KR100478114B1 - Metallic glass alloys for mechanically resonant marker surveillance systems - Google Patents

Abstract

The glassy metal alloy consists essentially of the formula Fe _a Co _b Ni _c M _d B _e Si _f C _g , wherein "M" is at least one member selected from the group consisting of molybdenum, chromium and manganese, and "a-g "Is an atomic percent," a "is in the range of about 30 to about 45," b "is in the range of about 8 to about 18," c "is in the range of about 20 to about 45, and" d "is about 0 to about 3, "e" ranges from about 12 to about 20, "f" ranges from about 0 to about 5, and "g" ranges from about 0 to about 2. The alloy can be cast into the ribbon by rapid solidification, cross-field annealed to improve magnetic properties, and formed into markers that are particularly suitable for use in self-mechanically driven article monitoring systems. Advantageously, the marker is characterized by a substantially linear magnetization reaction in a frequency system in which the harmonic marker system is magnetically operated. The detected voltage amplitude for the marker is high and ultimately the interference between the monitoring system and the harmonic re-radiation based on mechanical resonance is ultimately eliminated.

Description

METALLIC GLASS ALLOYS FOR MECHANICALLY RESONANT MARKER SURVEILLANCE SYSTEMS

Reference to related application

This application is part of US Patent Application Serial No. 08 / 465,051, filed June 6, 1995, which is also filed Serial No. 08, filed April 13, 1995 entitled Metal Glass Alloy for Mechanical Resonant Marker Monitoring Systems. It is part of / 421,094 filed.

The present invention relates to metal glass alloys, and more particularly to metal glass alloys suitable for use in mechanical resonant markers of article surveillance systems.

Numerous commodity surveillance systems are available today to help identify and / or protect a variety of biological and non-living objects. An example of the purpose of such a system is to secure the merchant's goods against identification and theft of employees with limited access to restricted areas.

An essential component of any surveillance system is a sensor or "marker" attached to the object to be detected. Other components of the system include transmitters and receivers that are appropriately located in the “interrogation” area. When the object with the marker enters the search zone, the functional part of the marker responds to the signal from the transmitter and this response is detected at the receiver. The information contained in the response signal is then processed for actions appropriate to the application, i.e. access denied, alarm triggered, and the like. Several other types of markers are disclosed and in use. In one type, the functional part of the marker consists of an antenna and a diode or a capacitor forming an antenna and a resonant circuit. When placed in the electromagnetic field transmitted by the searching device, the antenna-diode marker generates harmonics of the search frequency at the receiving antenna. Detection of harmonic or signal level changes indicates the presence of a marker. However, with this type of system, the reliability of marker identification is relatively low due to the wide bandwidth of a simple resonant circuit. Moreover, the marker should be removed after identification, which is not desirable in any case as a thief prevention system.

The second type of marker consists of a first elongate element of a highly magnetically permeable ferromagnetic material, which is disposed at least adjacent to a second element of ferromagnetic material having a higher coercive force than the first element. When dependent on the search frequency of electromagnetic radiation, the marker generates a wave of search frequency due to the nonlinear nature of the marker. Detection of such harmonics in the receiving coil indicates the presence of a marker. Deactivation of the marker is accomplished by changing the state of magnetization of the second element, which can be easily accomplished, for example, by passing the marker through a dc magnetic field. The harmonic marker system is superior to the radio frequency resonant system described above due to the improved reliability of marker identification and a simpler deactivation method.

However, two major problems exist in this type of system, one of which is the difficulty of detecting marker signals at a distance. The amplitude of the harmonics generated by the marker is much smaller than the amplitude of the search signal, limiting the detection isle width to less than about 3 feet. Another problem is that it is difficult to distinguish marker signals from false signals generated by other ferromagnetic objects such as belt buckle, pens, clips and the like.

Surveillance systems using a detection scheme that includes the fundamental mechanical resonance frequency of the marker material are particularly advantageous in that they provide a combination of high detection sensitivity, high operating reliability, and low operating costs. Examples of such a system are described in US Patent Nos. 4,510,489 and 4,510,490 (hereinafter referred to as '489 and' 490 patents).

