JPH06152002A - Ferromagnetic thin film magnetoresistive element and sensor using it - Google Patents

Abstract

(57) [Abstract] [Purpose] Regarding the circuit configuration of the ferromagnetic thin film type magnetoresistive element, the magnetoresistive output, which tends to fluctuate in response to the temperature change of the ambient atmosphere, is automatically compensated and the magnetic field is accurately detected and produced. The purpose is to improve the sex. A magnetic recording medium, which is multi-pole magnetized at a magnetizing pitch λ, is arranged to face the magnetized surface, and a leakage magnetic field from the magnetized surface is formed on a surface facing the magnetized surface. A ferromagnetic thin film type magnetoresistive element for detecting with a magnetic field detection pattern composed of a ferromagnetic thin film, the magnetic field detection pattern forming surface having the same width and the same width as the magnetic field detection pattern 21 in the vicinity of the magnetic field detection pattern. Two temperature compensation patterns 31 whose length is shortened by thickness and only resistance value is changed are displayed as “(2n−1).
λ / 4 where n is formed in a direction parallel to the magnetic field detection pattern 21 with an interval kept satisfying a positive integer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit structure of a ferromagnetic thin film type magnetoresistive element (hereinafter simply referred to as an MR element) for detecting a leakage magnetic field from a magnetic recording medium by utilizing the magnetoresistive effect of a ferromagnetic thin film. High-precision detection of magnetic field is realized by automatically compensating the magnetoresistive output, which tends to fluctuate according to the temperature change of the surrounding atmosphere, without using a special temperature compensation element, depending on the configuration of the sensor using it. And a sensor using the same.

MR elements are widely used in position sensors, angle sensors, rotary encoders, etc. because they are more sensitive to minute magnetic fields and superior in resolution than Hall elements or semiconductor type magnetoresistive elements. In particular, in order to detect a leakage magnetic field from a magnetic recording medium such as a multi-pole magnetized magnetic drum, it is necessary to bring the magnetic field detecting section close to the magnetized surface of the magnetic recording medium. The MR element located on the formation surface is optimal.

[0003]

2. Description of the Related Art FIG. 7 for explaining the technical background is a conceptual diagram for explaining an example of an MR element, and FIG. 8 in which only the magnetoresistive pattern area is extracted and enlarged is shown in FIG. It is a figure explaining with principle.

In FIG. 7, for example, in the MR element 2 for detecting the rotational speed and the rotational speed of the magnetic drum 11, the surface 2b on which the magnetoresistive pattern 2a made of a ferromagnetic thin film is formed faces the magnetized surface 11a around the magnetic drum. And is mounted on the circuit board 12 as described above.

Therefore, when the MR element 2 is brought close to the magnetized surface 11a of the magnetic drum 11 together with the circuit board 12 as shown by an arrow a, the MR element 2 is leaked from the magnetic drum 11 by the intensity of the magnetic field.
Since the resistance value in the region of the magnetoresistive pattern 2a of the element 2 varies, the leakage magnetic field strength from the magnetic drum 11 rotating with respect to the fixed MR element 2 is detected as a variation in resistance value as a result. The rotation speed and the rotation speed of the magnetic drum 11 can be detected from the periodicity of the resistance value fluctuation.

In FIG. 8 for explaining the circuit configuration, (8-1) is shown in FIG.
FIG. 8B is a front view of the pattern forming surface 2b of FIG. 8B, which is an enlarged view of the pattern region. In (8-1) of FIG. 8, the magnetoresistive pattern 2a is composed of four parallel magnetic field detection patterns 21 (21 _{-1 to} 21) made of a nickel-iron (Ni-Fe) alloy thin film with a film thickness of about 300 to 1000 Å. _-4 ) and an even number (4 in the figure) of external connection terminals 22 (22 _{-1 to} 22 _-4 ) made of a gold (Au) thin film patterned so as to connect between the respective patterns.
It consists of and.

