JP2000030921A - Co-BASED AMORPHOUS METALLIC THIN WIRE AND ITS MANUFACTURE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a Co-based amorphous thin wire which can obtain a large impedance variation against the variation of an external magnetic field by specifying the number of twists of the wire and making the wire exhibit an asymmetrical magnetic impedance effect against an external magnetic field when an asymmetrical alternating current is made to flow to the wire. SOLUTION: The number of twists of an amorphous metallic thin wire is set at >=25 twists/m so that the wire may exhibit an asymmetrical impedance effect (asymmetrical MI effect) and show high magnetic field sensitivity when an asymmetrical alternating current is made to flow to the wire. The 'thin wire' of this amorphous metallic thin wire is not limited particularly, but generally considered to be about <=200 μm. This amorphous metallic thin wire is manufactured by heat-treating a Co-based amorphous metallic thin wire at a temperature between 250 deg.C and the temperature of crystallization after the wire is twisted by >=25 times/m.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Co-based amorphous metal thin wire, and more particularly, to a new amorphous metal thin wire exhibiting an asymmetric magneto-impedance effect with respect to an external magnetic field, and its production. It is about the method.

[0002]

2. Description of the Related Art Fe-group-based amorphous metal fine wires have excellent soft magnetic properties. In particular, in the case of Co-based amorphous metal fine wires described in Japanese Patent Application Laid-Open No. 1-25932. High permeability magnetic fine wires are obtained in a specific composition region.
As described in JP-A-7-236317, when a high-frequency current is applied to generate a skin effect, the impedance (or voltage) between both ends of the amorphous thin wire becomes high. It is known that an electromagnetic phenomenon that is significantly changed by an external magnetic field, that is, a so-called magneto-impedance (MI) effect occurs. In particular, 30 to 50 μm
The Co-based amorphous metal thin wire near zero magnetostriction, which has been subjected to a heat treatment under tension after drawing to a diameter, has a remarkably high magnetic field detection sensitivity because the change in impedance reaches 40 to 60% with respect to an external magnetic field of 5 Oe or less. As shown in the figure, even when the wire length is set to 1 mm or less, it maintains excellent high-speed response and sensitivity, and is therefore applied as a magnetic element for a high-sensitivity micro magnetic sensor.

In order to detect the direction of an external magnetic field using the magneto-impedance effect of such an amorphous metal thin wire, a method of externally applying a bias DC magnetic field to the amorphous metal thin wire is used. . That is, by applying the bias magnetic field, the impedance change due to the external magnetic field varies depending on the direction of the external magnetic field, and an asymmetric magnetic impedance effect can be obtained. As a method of applying a bias magnetic field, a method in which a coil for bias is usually arranged around a thin wire is used. However, in order to make the most of the characteristics of the magneto-impedance effect to construct a magnetic micro element,
Disadvantages of the method of disposing the bias coil around the drawback are that the size of the magnetic element is inevitably large, and that the power consumption of the element increases due to the need to provide an electric circuit for the bias. Have been.

As a method for solving this drawback, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. -80133 discloses that in a magnetic impedance element, a magnetic material having a spiral magnetic anisotropy and a high-frequency current or a pulse current in which a direct current is superimposed on the magnetic material are applied to the magnetic material to thereby increase the voltage amplitude of the magnetic material. Has been proposed to be asymmetrical with respect to the sign (direction) of the external magnetic field. Then, as a method of manufacturing the element, a magnetic body (wire) having circumferential magnetic anisotropy is drawn finely, annealed in a state where the wire is given a predetermined twist, and then both ends of the wire are electroded. A fixing method has also been proposed. For a wire obtained by subjecting an Fe—Co—Si—B wire to 10-turn / m twisting and applying an electric joule heat treatment, a voltage amplitude (impedance) that is asymmetric with respect to the sign (direction) of the external magnetic field. Change) is also obtained.

