JPS6367249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetoresistive playback head, and more specifically, uses the magnetoresistive effect to convert the magnetic field of a magnetic recording medium such as a magnetic tape, magnetic disk, or magnetic scale into an electrical signal. This invention relates to a magnetoresistive reproducing head.

In a magnetoresistive element, the electric resistance R of the element changes depending on a magnetic field, and the process of this change is expressed by the following equation.

R=R ₀ +△R cos ² θ (1) The contents of this equation (1) will be explained using figures. 1st
In the figure, it is assumed that the reference numeral 1 indicates a magnetoresistive element, and a current flows through this element 1 in the direction indicated by an arrow 4. Assume that when a magnetic signal is applied from the outside in the direction shown by the arrow 3 in this state, the magnetization direction of the magnetoresistive element 1 made of a ferromagnetic material or a ferrimagnetic material becomes the direction shown by the arrow 2. If the angle between the current direction 4 and the magnetization direction 2 is θ, the resistance R at this time is expressed by equation (1). In equation (1)
R ₀ is the resistance value when the current flow direction and the magnetization direction form an angle of 90°, and ΔR is the maximum resistance change amount.

In this way, the magnetization direction of the element changes in response to an external magnetic signal, resulting in a change in resistance value.
The schematic structure of such a magnetic detection element is as shown in FIG.

That is, in FIG. 2, reference numeral 5 denotes a magnetoresistive element, which is formed on the side surface of the substrate 6 by a thin film deposition method such as resistance heating evaporation, EB (vacuum) evaporation, sputtering, plating, or CVD, and has a thickness of 0.01. ~0.1μm
The material is Ni-Fe alloy or Ni-Co
Alloys are common. Lead wires 7 are formed as a thin layer on both sides of the magnetoresistive element 5 and are electrically connected to the magnetoresistive element 5 by a thin film deposition method. Further, the shapes of the magnetoresistive element 5 and the lead wires 7 are adjusted using photolithography, which is known as an IC manufacturing technique.

The magnetic detection element having such a structure detects the y-direction component magnetic field from the magnetized portion 9 on the recording medium 8, and its resistance changes.

Since the magnetic field can be detected with such an extremely simple structure, it is often used as a thin film magnetic head for reproduction only. In order to further simplify manufacturing, the applicant previously proposed that the magnetoresistive element part and the lead wire part be made of the same material, and that the magnetic sensing element be made by one film formation and one photolithography process. has been proposed. Figure 3 shows an outline of this proposal.

In FIG. 3, the part designated by numeral 10 is a magnetic detection section, and the part designated by numeral 11 is a lead wire part, both of which are integrally formed of the same material.

Although such an integrated detection element has a simple structure and is easy to manufacture, the lead wire portion 11 exhibits a change in resistance value in response to an external noise magnetic field. Since they are connected in series, when the resistance change detected by the magnetic detection section 10 is small, there is a relatively large amount of noise, which may lead to a decrease in the SN ratio. Possible noise magnetic fields include the magnetic field of a motor, the magnetic field from a power transformer, the magnetic field from power lead wires, and the earth's magnetism.

Generally, in magnetic recording devices, a small amount of alternating magnetic field is emitted from the motor, power transformer, etc., and some kind of countermeasure is required.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetoresistive playback head that is less affected by magnetic noise and has an extremely good signal-to-noise ratio. .

In order to achieve the above object, the present invention provides a read head in which a magnetoresistive element and a lead wire portion are formed of the same material on the same substrate by a thin film deposition method, so that the directions of currents flowing through the lead wire portion are perpendicular to each other. The structure includes one or more first and second lead wire parts having substantially equal widths arranged so as to form the same width, and the first and second lead wire parts are connected in series, and the first lead wire A structure is adopted in which the total length of the second lead wire portion is substantially equal to the total length of the second lead wire portion.

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

FIG. 4 explains the basic structure of the present invention, and the magnetic detection element, which is indicated by the reference numeral 12 in the figure, is formed entirely from a material having a magnetoresistive effect by a thin film deposition method. This magnetic detection element 12
has a shape that is bilaterally symmetrical and bent at right angles,
The horizontal part at one end is a magnetic detection section 13, and both ends of this magnetic detection section 13 are continuous with rising sections 14, 14 bent at right angles, and the other end of this rising section 14 is a magnetic detection section. Continuing with the horizontal parts 15, 15 bent at right angles in a state parallel to 13,
The other end of the horizontal portion 15 is continuous with a rising portion 16 that rises at a right angle and is close to each other, and the other end of this rising portion 16 is continuous with horizontal portions 17, 17 that extend horizontally toward the outside. , horizontal part 17,1
7 further continues to the rising portion 18. Each of these parts 14 to 18 constitutes a lead wire part.

Therefore, if the direction of the current flowing through the rising portion 14 is indicated by an arrow 19, and the direction of the current flowing through the horizontal portion 15 is indicated by an arrow 20, they both flow in different directions at an angle of 90 degrees, and the direction of the current flowing through the rising portion 14 is indicated by an arrow 20. , horizontal part 15
are formed to have equal lengths.

When an external magnetic field indicated by the arrow 21 in FIG. direction. Note that in this case, since the film thickness of the element is extremely thin at 0.01 to 0.05 μm and the width is 10 to 50 μm, the demagnetizing field can be ignored.

Based on the above structure, if the angle between the arrow 22, which is the magnetization direction of the rising portion 14, and the arrow 19, which is the current direction, is θ, then the resistance R ₁₄ of this part is R ₁₄ = R _l + △R _l cos ² θ (2). In equation (2), R _l is the minimum resistance value of the rising portion 14, and ΔR _l is the maximum amount of change.