As shown in the enlarged view (8-2), each magnetic field detection pattern 21 in this case is formed by folding a pattern having a width W of about 10 μm and making two reciprocations over its entire length. , The respective end portions 21a and 21b are connected by the external connection terminals 22 (22 _{-1 to} 22 _-4 ) located between the adjacent magnetic field detection patterns.

The external connection terminal 22 _-1 of the four external connection terminals 22 is located between the magnetic field detection patterns 21 _-1 and 21 _-4 located at both ends of the four magnetic field detection patterns 21. To connect.

In particular, the pitch p between adjacent magnetic field detection patterns 21 in this case is 1/4 of the magnetizing pitch λ on the magnetic drum 11. This is the pattern
Patterns 21 _-1 and 21 _-4 located at both ends of 21 are "(3/4) ・
This means that they are arranged with a gap of λ ″.

Therefore, the leakage magnetic field strength of the recorded contents magnetized at the pitch λ on the magnetized surface 11a (shown in FIG. 7) of the magnetic drum 11 which moves relative to the magnetic resistance pattern 2a is detected by the magnetic field. External connection terminal connected to the pattern 21 _{-1 to} 21 _-4
22 (22 _{-1 to} 22 _-4 ), and as a result, the rotational speed and the rotational speed of the magnetic drum 11 can be detected.

[0011]

However, since the temperature coefficient of the magnetic field sensitivity of the conventional MR element is as large as "-0.1% / ° C", it is greatly affected by the ambient temperature. For example, when the ambient temperature becomes high, the resistance value becomes high. When the temperature of the output decreases and the temperature of the output decreases, the output of the output increases and a drift as the output occurs.

Further, variations in the thin film material and size of each magnetoresistive pattern 2a also cause an output fluctuation as a resistance value. Therefore, since the conventional MR element composed only of the magnetic field detection pattern cannot be expected to detect the magnetic field with high precision, the MR element 2 is mounted as shown in FIG. The temperature compensating device 13 is connected with the temperature compensating circuit section and the output amplifying section in the vicinity of the element of the circuit board 12 which is already installed, and there are measures such as eliminating the influence of the ambient temperature. There is a problem that productivity cannot be expected to improve because effective use of the circuit board surface is hindered.

[0013]

SUMMARY OF THE INVENTION The above-mentioned object is to face a magnetized surface of a magnetic recording medium which is multi-pole magnetized at a magnetized pitch λ, and to prevent a leakage magnetic field from the magnetized surface. A ferromagnetic thin film type magnetoresistive element for detecting with a magnetic field detection pattern formed of a ferromagnetic thin film formed on a surface facing a magnetized surface, wherein the magnetic field detection pattern is formed in the vicinity of the magnetic field detection pattern. Same width made of the same material as the pattern
Two temperature compensation patterns in which only the resistance value is changed by shortening the length by the thickness are used to detect the magnetic field with an interval kept satisfying “(2n−1) · λ / 4 where n is a positive integer”. This is solved by a ferromagnetic thin film type magnetoresistive element formed and formed in a direction parallel to the pattern.

[0014]

The pattern made of the same material as the magnetic field detection pattern, in other words, the pattern having the same temperature coefficient can cancel the resistance value variation generated in the magnetic field detection pattern due to the change of the ambient temperature in the vicinity of the magnetic field detection pattern. If at least the temperature compensation circuit is provided, the temperature drift of the output as the MR element can be automatically suppressed without providing the special temperature compensation device 13 as described in FIG.

Therefore, in the present invention, the resistance value is made of the same material as the pattern in the direction parallel to the pattern on both sides of the pattern on the conventional magnetic field detection pattern forming surface or in the vicinity of one side thereof, and only the length is changed. Of the temperature compensation pattern in which the interval p is “p = (2n−1) · λ
/ 4 However, it is formed so as to satisfy n = 1, 2, 3, ...

FIG. 1 is a diagram for schematically explaining a temperature compensation pattern according to the present invention. (1-1) shows the positional relationship between a magnetic recording medium multi-polarized with a pitch λ and the temperature compensation pattern. The relationship is shown in (1-2), which is a graph showing the magnetoresistive change as the temperature compensation pattern, where the horizontal axis X is time T and the vertical axis Y is resistance value R.