The marker in such a system is a strip or a plurality of strips of known length ferromagnetic material wrapped with a magnetically harder ferromagnetic material (a high coercive material) that provides a bias magnetic field to establish peak magneto-mechanical coupling. The ferromagnetic marker material is preferably a metal glass alloy ribbon because the efficiency of the magnetic-mechanical coupling in these alloys is very high. The mechanical resonance frequency of the marker material is essentially dictated by the length of the alloy ribbon and the bias field strength. When faced with a search signal tuned to this resonant frequency, the marker material responds with a large signal magnetic field detected by the receiver. The large signal magnetic field is due, in part, to the enhanced magnetic permeability of the marker material at resonant frequencies. Various marker structures and systems for searching and detecting using the above principles have been taught in the '489 and' 490 patents.

In one particularly useful system, the marker material is excited and oscillated by signal pulses or bursts at its resonant frequency generated by the transmitter. At the end of the excitation pulse, the marker material will experience attenuated vibrations at its resonant frequencies. That is, the marker material “rings down” after the end of the excitation pulse. The receiver "listens" the response signal during this ringing period. Under this arrangement the surveillance system is relatively immune to interference from various radiated or power line sources, thus eliminating the possibility of false alarms inherently.

A wide range of alloys have been claimed in the '489 and' 490 patents as suitable for marker materials for the various detection systems disclosed. Other metal glass alloys with high permeability are described in US Pat. 4,152,144.

The main problem in the use of an electronic article monitoring system is that the markers of the monitoring system based on mechanical resonance accidentally cause a detection system based on an alternating technology, such as the above-mentioned harmonic marker system. In other words, the nonlinear self-response of the marker is strong enough to generate harmonics in the alternating system and inadvertently results in a false response or "false alarm". The importance of avoiding interference or "pollution" between other surveillance systems is soon apparent. Consequently, there is a need in the art for resonant markers that can be detected in a highly reliable manner without causing pollution on systems based on alternating technologies such as harmonic reradiation.

There is also a need in the art for resonant markers that can be reliably cast in high yield quantities, consist of inexpensive raw materials, and meet the detection sensitivity and non-pollution criteria specified above.

The invention will be more fully understood and further advantages will become apparent upon reference to the following detailed description of the preferred embodiments of the invention and the accompanying drawings.

1A is a magnetization curve taken along the length of a conventional resonant marker, where B is magnetic induction and H is an applied magnetic field.

1B is a magnetization curve taken along the length of the resonant marker of the present invention, where H _a is the magnetic field at which B saturates above.

Figure 2 is a signal profile detected in a receiving coil depicting mechanical resonance excitation, termination of excitation and subsequent ringing at time t ₀ , where V ₀ and V ₁ are t = t ₀ and t = t ₁ (t _{0, respectively).} Signal amplitude in the receiving coil at 1 msec).

3 is the response signal V ₁ detected at the receiving coil at 1 msec after the termination of the mechanical resonant frequency f _r and the excitation ac magnetic field as a function of the bias field, H _b , where H _b1 and H _b2 are respectively the maximum V ₁ . , f _r is the minimum bias field.

Description of Preferred Embodiments

According to the present invention, a somatic marker system provides a magnetic metal glass alloy characterized by a substantially linear magnetic response in the frequency range in which it operates mechanically. This alloy demonstrates all the features necessary to meet the requirements of the marker for surveillance systems based on self-mechanical operation.

