JP2010101658A - Thin-film magnetic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film magnetic sensor capable of detecting a minute magnetic field in the vicinity of a zero magnetic field even if the sensor is heated up to a temperature in an extent of 100 to 200°C, or a temperature not lower than the temperature. <P>SOLUTION: The thin-film magnetic sensor includes a GMR film having a giant magnetoresistance effect, and thin-film yokes comprising soft magnetic materials connected electrically to both ends of the GMR film. In the thin-film magnetic sensor, each thin-film yoke is composed of a multilayer film which includes at least two soft magnetic layers formed of the soft magnetic materials, and a nonmagnetic layer formed of a non-magnetic material formed between the soft magnetic layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thin film magnetic sensor, and more particularly, detection of rotation information of an automobile axle, a rotary encoder, an industrial gear, etc., a stroke position of a hydraulic cylinder / pneumatic cylinder, a position / speed of a slide of a machine tool, etc. The present invention relates to a thin film magnetic sensor suitable for information detection, detection of current information such as arc current of an industrial welding robot, and a geomagnetic orientation compass.

  A magnetic sensor is an electromagnetic force (eg, current, voltage, power, magnetic field, magnetic flux, etc.), a mechanical quantity (eg, position, velocity, acceleration, displacement, distance, tension, pressure, torque, temperature, humidity, etc.), An electronic device that converts a detected amount such as a biochemical amount into a voltage via a magnetic field. Magnetic sensors are classified into Hall sensors, Anisotropic Magneto-Resistiity (AMR) sensors, Giant Magnetoresistance (GMR: Gaiant MR) sensors, etc., depending on the magnetic field detection method.

Among these, GMR sensors are
(1) The maximum value of the rate of change in electrical resistivity compared to the AMR sensor (ie, MR ratio = Δρ / ρ ₀ (Δρ = ρ _H −ρ ₀ : ρ _H is the electrical resistivity in the external magnetic field H) ρ ₀ is an extremely large electrical resistivity at zero external magnetic field)),
(2) The temperature change of the resistance value is small compared to the Hall sensor.
(3) Since the material having a giant magnetoresistance effect is a thin film material, it is suitable for microfabrication.
There are advantages such as. Therefore, the GMR sensor is expected to be applied as a high-sensitivity micromagnetic sensor used in computers, electric power, automobiles, home appliances, portable devices and the like.

  As a material exhibiting the GMR effect, a multilayer film of a ferromagnetic layer (for example, permalloy) and a nonmagnetic layer (for example, Cu, Ag, Au, etc.), an antiferromagnetic layer, a ferromagnetic layer (fixed layer), A metal artificial lattice composed of a multilayer film (so-called “spin valve”) having a four-layer structure of a non-magnetic layer and a ferromagnetic layer (free layer); nanometer-sized fine particles composed of a ferromagnetic metal (for example, permalloy); , Metal-metal nanogranular material having a grain boundary phase made of nonmagnetic metal (for example, Cu, Ag, Au, etc.), tunnel junction film in which MR (Magneto-Resistivity) effect is produced by spin-dependent tunnel effect, nm size A metal-insulator nanogranular material having a ferromagnetic metal alloy fine particle and a grain boundary phase made of a nonmagnetic / insulating material is known.

  Among these, a multilayer film represented by a spin valve is generally characterized by high sensitivity in a low magnetic field. However, the multilayer film needs to be laminated with high accuracy with thin films made of various materials, so that the stability and yield are poor, and there is a limit in suppressing the manufacturing cost. For this reason, this type of multilayer film is used only for high value-added devices (for example, magnetic heads for hard disks), and is applied to magnetic sensors that are forced to compete with AMR sensors and Hall sensors with low unit prices. Is considered difficult. In addition, diffusion between the multilayer films is likely to occur, and the GMR effect is easily lost.

On the other hand, nano-granular materials are generally easy to produce and have good reproducibility. Therefore, if this is applied to a magnetic sensor, the cost of the magnetic sensor can be reduced. In particular, metal-insulator nanogranular materials
(1) If the composition is optimized, a high MR ratio exceeding 10% is exhibited at room temperature.
(2) Since the electrical resistivity ρ is an order of magnitude higher, it is possible to simultaneously achieve the miniaturization and low power consumption of the magnetic sensor.
(3) Unlike spin valve films including antiferromagnetic films with poor heat resistance, they can be used in high-temperature environments.
There are advantages such as. However, the metal-insulator nanogranular material has a problem that the magnetic field sensitivity in a low magnetic field is very small. In addition, a change in electric resistance of the giant magnetoresistive thin film has a problem that it does not depend on the direction of the magnetic field and has isotropic characteristics.

