JPH0348571B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetoresistive head, and more particularly to a magnetoresistive head capable of improving reproduction output.

Conventional technology In general, a magnetoresistive head that utilizes the magnetoresistive effect of a ferromagnetic thin film has higher sensitivity in low-speed playback than an electromagnetic induction type thin-film magnetic head, and can easily be made into a narrow track, making it suitable for use as a multi-track magnetic head. Due to its advantages, it is used as a reproducing head for high-density magnetic recording media. This magnetoresistive head (hereinafter abbreviated as MR head) is
A so-called shield type in which a magnetoresistive element (hereinafter abbreviated as MR element) is exposed on the sliding surface of the recording medium.
There are non-shielded types and so-called yoke type types with improved reliability. 6th
7 and 7 show the structure of a conventional yoke type MR head. Note that FIG. 7 is a sectional view taken along the line A--A in FIG. 6, and the same components in each figure are given the same reference numerals and will be explained. In both figures, 1 is Mn
-Magnetic substrate made of Zn ferrite or Ni-Zn ferrite, etc., 2 is a bias line made of metal such as Al, Al-Cu, Mo, etc., 3 and 5 are electrical insulating films made of Al ₂ O ₃ or SiO ₂ , etc. , 4 indicates a thin film MR element such as Ni-Fe or Ni-Co, and 6a and 6b indicate magnetic yokes made of a soft magnetic film such as Permalloy or Sendust (registered trademark). Further, 7 is a magnetic gap (hereinafter referred to as the front gap) for detecting the signal magnetic field, and 8 is a magnetic gap (hereinafter referred to as the sensor gap) for supplying the magnetic flux of the signal magnetic field of the recording medium to the MR element 4. It is. Since the MR element 4 is not exposed on the tape sliding surface 9a, such a yoke type MR head 9 has superior corrosion resistance and reliability compared to the shield type or non-shield type.

Problems to be Solved by the Invention However, in the conventional MR head 9, the magnetic circuit composed of the front magnetic yoke 6a, the sensor gap 8, the MR element 4, the rear magnetic yoke 6b, and the magnetic substrate 1 is Most of the resistance is determined by the sensor gap length s of the sensor gap 8, and since the magnetic resistance of this part is larger than that of the front gap 7, it is larger than the front gap 7. Most of the incoming signal magnetic flux is short-circuited at the front gear 7.
As a result, the signal magnetic flux in the Sansei gap 8 for detecting the signal magnetic flux becomes small, and the reproduction efficiency of the MR head 9 decreases. In order to avoid this, there is a method of reducing the width d (life dimension) of the front gap 7 and relatively increasing the magnetic resistance of the front gap 7, but this results in a reduction in the life of the MR head 9. becomes. The reason for this will be explained below using FIG. FIG. 8 shows an equivalent circuit of the magnetic circuit of the MR head 9, in which the signal magnetic flux _φ0 flowing into the MR head 9 from the magnetic recording medium returns through the magnetic resistance Rg of the front gap 7 and the sensor gap φg. 8 magnetic resistance
Rsg and the magnetic flux φs that returns through the magnetic resistance Ry of the magnetic yokes 6a and 6b for transmitting the signal magnetic flux thereto.

The regeneration efficiency φs/φ ₀ needs to be as large as possible. Calculating φs/φ ₀ from the same figure, φs/φ ₀ = Rg/(Ry+Rsg+Rg)...(1) However, the magnetic yokes 6a and 6b are soft magnetic films, and the magnetic resistance is due to their high magnetic permeability. Therefore, equation ( ₁ ) can be generally ignored as Become.

From the above results, it is necessary to increase (Rg/Rsg) in order to increase the regeneration efficiency, but as mentioned above, the method to increase Rg is to reduce the life dimension d of the head, or to increase the front gear. There are methods such as increasing the thickness g of the sensor gap 8, but all of them result in deterioration of the quality of the MR head 9. With the conventional structure, it is not possible to increase the regeneration efficiency beyond the processing limit of the sensor gap 8. do not have. For this reason, the yoke type MR head 9, which has achieved practical electromagnetic characteristics and sensitivity, has a problem in that it has a short life span and can only provide inferior reproduction characteristics.

