JPH11296820A - Magnetic head of magnetoresistance type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain satisfactory reproducing characteristic reducing the asymmetry of reproduced waveform and the variation of an reproduced output even in a case that the reproducing track width becomes narrow by allowing the relation between the residual magnetic film and the thick film of a reproduced track width and a permanent magnetic film to meet a prescribed relation and to regulate the reproducing track width. SOLUTION: In order to control the asymmetry of the reproducing signal of an MR head applied with a permanent magnetic bias in the range within ±10%, the product Mrt [memu/cm<2> ] of the residual magnetic(Mr) and the film of the permanent magnetic film and the reproducing track width w [μm] are selected so as to meet a range regulated by an expression I and an expression II. In this case, the upper limit of the reproducing track width (w) is 1.5 μm. This value corresponds to the face recording density of the degree of 2GB/in<2> . In order that the reproducing characteristic of an MR head show asymmetry close to 0, the relation of the product Mrt of the residual magnetic and film thickness of the permanent magnetic film with respect to the width (w) is desirably in the range of setting the expression I to be its lower limit and the expression II to be an upper limit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-resistance effect type magnetic head (MR head) used for a magnetic recording device such as a hard disk drive and a VTR, and more particularly to a film thickness of a permanent magnet film constituting a reproducing element portion. And the relationship between the residual magnetization and the reproduction track width.

[0002]

2. Description of the Related Art In a magnetic recording apparatus such as a hard disk drive or a VTR, the miniaturization and the increase in capacity due to a high recording density are progressing rapidly. In response to such a trend, the performance of magnetic heads has been improved, and instead of the thin film magnetic head of the electromagnetic induction type, an MR head using a magnetoresistance effect phenomenon as a reproducing element has been applied.

[0003] Such a conventional MR head, for example,
Vol. 26 (1990) pp1689. The outline will be described with reference to FIG. A magnetoresistive element (MR element) 91 for reproducing a magnetic signal on a magnetic recording medium is formed of a thin film of a material having a magnetoresistive effect such as permalloy. The MR element 91 has a shield magnetic film 93 through a read gap 92 made of a non-magnetic material.
And 94.

The MR head shown in FIG. 12 is of a type in which a recording head and a reproducing head are separated.
The reproducing head is an MR element 91, and the MR element 9 is used during reproduction.
Use 1 to read the signal information. The recording head is an inductive magnetic head for recording only, comprising a recording magnetic pole 84 and a coil 80. As shown in FIG. 12, the recording magnetic pole 84 and the coil 80 constituting the recording head are arranged above the MR element 91 constituting the reproducing head.

In order to increase the recording capacity of a magnetic recording apparatus, it is usual to increase the track density or the linear recording density. Therefore, in order to increase the track density, the track width must be reduced. As the track width is reduced, the following problems occur.

That is, since the length of the MR element is shortened, the resistance of the MR element itself is reduced, and the reproduction output is significantly reduced. For this reason, in order to keep the reproduction output to a level that does not cause a practical problem, it is necessary to increase the resistance of the reproduction element or take measures to improve the reproduction sensitivity of the MR element.

On the other hand, the MR element, which is a detection / reproduction element, is susceptible to the influence of domain walls and magnetic domain structures generated in the element, and is superimposed on the reproduction signal as noise during reproduction. Such a noise signal is called Barkhausen noise, and its suppression and regulation have been problematic, and countermeasures have been taken. As means for suppressing the generation of magnetic domains, for example, IEEE Trans.Mag
n. Vol. 32 (1996), pp. 19, discloses a method of forming and arranging a permanent magnet film adjacent to an MR element and applying a bias magnetic field to the MR element. According to this method, the applied bias magnetic field can reduce the influence of the demagnetizing field generated at the track end of the MR element, and as a result, it is possible to suppress the occurrence of magnetic domains and the like in the element.

However, if the magnetic domain structure is stabilized by using a permanent magnet film, the reproduction sensitivity of the element may be reduced. Therefore, care must be taken in selecting the bias magnetic field strength for stabilization.

That is, it is required to apply a necessary magnetic field strength so as not to generate Barkhausen noise, and to maintain the strength of the bias magnetic field within an appropriate range so as not to lower the reproduction sensitivity. In addition, when the intensity of the bias magnetic field is changed, the asymmetry, which is an index of the linearity of the reproduced signal, also changes. Therefore, it is necessary to set a satisfactory optimal bias magnetic field for all of these factors.