In order to solve this problem, various proposals have heretofore been made.
For example, Patent Document 1 describes that a soft magnetic thin film is disposed on both ends of a giant magnetoresistive thin film to increase the magnetic field sensitivity of the giant magnetoresistive thin film. In this document, a permalloy thin film (soft magnetic film) having a thickness of 2 μm is formed on a substrate, a gap of about 9 μm is formed on the permalloy thin film using an ion beam etching apparatus, and Co _{38.6 is formed} in the gap. A method of manufacturing a thin film magnetic sensor in which nanogranular GMR films having a Y _41.0 O _47.4 composition are stacked is described.

  In Patent Document 2, in order to further improve magnetic field sensitivity in a thin film magnetoresistive element in which soft magnetic thin films are arranged at both ends of a giant magnetoresistive thin film, the thickness of the giant magnetoresistive thin film is set to the thickness of the soft magnetic thin film. The following points are described.

  Patent Document 3 discloses a magnetic field sensor in which a laminated film composed of a soft magnetic thin film and an antiferromagnetic thin film is arranged at both ends of a giant magnetoresistive thin film. This document describes that since the bias magnetic field generated from the antiferromagnetic thin film is applied to the giant magnetoresistive thin film, the magnitude and polarity of the external magnetic field can be detected simultaneously.

Further, although Patent Document 4 does not describe a magnetic sensor using a giant magnetoresistive thin film, a magnetic thin film having a thickness of 0.1 μm composed of (Co _1-x Fe _x ) ₈₄ (Si _0.48 B _0.52 ) ₁₆ and Discloses a high-frequency, low-loss magnetic thin film composed of a multilayer film formed by alternately laminating 0.05 μm thick insulating thin films formed using a SiO ₂ target. This document describes that the value of the real part of the complex permeability is almost constant with respect to the Fe concentration, but the imaginary part becomes smaller as the Fe concentration increases (that is, as the saturation magnetic flux density increases). Yes.

Japanese Patent Laid-Open No. 11-087804 JP 11-274599 A JP 2003-078187 A Japanese Patent Laid-Open No. 9-74015

A soft magnetic material having a large saturation magnetization and a high magnetic permeability has a very high magnetic field sensitivity and exhibits a very large magnetization in a relatively weak external magnetic field. Therefore, when a thin film yoke made of a soft magnetic material is brought close to both ends of the GMR film, the external magnetic field is amplified by the thin film yoke, and a strong magnetic field 100 to 10,000 times the external magnetic field acts on the GMR film. As a result, the magnetic field sensitivity of the GMR film can be significantly increased.
Further, the strength of the magnetic field generated in the GMR film also depends on the shape of the thin film yoke. As the shape of the thin film yoke is elongated, a stronger magnetic field is generated in the GMR film. This is because the demagnetizing field in the magnetosensitive direction is reduced by elongating the shape of the thin film yoke. The “magnetic sensitivity direction” refers to an external magnetic field application direction when the magnetic field sensitivity of the GMR film is maximized.

  However, when a thin film magnetic sensor having such a GMR film is heated to a predetermined temperature or more, a phenomenon occurs in which the sensor does not react (a dead zone occurs) with a minute magnetic field in the vicinity of the zero magnetic field. The temperature at which this phenomenon occurs varies depending on the thin film yoke material, but is generally about 100 to 200 ° C. This level of temperature is a temperature that is normally exposed in the board mounting process of electronic components, which is a serious problem in practical use.

  An object of the present invention is to provide a thin film magnetic sensor capable of detecting a minute magnetic field in the vicinity of a zero magnetic field even when heated to a temperature of about 100 to 200 ° C. or higher.

In order to solve the above problems, a thin film magnetic sensor according to the present invention provides:
A GMR film having a giant magnetoresistance effect;
A thin film yoke including a soft magnetic material electrically connected to both ends of the GMR film,
The gist of the invention is that the thin-film yoke is composed of a multilayer film including at least two soft magnetic layers made of the soft magnetic material and a nonmagnetic layer made of a nonmagnetic material formed between the soft magnetic layers. To do.

