KR20020006170A - Magnetized Self-Biased Magnetoelastic Sensor for Electronic Article Surveillance and Article Identification - Google Patents

Abstract

PURPOSE: A method for manufacturing a micro self-biased magnetic thin film sensor used for distinguishing physical distribution is provided to solve the problem arising from a miniaturization of products in a system for preventing the products from being stolen or lost and to reduce cost for physical distribution, by directly mounting the micro self-biased magnetic thin film sensor inside the products. CONSTITUTION: A base on which Co-based, Fe-based or an alloy thereof is coated is prepared. A predetermined electric filed is applied in the abscissa direction of the base to perform a heat treatment process. The base is cooled at a room temperature so that the base is spontaneously demagnetized. A magnetic filed is applied in the longitudinal direction of the cooled base to perform a heat treatment process.

Description

Ultra-Small Self-Biased Logistic Distinction Magnetic Thin Film Sensor Device and Method for Manufacturing thereof {Magnetized Self-Biased Magnetoelastic Sensor for Electronic Article Surveillance and Article Identification}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for preventing loss and distribution of goods, and more particularly, to an ultra-small self-biased magnetic thin film sensor element used in an electronic component monitoring system for distinguishing goods and preventing theft, and a manufacturing method thereof.

Recently, an electronic article surveillance (EAS) tag made of an amorphous soft magnetic thin film has been developed and commercialized in an electronic component monitoring system for preventing theft or loss of a product or a collection of books in a retail store or a library. These tags are individually attached to each product to be protected and play a role of preventing theft or loss by sounding an alarm in the detection unit according to the degree of activation of the attached tag.

In general, an anti-theft tag installed in the past is detected according to the degree of activation when passing through a detection system consisting of a signal emitter for generating electromagnetic waves and a detector for receiving electromagnetic signals amplified by the activated tag.

Such an electronic component monitoring system is disclosed in Korean Patent Laid-Open Publication No. 1991-0013024. That is, in the above publication, a label including a resonance circuit for interacting with an electromagnetic field is used, and an electromagnetic field is generated at a transmitter and a transmission antenna, and the electromagnetic field is detected by a receiver and a receiving antenna installed nearby, so that the product is lost or stolen. Disclosed is a technique for monitoring.

The commercialized EAS tag is mainly based on the EM (electro magnetic) method, which is divided into two types, a harmonic sensor and a magnetoelastic (ME) sensor.

Harmonic sensor mainly heats Co alloy (A, Si, etc.) alloy type amorphous ribbon and reacts easily to a specific frequency so that the magnetic field can detect the voltage difference generated from pick-up antenna according to the change of external magnetic field. To sense. In this way, the logistics equipped with harmonic sensors are detected when they pass through the detection system and applied to prevent theft or loss, or to distinguish logistics.

In the magnetic elastic sensor, the sensor material changes its magnetization direction according to a similar principle or an external signal pulse, and accordingly, resonates with the external signal. Prevention and logistics control.

Below. The specific operation principle of the ME sensor which can be miniaturized among the above-described EM sensors will be described.

The principle of operation of a magnetoelastic tag (ME Tag) can be easily explained by considering a system in which the two modes are interconnected by coupling coefficients d, which act as spring constants in magnetic and elastic modes. In other words, if a current is applied to the ME tag by the signal generator for a very short time (excitation of a pulse), this causes a magnetic field to be formed, which causes the magnetization formed in the tag to change to an elastic mode. At this time, the efficiency of the magnetic mode transition to the elastic mode is determined by the intensity of d.

The magnetic energy converted to this elastic mode stops oscillating very quickly (within a few nanoseconds) because the external antenna loses power (i.e. when the magnetic field is turned off), the magnetic mode has no so-called inertial mass. The energy stored in the elastic mode resonates in the vibrational mode, releasing energy for a very short period of time (ring-down period). At this time, the energy release appears as a voltage signal, and when this voltage is detected by an external receiving antenna, an alarm sounds.

The combination of the magnetic and elastic modes occurs most effectively when the constant d is at its maximum. In other words, when the two modes are effectively connected by a spring, the magnetic mode and the elastic mode, which vibrate rapidly at different frequencies, suddenly vibrate at a low common frequency, and the resonant frequency rapidly decreases. The energy vibrates and releases.

Therefore, in order for the ME tag to work efficiently, the constant d must have a maximum value, which is obtained from the strength of the magnetic field corresponding to the so-called knee ("knee") in the M-H loop.