On the other hand, US Pat. No. 5,434,826 discloses a preferable material and composition of the permanent magnet film. The permanent magnet films disclosed therein are CoCrPt, CoCrT.
a, CoCrTaPt and CoCrPtB, etc.
It is an original measurement that the optimum range is obtained when the product of the residual magnetization and the film thickness is 2.38 to 3.78 [memu / cm ² ] for the film thickness in the range of 50 to 60 nm. We clarify using device.

Further, the magnetic characteristics of the permanent magnet film naturally have a great influence on the reproduction characteristics of the MR head. Japanese Patent Application Laid-Open No. 7-93714 discloses that the characteristics of the coercive force Hc of the permanent magnet film are improved. Thus, it is described that Barkhausen noise or variation in reproduction output of the MR head can be reduced.

[0012]

The bias magnetic field generated by the permanent magnet film has the effect of suppressing and stabilizing the magnetization rotation in the MR element. However, if the distance between adjacent permanent magnet films becomes narrower than conventionally thought as the track width becomes narrower to improve the recording density, the intensity of the bias magnetic field becomes excessively large. As a result, M
The sensitivity of the R element decreases, and a reduction in the reproduction output cannot be avoided. Furthermore, since the effect of the bias magnetic field deviates from an appropriate value, the linear range of the reproduced signal for ensuring the symmetry of the reproduced waveform is rapidly narrowed, and the asymmetry of the reproduced waveform is simultaneously increased, and the error rate of the reproduced signal is increased. Leads to.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the reproduction instability of an MR element observed in the occurrence of Barkhausen noise, increase the reproduction signal output, and reduce the waveform asymmetry.
It is to provide a practical solution for obtaining an R head. In addition, it is intended to provide an optimum application of the permanent magnet film corresponding to the reduction of the track width. Hereinafter, the present invention will be described in detail.

[0014]

In order to solve the above-mentioned technical problems, the present invention is directed to a permanent magnet film and a physical dimension of a reproduction track width or a reproduction track width, which have a great influence on reproduction output and reproduction noise of an MR element. It was conceived as a result of considering physical properties and the like and searching for a specific method that can be appropriately reflected in the design.

The permanent magnet film used in the MR head performs noise control by applying a bias magnetic field to the element.
However, if the bias magnetic field is too large, the reproduction sensitivity is reduced, which causes a shortage of output. The efficiency of the effect of the bias magnetic field by the permanent magnet film varies depending on the reproduction track width, the permanent magnet film thickness, and the residual magnetic flux density of the permanent magnet. Further, the physical property value of the permanent magnet film has a strong influence on the intensity and distribution of the bias magnetic field.

Therefore, while it is very difficult in practice to properly combine and regulate these many parameters, the present invention makes it easy to carry out and controls the conventional MR.
M that has much better output characteristics and noise characteristics than the head
An R head can be obtained.

In the present invention, the main technique is to stabilize the MR element, which is a detecting element having a magnetoresistance effect, by a bias magnetic field. The MR head according to the present invention has a reproducing track width of w [μm] in an MR element having a magnetoresistance effect and a magnetoresistance effect type magnetic head including a permanent magnet film for applying a magnetic bias magnetic field to the MR element. When the product of the residual magnetization Mr of the permanent magnet film and the film thickness t is Mrt [memu / cm ² ], the relationship between the reproduction track width and the product of the residual magnetization film thickness Mrt of the permanent magnet film is as follows: Mrt ≧ 1.0 × w + 0.5 (1) It is required that a relationship satisfying Mrt ≦ 3.6 × w−0.4 (2) be satisfied and that the reproduction track width w be 1.5 μm or less.

By using this MR head, it is possible to obtain good reproduction characteristics with asymmetry of the reproduction waveform, reproduction output and little variation in the reproduction output even if the reproduction track width is narrowed in accordance with the high track density. Become. Furthermore, since the relationship between the permanent magnet film capable of effectively removing Barkhausen noise and the reproduction track width can be used, high performance can be obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a magnetic pole portion of an MR head according to the present invention will be described with reference to FIG. In FIG. 8, reference numeral denotes an MR element, and a permanent magnet film 81 is formed adjacent to the MR element. Also, reference numeral 83
Is an electrode for supplying current to the MR element, and 84 is a recording magnetic pole. The MR element 82 is magnetically shielded by a lower shield film 85 and an upper shield film 86.