Also, if we pay attention to the direction in which the bias magnetic field is applied to the MR element 4 by the bias line 2, in a configuration in which the bias line 2 is arranged approximately parallel to the extending direction of the MR element 4, the bias magnetic field is applied to the MR element 4. 2 is applied in a direction perpendicular to the direction in which it extends. in general
Regarding MR head odor, it is known to apply a bias magnetic field in the longitudinal direction of the MR element as a method to improve the reproduction characteristics of the MR element and reduce Barkhausen noise.
In the case of MR head 9, the bias magnetic field is applied to MR element 4.
It is difficult to apply it in the longitudinal direction. Sideways
The MR head 9 has a problem in that it is extremely difficult to improve the reproduction characteristics and reduce Barkhausen noise.

Therefore, in the present invention, the sensor gap and
The object of the present invention is to provide a magnetoresistive head that solves the above problems by forming an MR element in a non-linear shape on a substrate.

Means and Effects for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a magnetoresistive device in which a magnetoresistive element is disposed opposite a magnetic gap provided with a yoke made of a soft magnetic thin film. In the effect head, the magnetic gap formed between the yokes was formed in a non-linear shape, and the magnetoresistive element was formed in a non-linear shape along the magnetic gap.

Further, a magnetoresistance effect element is provided to face a magnetic gap provided on a yoke made of a soft magnetic thin film, and a conductor forming a current path for applying a bias magnetic field to the magnetoresistive effect element is provided. In the magnetoresistive head, the magnetic gap formed between the yokes is formed in a non-linear shape, the magnetoresistive element is formed in a non-linear shape along the magnetic gap, and the conductor is formed in a non-linear shape. The magnetoresistive element and the magnetic gap were shaped to have opposite widths over the entirety thereof.

By configuring the magnetoresistive head as described above, the effective length of the magnetic gap becomes large, the opposing area of the yoke in the magnetic gap becomes large, and the magnetic resistance of the yoke can be reduced. Further, since the bias magnetic field generated by the conductor is applied to the magnetoresistive element formed in a non-linear shape, it is possible to apply the bias magnetic field in the longitudinal direction of the magnetoresistive element.

Embodiment FIGS. 1 and 2 show a first embodiment of a magnetoresistive head (MR head) according to the present invention. Note that Fig. 1 shows two MR heads installed side by side, and Fig. 2 shows the B-B in Fig. 1.
A cross section along line B is shown. The MR head 10 shown in the figure is formed using thin film forming technology, and is used, for example, as a reproduction head of a multi-track digital audio tape recorder. This MR head 10 includes a magnetic substrate 11 made of Mn-Zn ferrite or Ni-Zn ferrite,
A bias line 12, a magnetoresistive element (MR element) 13, and an upper yoke 1 are formed on this substrate 11.
4. Consists of lead wires 15a, 15b, etc.