The correlation between the magnetic distortion (d), the resonance frequency (Ω) and the B-H loop is shown in FIG. 1. As can be seen in Fig. 1, the resonance frequency is minimized at the point where the magnetic distortion is maximum, which is obtained at the knee portion of the B-H loop.

Therefore, in order to obtain the maximum value of d, the magnetic sensor should be biased near the knee, and the normal ME tag is a magnetoelastic sensor (ie, a resonator) and a bias magnet for biasing the sensor. It consists of two parts. The process in which the bias magnet hangs the field on the resonator and the structure of the synthetic ME tag (resonator and bias magnet) are shown in FIGS. 2 and 3.

That is, FIG. 2 is a schematic diagram showing a phenomenon in which the bias magnet is biased to the resonator and sensor operation occurs in the knee portion of the M-H loop, and FIG. 3 is a schematic diagram of the structure of the composite ME tag (resonator and bias magnet).

As shown in Fig. 3, the synthetic ME tag consists of a cavity 1 made of styrene and an adhesive layer 2 having an adhesive force to shield the cavity 1 and attach it to an anti-theft product. And a partition 5 made of a PE film to separate the magnetoelastic sensor 3, the bias magnet 4 and the magnetoelastic sensor 3 and the bias magnet 4 inserted into the cavity 1. Is done.

However, in the ME biased tag as described above, it is a relatively complicated structure consisting of five members in construction, and the process for manufacturing it is complicated, and thus the manufacturing cost is high.

In addition, in the above structure, since the size of the bias magnet 4 is large, about several centimeters by several centimeters, it may bring inefficiency of the package, cause environmental problems, and be careful about the packaging of important products. For example, it can damage the design and cause a legal dispute.

In addition, the structure shown in Fig. 3 has a problem in that if the bias magnet 4 is intentionally damaged, the original function for preventing the loss or theft is lost.

An object of the present invention is to solve the problems described above, to provide a small self-biased magnetic thin film sensor element and a manufacturing method thereof that can be attached to the product itself in a small size and can be operated by a commercially available sensing device will be.

Another object of the present invention is to provide a self-biased magnetic thin film sensor element and a method of manufacturing the same, which are not provided with a biasing magnet in order to simplify the tag assembly process as well as reduce material costs.

That is, in the present invention, the CoFeSiB and FeSiB systems are subjected to multi-step heat treatment to change the microstructure to control the magnetic domain structure so that the tag itself has a bias portion, so that the sensor self-biass without a bias magnet. It works at the "knee" of the MH loop and provides a single member tag structure.

1 is a correlation diagram of a conventional magnetic coupling (d), the resonance frequency (Ω) and the B-H loop,

2 is a schematic diagram showing a phenomenon in which the bias magnet is biased to the resonator and sensor operation occurs in the knee portion of the M-H loop.

3 is a schematic diagram of a structure of a composite ME tag composed of a resonator and a bias magnet;

4 is a view showing a horizontal axis annealing (a) for forming a self bias according to the present invention, the formation of strip magnetic domain after the potato (b) and the formation of a sloped anisotropy (c) after the long axis annealing,

5 is a diagram showing a relationship between a magnetic coupling d and θ,

6 is a view showing the relationship between the magnetization and the temperature of the heat treatment for producing the inclined anisotropy according to the present invention,

Fig. 7 is a diagram showing the d value after one step annealing (horizontal axis annealing) and the d value after two step annealing (horizontal axis long annealing) according to the present invention.

In order to achieve the above object, the present invention is a manufacturing method of the ultra-small self-biased magnetic thin film sensor element used in electronic parts monitoring system and logistics distinction to prevent the loss or theft of goods, Co-based and Fe-based or alloys thereof A step of preparing a substrate coated with a system, a first heat treatment step of applying a predetermined magnetic field in the transverse direction of the substrate and heat treatment, and a step of naturally cooling the substrate at room temperature so that the substrate subjected to the first heat treatment is spontaneously demagnetized And a second heat treatment step of applying a magnetic field to the cooled substrate in the longitudinal direction to perform heat treatment.

In addition, in order to achieve the above object, the ultra-small self-biased magnetic thin film sensor element of the present invention is a substrate coated with Co-based and Fe-based alloys or alloys thereof, the first heat treatment by applying a predetermined magnetic field in the transverse direction of the substrate Heat treatment means, means for cooling the substrate at room temperature so that the substrate subjected to the first heat treatment is spontaneously demagnetized, and second heat treatment means for applying heat treatment by applying a magnetic field in the longitudinal direction to the cooled substrate.