[0005]

However, when the method disclosed in Japanese Patent Application Laid-Open No. 9-80133 is actually examined, it is found that Fe-Co-Si-B and Co-S
In the case where a magnetic impedance element is formed by applying a heat treatment (annealing) to the i-B amorphous thin wire by applying a twist of about 10 times / m and changing various temperatures to form a magneto-impedance element, it is true that the voltage amplitude is asymmetric with respect to the direction of the external magnetic field. In other words, although an asymmetrical magnetic impedance effect can be obtained, even if the magnitude of the alternating current or superimposed direct current flowing through the thin wire after the torsion heat treatment is variously examined, a large change rate of the voltage amplitude with respect to the change of the magnetic field (the fine wire impedance) (A rate of change with respect to the change in the magnetic field) cannot be obtained.

Therefore, the above-mentioned problems are solved, and the magneto-impedance effect that the direction of the external magnetic field can be detected without arranging the bias coil and applying the bias magnetic field, ie, the external magnetic field, There has been a demand for the development of a new amorphous metal wire and a method for manufacturing the same, which can obtain a large impedance change (high magnetic field sensitivity) with respect to a change in an external magnetic field in an amorphous metal wire showing an asymmetric impedance change.

[0007]

In order to solve the above-mentioned problems, the invention of the present application firstly requires that the number of twists is 25 times / m or more and that an asymmetrical alternating current is supplied. A Co-based amorphous metal thin wire characterized by exhibiting an asymmetric magneto-impedance effect with respect to an external magnetic field when performed.

[0008] The invention of the present application is, secondly, 25.
The present invention also provides a method for producing the Co-based amorphous metal thin wire, wherein a heat treatment is performed in a temperature range of 250 ° C. or more and a crystallization temperature or less in a state where a twist of at least times / m is applied. As described above, in the invention of this application, a Co-based amorphous metal thin wire having a specific number of twists of 25 times / m or more, which was first discovered by the inventors, was subjected to an asymmetrical alternating current. It has been completed based on the finding that it exhibits an asymmetric magneto-impedance effect with respect to an external magnetic field and exhibits high magnetic field sensitivity.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and the embodiments of the invention will be described in detail below. First, in the amorphous metal thin wire of the invention of this application, it is important to maintain a "twist" of a critical value or more even in a state where no stress is applied, and the number of twists is 25 times / m or more. is necessary. Here, the “twist” of the fine wire is a form in which the amorphous metal fine wire is shaped by the torsional stress received during the heat treatment.
As shown in (1), it is defined based on the processing trace (2) on the surface parallel to the longitudinal direction of the fine wire (1) formed when the wire drawing is performed. That is, as shown in FIG. 2, in a thin wire (3) having “twist”, an angle θ between a linear processing trace (2) and the longitudinal direction (axial direction) of the thin wire is obtained, and the following equation (1) is obtained. Gives the number of twists.

N = tan θ / πD (1) Here, N is the number of twists [times / m], and D is the wire diameter [m] of the thin wire. Therefore, by observing the processing trace (2) on the surface of the amorphous fine wire with an optical microscope or a scanning electron microscope, it is possible to determine the number of twists of the fine wire without stress.

In order to exhibit an asymmetric magneto-impedance effect (hereinafter referred to as an asymmetric MI effect) and an excellent magnetic field sensitivity to an external magnetic field when an asymmetrical alternating current is applied, the amorphous structure of the invention of the present application has been disclosed. In the case of a thin metal wire, the number of twists needs to be 25 times / m or more. In order for a thin line to exhibit a more sensitive asymmetric MI effect, the rate is more preferably 35 times / m or more, and most preferably 50 times / m or more. When the number of twists of the amorphous thin wire is less than 25 times / m, a large change rate of the voltage amplitude with respect to the change of the magnetic field (the thin wire impedance) can be obtained even if the magnitude of the alternating current or the direct current to be superimposed on the thin wire is variously examined. Change rate with respect to the change in the magnetic field) cannot be obtained.