  When a multilayer film in which soft magnetic layers and nonmagnetic layers are alternately stacked is used as the thin film yoke, a dead zone is unlikely to occur in the vicinity of the zero magnetic field even when heated to a temperature of 100 to 200 ° C. or higher. This is presumably because sticking of the domain wall of the soft magnetic layer is suppressed by using a multilayer film in which soft magnetic layers and nonmagnetic layers are alternately laminated as the thin film yoke.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Thin film magnetic sensor]
The thin film magnetic sensor according to the present invention includes a GMR film having a giant magnetoresistance effect, and a thin film yoke including a soft magnetic material electrically connected to both ends of the GMR film.

[1.1 GMR film]
The GMR film is for sensing a change in the external magnetic field as a change in the electric resistance R and consequently detecting it as a change in the voltage, and is made of a material having a giant magnetoresistance (GMR) effect. In order to detect a change in the external magnetic field with high sensitivity, the absolute value of the MR ratio of the GMR film is preferably as large as possible. Specifically, the absolute value of the MR ratio of the GMR film is preferably 5% or more, and more preferably 10% or more.

Further, since the GMR film is directly electrically connected to the thin film yoke, a GMR film having a higher electric specific resistance ρ than the thin film yoke is used. In general, if the electrical specific resistance ρ of the GMR film is too small, the thin film yoke is electrically short-circuited, which is not preferable. On the other hand, when the electrical specific resistance ρ of the GMR film is too high, noise increases and it becomes difficult to detect a change in the external magnetic field as a voltage change. Specifically, the electrical resistivity ρ of the GMR film is preferably 10 ³ μΩcm or more and 10 ¹² μΩcm or less, and more preferably 10 ⁴ μΩcm or more and 10 ¹¹ μΩcm or less.

  There are various materials satisfying such conditions, and among them, the above-described metal-insulator nanogranular material is particularly suitable. Metal-insulator nanogranular materials not only have high MR ratio and high electrical resistivity ρ, but also MR ratio does not fluctuate greatly due to slight composition fluctuations, so that thin films with stable magnetic properties can be reproduced. There is an advantage that it can be manufactured at low cost.

As a metal-insulator nanogranular material used as a GMR film, specifically,
_{(1) Co-Y 2 O} 3 system nano granular alloy, Co-Al ₂ O ₃ system nano granular alloy, Co-Sm ₂ O ₃ system nano granular alloy, Co-Dy ₂ O ₃ system nano granular alloy, FeCo-Y ₂ O ₃ system Oxide nanogranular alloys such as nanogranular alloys,
(2) Fluoride-based nanogranular alloys such as Fe—MgF ₂ , FeCo—MgF ₂ , Fe—CaF ₂ , FeCo—AlF ₃ ,
and so on.

  The shape and dimensions of the GMR film are not particularly limited, and are determined so that the desired magnetic field sensitivity can be obtained. In general, since the resistance value is proportional to the length of the resistor and inversely proportional to the cross-sectional area, the electrical resistance R is increased as the thickness of the GMR film is decreased, the length is decreased, or the lateral width is decreased. Can do. By increasing the electrical resistance R, the power consumption of the device can be reduced. However, if the electrical resistance R of the GMR film becomes too high, an impedance failure may occur with the amplifier.

[1.2 Thin film yoke]
The thin film yokes face each other through a gap, and the GMR film is electrically connected to the thin film yoke in or near the gap.
Here, “near the gap” refers to a region affected by the large amplified magnetic field generated at the tip of the thin film yoke. Since the magnetic field generated between the thin film yokes is the largest in the gap, it is most preferable to form the GMR film in the gap. However, when the magnetic field acting on the GMR film is sufficiently large in practice, This means that all or part of the gap may be outside the gap (for example, the upper surface side or the lower surface side of the thin film yoke).

  The thin film yoke is for increasing the magnetic field sensitivity of the GMR film and includes a soft magnetic material. In the present invention, the thin film yoke is composed of a multilayer film including a soft magnetic layer made of at least two soft magnetic materials and a nonmagnetic layer made of a nonmagnetic material formed between the soft magnetic layers. This is different from conventional thin film magnetic sensors.