A concave groove 16 is cut into the substrate 11, and this concave groove 16 is filled with a non-magnetic insulator 17 such as glass. Further, in a predetermined position of the insulator 17, a bias line 12 made of a conductor such as Al, Al-Cu, Mo, etc. is buried, and applies a bias magnetic field to the MR element 13 as described later. In this way, the MR head 10 applies a bias magnetic field by passing a current through the bias line 12.
Since a current bias method is adopted in which a bias magnetic field is applied to the MR element 13, the MR element 13
The magnitude of the current (that is, the magnitude of the applied magnetic field) can be easily changed according to the magnitude of the anisotropic magnetic field, and an appropriate operating point can be easily obtained.
The concave groove 16 in which the bias line 12 and the insulator 17 are formed is formed to extend substantially parallel to the tape sliding surface 10a. The upper surface of the substrate 11 on which the bias line 12 etc. are formed is subjected to surface polishing, and then an insulating film 18 (this insulating film 18 also functions as a gap material) made of SiO ₂ or the like is interposed.
As shown in FIG. 1, the MR element 13 made of Ni--Fe, Ni--Co, etc. is patterned in a substantially V-shape (this will be described in detail later). This MR element 13 is formed on an insulator 17 filled in a concave groove 16 so as to be magnetically insulated from the magnetic substrate 11. Further, at both ends of the MR element 13, lead wires 15a patterned on the substrate 11,
15b is electrically connected. Further, on the substrate 11 on which the MR element 13 and lead wires 15a and 15b are formed, an upper yoke 14 made of a soft magnetic film such as Permalloy or Sendust is formed with an insulating film 19 interposed therebetween. A magnetic gap 20 (hereinafter referred to as a sensor gap) is located on the upper yoke 14 at a position facing the MR element 13.
is formed. In other words, the sensor gap 20 is an MR pattern formed in a substantially V-shape.
It is formed along the element 13. The sensor gap 20 defines the upper yoke 14 into yoke halves 14a and 14b. Further, on the tape sliding surface 10a, the front yoke half 14a faces the magnetic substrate 11 with an insulating film 18 interposed therebetween, forming a magnetic gap 21 (hereinafter this magnetic gap will be referred to as a front gap). Furthermore, the rear yoke half 14b connects to the magnetic substrate 11 through through holes 22 formed in the insulating films 18 and 19.
The magnetic resistance in the so-called back gap is extremely small.

The reason and effect of making the sensor gap 20 non-linear and approximately V-shaped instead of the conventional linear shape will be described in detail below. First, the ratio of the magnetic resistance Rg of the front gap 21 to the magnetic resistance Rsg of the sensor gap 20 in equation (2) described above (hereinafter this ratio will be referred to as magnetic resistance ratio X ₀ ) is calculated. The magnetic resistance Rsg of the front gap 21 is Rg=g/(μ ₀・W・d) ……(3) g: Thickness dimension of the front gap 21 μ ₀ : Magnetic permeability of the front gap 21 W: Track Width d: expressed as the life dimension, and the magnetic resistance Rsg of the sensor gap 20 is determined by the magnetic coupling between the upper yoke 14 and the MR element 13, and its value is Rsg =Wy/(μ _MR・L・t _MR ) ...(4) Wy: Length of sensor gap 20 μ _MR : Magnetic permeability t of MR element 13 _MR : Thickness of MR element 13 L: Thickness of MR element 13 It can be approximated as length. Also, the magnetoresistance ratio x ₀ is X ₀ = Rg/Rsg (5), so by substituting equations (3) and (4) into equation (5), X ₀ = g・μ _MR・t _MR /Wy・μ ₀・d・1/W……
(6) becomes. In the conventional MR head 9 (shown in FIG. 6), the track width W and the length L of the MR element 13 are
were approximately equal values (L≈W), so equation (6) could be approximated as X ₀ =g・μ _MR・t _MR /Wy・μ ₀・d (7). However, as shown in Figure 1
In the MR head 10, a pair of yoke halves 1
The sensor gap 20 formed between 4a and 14b has a non-linear approximately V-shape, and the MR
Element 13 also has a non-linear shape along sensor gap 20. Therefore, the length L of the MR element 13 and the extension length of the sensor gap 20 are longer than the track width W, and if they are n times the track width W (L=n·W), then The magnetoresistance ratio X ₁ in the assumed case is X ₁ =n·X ₀ (8). Substituting equation (8) into equation (2), regeneration efficiency φs/φ ₀
When calculating the improvement rate α, α=(n・X ₀ /1+n・X ₀ )/(X ₀ /1+X ₀ ) =1+n−1/1+n・X ₀ ……(9), and in Equation (9), The improvement in regeneration efficiency shown can be achieved.