The amorphous metal fine wire of the present invention has "twist" even when no stress is applied.
A magnetic element exhibiting an asymmetric MI effect can be easily manufactured by performing solder joining or spot welding joining of both ends of the thin wire to an electrode. Here, the asymmetric MI effect exhibited by the amorphous thin wire of the present invention is obtained when an asymmetric current obtained by superimposing a DC bias current on an AC current is used as a current flowing through the thin wire. Normally, when a DC current of 5% or more is superimposed on an effective value of a high-frequency AC current of 100 kHz or more, a large impedance change only for one magnetic field with respect to the sign (direction) of the external magnetic field. , A remarkable asymmetry of the MI effect. Also, the effective value of the alternating current to be applied is
It is preferable that the amorphous fine wire has a magnitude of 0.5 Oe or more in terms of a circumferential magnetic field (see the following equation (2)) on the fine wire surface.

Hθ = I / πD (2) where Hθ is a circumferential magnetic field on the surface of the fine wire, I is an effective value of an alternating current to be applied, and D is a wire diameter. Further, with respect to the asymmetric MI effect exhibited by the amorphous thin wire of the present invention, the impedance change with respect to a change in the magnetic field of 1 Oe is 30% or more by appropriately adjusting the magnitude of the DC current to be superimposed on the AC current to be supplied. In particular, when a thin wire having an optimum number of twists is used, a change in the impedance with respect to a change in the magnetic field of 1 Oe is as high as 50% or more, and a very high magnetic field sensitivity is obtained. .

The composition of the amorphous metal wire of the present invention is not particularly limited as long as it is a Co-based amorphous metal wire exhibiting an excellent magneto-impedance effect, but Co or Co and Fe, Si, and B is preferably contained. That is, in the amorphous thin wire of the present invention, Co or Co and Fe are indispensable elements for obtaining a thin wire exhibiting a magnetic impedance effect for detecting a voltage generated from both ends of the thin wire. The content is suitably at least 65 atomic% in total of Co or Co and Fe. More preferably, it is 69 to 83 atomic%, and most preferably, it is 70 to 80 atomic%. When Co and Fe are contained, it is appropriate that Fe is contained at a ratio of 20% or less in atomic% in the sum of the Fe amount and the Co amount.
Is preferably contained at a ratio of 4% to 8%, and most preferably Fe is contained at a ratio of 5% to 7%. Here, in the sum of the Fe amount and the Co amount, the ratio of Fe is 2
If it exceeds 0%, it becomes difficult to obtain an excellent magnetic impedance effect even if a voltage generated from both ends of the thin wire is detected. In the present invention, the content of Si is 7-1.
It is suitably 7.5 atomic%, and preferably 9 to
15 atomic%. When the content of Si is less than 7 atomic% or more than 17.5 atomic%, it is difficult to obtain an amorphous metal thin line composed of an amorphous single phase, and it is not practical. Similarly, the content of B is suitably from 10 to 18 atomic%, and preferably from 12 to 16 atomic%. The content of B is less than 10 atomic%;
If the content exceeds atomic%, it is difficult to obtain an amorphous metal thin line composed of an amorphous single phase, and it is not practical. Further, for example, elements such as Cr, Mo, Ta, Nb, Mn, and Ni may be contained at 10 atomic% or less as long as the magnetic impedance effect indicated by the fine wire is not impaired.

The "fine wire" in the Co-based amorphous metal fine wire of the present invention is not particularly limited, but generally means a wire having a diameter of 200 μm or less. More suitably, it will be exemplified as that of 10 to 100 μm. The amorphous metal thin wire according to the present invention has a temperature range of 250 ° C. or more and a crystallization temperature or less in a state where a twist of 25 times / m or more is given using the Co-based amorphous metal thin wire having the above composition range. It is manufactured by performing a heat treatment.