Similarly, the resistance R ₁₅ of the horizontal portion 15 is expressed by the following equation, where R _r is the minimum resistance value and ΔR _r is the maximum resistance change.

R ₁₅ =R _r +△R _r cos ² φ (3) In equation (3), the angle φ is expressed using θ as the following equation.

φ=90゜−θ (4) Therefore, equation (3) can be transformed as shown below.

R ₁₅ = R _r + △R _r sin ² θ (3)' Here, the rising part 14 and the horizontal part 15 are connected in series, and further, R _r = R _l and △R _r = △R _l . If the shape is set to , the sum R of both resistances will be a constant value as shown in the following equation.

R = R ₁₄ + R ₁₅ = 2R _r + △R _r (cos ² θ + sin ² θ) = 2R _r + △R _r = constant (5) In this way, the first and second lead wire parts are provided in the lead wire part. If both parts are connected in series and the direction of the current flowing through both parts is set at a 90° angle, the lead wire part and the magnetic detection part can be integrally formed by the thin film deposition method. A magnetic detection element with a good signal-to-noise ratio, which is not affected by magnetic noise.
Therefore, a reproducing head can be obtained.

FIG. 5 illustrates an embodiment of the present invention.
In the figure, the same or corresponding parts as in FIG. 4 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 5, the length of the magnetic detection section 13 is 2l ₁ ,
If the length of the rising part 14 is l ₂ and l ₁ = l ₂ , then the noise appearing in the magnetic detection part 13 will also be the same as that of the rising part 1.
4, which is effective in improving the signal-to-noise ratio.

FIG. 6 explains another embodiment of the present invention, in which bent portions 24 are symmetrically bent inward from both ends of the magnetic detection portion indicated by reference numeral 13 in the figure in a dogleg shape. , 25 are continuous, and both bent portions 24 and 25 intersect at right angles. and,
The bent portion 24 and the magnetic detection portion 13 intersect at an angle of 45°.

If such a structure is adopted, the length of the lead wire portion can be shortened, the resistance value can be reduced, and the thermal noise due to the resistance can be reduced. In reality, the resistance of the lead wire section is within the same dimensions as shown in Figure 4, assuming that the length of the magnetic detection section 13 in FIG. This is 1/√2 compared to the case where the structure based on the principle shown in is adopted, and the excellent effect that the noise resistance remains unchanged can be obtained.

FIG. 7 illustrates another embodiment of the present invention, which is an example in which the resistance value of the lead wire portion is attempted to be lowered as much as possible. If it is desired to lower the resistance value of the lead wire portion, it is desirable to use the entire allowable line width of the lead wire portion. In addition to this purpose, FIG. 7 shows a structure intended to further increase noise resistance. That is, in FIG.
The part indicated by 6 is a lead wire part, and since it is formed symmetrically, only one side is shown. This lead wire portion 26 is formed to be as wide as possible. However, this lead wire portion 26 has a plurality of meandering current paths 27 formed therein by etching a plurality of thin grooves 27a that meander at right angles in parallel. What is indicated by the reference numeral 28 is a groove for separating the bent portions of the current path.

Now, select one of the current paths configured as above and conduct AB for one period of the repeated pattern.
Considering the distance between the two, let r ₁ , r ₂ , r ₃ be the lengths of the parts where the current flows at right angles to the magnetic detection unit 13, and l ₁ , l ₂ be the lengths of the parts where the currents flow in parallel, then l ₁ + l ₂ = A current path pattern can be configured such that r ₁ +r ₂ +r ₃ = const (constant) (6).

If such a structure is adopted, the lead wire portion 2
6.The overall cross-sectional area has been increased, making it possible to obtain a lead wire portion with low resistance, and the current path is bent at right angles, making it possible to eliminate in-phase noise and creating a playback head with an extremely excellent signal-to-noise ratio. can be obtained.

As is clear from the above description, according to the present invention, it is possible to obtain a reproducing head that is less susceptible to magnetic noise and has an extremely good signal-to-noise ratio.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of a magnetoresistive effect element, FIGS. 2 and 3 are perspective views and front views of the element portion, respectively, illustrating different structures of a conventional magnetoresistive read head. The figure is an explanatory diagram of the principle of the invention, and FIGS. 5 to 7 are front views illustrating different embodiments of the invention. 5... Magnetoresistive element, 6... Substrate, 12...
...Magnetic detection element, 13... Magnetic detection section, 14...
Rising part, 15...Horizontal part, 24, 25...Bending part, 26...Lead wire part, 27...Current path,
27a...Narrow groove.

Claims (1)

[Scope of Claims] 1. In a magnetoresistive playback head in which a magnetic detection section and a lead wire section are integrally formed on the same substrate using a magnetoresistive material, which is a ferromagnetic material or a ferrimagnetic material, by a thin film deposition method. , the lead wire portion has first and second lead wires having substantially equal widths arranged such that the directions of current flowing through the lead wire portions are perpendicular to each other.
the first and second lead wire portions are connected in series, and the first and second lead wire portions are connected in series;
A magnetoresistive effect type read head, characterized in that the total length of the second lead wire portion is substantially equal to the total length of the second lead wire portion. 2. Claim 1, characterized in that the length of the first or second lead wire section directly connected to the magnetic detection section is 1/2 of the length of the magnetic detection section. magnetoresistive playback head. 3. A patent claim characterized in that the direction of the current flowing through the first or second lead wire section directly connected to the magnetic detection section is arranged at an angle of 45 degrees with the axial direction of the magnetic detection section. A magnetoresistive read head according to item 1 or 2. 4. The magnetic resistance according to claim 1 or 2, wherein the lead wire portion is formed by a plurality of parallel wires in which first and second lead wire portions are connected in series. Effective regeneration head.