A first embodiment will be described. In this embodiment, an object is to find a condition for realizing an asymmetric object in which the reproduction characteristic of the MR head is close to 0.

FIG. 1 shows that the reproduction track width w is 0.7-1.
For each case of 5 μm, the residual magnetization M of the permanent magnet film 81
The relationship between the product of r and the film thickness t (hereinafter referred to as the product of the residual magnetization and the film thickness of the permanent magnet film) Mrt and the asymmetric characteristic of the reproduced waveform is shown. The horizontal axis of the graph in FIG. 1 represents the residual magnetization / film thickness product Mrt [memu / cm ² ] of the permanent magnet film, and the vertical axis represents the reproduction waveform asymmetry in%. Here, the asymmetry of the reproduced waveform is defined by the following equation. Asymmetry _{[%] = [(V +} -V -) / (V + + V -)]
× 100 In the above equation, V ₊ and V ₋ represent a positive signal output and a negative signal output, respectively.

When reproducing a digitally encoded signal recorded as in a hard disk drive, the reproduced waveform obtained from the magnetic head is an analog signal, and it is necessary to reproduce the signal into digital codes of 0 and 1. In this process, if the asymmetry increases, the reproduced waveform is distorted, and the 0 and 1 codes cannot be reproduced correctly.

Generally, for an MR head incorporated in a hard disk drive, the allowable limit of asymmetry is -15.
To + 15%. However, since the error rate of the reproduced code may increase about 10 to 100 times at the allowable limit of the asymmetry, the asymmetry is desirably in the range of -10 to + 10%.

Therefore, in the present invention, the reproducing characteristics of the MR head are set so as to realize asymmetry of -10 to + 10%. As is clear from the characteristic curve group shown in FIG. 1, as the Mrt of the permanent magnet film is increased with respect to the reproduction track width w of 0.7 to 1.5 μm, the value of asymmetry changes from positive. Changes negatively.

For example, when the reproduction track width is 0.7 μm, the product of the residual magnetization and the film thickness of the permanent magnet film, Mrt = 0.8
In the case of [memu / cm ² ], the asymmetry was + 33%, but when Mrt = 1.20 [memu / cm ² ], the asymmetry is improved to + 10%. In addition, Mrt
= 2.24 [memu / cm ² ] or more, the asymmetry becomes -10% or more. From the above results, when the reproduction track width w is 0.7 μm, the lower limit of the product Mrt of the residual magnetization and the thickness of the permanent magnet film is 1.20 [memu / cm ² ], and the upper limit is 2.24. [Memu / cm ² ].

The above procedure is repeated for the reproduction track width w = 0.
Table 1 below shows the upper limit and lower limit of the product Mrt of the residual magnetization and the thickness of the permanent magnet film at each track width by applying the values other than the above.

[0027]

[Table 1]

The relationship between the lower limit and the upper limit of the product Mrt of the remanent magnetization / film thickness of the permanent magnet film obtained in Table 1 and the reproduction track width w is expressed by a linear equation. The lower limit of Mrt is as follows: = 1.0 × w + 0.5 (1), and the upper limit of Mrt is as follows: Mrt = 3.6 × w−0.4 (2)

From these results, it was found that in the MR head to which the permanent magnet bias was applied, the asymmetry of the reproduction signal was ± 10%.
In this case, it is necessary to select the product Mrt of the residual magnetization and the thickness of the permanent magnet film and the reproduction track width w so as to satisfy the range defined by the equations (1) and (2). is necessary.

Since the waveform asymmetry of the reproduction is better as the value is closer to 0, the relationship between the reproduction track width w and the Mrt of the permanent magnet film is determined from the result shown in FIG. It can be seen that it is most desirable to satisfy the following relationship: w + 0.4 (3)

From the above, in order for the reproduction characteristic of the MR head to exhibit an asymmetry close to 0, the relationship between the reproduction track width w and the product Mrt of the residual magnetization / film thickness of the permanent magnet film is determined by the above (1). It can be seen that it is desirable to set the upper limit to the expression (2) and the upper limit to the expression (2), or to make the expression as close as possible to the expression (3).

The upper limit of the reproduction track width w specified in the present invention is 1.5 μm. That is, the upper limit of the reproduction track width w is set to w = 1.5 (4). w = 1.5 [μm] is also a reproduction track width corresponding to a surface recording density of about 2 GB / in ² .