Here, the heat treatment conditions for the amorphous metal fine wire include that the heat treatment is performed using an amorphous metal thin wire having an arbitrary wire diameter and giving a twist of 25 turns / m or more. This is necessary in order to exhibit a highly sensitive asymmetric MI effect as the magnetic characteristics of the thin line, and in order to obtain a thin line exhibiting a remarkable asymmetric MI effect having a higher magnetic field sensitivity,
Preferably, a twist of 35 times / m or more is applied, and most preferably, a twist of 50 times / m or more is applied. The tension applied at the same time is 0.001 kg / mm ² to
The range may be 50 kg / mm ² .

Further, as the heat treatment conditions for the amorphous metal fine wire of the present invention, it is appropriate to perform the heat treatment in a temperature range of 250 ° C. or more and a crystallization temperature or less in order to fix the introduced twist to the fine wire. If the temperature is less than 250 ° C., it is difficult to fix the twist to the fine wire, and even if the number of twists applied during the heat treatment is increased, it is not possible to obtain a desirable asymmetric MI characteristic. Further, when crystallization occurs in the fine wire, the magnetic impedance effect itself cannot be obtained as the magnetic characteristics of the fine wire. The magnetic properties of the thin wire after heat treatment
In order to obtain a thin line having a higher magnetic field sensitivity and exhibiting a remarkable asymmetric MI effect, the heat treatment is preferably performed at a temperature of 350 to 530 ° C.

Although the heat treatment time depends on the stress state held before the heat treatment of the amorphous fine wire, in the present invention, the heat treatment for 0.05 to 3000 seconds is carried out to obtain a desired heat treatment. An amorphous metal thin wire having magnetic properties can be obtained. Examples of the amorphous metal fine wire before twisting that can be used in the present invention include Fe—C
It can be obtained by melting an alloy containing o-Si-B or Co-Si-B as a main component and cooling and solidifying it in a cooling liquid. Various methods can be mentioned as a method for solidifying, and a preferable method is, for example, JP-A-56-165016 or JP-A-57-7905.
The so-called spinning in liquid spinning method described in JP-A No. 2 (Kokai) No. 2 can be mentioned. Further, amorphous metal fine wires having various wire diameters are also provided by performing cold working of the rapidly cooled amorphous fine wire in a drawing step. Here, as the drawing conditions of the amorphous metal thin wire, the area reduction rate in one die is 5 to 15%.
And wire drawing can be performed to an arbitrary wire diameter using a plurality of dies. Further, even if the amorphous metal thin wire used in the present invention is subjected to heat treatment under no tension or under tension, if the twisting heat treatment of the present invention is given a predetermined number of twists, the magnetic characteristics of the fine wire can be asymmetrically sensitive. The MI effect appears.

Since the twist of the amorphous thin metal wire of the present invention is fixed by the torsion heat treatment, it exhibits a coercive force of 0.05 to 0.25 (Oe) as the magnetic property in the longitudinal direction of the thin wire. .

[0020]

Next, the present invention will be specifically described with reference to examples. (Example 1) Co _72.5 S drawn to a diameter of 50 μm
i _12.5 B ₁₅ using the amorphous thin lines, 15 minutes at 460 ° C. 1
Heat treatment was performed by applying a twist of 30 times / m. And
When the surface of the fine wire was observed with a scanning electron microscope after the heat treatment, an amorphous fine wire having a twist frequency of 130 times / m was obtained. Next, the fine wire was cut into a length of 5 mm, and the MI effect of the fine wire was examined by soldering both ends to electrodes. FIG. 3 shows the results of the obtained MI effect. The vertical axis shows the voltage Ew (pp) generated at both ends of the thin line, and the horizontal axis shows the external magnetic field Hex in the longitudinal direction of the thin line.

The evaluation of the MI effect was performed using the circuit shown in FIG. The circuit shown in FIG. 4 comprises an amorphous thin wire (4) of the present invention, a high-frequency power supply (5), a DC power supply (6), and a resistor (7).
The voltage (amplitude) E generated at both ends of the amorphous thin wire (4) when a current in which ac and the DC current Idc are superimposed is applied.
w can be detected with respect to the external magnetic field Hex.