The glass metal alloys of the invention generally mentioned consist essentially of the formula Fe _a Co _b Ni _c M _d B _e -Si _f C _g , where "M" is selected from molybdenum, chromium and manganese, and "a" , "b", "c", "d", "e", "f" and "g" are atomic percent, "a" ranges from about 30 to about 45, and "b" ranges from about 8 to about 18 is in a range of about 20 to about 45, "d" is in a range of about 0 to about 3, "e" is in a range of about 12 to about 20, and "f" is about 0 To about 5, and "g" has a composition in the range from about 0 to about 2. The purity of the composition is that found in common commercial practice. The ribbons of these alloys are annealed with a magnetic field applied substantially in the plane of the ribbon across the width of the ribbon at high temperatures below the alloy's crystallization temperature for a given period of time. The magnetic field strength during annealing is such that the ribbon magnetically saturates along the magnetic field direction. The annealing time depends on the annealing temperature and typically ranges from about 2-3 minutes to about 2-3 hours. For commercial production, continuous reel-to-reel annealing furnaces are preferred. In this case, the ribbon travel speed can be set at about 0.5 to about 12 meters per minute. For example, an annealed ribbon with a length of about 38 mm exhibits a substantially linear magnetic response to magnetic fields up to 8 Oe applied in parallel to the marker length direction and mechanical resonance in the frequency range of about 48 kHz to about 66 kHz. Indicates. The linear magnetic response region extending to the level of 8 Oe is sufficient to avoid causing anything in the harmonic marker system. In the more stringent case, the linear magnetic response region extends beyond 8 Oe by changing the chemical composition of the alloy of the present invention. Annealed ribbons at lengths shorter or longer than 38 mm show mechanical resonances higher or lower than the 48-66 kHz range. The annealed ribbon is soft so that post-anneal cutting and handling do not cause problems in marker manufacture.

Most metal glass alloys outside the scope of the present invention typically exhibit a non-linear magnetic response area below 8 Oe levels or exhibit _a near H _a level close to the working magnetic excitation level of many article detection systems using sowing markers. Resonant markers composed of these alloys inadvertently cause many object detection systems of varying harmonic reradiation types, thereby causing pollution.

There are a few metal glass alloys outside the scope of the present invention which exhibit a linear magnetic response to the acceptable magnetic field range. However, these alloys contain high levels of cobalt or molybdenum or chromium, resulting in increased raw material costs and / or reduced ribbon casting properties due to higher melting points of the elements such as molybdenum or chromium. The alloys of the present invention are advantageous in that they provide extended linear magnetic response, improved mechanical resonance performance, good ribbon casting properties and the economics of ribbon making available.

Apart from avoiding interference between other systems, markers made of alloys of the present invention generate higher signal amplitudes in the receiving coils than conventional mechanical resonant markers. This makes it possible to reduce the size of the marker or increase the detection isle width, both of which are desirable features of an article surveillance system.

Examples of metal glass alloys of the present invention;

It includes.

The magnetization, characterized by the B-H curve, is shown in Figure 1a for a conventional mechanical resonant marker. Where B is magnetic induction and H is the applied magnetic field. The entire B-H curve is transformed into a nonlinear hysteresis loop present in the low magnetic field. This non-linear feature of the marker leads to higher harmonic generation which leads to some harmonic marker systems and thus interference between other article monitoring systems.

The definition of the linear magnetic response is given in FIG. 1B. As the marker is magnetized along the longitudinal direction by an external magnetic field, H, the magnetic induction, B, is brought to the marker. The magnetic response is substantially linear up to H _a , otherwise the marker is magnetically saturated. The amount H _a depends on the physical dimension of the marker and its magnetic anisotropy magnetic field. To prevent the resonant marker is accidentally induced by the surveillance system based on harmonic re-emitted H _a should be above the operating field intensity region of the harmonic marker systems.

The marker material is exposed to a burst of excitation signals of constant amplitude, called excitation pulses, which are tuned to the frequency of the mechanical resonance of the marker material. The marker material responds to the excitation pulse and generates an output signal at the receiving coil along a curve leading to V ₀ in FIG. 2. At time t ₀ , the excitation is terminated and the marker begins to ring and echoes in the output signal which decreases from V ₀ to zero over a period of time. At the time t ₁ , 1 msec after termination, the output signal is measured and denoted by the amount V ₁ . Thus V ₁ / V ₀ is a measure of ringing. The operating principle of the monitoring system does not depend on the shape of the wave of excitation pulses, but the waveform of this signal is usually a sine wave. Marker material resonates under this excitation.