[1.2.1 Soft magnetic layer]
In order to obtain a high magnetic field sensitivity to a weak magnetic field, it is preferable to use a soft magnetic material having a high permeability μ and / or saturation magnetization Ms for the soft magnetic layer. Specifically, the magnetic permeability μ is preferably 100 or more, and more preferably 1000 or more. The saturation magnetization Ms is preferably 5 (kGauss) or more, and more preferably 10 (kGauss) or more.

Specific examples of materials for the soft magnetic layer include permalloy (40 to 90% Ni—Fe alloy), sendust (Fe ₇₄ Si ₉ Al ₁₇ ), hard palm (Fe ₁₂ Ni ₈₂ Nb ₆ ), and Co ₈₈ Nb _6. Zr ₆ amorphous alloy, (Co ₉₄ Fe ₆ ) ₇₀ Si ₁₅ B ₁₅ amorphous alloy, fine met (Fe _75.6 Si _13.2 B _8.5 Nb _1.9 Cu _0.8 ), nanomax (Fe ₈₃ Hf ₆ C ₁₁ ), Fe ₈₅ Zr ₁₀ B ₅ alloy, Fe ₉₃ Si ₃ N ₄ alloy, Fe ₇₁ B ₁₁ N ₁₈ alloy, Fe _71.3 Nd _9.6 O _19.1 nano granular alloy, Co ₇₀ Al ₁₀ O ₂₀ nano granular alloy, Co ₆₅ Fe ₅ Al ₁₀ O ₂₀ alloy and the like are suitable. is there.
The number of laminated soft magnetic layers is not particularly limited, and may be two or more. In this case, the materials of the soft magnetic layers may be the same or different from each other.

The thickness of the soft magnetic layer affects the size of the dead zone generated after heating the thin film magnetic sensor. Generally, as the thickness of the soft magnetic layer increases, the width of the dead zone increases. The allowable width of the dead zone varies depending on the application, but is generally preferably 1 [Oe] or less. For this purpose, the thickness of the soft magnetic layer is preferably 0.6 μm or less.
Further, in order to use as a sensor with higher sensitivity, it is necessary to reduce the width of the dead zone to such an extent that it cannot be detected. For this purpose, the thickness of the soft magnetic layer is preferably 0.3 μm or less.

In general, as the thickness of the soft magnetic layer decreases, the dead zone is less likely to occur. However, if the thickness of the soft magnetic layer becomes too thin, not only the dead zone suppression effect is saturated, but also it becomes difficult to form a uniform thin film. Therefore, the thickness of the soft magnetic layer is preferably 10 nm or more.
The thicknesses of the soft magnetic layers may be the same or different from each other. In order to reduce the width of the dead zone or facilitate the formation of a uniform thin film, the thickness of each soft magnetic layer is preferably in the above-described range.

The total thickness of the soft magnetic layer affects the magnetic field sensitivity of the thin film magnetic sensor. In general, as the total thickness of the soft magnetic layer increases, the external magnetic field is greatly amplified, so that high magnetic field sensitivity can be obtained. For this purpose, the total thickness of the soft magnetic layer is preferably 0.5 times or more the thickness of the GMR film. In order to obtain high sensitivity, the total thickness of the soft magnetic layer is preferably as thick as possible.
The total thickness of the soft magnetic layers can be controlled by the thickness of each soft magnetic layer and the number of stacked layers.

[1.2.2 Nonmagnetic layer]
The nonmagnetic layer is disposed at least between the soft magnetic layers. The nonmagnetic layer is considered to have an action of suppressing the fixation of the domain wall of the soft magnetic layer by heating.
The nonmagnetic material constituting the nonmagnetic layer is not particularly limited, and various nonmagnetic materials can be used.
Specifically, as a non-magnetic material,
(1) Cu, Al, Nb, Mo, W, Zr, Cr, Pt, Ag, Au, or a metal-based nonmagnetic material made of an alloy containing any two or more of these,
(2) SiO ₂ , MgO, Al ₂ O ₃ , ZrO ₂ , or an oxide-based nonmagnetic material comprising a solid solution or compound containing any two or more of these,
(3) MgF ₂ , AlF ₃ , or a fluoride-based nonmagnetic material comprising a solid solution or compound containing any two or more of these,
(4) Nitride-based nonmagnetic materials such as BN,
(5) Nonmagnetic materials such as C and Si,
(6) The combination of (1) to (5) described above,
and so on.
The number of nonmagnetic layers stacked is not particularly limited, and may be one or more. The nonmagnetic layer may be formed at least in the middle of the soft magnetic layer. The outermost surface may be either a soft magnetic layer or a nonmagnetic layer. When two or more nonmagnetic layers are included, the materials of the respective nonmagnetic layers may be the same as or different from each other.