FIG. 3 shows that the MI effect obtained when an alternating current of 15 mA having a frequency of 1 MHz is applied has a bimodal MI characteristic symmetrical with respect to an external magnetic field as shown by a mark. In contrast, MI obtained when an asymmetric current obtained by superimposing a DC of 2.5 to 7.5 mA on the AC is supplied.
The effect has a remarkable asymmetric characteristic with respect to an external magnetic field as shown by marks ●, ○ and □. And Hex
= 33% to 5 for a change in the external magnetic field of 1 Oe near = 0
Highly sensitive impedance change (voltage amplitude change) of 5%
Has been obtained.

As described above, in the amorphous metal thin wire of the present invention, by adjusting the magnitude of the alternating current to be passed and the direct current to be superimposed appropriately, high sensitivity and a remarkable asymmetric M
The I effect is obtained. (Example 2) Wire drawing was performed to a diameter of 50 μm (Co _0.94
Fe _0.06 ) _72.5 Si _12.5 B ₁₅
Heat treatment was performed at 0 ° C. for 15 minutes by applying a twist of 280 times / m. When the surface of the fine wire was observed after the heat treatment, an amorphous fine wire having a twist of 280 times / m was obtained. Next, this thin wire was cut into a length of 5 mm.
In the same manner as described above, the MI effect of the thin wire was examined. FIG. 5 shows the results of the obtained MI effect.

As shown in FIG. 5, the MI effect obtained when a 15 mA alternating current having a frequency of 1 MHz is applied has a bimodal MI characteristic symmetrical with respect to an external magnetic field as indicated by a mark. On the other hand, -7.5mA or 9mA
M obtained when an asymmetric current superimposed with
The I effect has a remarkable asymmetric characteristic with respect to an external magnetic field as indicated by a circle or a triangle. And Hex =
33% to 35 for a change in the external magnetic field of 1 Oe near 0
%, A highly sensitive impedance change (voltage amplitude change) is obtained.

Here, as in the case where a direct current of -7.5 mA or 9 mA in FIG.
Just by changing the direction and magnitude of the superimposed DC current,
It can be seen that there is a characteristic that the direction (sign of the magnetic field) of the magnetic field showing asymmetry can be changed. Therefore, by combining two magnetic elements each having an asymmetric MI effect made of an amorphous thin wire according to the present invention, a magnetic element for a linear magnetic field sensor having an extremely simple structure without using a bias coil can be easily realized. (Comparative Example 1) Co _72.5 S drawn to a diameter of 50 µm
i _12.5 B ₁₅ using the amorphous thin lines, 15 minutes at 460 ° C. 1
Heat treatment was performed by applying a twist of 6 times / m. When the fine wire surface was observed after the heat treatment, the number of twists was 16 times /
An amorphous thin wire having a twist of m was obtained. Next, the fine wire was cut into a length of 5 mm, and the MI of the fine wire was cut in the same manner as in Example 1.
The effect was examined. FIG. 6 shows the results of the obtained MI effect.

As shown in FIG. 6, the MI effect obtained when a 15 mA alternating current having a frequency of 1 MHz is applied has a bimodal MI characteristic that is symmetric with respect to an external magnetic field, as indicated by a triangle. In addition, 4.5mA or 7.5mA
M obtained when an asymmetric current superimposed with
The I effect also remains as a bimodal MI effect that is almost symmetric with respect to an external magnetic field, as indicated by ○ and □ marks.
Further, although not shown in FIG. 6, even in the case of −0.1 mA to −9 mA in which the direction of superposition of the DC current is changed,
It was confirmed that only an almost symmetric MI effect was obtained. This amorphous thin wire has a twist frequency of 16 times / m.
And the sign (direction) of the external magnetic field because it is outside the scope of the present invention.
Did not show a significant asymmetric MI effect. (Examples 3 to 5, Comparative Examples 2 and 3) Using (Co _0.94 Fe _0.06 ) _72.5 Si _12.5 B ₁₅ amorphous fine wire drawn to a diameter of 30 μm, described in Table 1 at 500 ° C. for 15 minutes. The heat treatment was performed with the given number of twists (number of twists N). And about the fine wire after heat processing, the twist of the fine wire surface was observed with the scanning electron microscope, and the number of twists N was obtained. Further, a magnetic element having a length of 5 mm was manufactured in the same manner as in Example 1, and its MI
The effect was examined. Table 1 shows the obtained results. Here, Table 1 shows the effective value I of the supplied 1 MHz AC current.
ac shows the magnitude of the DC current Idc to be superimposed.
In addition, as for the obtained asymmetric MI effect, a value η calculated by calculating the presence or absence of asymmetry and the impedance change (voltage amplitude change) with respect to a magnetic field change of 1 (Oe) near Hex = 0 based on the following equation (3) is described. are doing.