Here, we will actually calculate the regeneration efficiency by substituting numerical values into each equation. t _MR = 0.03μm, d = 10μm, g = 0.5μ
Formula as m, W = 60μm, Wy = 5μm, μ _MR /1000
Calculating (7), the magnetoresistance ratio X ₀ is X ₀ = 0.3,
Further, when this is substituted into equation (2), the regeneration efficiency φs/φ ₀ becomes φs/φ ₀ =0.23. However, the MR of the present invention
According to the head 10, the length L of the MR element 13 and the extended length of the sensor gap 20 are the track width W.
Therefore, if n=10, the regeneration efficiency φs/φ ₀ becomes φs/φ ₀ =0.75, and the regeneration efficiency can be dramatically improved. Furthermore, when the regeneration efficiency is selected to be approximately equal to that of the conventional MR head, that is, when X ₁ = X ₀ , Equations (7) and (8)
From X ₀ = n・g・μ _MR・t _MR /Wy・μ ₀・n・d……
(10), which means that the life dimension d can be increased. Yotsutte MR head 10
By appropriately selecting the regeneration efficiency and making the shape of the sensor gap 20 non-linear,
The life span d of the MR head 10 can be increased, and the reliability as a thin film magnetic head can be improved. As mentioned above, by increasing the length of the MR element 13, the electrical resistance of the MR element 13 can be increased, and therefore, if the resistance change rate is the same, a large resistance change can be obtained, and the reproduction output can be improved. can be done. Further, to explain the magnetic flux of the signal magnetic field entering the upper yoke 14 from the recording medium in the sensor gap 20,
As mentioned above, since the sensor gap 20 has a non-linear shape, the sensor gap 2
Since the magnetic resistance Rsg at 0 is smaller than that of a conventional MR head, the magnetic flux of the signal magnetic field recorded on the recording medium easily enters the magnetic circuit formed by the MR head 10. Therefore, a large amount of magnetic flux enters the front yoke half 14a, and in the sensor gap 20, this magnetic flux advances in the direction shown by the arrow in FIG. 1 and enters the rear yoke half 14b, and in this process, The change in magnetic flux is converted into a magnetic field by the MR element 13, and is extracted as a reproduced signal from the lead wires 15a and 15b. As mentioned above, a large number of magnetic fluxes are MR
Since the magnetic flux enters the head 9, the reproduction output is improved, but the amount of change in the magnetic flux is also increased, causing a problem of Barkhausen noise. However, since the sensor gap 20 has a non-linear shape, in other words, it has a shape that extends long on the substrate 11, the magnetic flux penetrating between the sensor gap 20 per unit length is small, and the relative The amount of change in magnetic flux is small. Therefore, 1 MR element per unit length
Since the amount of change in the magnetic flux applied to 3 is also small, even if the bias point is different for each track in a multi-track MR head, for example, the reproduced output can be made uniform and there is no Barkhausen noise. can be prevented from occurring. Note that even though the amount of change in magnetic flux per unit length of the MR element 13 is small, the overall length of the MR element 13 is large.
It is obvious that the total reproduction output of the entire MR element 13 is large.

Also, MR element 13 and sensor gap 20
In order to increase the length, the MR head 25 may have the MR element 23 and the sensor gap 24 in a non-linear substantially W-shape as shown in FIG. With this configuration, the MR shown in Fig.
Compared to the head 10, the MR element 23 and sensor
The gap 24 becomes longer, and as mentioned above, it is expected that the regeneration efficiency will be improved. However, what should be noted here is that the yoke 14 has a long sensor.
By forming the gap 24, a narrow space (indicated by a middle arrow C in FIG. 3) is formed partially on the upper yoke 14. In this narrow area C, the magnetic resistance of the upper yoke 14 itself becomes large, and it is conceivable that the magnetic resistance of the magnetic circuit of the MR head 25 as a whole becomes large. Therefore, it is necessary to select an appropriate shape for the sensor gap 24 so that the magnetic resistance of the magnetic circuit as the MR head 25 can be made small, and the magnetic resistance of the sensor gap 24 can be made small. In FIG. 3, the same components as those in FIG. 1 are given the same reference numerals, and their explanations are omitted.

A second embodiment of the present invention is shown in FIGS. 4 and 5. Note that FIG. 5 shows a cross section taken along the line DD in FIG. 4, and the same components as those shown in FIG. The MR head 26 shown in the figure has a wide conductor 23 that forms a current path for applying a bias magnetic field to the MR element 13 on an insulator 17 such as glass that is filled in a concave groove formed in a magnetic substrate. The structure is arranged in This conductor 23
It is formed approximately parallel to the tape sliding surface 26a using a thin film formation technique of Al, Al-Cu, Mo, etc.
Further, the conductor 23 is formed with a width dimension so as to face the MR element 13 and the sensor gap 20, which are formed in a non-linear substantially V-shape on the conductor 23, over the entirety thereof.