The thickness of the nonmagnetic layer affects the size of the dead zone generated after the thin film magnetic sensor is heated. In general, when the thickness of the nonmagnetic layer becomes too thin, the effect of interposing the nonmagnetic layer as an intermediate layer is reduced, and the width of the dead zone is increased. In order to make the dead zone width 1 [Oe] or less, the thickness of the nonmagnetic layer is preferably 0.02 μm or more.
In order to reduce the width of the dead zone to such an extent that it cannot be detected, the thickness of the nonmagnetic layer is preferably 0.05 μm or more.

In general, as the thickness of the nonmagnetic layer increases, the dead zone is less likely to occur. However, if the thickness of the nonmagnetic layer becomes too thick, not only the dead zone suppression effect is saturated, but also the matching with the magnetic sensitive portion becomes worse. Therefore, the thickness of the nonmagnetic layer is preferably not more than twice the thickness of the adjacent soft magnetic layers.
When there are two or more nonmagnetic layers, the thickness of each nonmagnetic layer may be the same or different. In order to reduce the width of the dead zone or to improve the matching with the magnetic sensitive portion, the thickness of each nonmagnetic layer is preferably set in the above-described range.

[1.2.3 Shape of thin-film yoke]
The thin film yoke has an effect of amplifying the external magnetic field and increasing the magnetic field sensitivity of the GMR film. This amplification effect can be enhanced not only by the material of the thin film yoke but also by optimizing the shape.
In the present invention, the shape of the thin film yoke is not particularly limited, and various shapes can be used. The shape of the thin film yoke may be bilaterally symmetric or asymmetric.

[2. Action of thin film magnetic sensor]
In general, a thin film magnetic sensor using a GMR film has a structure in which a GMR film is sandwiched between soft magnetic films processed into a yoke shape. The sensitivity of the sensor can be arbitrarily designed by the shape of the thin film yoke. In addition, a weak magnetic field can be detected by collecting magnetic flux with a thin film yoke. In a conventional thin film magnetic sensor using a GMR film, a thin film made of only a soft magnetic material is used for the thin film yoke.
However, when such a thin film magnetic sensor is heated to a predetermined temperature or higher, a phenomenon that the sensor does not react with a minute magnetic field in the vicinity of the zero magnetic field occurs. This is because the magnetic wall of the thin film yoke is fixed by heating the thin film yoke to a predetermined temperature or higher. The domain wall is fixed by heating the soft magnetic material because the magnetic atoms in the soft magnetic material are diffused by heating, and the magnetic atoms are aligned in one direction due to the spontaneous magnetization of the magnetic atoms themselves. (See, for example, H. Fujimori et al., J. Appl. Phys. 52, p1893 (1981)).

On the other hand, when the thin film yoke has a multilayer structure of a soft magnetic layer made of a soft magnetic material and a nonmagnetic layer made of a nonmagnetic material, it is possible to suppress the adhesion of the domain wall due to heating. In particular, when the thickness of each soft magnetic layer is set to a certain value or less, the width of the dead zone can be made substantially zero.
this is,
(1) By dividing the soft magnetic layer by the nonmagnetic layer, the domain walls of the upper and lower soft magnetic layers are magnetostatically coupled to form a domain wall pair, and (2) the energy density of the domain wall is reduced by the domain wall pair. And the domain wall moves easily,
it is conceivable that.
Furthermore, dividing the soft magnetic layer with the nonmagnetic layer not only facilitates the movement of the domain wall in a minute magnetic field, but also reduces the loss in an environment where a large alternating magnetic field acts. Therefore, the high frequency characteristics of the thin film magnetic sensor can also be improved.