The physical principle governing this resonance can be summarized as follows: When a ferromagnetic material is subject to a magnetic field, it experiences a change in length. The change in the fraction of the length of the material from its original length is called magnetostriction and is denoted by the symbol λ. If the length occurs parallel to the magnetic field, the positive sign is given to λ. Both λ increase with the magnetic field magnetizing and reach the maximum value of the saturation magnetostriction, λ _s .

Definition When a ribbon of magnetostricted material receives an external magnetic field that changes into its applied sine wave along its length, the ribbon will undergo a periodic change in length. The ribbon will vibrate. For example, an external magnetic field can be generated by a solenoid with a current that changes into a sine wave. When the half-wave length of the ribbon's oscillating wave fits the length of the ribbon, it results in mechanical resonance. The resonance frequency f _r is given by the following relationship.

f _r = (1 / 2L) (E / D) ^0.5

Where L is the ribbon length, E is the Young's modulus of the ribbon, and D is the density of the ribbon.

The magnetostrictive effect is observed in ferromagnetic materials only when the magnetization of the material proceeds through the magnetization rotation. No magnetostriction is observed when the magnetization progresses through the magnetic domain wall motion. Since the magnetic anisotropy of the marker of the alloy of the present invention is caused to cross in the width direction of the marker by magnetic field-annealing, the dc magnetic field, called the bias field applied along the length of the marker, is responsible for the efficiency of the magnetic-mechanical response from the marker material. Improve. In addition, it is well understood in the art that the bias field serves to change the effective value for E, Young's modulus in the ferromagnetic material so that the mechanical resonance frequency of the material can be changed by appropriate selection of the bias field strength. Figure 3 further illustrates the situation: the resonant frequency, f _r , decreases with increasing bias magnetic field, H _b , reaching the minimum value f _{r min} at H _b2 . The amount H _b2 relates to the magnetic anisotropy of the marker and directly to the amount H _a defined in FIG. 1B. Thus, the use of H _b2 can be conveniently adopted as _a measure of both H _a . So to speak the receiving coil t = t a response signal V ₁ detected at ₁ increases with H _b, and reaches the maximum value V _m at H _b1. The slope df _r / dH _b near the working bias field is important because it relates to the sensitivity of the surveillance system.

Summarizing the above, a ribbon of positive magnetostrictive ferromagnetic material will vibrate at the frequency of the driving ac magnetic field when exposed to an ac magnetic field driving in the presence of a dc bias magnetic field, which frequency is the mechanical resonance frequency of the material, f _r. When it coincides with, the ribbon resonates and provides increased response signal amplitude. In fact, the bias field is provided by a ferromagnetic material having a higher coercivity than the marker material present in the "marker package".

Table 1 shows V _m , H _b1 , (f _r ) _min and the conventional mechanical resonant markers based on glassy Fe ₄₀ Ni ₃₈ Mo ₄ B _{18. List} typical values of H _b2 . And H _b2 related to the presence of a non-linear BH acts under a low value of H _b2 is a tendency to a marker of the alloy base material accidentally caused by some of the harmonic marker systems, and interference between the mechanical resonance and harmonic re-radiation article surveillance system based on Bring.

TABLE 1

V _m , H _b1 , (f _r ) _min for conventional mechanical resonant markers based on glassy Fe ₄₀ Ni ₃₈ Mo ₄ B ₁₈ and Typical value of H _b2 . With a dimension of about 38.1 mm x 12.7 mm x 20 μm, the ribbon has a resonant frequency in the range of about 57 to 60 kHz.

V _m (mV) H _b1 (Oe) (f _r ) _min (kHz) H _b2 (Oe) 150-250 4-6 57-58 5-7

Table 2 shows H _a , V _m , H _b1 , (f _r ) _min , for alloys outside the scope of this patent. List typical values of H _b2 and df _r / dH _b . The magnetic field-annealing was performed at 380 ° C. in a continuous reel-to-reel furnace on a 12.7 mm wide ribbon. In this case, the ribbon speed was about 0.6 m / min to about 1.2 m / min. The size of the ribbon marker was about 38.1 mm × 12.7 mm × 20 μm.