In the example (1-1) where the pattern interval P of the temperature compensation pattern is "p = 3λ / 4" where n is 2, 11 is magnetically recorded in FIG. In the magnetic drum described above, R ₁ and R ₂ represent the resistance values of the two patterns 25a and 25b forming the temperature compensation pattern 25. The respective patterns 25a and 25b depend on the above conditions.
They are arranged with an interval of 3λ / 4.

Then, in this case, each pattern 25a,
Since 25b is always located in either a strong magnetic field region or a weak magnetic field region as shown in the figure, as a result, magnetic resistance change curves R ₁ and R ₂ shown in (1-2) are mutually Since the magnetic resistance change as the temperature compensation pattern 25 can be reduced in total due to the phase shifts canceling each other, by combining with the above-mentioned magnetic field detection pattern in the state of being connected to a temperature compensation circuit (not shown), at least FIG. It is possible to configure a required MR element capable of realizing temperature compensation with higher accuracy than before without using the temperature adjustment device described in.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a diagram for explaining a circuit configuration example of an MR element according to the present invention, FIG. 3 is a diagram showing another circuit configuration example, and FIG.
It is a figure which shows the structural example as an R element.

FIG. 5 is a diagram showing an example in which the MR element of the present invention is used for a sensor, and FIG. 6 shows another sensor configuration example. In each of the figures, the MR element based on the magnetoresistive pattern 2a described with reference to FIGS. 7 and 8 is taken as an example, and therefore, the same target members and parts as those in FIGS. And redundant description will be omitted.

FIG. 2 shows an example in which temperature compensation patterns having the same structure as the temperature compensation pattern 25 in FIG. 1 are located on both sides of the magnetoresistive pattern. 7 is a front view of the pattern forming surface 2b of No. 7, (2-2) is a further enlarged view of the pattern area.

Only the circuit pattern formation surface is extracted from (2
-1), (2-2), the circuit pattern 3a as the MR element according to the present invention is the outside of the magnetic field detection patterns 21 _-1 , 21 _-2 located on both sides of the magnetoresistive pattern 2a described in FIG. At the corresponding position in the vicinity, the width is 10 μm and the film thickness is 300
~1000Å about nickel - iron alloy thin film two parallel the temperature compensation consisting pattern 31 _-1, 31 with _-2 are formed in a length shorter than the magnetic field detection pattern 21, each of said temperature compensating pattern 31 _{- One} end of ₁ , 31 _-2 is a conductor 32a made of gold thin film
And the other end of each is formed by patterning external connection terminals 32 _-1 , 32 _-2 similar to the external connection terminal 22 described in FIG. 7.

In particular, each temperature compensation pattern in this case
The pitch P ₁ between 31 _-1 and 31 _-2 is "P = (2
n-1) .lamda. / 4, where n = 1, 2, 3, ..., For example, “P ₁ = 11λ / 4 where n
= 5 ".

In the MR element 3 having such a circuit pattern 3a, the temperature compensation patterns 25 _-1 , 25 _-2 described in FIG.
= 3 [lambda] / 4 from having the same effect as if it is formed on the "respective temperature compensating pattern 31 _-1, the external connection terminal 32 _-1 connected to the 31 _-2, 32 _-2 and the magnetoresistance pattern 2a By combining and with a temperature compensation circuit, an output amplifier circuit, and the like (not shown), highly accurate temperature compensation can be easily realized.

FIG. 3 shows another example of a circuit configuration, the temperature compensation pattern 31 _-1 described in FIG. 2, 31 _-2 temperature compensation patterns 41 _-1 arranged on one side near the magnetic detection pattern 21,
This is an example of the case where the circuit pattern 4a is formed by substituting it with 41 _-2 .