(Examples 1 to 21, Comparative Example 1)
[1. Preparation of sample]
Thin film magnetic sensors in which various thin film yokes made of a laminated film of a soft magnetic layer and a nonmagnetic layer were formed on both ends of a GMR film (Examples 1 to 21). For comparison, a thin film magnetic sensor in which the thin film yoke is composed only of the soft magnetic layer was also manufactured (Comparative Example 1).
The size of the soft magnetic layer was 20 μm wide × 200 μm long × 0.1 μm to 1 μm thick. Various metal-based nonmagnetic materials were used for the nonmagnetic layer.
For the GMR film, an FeCo—MgF ₂ nanogranular alloy was used. The size of the GMR film was such that the film thickness = 500 nm, the width = yoke width, and the gap interval = 1 μm.
[2. Test method]
The obtained thin film magnetic sensor was heat-treated at 200 ° C. for 30 minutes. The MR characteristics were measured before and after heating, and the presence or absence of the dead zone was examined.

[3. result]
Table 1 shows the results. Table 1 also shows the composition, film thickness and number of layers (number of soft magnetic layers) of the soft magnetic layer, and the composition and film thickness of the nonmagnetic layer. FIGS. 1A and 1B show MR characteristics before and after heating of the thin film magnetic sensor obtained in Comparative Example 1, respectively. In FIG. 1, “●” indicates the MR ratio when the magnetic field is increased, and “◯” indicates the MR ratio when the magnetic field is decreased.
Even when the thin film yoke is composed only of a soft magnetic layer, as shown in FIG. 1A, no dead zone was generated before heating to 200 ° C., and high sensitivity was exhibited even in a minute magnetic field. However, after heating to 200 ° C., a dead zone of about 3 [Oe] occurred as shown in FIG.
On the other hand, when the thin film yoke is a laminated film, the generation of the dead zone can be suppressed regardless of the material, the film thickness, and the number of laminated layers.

(Examples 22 to 42)
[1. Preparation of sample]
Thin film magnetic sensors similar to those in Examples 1 to 21 were prepared except that various nonmetallic nonmagnetic materials were used as the nonmagnetic layer.
[2. Test method]
The obtained magnetic sensor was heat-treated at 200 ° C. for 30 minutes. MR characteristics were measured after heating, and the presence or absence of a dead zone was examined.

[3. result]
Table 2 shows the results. Table 2 also shows the composition, film thickness and number of layers (number of soft magnetic layers) of the soft magnetic layer, and the composition and film thickness of the nonmagnetic layer.
From Table 2, it can be seen that when the thin film yoke is a laminated film, the generation of the dead zone can be suppressed regardless of the material, the film thickness, and the number of laminated layers.

(Reference Examples 1 and 2)
[1. Preparation of sample]
A thin film magnetic sensor in which thin film yokes of different materials and thicknesses were formed on both ends of the GMR film was manufactured. However, the thin film yoke was not laminated in order to investigate the effect of the thickness of the soft magnetic layer, and only the soft magnetic layer was used. In the soft magnetic layer, the same dead zone is generated when heated to 150 ° C. or higher (Co ₉₄ Fe ₆ ) ₇₀ Si ₁₅ B ₁₅ (Reference Example 1), or Co ₈₈ Zr ₆ Nb ₆ (Reference Example 2). Was used. The yoke size was 20 μm wide × 200 μm long × 0.1-1 μm thick.
For the GMR film, an FeCo—MgF ₂ nanogranular alloy was used. The size of the GMR film was set such that the film thickness = 500 nm, the width = yoke width, and the gap interval = 1 μm.
[2. Test method]
The obtained thin film magnetic sensor was heat-treated at 200 ° C. for 30 minutes. MR characteristics were measured after heating to determine the width of the dead zone.

[3. result]
FIG. 2 shows the relationship between the thickness of the soft magnetic layer and the dead band width. From FIG. 2, it can be seen that the width of the dead zone becomes narrower as the thickness of the soft magnetic layer becomes thinner. Although the allowable width of the dead zone varies depending on the application, it is generally preferably 1 [Oe] or less. In order to obtain a sensor with higher sensitivity, it is desirable to reduce the dead band width to such an extent that it cannot be detected.
From FIG.
(1) When the thickness of the soft magnetic layer is 0.6 μm or less, the width of the dead zone can be 1 [Oe] or less.
(2) When the thickness of the soft magnetic layer is 0.3 μm or less, the width of the dead zone can be made almost zero.
I understand that.