As described above, the desired relationship between the reproduction track width w and the product Mrt of the residual magnetization / film thickness of the permanent magnet film, which is defined by the equations (1), (2) and (4), is shown by a graph. 2, a hatched area surrounded by straight lines 22, 21 and 23. In FIG. 2, the horizontal axis is the reproduction track width w [μm], and the vertical axis is the product Mrt [memu / cm ² ] of the residual magnetization / film thickness of the permanent magnet film. In FIG. 2, a straight line 21 is an equation (1) defining the lower limit of Mrt, and a straight line 22 is defining the upper limit of Mrt (2).
Equation (4) defines the upper limit of the playback track width w.

That is, the hatched area satisfies the following three equations. Mrt ≧ 1.0 × w + 0.5 (1 ′) Mrt ≦ 3.6 × w−0.4 (2 ′) w ≦ 1.5 (4 ′)

The left side of the equation (1) or (2) indicates the product of the residual magnetism film thickness Mrt of the permanent magnet film, and the dimension thereof is [memu / cm ² ]. Note that the reproduction track width w is expressed in μm. Since the left side has the above-described dimensions, the constant coefficient of the first term on the right side is [memu / cm ² / μm], and the constant coefficient of the second term is [m
emu / cm ² ].

A second embodiment according to the present invention will be described. In this embodiment, a condition that the MR head can secure a specified output is added to the condition for realizing the asymmetry within ± 10% of the reproduction characteristic of the MR head (the condition in the first embodiment). Is done.

The hard disk drive uses the phenomenon of reversal of the magnetization recorded on the magnetic recording medium to record and reproduce the codes of 0 and 1. The change in the magnetic field due to the reversal of the magnetization in the magnetic recording medium is converted from the waveform reproduced by the MR head to codes of 0 and 1. For example, when the code array is {0000} and the 0 code signal is continuous, When the magnetization reversal cycle is long and, on the contrary, 1 continues like {1111}, the magnetization reversal cycle becomes short.

At present, in the code reproducing method used for the hard disk drive, the ratio of the lowest frequency to the highest frequency is set in the range of 1: 5 to 1: 6, but the reproduction is performed by overlapping the adjacent signal waves. Due to the interference effect of the waveform, the reproduction output tends to decrease as the frequency increases. At this time, the amplitude intensity ratio between the reproduced output for the highest frequency and the reproduced output for the lowest frequency is about 25 to 35%.

On the other hand, in order for the hard disk device to reproduce the code without error, the reproduction output from the MR head is required to be about 1 mV.
Desirably, it is 3 to 0.4 mV. For this reason, in the present invention, the product Mrt of the residual magnetization and the film thickness of the permanent magnet film capable of securing the reproduction output in the low frequency range of 0.4 mV or more has been found.

FIG. 3 shows that the reproduction track width w is 0.7-1.
The relationship between the product Mrt of the residual magnetization and the film thickness of the permanent magnet film and the reproduction output of the isolated reproduction wave for each case of 5 μm is shown. The horizontal axis of the graph of FIG. 3 is the product Mrt [memu / cm ² ] of the residual magnetization / film thickness of the permanent magnet film, and the vertical axis is the reproduction output [mV].

According to FIG. 3, for example, the reproduction track width w
Is 0.7 μm, the product M of the residual magnetization and the thickness of the permanent magnet film is M
When rt is 0.88 [memu / cm ² ], about 0.5
It can be seen that a reproduction output of 5 [mV] is given. Furthermore, when the reproduction track width w is 0.7 to 1.5 μm, the reproduction output generally tends to decrease as the product Mrt of the residual magnetization / film thickness of the permanent magnet film increases.

FIG. 3 shows that the reproduction track width w = 0.
In the case of 7 μm, in order to obtain a reproduction output of 0.4 [mV] or more, the product Mrt of the residual magnetization / film thickness of the permanent magnet film is set to 1.
It can be seen that it is necessary to be 27 [memu / cm ² ] or less. Similarly, when the reproduction track width w is 0.7
Even in cases other than μm, the product M of the residual magnetization and the film thickness of the permanent magnet film to obtain a reproduction output of 0.4 [mV] or more.
When the upper limit value of rt is obtained, it becomes as shown in Table 2 below.