In the MR head 26 configured as described above, when a current flows through the conductor 23 in the direction of arrow E in the figure, the conductor 23
generates a magnetic field, and the direction of the magnetic field is the direction indicated by arrow F in FIG. This magnetic field functions as a bias magnetic field for the MR element 13, and the direction of its application is not perpendicular to the extending direction of the MR element 13, that is, the biasing direction is in the extending direction (longitudinal direction) of the MR element 13. The direction has a component that can apply a magnetic field. As mentioned above, in general, in MR heads, a method of applying a bias magnetic field in the longitudinal direction of the MR element is known as a method of improving the reproduction characteristics of the MR element and reducing Barkhausen noise. In the MR head 26 with the above configuration, the bias magnetic field can be controlled by appropriately selecting the pattern shape of the MR element 13.
It becomes possible to apply the voltage in the longitudinal direction of the MR element 13. This makes it possible to improve reproduction characteristics and reduce impulsive Barkhausen noise.

Effects of the Invention As described above, according to the MR head of the present invention, the sensor gap is formed in a non-linear shape and the MR element is formed in a non-linear shape along the sensor gap. The magnetic resistance at the
The magnetic resistance of the magnetic circuit configured in the MR head can be made small, and the magnetic flux of the signal magnetic field recorded on the recording medium can easily enter the magnetic circuit, so that the reproduction rate can be improved. In addition, if the reproduction efficiency is selected to be the same as that of conventional MR heads, the life span can be increased and the reliability as a thin film magnetic head can be improved. a non-linear
By making the MR element and the sensor gap have opposing widths, the MR
A bias magnetic field can be applied in the longitudinal direction of the element, which can reduce the reproduction characteristics of the MR head and the generation of Barkhausen noise.
In addition, by increasing the length of the MR element, the electrical resistance of the MR element can be increased, and therefore, if the resistance change rate is the same, a large resistance change can be obtained, and the reproduction output can be improved. It has the following features.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of the MR head according to the present invention, FIG. 2 is a sectional view taken along line B-B in FIG. 1, and FIG. 3 is a comparison of the MR head shown in FIG. FIG. 4 is a plan view showing a second embodiment of the MR head according to the present invention; FIG.
FIG. 5 is a sectional view taken along line D-D in FIG. 4,
Figure 6 is a plan view of an example of a conventional MR head; Figure 7 is a plan view of an example of a conventional MR head;
The figure is a sectional view taken along line A-A in Figure 6,
This figure shows an equivalent magnetic circuit of the MR head shown in FIG. 6. 10, 25, 26... MR head, 11... Magnetic substrate, 12... Bias line, 13, 23...
MR element, 14... Upper yoke, 14a, 14b
... Yoke half body, 15a, 15b ... Lead wire,
20, 24...sensor gap, 21...front gap, 23...conductor.

Claims (1)

[Scope of Claims] 1. A magnetoresistive head in which a magnetoresistive element is arranged opposite to a magnetic gap provided on a yoke made of a soft magnetic thin film, in which the magnetic gap formed between the yokes is not 1. A magnetoresistive head, characterized in that the magnetoresistive head is formed in a linear shape and the magnetoresistive element is formed in a non-linear shape along the magnetic gap. 2. A magnetoresistive element disposed opposite to a magnetic gap provided on a yoke made of a soft magnetic thin film;
In the magnetoresistive head which is provided with a conductor constituting a current path for applying a bias magnetic field to the magnetoresistive element, the magnetic gap formed between the yokes is formed in a non-linear shape, and the magnetic gap formed between the yokes is formed in a non-linear shape. The magnetoresistive element is formed in a non-linear shape along the magnetic gap, and the conductor has a width that faces across the non-linear magnetoresistive element and the magnetic gap. magnetoresistive head.