TABLE 2

H _a , V _m , H _b1 , (f _r ) _min , taken at H _b = 6 Oe for alloys outside the scope of this patent; Values of H _b2 and df _r / dH _b . The magnetic field-annealing was carried out at 380 ° C. in a continuous reel-to-reel furnace. At this time, the ribbon speed was about 0.6 m / min to about 1.2 m / min, and a magnetic field of about 1.4 kOe was applied perpendicular to the ribbon length direction.

Alloys A and B exhibit a linear magnetic response over the acceptable magnetic field range but contain high levels of cobalt and result in increased raw material costs. Alloys C and D have low H _b1 values and high df _r / d H _b values, a combination of which is undesirable in view of the operation of the resonant marker system.

Summary of the Invention

The present invention features a substantially linear magnetic response in a frequency system and provides at least 70% glassy magnetic alloy that is cross-annealed to improve the magnetic properties of the sonic marker system to operate magnetically.

Such alloys can be cast into ribbons using rapid solidification or otherwise formed into markers having magnetic and mechanical characteristics that are particularly suitable for use in surveillance systems based on the magnetic-mechanical operation of the markers. As used herein, the term "cross-field annealed" means an anneal performed on a strip having a longitudinal and a width direction, wherein the magnetic field used for the anneal is substantially in the width direction. It is applied to the plane of the ribbon across, and the direction of the magnetic field is about 90 ° to the longitudinal direction.

Generally mentioned glassy metal alloys of the present invention are essentially formulas of Fe _a Co _b Ni _c M _d B _e − Si _f C _g , wherein “M” is selected from molybdenum, chromium and manganese, and “a”, “b”, “c”, “d”, “e”, “f” and “g” are Atomic percent, "a" ranges from about 30 to about 45, "b" ranges from about 8 to about 18, "c" ranges from about 20 to about 45, and "d" ranges from about 0 to about In the range of about 3, "e" in the range of about 12 to about 20, "f" in the range of about 0 to about 5, and "g" in the range of about 0 to about 2.

Ribbons of these alloys having dimensions of about 38 mm × 12.7 mm × 20 μm are characterized by the resonance frequency for the bias field between about 500 Hz / Oe and 750 Hz / Oe when mechanically resonating at frequencies in the range of about 48 to about 66 kHz. Not only the slope but also the applied magnetic field above 8 Oe demonstrates substantially linear magnetization. Moreover, the voltage amplitude detected at the receiving coil of a typical resonant-marker system for a marker made of the alloy of the present invention is comparable or higher than the voltage amplitude of existing resonant markers of comparable magnitude. These features ensure that interference between systems based on mechanical resonance and harmonic re-radiation is avoided.

The metallic glass of the present invention is particularly suitable for use as an active element in markers associated with article surveillance systems using the excitation and detection of the above-described magnetic-mechanical resonances. Other applications can be found in sensors that take advantage of magneto-mechanical operation and its associated effects, and in magnetic components that require high magnetic permeability.

Example 1 Fe-Co-Ni-B-Si Metallic Glass

1. Sample Manufacturing

In the Fe-Co-Ni-B-Si system, the glassy metal alloy is described in US Pat. It was rapidly quenched from the melt following the technique taught by Narasimhan at 4,142,571. The above specification is incorporated herein by reference. All castings were made in inert gas using 0.1-60 kg melt. The resulting ribbons, typically 25 μm thick and about 12.7-50.5 mm wide, were determined to be free of significant crystallinity by X-ray diffraction and differential scanning calorimetry using Cu-Kα radiation. Each of the alloys was at least 70% glassy and in many cases the alloys were at least 90% glassy. The ribbons of these glassy metal alloys were strong, shiny, hard and ductile.

The ribbon for self-mechanical resonance characterization was heat treated with an applied magnetic field across the width of the ribbon and cut to a length of about 38 mm. The strength of the magnetic field was 1.4 kOe and its direction was about 90 ° to the ribbon longitudinal direction and was substantially in the plane of the ribbon. In a reel-to-reel annealing furnace the speed of the ribbon varied from about 0.5 meters per minute to about 12 meters per minute.