[0043]

[Table 2]

The relationship between the reproduction track width w and the product Mrt of the residual magnetization and the film thickness of the permanent magnet film obtained in Table 2 is represented by the following equation: Mrt = 4.5 × w−2.0 (5). That is, in order to ensure a reproduction output of 0.4 [mV] or more, it is necessary that Mrt ≦ 4.5 × w−2.0 (5 ′).

As described above, in the MR head using the bias magnetic field by the permanent magnet film, the asymmetry of the reproduction signal is restricted within the range of ± 10%, and the reproduction output is 0.4%.
In order to secure the voltage of [mV] or more, the above equation (1 ′) is used.
Equations (2 '), (4') and (5 ') must all be satisfied. Such an area is indicated by hatching in FIG.

In FIG. 4, the horizontal axis represents the reproduction track width w [μ].
m], and the vertical axis represents the product Mrt [m of the residual magnetization / film thickness of the permanent magnet film.
emu / cm ² ]. In FIG. 4, straight lines 21, 22 and 2
Reference numeral 3 denotes the expressions (1), (2) and (4), as in the case of FIG. 2, and the straight line 33 denotes the above expression (5).

As described above, in the MR head using the bias magnetic field generated by the permanent magnet film, the asymmetry of the reproduction signal can be reduced by ± 10% by selecting the region indicated by the diagonal lines in FIG. And the reproduction output can be secured to 0.4 [mV] or more.

Next, a third embodiment will be described. In this embodiment, the condition that the reproduction characteristic of the MR head achieves asymmetry within ± 10% (the condition given in the first embodiment)
Furthermore, a condition is added that the hysteresis characteristic of the permanent magnet film is reduced. Here, the hysteresis means the hysteresis that appears on the output change characteristic curve of the MR element when a continuously changing external magnetic field is applied to the MR head. This hysteresis is given by a change in the applied magnetic field and a change in the output. In the present invention, the dimension of the hysteresis is [mV · Oe].

FIG. 5 shows that the reproduction track width w is 0.7-1.
For each case of 5 [μm], the residual magnetization of the permanent magnet film
It is a graph which shows the relationship of the hysteresis with respect to the product Mrt of the film thickness. The vertical axis of the graph of FIG. 5 is the hysteresis [mV · Oe], and the horizontal axis is the residual magnetization of the permanent magnet film.
The product of the film thicknesses is Mrt [memu / cm ² ].

According to FIG. 5, for example, the reproduction track width w
Is 0.7 [μm], the hysteresis is 4.2 [mV · Oe] when the product Mrt of the residual magnetization / film thickness of the permanent magnet film is 0.88 [memu / cm ² ]. When Mrt is further increased to 1.6 [memu / cm ² ],
The hysteresis sharply decreases to 1.2 [mV · Oe]. Further, Mrt increases to 3.9 [memu / cm
² ], the hysteresis further decreases to 0.2
[MV · Oe].

In general, it is known that the hysteresis appearing in the reproducing element causes a variation in the reproducing output and becomes a noise source of the disk drive. For this reason, the maximum allowable output variation of the disk drive device is about 5 to 10%. Considering this in the case of the minimum value of the reproduction output of 0.4 [mV], the range of the allowable variation is as follows. 0.03 [mV].

On the other hand, regarding the magnitude of the signal magnetic field generated from the magnetic recording medium of the disk drive device, Mrt of the magnetic recording medium is 0.5 to 0.8 [memu / c].
m ² ], it is considered that a magnetic field of about 40 [Oe] is applied to the magnetoresistive head.

From this result, it can be seen that the maximum value of the allowable hysteresis is defined as the product of the magnitude of the applied magnetic field and the allowable variation of the output, and is 1.2 [mV · Oe]. In order to obtain a magnetoresistive head with less variation in reproduction output, the hysteresis is 1.2 [mV · Oe].
It is necessary to control Mrt of the permanent magnet film so as to be as follows.

Based on the result obtained in FIG. 5, the lower limit value of the product Mrt of the residual magnetization / film thickness of the permanent magnet film is determined for each case where the reproduction track width w is 0.7 to 1.5 [μm]. Once obtained, the results are as shown in Table 3 below.