Further, in the self-biased magnetic thin film sensor element of the present invention, the Co-based and Fe-based Co _{40 + x} Fe _30-y (SiB) _{30-x + y} (where x = 0-10, y = 0-0-) 10).

In the self-biased magnetic thin film sensor element of the present invention, the substrate is made of an amorphous ribbon.

In the self-biased magnetic thin film sensor element of the present invention, the first heat treatment is performed at a temperature of 300 to 450 ° C. for 10 to 30 minutes under a magnetic field of 3 to 50 Oe.

Further, in the self-biased magnetic thin film sensor element of the present invention, the second heat treatment is performed by maintaining a magnetic field of 0.5 to 10 Oe at a temperature of 200 to 500 占 폚 for 0.5 to 1 hour.

In the self-biased magnetic thin film sensor element of the present invention, the substrate is inclined by a second heat treatment step so that the substrate has a bias function itself.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

The manufacturing process of the self-biased tag according to the present invention is produced by a two-step heat treatment. In other words, in the first step of heat treatment, when the annealed and saturated the magnetic field between 0.5 to 10 Oe in the perpendicular direction of the long axis of the amorphous ribbon specimen, the specimen is demagnetized after transverse annealing heat treatment. (striped domain) structure.

Next, in the second step of heat treatment, a long annealing is performed while applying a magnetic field in the longitudinal direction of the specimen. At this time, the magnetization is formed to have anisotropy so that the magnetization is inclined at θ ° with respect to the long axis direction of the specimen without saturation in the long axis direction, and when the arrangement of the magnetic domains of the specimen is biased under the conventional two-member composite tag. Can be made into a similar lexical array.

The manufacturing method of the ultra-small self-biased magnetic thin film sensor according to the present invention will be described in the following order.

First, a ribbon is formed as a substrate having a width of 10 to 20 mm and a thickness of 20 μm using a planar flow casting process with a Co _{40 + x} Fe _30-y (SiB) _{30-x + y} composition (where x = 0-10, y = 0-10).

Next, the substrate formed as described above is heat-treated at a temperature of 300 to 450 ° C. for 10 to 30 minutes under a magnetic field of 3 to 50 Oe. The magnetic field is applied in the transverse direction of the substrate to saturate magnetization.

Thereafter, the heat-treated substrate is naturally cooled to room temperature to spontaneously demagnetize.

In the second heat treatment step, a magnetic field of 0.5 to 10 Oe is applied at a temperature of 200 to 500 ° C. in the direction of the major axis of the substrate, and maintained for 0.5 to 1 hour.

The process of the heat treatment of the first and second steps is shown in FIG. 4.

FIG. 4 is a diagram showing transverse annealing (a) to form self bias, formation of strip domains after demagnetization (b) and formation of canted anisotropy after long-axis annealing.

Thus it is determined to produce a self-bias field sensors _(external H) to obtain a given angle θ with the angle in Fig.

In order to determine this, the relation between magnetic distortion d and θ is derived, and at this time, the angle θ of inclined anisotropy can be determined by obtaining θ having the maximum value d.

According to Chikazumi et al., The magnetic distortion d is

The relationship between d and θ ₀ is as shown in FIG. 5.

FIG. 5 shows the relationship between the magnetic distortion d and θ, and as can be seen from FIG. 5, d has a maximum value at θ = 55 °. 6 is a figure which shows the relationship between the magnetization and temperature of the heat processing for producing the inclined anisotropy.

In addition, the magnitude | size of the field at the time of long-axis annealing is given by the following formula.

H _anneal = H _κ (T _a ) cosθ ₀ = cosθ ₀ [M _s (T _a ) / M _s (0)] H _κ (0)

(Where a is annealing temperature and 0 is room temperature)

H _k (0) = 5 Oe (ie anisotropic magnetic field at room temperature) Is assumed to change as shown in FIG. 6, and the annealing temperature is T _a = 300 ° C., [M _s (T _a ) / M _s (0)] = 0.3 is obtained, H _anneal = 1.5 cosθ ₀ = 1.5 cos55 ° It is obtained as 0.860e.

Therefore, when 0.860e is applied to the longitudinal field of the long axis during the long axis annealing process, the inclined anisotropy having θ = 55 ° is formed in the tag. As a result, the arrangement of magnetic domains is similar to when biased, and thus self-biasing is performed without a bias magnet.

That is, in the configuration of the present invention, the bias and the resonator exist in a single tag, so that the tag of the self bias can be manufactured.

Fig. 7 shows the d value after one step annealing (horizontal axis annealing) and the d value after two step annealing (horizontal axis long axis annealing). In Fig. 7,? Indicates annealing T on the horizontal axis, and? Indicates annealing on the horizontal axis and long axis (T-L).