2. Characterization of magnetic properties

Test each marker material with dimensions of about 38.1 mm × 12.7 mm × 20 μm or 38.1 mm × 6.0 mm × 20 μm by applying an applied magnetic field along the length of each alloy marker with a dc bias magnetic field varying from 0 to about 15 Oe. It was. The sensing coil detected the magneto-mechanical response of the alloy marker to ac excitation. These marker materials mechanically resonate between about 48 and 66 kHz. The quantities characterizing the auto-mechanical response were measured and listed in Tables 3 and 4.

TABLE 3

H _a , V _m , H _b1 , (f _r ) _min taken at H _b = 6 Oe for the alloy of the invention heat-treated at 360 ° C. in a continuous reel-to-reel furnace at a ribbon speed of about 8 m / _min. , _{Values of} H _b2 , and df _r / dH _b . The annealing magnetic field was about 1.4 kOe applied perpendicular to the ribbon length direction and substantially in the plane of the ribbon. The size of the ribbon marker was about 38.1 mm x 12.7 mm x 20 μm. An asterisk indicates 'not measured' due to instrument restrictions.

All alloys listed in Table 3 exhibit H _b2 values above 8 Oe. These values make it possible to avoid the above mentioned problem of interference. Good sensitivity (df _r / dH _b ) and large response signal (V _m ) result in small markers for the resonant marker system.

As an example of small markers, markers with widths less than half of conventional markers were tested. The amounts characterizing the magneto-mechanical resonance of the marker material with dimensions of about 38.1 mm × 6.0 mm × 20 μm are summarized in Table 4.

TABLE 4

H _b = 6 Oe for an alloy of the present invention which was heat treated at 360 ° C. in a continuous reel-to-reel furnace at a ribbon speed of about 8 m / min and cut into strips having dimensions of about 38.1 mm × 6.0 mm × 20 μm. H _a , V _m , H _b1 , (f _r ) _min , taken from _{Values of} H _b2 , and df _r / dH _b . The annealing magnetic field was about 1.4 kOe applied perpendicular to the ribbon length direction and substantially in the plane of the ribbon. An asterisk indicates 'not measured' due to instrument restrictions.

All alloys listed in Table 4 exhibited H _b2 values in excess of 8 Oe, which make it possible to avoid the above mentioned problem of interference. Good sensitivity (df _r / dH _b ) and large magneto-mechanical resonance response signal (V _m ) result in small markers for the resonance marker system. Markers of the present invention having a width less than half of the conventional markers in Table 1 can achieve the level of self-mechanical resonance response of the conventional markers.

While the present invention has been described in sufficient detail to the extent that it is not necessary to strictly adhere to these details, it will be understood that further changes and modifications are suggested to those skilled in the art and all fall within the scope of the invention as defined in the appended claims. .

Claims (26)

