JPH0125431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature-compensated magnetoresistive thin film magnetic sensor (hereinafter referred to as a temperature-compensated MR sensor). The present invention relates to a temperature-compensated MR sensor that is not easily affected by temperature and is configured to respond greatly to temperature.

MR sensors that use magnetoresistive elements (MR elements) made of Fe, Ni alloys, NiCo alloys, etc. are widely known, but the resistance of the element itself is temperature dependent and requires temperature compensation. .

The structure of this type of conventional temperature compensated MR sensor is shown in FIG. That is, the reference numeral 1 in FIG. 1 is a substrate made of glass or the like, and an MR element 2 serving as a magnetic signal detection section is formed on the side surface of the substrate 1 in the vicinity of the sliding magnetic recording medium by a thin film deposition method. has been done. The magnetic anisotropy direction of this MR element 2 is formed in the direction shown by arrow 5 in FIG. Further, an MR element 3 is located a predetermined distance p from this MR element 2 and serves as a temperature compensator.
are formed parallel to the MR element 2 by a thin film deposition method. These MR elements 2 and 3 are formed by a thin film deposition method and then shaped by a photolithography technique.

After forming these MR elements 2 and 3, Al or Cu
The electrode 4 is formed by a thin film deposition method, and is electrically connected to the MR elements 2 and 3.

In this way, a temperature-compensated MR sensor is obtained, but when it is subsequently mounted, various steps such as attaching a protective film, attaching a cover glass, cutting and polishing the end face, etc., are necessary. pass

FIG. 2 shows an example of a simple circuit in which such a temperature-compensated MR sensor is used. In FIG. 2, MR1 corresponds to the MR element 2, and MR2
corresponds to the MR element 3 described above. Ra and Rb show resistance. When a bridge is formed in this way, the balanced state of the bridge is expressed by the following equation (1).

MR1×Rb=MR2×Ra (1) In equation (1), when no signal magnetic field is applied to MR1 at any temperature, the voltage of V becomes 0, and when a signal magnetic field is applied to MR1, the MR of the detection part Only the resistance of the element MR1 changes, resulting in voltage fluctuation and output. Therefore, if MR2, which is an MR element that plays the role of temperature compensation by the signal magnetic field,
If the resistance value changes, correct signal output will not be obtained.

As mentioned above, in the conventional temperature-compensated MR sensor, it is necessary to take into account that the resistance value of the temperature-compensating part is difficult to change due to external magnetic fields. 3. It is necessary to take a large interval P. For example, as shown in FIG. 1, when the width of the MR element 2 is w and the length is l, then w
When P=20μ and l=150μm, P=250μm or more is required. As a result, the overall size has increased, the accuracy of temperature compensation has deteriorated, and there have been various drawbacks such as a time lag in temperature compensation.

The purpose of the present invention is to apply a temperature compensator to an external signal magnetic field.
An object of the present invention is to provide a temperature-compensated MR sensor in which an MR element is not easily affected and the temperature compensation function is significantly improved.

In order to achieve the above object, in the present invention, a magnetoresistive element for signal magnetic field detection is formed on the magnetic recording medium sliding surface side of the substrate, and a magnetoresistive element for temperature compensation is formed inside this. In addition, in a thin film magnetic sensor in which the axial directions of both magnetoresistive elements are non-parallel to each other, the width and film thickness dimensions of the magnetoresistive element for temperature compensation are set in a demagnetizing field.
A structure was adopted in which dimensions were set such that Hd > Hk with respect to Hd and anisotropic magnetic field Hk.

Hereinafter, details of the present invention will be explained based on embodiments shown in the drawings.

FIG. 3 illustrates an embodiment of the present invention.
In the figure, parts that are the same as or correspond to those in FIG.

In this embodiment, the MR element 3 of the temperature compensating section is formed in a direction substantially perpendicular to the MR element 2 of the detecting section, and has a width of 20 to 40 .mu.m. The magnetic anisotropy of both MR elements 2 and 3 is in the direction shown by arrow 5 in FIG. If such a structure is adopted, the MR element 3 of the temperature compensator will not be affected by the external signal magnetic field, and the reason for this will be explained below.

In FIG. 4, if the direction of the current flowing through the MR element 3 is indicated by arrow 7, the axis of easy magnetization of the MR element 3 is indicated by arrow 6, and the angle φ between the two is 90 degrees. If the direction of magnetization is indicated by arrow 8,
When the angle between the current direction 7 and the magnetization direction 8 is θ, the magnetization energy E is expressed by the following equation (2).

E=-Ku sin ² (π/2-θ)+1/2 MHd cos (π/2+θ) (2) In equation (2), Ku is the magnetization anisotropy constant, M is the magnitude of magnetization, and Hd is the shape Due to the demagnetizing field due to anisotropy,
It is expressed by the following equation (3).

Hd=t/wM sinθ (3) In equation (3), t is the film thickness of the MR element, and w is the width. From the above equations (2) and (3), the magnetization energy E is expressed by the following equation (4).