In this case, each temperature compensation pattern 41 _-1 , 41
The condition pitch P ₂ between _{-2 "P = (2n-1} ) · λ / 4
However, for example, "P ₂ = λ / 4, where n = 1" is formed so as to satisfy n = 1, 2, 3, ..., So that the same effect as in the case of FIG. 2 can be obtained. There is an advantage that the size of the circuit pattern 4a can be made smaller than that of the circuit pattern 3a of FIG.

In FIG. 4, a chip circuit (temperature compensating circuit) 52 in which a temperature compensating circuit, an output amplifying circuit, etc. are integrated is formed on a circuit board 51 on which the above-mentioned circuit pattern 3a is formed to form an MR.
This is an example of the case where the element 5 is configured.

In particular, the temperature compensation circuit in this case is
The current applied to the magnetic field detection pattern 21 is changed from the resistance fluctuation value in the temperature compensation pattern 31 to keep the resistance value output from the magnetic field detection pattern 21 constant.

In the MR element 5, not only the temperature compensating device described in FIG. 7 but also the temperature compensating circuit and the output amplifying section can be mounted together on the circuit board 51, so that further improvement in productivity can be expected. You can

FIG. 5 for explaining an example of the configuration of a sensor using the MR element having the above-mentioned temperature compensation pattern is shown in FIG. 5, which is a rotation detection for detecting a rotation angle, a rotation speed, a rotation unevenness, a rotation speed, etc. of a rotating motor shaft. It shows a sensor.

That is, in FIG. 5, the rotation detecting sensor 6 is the magnetic recording medium 61 which is multi-pole magnetized at the magnetizing pitch λ on the peripheral surface of the disk 61b having the central axis 61a, and is described with reference to FIG. 2 or FIG. The MR element 3 or 4 having the circuit pattern 3a or 4a.

Therefore, the magnetic recording medium 61 is tested by a rotating body.
When the rotating body 62 is rotated after the rotation axis is fixed to 62 and brought into the state shown in the drawing, the leakage magnetic field from the magnetic recording medium 61 can be detected by the MR element 3 or 4 having the temperature compensation pattern. Thus, it is possible to realize a highly accurate rotation sensor that can automatically suppress the temperature drift of the output as the MR element and is not affected by the change in the ambient temperature.

FIG. 6 for explaining a configuration example of another sensor shows a linear sensor for detecting, for example, a moving speed, a moving unevenness, a moving amount and the like of a test moving body which moves linearly. That is, in FIG. 6, the linear sensor 7 is a rectangular straight body 71a.
The magnetic scale 71 is attached to one side surface 71b of the magnetic recording medium 71c which is multi-pole magnetized at the magnetic pitch λ, and the MR element 3 or 4 having the above-mentioned circuit pattern 3a or 4a.

Therefore, for example, the MR element 3 or 4 is fixed to the test moving body 72, and the rectangular parallelepiped 71a is attached to the magnetic recording medium 71c along the moving direction of the test moving body 72.
Is placed so as to face the circuit pattern surface of the MR element 3 or 4 and brought into the state shown in the figure, and then the test moving body 72 is moved, so that the leakage magnetic field from the magnetic recording medium 71c is MR having a temperature compensation pattern. Since it can be detected by the element 3 or 4, a linear sensor which can automatically suppress the temperature drift of the output of the MR element even when the ambient temperature changes and can detect highly accurate movement information is configured. be able to.

[0035]

As described above, according to the present invention, the magnetoresistive output, which tends to fluctuate according to the temperature change of the surrounding atmosphere, is automatically compensated without using a special temperature compensating element, and the magnetic field can be accurately detected. It is possible to provide a realized MR element and a sensor using the MR element.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a temperature compensation pattern according to the present invention.

FIG. 2 is a diagram illustrating an example of a circuit configuration of an MR element according to the present invention.

FIG. 3 is a diagram showing another circuit configuration example.

FIG. 4 is a diagram showing a configuration example as an MR element.

FIG. 5 is a diagram showing an example in which the MR element of the present invention is used for a sensor.