At least about 70% glassy, cross-field annealed to improve magnetic properties, consisting essentially of the formula Fe _a Co _b Ni _c M _d B _e Si _f C _g , where "M" is molybdenum, chromium and manganese At least one member selected from the group consisting of: "a", "b", "c", "d", "e", "f" and "g" are atomic percent, and "a" is from about 30 to Is in the range of about 45, "b" is in the range of about 8 to about 18, "c" is in the range of about 20 to about 45, "d" is in the range of about 0 to about 3, and "e" is about 12 to about 20, "f" ranges from about 0 to about 5, and "g" has a composition ranging from about 0 to about 2, Has the form of a strip representing mechanical resonance, A magnetic metal glass alloy, having a substantially linear magnetization up to a minimum applied magnetic field of about 8 Oe. 2. The magnetic metal glass alloy of claim 1, wherein the magnetic metal glass alloy has a separate length and is in the form of a soft heat treated strip piece exhibiting mechanical resonance in the range of frequencies determined by the length. 3. The magnetic metal glass alloy of claim 2, wherein the strip has a length of about 38 mm and the mechanical resonance has a vibration range of about 48 kHz to about 66 kHz. 3. The magnetic metal glass alloy of claim 2, wherein the slope of the mechanical resonance frequency with respect to the bias magnetic field at about 6 Oe is about 500 to 750 Hz / Oe. 3. The magnetic metal glass alloy of claim 2, wherein the bias magnetic field having a minimum mechanical resonance frequency is close to or exceeds about 8 Oe. 3. The magnetic metal glass alloy of claim 2, wherein M is molybdenum. 3. The magnetic metal glass alloy of claim 2, wherein M is chromium. 3. The magnetic metal glass alloy of claim 2, wherein M is manganese. The method of claim 1, Magnetic metal glass alloy, characterized in that having a composition selected from the group consisting of. In an article monitoring system adapted to detect a signal caused by mechanical resonance of a marker in an applied magnetic field, the marker is at least about 70% glassy, cross-field annealed to improve magnetic properties, and is essentially of the formula Fe _a Co. _b Ni _c M _d B _e Si _f C _g , wherein “M” is at least one member selected from the group consisting of molybdenum, chromium and manganese, and “a”, “b”, “c”, “d "," e "," f "and" g "are atomic percent," a "is in the range of about 30 to about 45," b "is in the range of about 8 to about 18, and" c "is about 20 To about 45, "d" ranges from about 0 to about 3, "e" ranges from about 12 to about 20, "f" ranges from about 0 to about 5, and "g" is An article surveillance system, comprising at least one strip of ferromagnetic material having a composition in the range of about 0 to about 2. 11. The article surveillance system of claim 10, wherein the strip is selected from the group consisting of ribbons, wires, and sheets. 12. The article surveillance system of claim 11, wherein the strip is a ribbon. 11. The strip of claim 10, wherein the strip has the form of a ductile heat-treated strip that exhibits mechanical resonances in the range of frequencies determined by its length and has a substantially linear magnetization up to a bias magnetic field of at least 8 Oe. Goods monitoring system. 11. The article surveillance system of claim 10, wherein the strip has a length of about 38 mm and exhibits mechanical resonance in the frequency range of about 48 kHz to about 66 kHz. 15. The article surveillance system of claim 14, wherein the slope of the mechanical resonance frequency with respect to the bias field for the strip at a bias field of about 6 Oe ranges from about 500 Hz / Oe to about 750 Hz / Oe. 15. The article surveillance system of claim 14, wherein the bias magnetic field having a minimum mechanical resonance frequency of the strip is close to or exceeds about 8 Oe. 11. The article surveillance system of claim 10, wherein M is molybdenum. The article monitoring system according to claim 10, wherein M is elemental chromium. 11. The article monitoring system according to claim 10, wherein M is elemental manganese. The method of claim 10, wherein the strip; Article monitoring system characterized in that it has a composition selected from the group consisting of. 3. The magnetic metal glass alloy of claim 2, wherein the magnetic metal is heat treated with a magnetic field. 22. The magnetic metal glass alloy of claim 21, wherein the magnetic field is applied with a magnetic field strength to cause the strip to magnetically saturate along the magnetic field direction. 23. The method of claim 22, wherein the strip has a longitudinal direction and a width direction and the magnetic field is applied to a plane of the ribbon substantially across the width direction, the direction of the magnetic field being about 90 ° with respect to the longitudinal direction. Magnetic metal glass alloy. 22. The magnetic metal glass alloy of claim 21, wherein the magnetic field has a size in a range from about 1 to about 1.5 kOe. 22. The magnetic metal glass alloy according to claim 21, wherein the heat treatment step is performed for a period ranging from 2 to 3 minutes to 2 to 3 hours. 3. The heat treatment of claim 2, wherein the heat treatment is performed in a continuous reel-to-reel furnace, wherein the magnetic field is substantially in the plane of the strip across the strip width direction making an angle of about 90 ° with respect to the strip length direction. A magnetic metal glass alloy having a size in the range of about 1 to 1.5 kOe applied, said strip having a width in the range of about 1 mm to about 15 mm and a speed in the range of about 0.5 m / min to about 12 m / min.