As can be seen in FIG. 7, since d has a maximum value at a certain bias value (H = 40e) only after one-step annealing, a bias magnet is required to maintain it. However, according to the present invention, after the two-stage annealing, even if there is no bias magnet (that is, H = 0), a large d value of 0.8 × 10 ⁻⁵ or more can be obtained, thereby making a self-biasing tag.

In other words, d value at the time of annealing (T) of the horizontal axis and d value at the time of the annealing (TL) of the horizontal axis and the long axis shows that d has a large value in the self-biased state even if there is no bias field after the TL. It can be seen.

Although the invention made by the present inventors has been described in detail according to the above embodiments, the present invention is not limited to the above embodiments, and of course, various modifications such as distribution can be made without departing from the gist of the present invention.

As described above, according to the ultra-small self-biased magnetic thin film sensor element of the present invention and a method for manufacturing the same, it is possible to prepare for theft or loss due to the miniaturization of the product in the system for preventing theft or loss of the product, and to distinguish the inside of the product for the purpose of distinguishing logistics It can be mounted directly on the floor, thereby reducing the logistics cost.

In addition, according to the ultra-small self-biased magnetic thin film sensor element of the present invention and a method for manufacturing the same, it is possible to manufacture less than 50% of the existing sensor element by reducing the cost of production, it is possible to reduce the manufacturing cost.

In addition, the price competitiveness of ME sensors enables real-time logistics control.

Claims (12)

As a manufacturing method of an ultra-small self-biased magnetic thin film sensor element used for electronic component monitoring system and logistics discrimination to prevent the loss or theft of goods, Preparing a substrate coated with Co and Fe or alloys thereof, A first heat treatment step of applying heat by applying a predetermined magnetic field in the horizontal axis direction of the substrate, Naturally cooling the substrate at room temperature to spontaneously demagnetize the substrate subjected to the first heat treatment; And a second heat treatment step of applying a magnetic field to the cooled base material in a long axis direction to perform heat treatment. The method of claim 1, The Co-based and Fe-based self-biased magnetic thin films are made of Co _{40 + x} Fe _30-y (SiB) _{30-x + y} (where x = 0-10, y = 0-10). Method for manufacturing sensor element. The method of claim 1, The substrate is a method of manufacturing a self-biased magnetic thin film sensor element, characterized in that the ribbon of an amorphous structure. The method of claim 1, The first heat treatment step is a method of manufacturing a self-biased magnetic thin film sensor element, characterized in that the heat treatment at 300 ~ 450 ℃ temperature for 10 to 30 minutes under a magnetic field of 3 to 50 Oe. The method of claim 1, The second heat treatment step is a method of manufacturing a self-biased magnetic thin film sensor element, characterized in that the heat treatment by maintaining a magnetic field of 0.5 to 10 Oe for 0.5 to 1 hour at a temperature of 200 ~ 500 ℃. The method of claim 1, And the substrate has an inclined magnetization structure by the second heat treatment step, so that the substrate has a bias function by itself. As an ultra-small self-biased magnetic thin film sensor element used to distinguish electronic parts monitoring system and logistics to prevent the loss or theft of goods, A substrate coated with Co and Fe or alloys thereof, First heat treatment means for heat treatment by applying a predetermined magnetic field in the horizontal axis direction of the substrate, Means for cooling the substrate at room temperature to spontaneously demagnetize the substrate subjected to the first heat treatment; A self-biased magnetic thin film sensor element comprising: a second heat treatment means for heat treatment by applying a magnetic field in a long axis direction to the cooled substrate. The method of claim 7, wherein The Co-based and Fe-based self-biased magnetic thin films are made of Co _{40 + x} Fe _30-y (SiB) _{30-x + y} (where x = 0-10, y = 0-10). Sensor element. The method of claim 7, wherein The substrate is a self-biased magnetic thin film sensor element, characterized in that the amorphous structure of the ribbon. The method of claim 7, wherein And said first heat treatment means is carried out at a temperature of 300 to 450 [deg.] C. for 10 to 30 minutes under a magnetic field of 3 to 50 Oe. The method of claim 7, wherein The second heat treatment means is performed by maintaining a magnetic field of 0.5 to 10 Oe at a temperature of 200 to 500 ° C. for 0.5 to 1 hour. The method of claim 7, wherein The substrate is made of an inclined magnetization structure, and the substrate is a self-biased magnetic thin film sensor element, characterized in that it has its own bias function.