E=-Ku sin ² (π/2-θ)-1/2M ² t/wsin ²
θ(4) The magnetization is stabilized in the direction θ where the value of the energy E shown by equation (4) becomes minimum. When this magnetization is stable, the value obtained by differentiating equation (4) is O, which is expressed by the following equation (5).

∂ _E /∂θ=2Ku sinθcosθ−M ² t/w sinθcosθ=O (5) From equation (5), when θ=O or π/2 is the stable direction of M, and when Hd>Hk, θ=O ( 6) When Hd<Hk, θ=π/2 (7). Therefore, if the demagnetizing field Hd is larger than the anisotropic magnetic field Hk, the direction of magnetization M will be in the current direction, and since the signal magnetic field always matches the current direction of the MR element 3, there will be no change in the signal magnetic field. Don't do it. That is, θ=O.

Usually, the film thickness of the MR element is 0.05 to 0.1μ, Hk is 5 to 10¨0, and the magnetization strength 4πMs is about 8000 Gauss. The width of 3 is preferably 40μ or less. or,
If the MR elements 2 and 3 are arranged at right angles so that Hd>Hk, the MR element 3 of the temperature compensator will not receive a signal magnetic field no matter how close they are brought together.

Since this embodiment is configured as described above,
It can be configured so that the resistance of the MR element in the temperature compensation section does not change with respect to the signal magnetic field, (1) the structure is simple, (2) it can be made smaller, and (3) the MR element in the detection section and temperature compensation section
Because it is configured so that the element can be approached,
With temperature compensation, which has excellent advantages such as improved temperature compensation accuracy and (4) no time lag in temperature compensation.
An MR sensor is obtained.

FIG. 5 shows another embodiment of the present invention.
In this embodiment, the MR element 3 of the temperature compensation section and
MR element 2 has a similar shape, and MR element 3
The width _w2 is set to 40μ or less so that Hd>Hk.

If MR elements 2 and 3 have similar shapes in this way, the resistance R ₁ of MR element 2 and the resistance of MR element 3
R ₂ is expressed by equations (8) and (9) where ρ is the individual resistance.

R ₁ = ρ ₁ l ₁ /t ₁ w ₁ (8) R ₂ = ρ ₂ l ₂ /t ₂ w ₂ (9) When MR elements 2 and 3 are formed at the same time, ρ ₁ = ρ ₂ ,
Since t ₁ = t ₂ and MR elements 2 and 3 are formed similarly, their lengths are l ₁ and l ₂ and their widths are W ₁ and W _2.
Then, l ₁ /w ₁ =l ₂ /w ₂ , R ₁ =R ₂ can be set, and the demagnetizing field of the MR element 3 can be arbitrarily controlled.

At this time, in the circuit shown in Figure 2, Ra=Rb
Therefore, a circuit can be constructed that is easy to maintain bridge balance, and the output can be obtained most efficiently with respect to the resistance change of the MR element 2 of the detection section.

In both embodiments, each MR element has been described as being at a right angle, but it is not necessarily limited to a right angle, and even if the angle is close to a right angle, the influence of the signal magnetic field can be substantially eliminated. Also, other angles (non-parallel)
Even if it is, the influence of the signal magnetic field can be removed in accordance with the angle.

As is clear from the above explanation, according to the present invention, the MR element of the temperature compensation section can be configured so as not to be sensitive to the signal magnetic field, and the MR element of the detection section and the temperature compensation section can be placed very close together. Therefore, (1) it has an extremely simple structure, and (2)
Temperature compensation has excellent effects such as being smaller, (3) improving temperature compensation accuracy, and (4) allowing the MR element of the temperature compensation section to be placed close to the detection section, so there is no time lag in temperature compensation. MR sensor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating a conventional structure, FIG. 2 is a circuit diagram when the sensor having the structure shown in FIG. 1 is used, and FIG. 3 is a perspective view illustrating an embodiment of the present invention. Figure 4 shows the MR of the temperature compensation section shown in Figure 3.
FIG. 5, which is an explanatory diagram of the magnetization direction of the element, is a perspective view showing another embodiment of the present invention. 1... Substrate, 2, 3... MR element, 4... Electrode.

Claims (1)

[Claims] 1. A magnetoresistive element for detecting a signal magnetic field is formed on the side of the magnetic recording medium sliding surface of the substrate, and a magnetoresistive element for temperature compensation is formed inside this, and both magnetoresistive effects In a thin film magnetic sensor in which the axial directions of the elements are non-parallel to each other, the width and film thickness of the magnetoresistive element for temperature compensation are determined by the demagnetizing field.
A magnetoresistive thin film magnetic sensor with temperature compensation, characterized in that dimensions are set such that Hd>Hk with respect to Hd and anisotropic magnetic field Hk. 2. The magnetoresistive thin film magnetic sensor with temperature compensation according to claim 1, wherein the magnetoresistive elements for signal magnetic field detection and temperature compensation are formed to have similar shapes.