(Examples 43 to 47)
[1. Preparation of sample]
A thin film magnetic sensor in which a thin film yoke composed of a laminated film of a soft magnetic layer and a nonmagnetic layer was formed on both ends of the GMR film was produced. (Co ₉₄ Fe ₆ ) ₇₀ Si ₁₅ B ₁₅ was used for the soft magnetic layer. The size of the soft magnetic layer was 20 μm wide × 200 μm long × 0.1 μm thick, and the number of soft magnetic layers was ten.
For the nonmagnetic layer, Cu (Example 43), Mo (Example 44), W (Example 45), SiO ₂ (Example 46), or MgF ₂ (Example 47) is used. The thickness was 0.002 to 0.1 μm.
For the GMR film, an FeCo—MgF ₂ nanogranular alloy was used. The size of the GMR film was set such that the film thickness = 500 nm, the width = yoke width, and the gap interval = 1 μm.
[2. Test method]
The obtained thin film magnetic sensor was heat-treated at 200 ° C. for 30 minutes. MR characteristics were measured after heating to determine the width of the dead zone.

[3. result]
It was found that if the yoke thickness was reduced in Reference Examples 1 and 2, the dead band width decreased. However, simply reducing the thickness of the yoke leads to a decrease in the volume of the yoke, and the magnetic field applied to the GMR section is reduced. Therefore, an attempt was made to insert a nonmagnetic layer between thin soft magnetic layers and stack them.
FIG. 3 shows the relationship between the thickness of the nonmagnetic layer and the dead band width. From FIG. 3, it can be seen that as the thickness of the nonmagnetic layer increases, the width of the dead zone becomes narrower. Although the allowable width of the dead zone varies depending on the application, it is generally preferably 1 [Oe] or less. In order to obtain a sensor with higher sensitivity, it is desirable to reduce the dead band width to such an extent that it cannot be detected.
From FIG.
(1) When the thickness of the nonmagnetic layer is 0.02 μm or more, the width of the dead zone can be 1 [Oe] or less.
(2) When the thickness of the nonmagnetic layer is 0.05 μm or more, the width of the dead zone can be made almost zero.
I understand that.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

The thin film magnetic sensor according to the present invention detects rotation information of automobile axles, rotary encoders, industrial gears, etc., detects position / velocity information such as hydraulic cylinder / pneumatic cylinder stroke positions, machine tool slides, It can be used for detection of current information such as arc current of an industrial welding robot, a geomagnetic compass, and the like.
A magnetoresistive element having a GMR film and thin film yokes disposed at both ends thereof is particularly suitable as a magnetic sensor. However, the use of the magnetoresistive element is not limited to this, but a magnetic memory, magnetic It can also be used as a head or the like.

1 (a) and 1 (b) show MR characteristics before heating and after heating at 200 ° C., respectively, of a thin film magnetic sensor (Comparative Example 1) provided with a thin film yoke made of only a soft magnetic layer. FIG. It is a figure which shows the relationship between the soft magnetic layer thickness after 200 degreeC x 30 minute heating of a thin film magnetic sensor (Reference Examples 1 and 2) provided with the thin film yoke which consists only of a soft magnetic layer, and a dead zone width | variety. It is a figure which shows the relationship between the nonmagnetic layer thickness after 200 degreeC * 30 minute heating and a dead zone width | variety of the thin film magnetic sensor (Examples 43-47) provided with the thin film yoke which consists of a laminated film of a soft magnetic layer and a nonmagnetic layer. .

Claims (5)

A GMR film having a giant magnetoresistance effect;
A thin film yoke including a soft magnetic material electrically connected to both ends of the GMR film,
The thin film yoke is a thin film magnetic sensor comprising a multilayer film including at least two layers of a soft magnetic layer made of the soft magnetic material and a nonmagnetic layer made of a nonmagnetic material formed between the soft magnetic layers.   The thin film magnetic sensor according to claim 1, wherein each of the soft magnetic layers has a thickness of 0.6 μm or less.   3. The thin film magnetic sensor according to claim 1, wherein each of the nonmagnetic layers has a thickness of 0.02 μm or more.   4. The thin film magnetic sensor according to claim 1, wherein a total thickness of the soft magnetic layer is 0.5 times or more of a thickness of the GMR film.   The thin film magnetic sensor according to claim 1, wherein the GMR film is made of a metal-insulator nanogranular material.

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