FIG. 6 is a diagram showing another sensor configuration example. ,

FIG. 7 is a conceptual diagram illustrating an example of an MR element.

FIG. 8 is a diagram for explaining in principle the circuit configuration of a conventional MR element, together with its function.

[Explanation of symbols]

2a Magnetic resistance pattern 3,4,5 Ferromagnetic thin film type magnetic resistance element 3a, 4a Circuit pattern 11 Magnetic drum 21, 21 _{-1 to} 21 _-4 Magnetic field detection pattern 22, 22 _{-1 to} 22 _-4 , 32 _-1 , 32 _-2 External connection terminal 25 _-1 , 25 _-2 , 31 _-1 , 31 _-2 , 41 _-1 , 41 _-2 Temperature compensation pattern 32a Conductor 51 Circuit board 52 Chip circuit (temperature compensation circuit) 6 Rotation detection sensor 61 Magnetic recording medium 61a Center axis 61b Disc 62 Test rotor 7 Linear sensor 71 Magnetization scale 71a Rectangular straight body 71b Side surface (flat surface) 71c Magnetic recording medium 72 Test moving body 72

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naruse Tani 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (5)

[Claims] 1. A magnetic recording medium, which is multi-pole magnetized at a magnetizing pitch λ, is arranged so as to face the magnetized surface, and a leakage magnetic field from the magnetized surface is placed on the surface facing the magnetized surface. A ferromagnetic thin film type magnetoresistive element for detecting with a magnetic field detection pattern formed of a ferromagnetic thin film formed, in the vicinity of the magnetic field detection pattern on the magnetic field detection pattern forming surface,
The same width made of the same material as the magnetic field detection pattern (21)
The two temperature compensation patterns (31), in which only the resistance value is changed by shortening the length by the thickness, keep the interval that satisfies “(2n−1) · λ / 4 where n is a positive integer”. A ferromagnetic thin film type magnetoresistive element characterized by being formed in a direction parallel to the magnetic field detection pattern (21). 2. The two temperature compensation patterns according to claim 1, one on each side outside the magnetic field detection pattern (21) or formed on one side of the magnetic field detection pattern (21). A ferromagnetic thin film type magnetoresistive element characterized by being provided. 3. The ferromagnetic thin film magnetoresistive element according to claim 1, wherein the magnetic field detection pattern (21) is changed by changing the current applied to the magnetic field detection pattern (21) from the resistance fluctuation value in the temperature compensation pattern (31). ), A ferromagnetic thin film magnetoresistive element characterized by comprising at least a temperature compensating circuit (52) for keeping the resistance value output from (4) constant. 4. A magnetic recording medium (61) having a disk shape fixed to the test rotating body (62) with its rotation axis aligned and having its peripheral surface multi-polarized at a magnetic pitch λ, The magnetic recording medium (61) is arranged in the vicinity of the peripheral surface so as to face the magnetic recording medium (61).
A rotation detection sensor which is composed of a magnetoresistive element having a magnetic field detection pattern made of a ferromagnetic thin film for detecting the leakage magnetic field from 1) and which detects the rotation speed, rotation unevenness, rotation speed, etc. of the rotating body (62). A rotation detecting sensor, wherein the magnetoresistive element is the ferromagnetic thin film type magnetoresistive element according to claim 1. 5. A magnetizing scale formed on a magnetic recording medium (71c), which is rod-shaped having at least one flat side surface along the longitudinal direction, and the flat side surface is multi-pole magnetized at a magnetizing pitch λ. 71) and the magnetic recording medium when fixed to the test moving body (72) capable of relatively moving along the longitudinal direction thereof.
The magnetic field detection pattern composed of a ferromagnetic thin film for detecting the leakage magnetic field from (71c) is composed of a magnetoresistive element configured so as to closely face the surface of the magnetic recording medium and moves linearly. A linear sensor for detecting the speed, speed unevenness, moving distance, etc. of a moving body, wherein the magnetoresistive element is the ferromagnetic thin film magnetoresistive element according to claim 1.