature in a range between about 300.degree. C. and about 400.degree. C. for less than one minute for producing said annealed amorphous magnetostrictive alloy having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least about 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and having an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• placing said resonator adjacent a magnetized ferroelectric bias element;
• and
• encapsulating said resonator and said bias element in a housing.

A method of making a marker for use in a magnetomechanical electronic article surveillance system, comprising the steps of:

• providing an amorphous magnetostrictive alloy having a composition Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y, wherein a, b, c, x and y are at % and a+b+c+x+y=100, said alloy being selected from the group of alloy sets consisting of a first alloy set wherein a is at least about 15 and b is at least about 32, a second alloy set wherein a ranges between about 15 and about 40, and a third alloy set wherein a ranges between 15 and about 42, b ranges between about 18 and about 32, and c is at least about 10;
• annealing said amorphous magnetostrictive alloy in a transverse magnetic field and at a temperature in a range between about 300.degree. C. and about 400.degree. C. for less than one minute for producing said annealed amorphous magnetostrictive alloy having a linear B-H loop up to a minimum field strength of about 8 Oe, a quality Q between about 100 and 600, an anisotropy field H.sub.k of at least about 10 Oe and, when excited to resonate in the presence of a bias magnetic field H.sub.b, producing a signal at a mechanical resonant frequency f.sub.r having an amplitude at approximately 1 ms after excitation which is no more than 15 dB below an amplitude of said signal immediately after excitation and having an amplitude at approximately 7 ms after excitation which is at least 15 dB below said amplitude at 1 ms after excitation;
• placing said resonator adjacent a magnetized ferroelectric bias element;
• and
• encapsulating said resonator and said bias element in a housing.