Η = 100 × {Ew (Hex = 1 or Hex = −1) −Ew (Hex = 0)} / Ew (Hex = 0) (3)

[0028]

[Table 1]

From Table 1, it can be seen that the amorphous metal fine wires of Examples 3 to 5 according to the present invention have a highly sensitive impedance change (voltage amplitude) of 32% to 55% with respect to a change of an external magnetic field of 1 Oe near Hex = 0. Change) is obtained. On the other hand, the thin wires of Comparative Examples 2 and 3 which were heat-treated in a state where the twist was out of the range of the present invention had a twist number of 25 times / m.
Therefore, even when the magnitude of the superimposed DC current was examined in various ways, no remarkable asymmetric MI characteristic was observed for an external magnetic field.

[0030]

As described in detail above, the sign (direction) of the external magnetic field can be obtained by the amorphous metal thin wire of the present invention.
Which exhibit a highly sensitive asymmetric MI effect. Therefore, by using the thin wire of the present invention, it is possible to realize a novel magnetic element based on the magneto-impedance effect with small size and high sensitivity without using a bias coil, and application to various micro magnetic elements becomes possible. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a processing trace on the surface of an amorphous metal thin wire used for heat treatment of an amorphous metal thin wire according to the present invention.

FIG. 2 is a schematic diagram showing a processing trace on the surface of a twisted amorphous metal thin wire according to the present invention.

FIG. 3 is a characteristic diagram showing a magneto-impedance effect of the amorphous thin metal wire of Example 1 of the present invention.

FIG. 4 is a configuration diagram of a circuit for measuring a magneto-impedance effect of an amorphous metal thin wire in the present invention.

FIG. 5 is a characteristic diagram showing a magneto-impedance effect of the amorphous metal thin wire of Example 2 of the present invention.

FIG. 6 is a characteristic diagram showing a magneto-impedance effect of the amorphous metal thin wire of Comparative Example 1 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Amorphous thin metal wire 2 Trace of processing received in drawing process 3, 4 Amorphous thin metal wire having twist of the present invention 5 High frequency AC power supply Eac 6 DC power supply Edc 7 Resistance R Hex External magnetic field

Continuing from the front page (72) Inventor Shuji Ueno 23 Uji Kozakura, Uji-city, Kyoto Prefecture, Unitika Central Research Laboratory (72) Inventor Katsuhiro Kawashima 23 Uji Kozakura, Uji-shi, Kyoto Unitika Central Research Laboratory (72) ) Inventor Isamu Ogasawara 23 Uji Kozakura, Uji-city, Kyoto F Unit in Central Research Laboratory of Unitika Ltd. 2G017 AA03 AC09 AD69 BA02 BA03 5E041 AA14 AA19 BD03 CA10 NN01 NN18

Claims (2)

[Claims] 1. A Co-based amorphous metal having a number of twists of 25 times / m or more and exhibiting an asymmetrical magnetic impedance effect with respect to an external magnetic field when an asymmetrical alternating current is applied. Thin line. 2. In a state where a twist of 25 times / m or more is given,
2. The method for producing a Co-based amorphous metal thin wire according to claim 1, wherein the heat treatment is performed in a temperature range from 250 ° C. to a crystallization temperature.