[0055]

[Table 3]

The relationship between the product Mrt of the residual magnetization and the film thickness of the permanent magnet film obtained in Table 3 and the reproduction track width w is represented by a linear equation, as follows: Mrt = 3.7 × w-1.2 (6). That is, in order for the magnitude of the hysteresis defining the variation of the reproduction output to be 1.2 [mV · Oe] or less, the following condition must be satisfied: Mrt ≧ 3.7 × w−1.2 (6 ′) Is required.

As described above, in the MR head of the permanent magnet bias system, the asymmetry of the reproduced signal is controlled within the range of ± 10%, and the magnitude of the hysteresis is set to 1.2.
In order to obtain reproduction characteristics of [mV · Oe] or less, it is necessary to use the above formulas (1 ′), (2 ′), (4 ′) and (6 ′).
All expressions must be satisfied. Such an area is indicated by hatching in FIG.

In FIG. 6, the horizontal axis is the reproduction track width w [μm].
The vertical axis represents the product Mrt of the residual magnetization and the film thickness of the permanent magnet film.
[memu / cm ² ]. In FIG. 6, straight lines 21, 22, and 23 represent the equations (1), (2), and (4) as in the case of FIG. 2, and the straight line 53 represents the above equation (6).

Next, a fourth embodiment will be described. In this embodiment, the conditions for realizing the asymmetry of the reproduction characteristic of the MR head within ± 10% (the conditions in the first embodiment);
Further, a condition for reducing the hysteresis characteristic of the permanent magnet film (the condition in the third embodiment) is superimposed and added.

Therefore, this embodiment is different from the above (1)
'), (2'), (4 '), (5') and (6)
') All of the expressions must be satisfied. Such an area is indicated by hatching in FIG.

In FIG. 7, the horizontal axis is the reproduction track width w [μm].
The vertical axis represents the product Mrt of the residual magnetization and the film thickness of the permanent magnet film.
[memu / cm ² ]. In FIG. 7, straight lines 21, 22, and 23 represent the equations (1), (2), and (4), as in the case of FIG. 2, and the straight line 33 represents the above equation (5). The straight line 53 represents the equation (6).

Next, a fifth embodiment will be described. This example is
In the MR head according to the first to fourth embodiments, the squareness ratio S is defined. The squareness ratio S is a ratio of the residual magnetization Mr and the saturation magnetization Ms of the permanent magnet film, which is a means for applying a magnetic bias, (ie, S = Mr
/ Ms). In the MR head according to this embodiment, the squareness ratio is defined to be 0.7 or more and 1.0 or less.

In the MR head shown in FIG. 8, the saturation magnetization Ms of the permanent magnet film 81 is 450 to 800 [emu / c].
m ³ ]. At this time, if the squareness ratio S is 1,
The product Mrt of the residual magnetization / film thickness of the permanent magnet film is 1 [memu].
/ Cm ^2] is film thickness required for a 120 to 220
[Å]. On the other hand, when the squareness ratio S is 0.1, the film thickness required for Mrt to be 1 [memu / cm ² ] reaches 1200 to 2200 [Å], and both sides of the reproducing track of the reproducing element are thick. turn into.

The shape around the reproducing element also affects the shape of the recording magnetic pole. In order to reduce the shape effect around the reproducing element, it is necessary to flatten the surface on which the magnetic poles are arranged before forming the recording magnetic pole, or to keep the reproducing element shape flat. However, the flattening operation has disadvantages in that the number of man-hours for manufacturing the magnetic head increases and the cost increases. On the other hand, the technology for keeping the shape of the reproducing element flat makes it possible to reduce the time required for film formation by reducing the thickness of the permanent magnet film without going through an extra step, thereby reducing the productivity of the MR head. It can be improved.

The maximum value of the product Mrt of the residual magnetization and the film thickness of the permanent magnet film 81 used in this embodiment is 5.29 [memu].
/ Cm ² ]. For example, when a permanent magnet material having a saturation magnetization Ms of 450 [emu / cm ³ ] is used for the permanent magnet film 81, the film thickness is given by the following relationship. Permanent magnet film thickness = (Maximum value of product Mrt of residual magnetization / film thickness) / (Residual magnetization Mr) = Mrt / (Ms × S) = 5.29 [memu / cm ² ] / Mr [emu / cm ³ ] = 5.29 [memu / cm ² ] / (450 [emu / cm ³ ] × S).

Therefore, the minimum thickness of the permanent magnet film is obtained when the squareness ratio S is 1, and is 1176 [Å]. As the squareness ratio S decreases, the thickness of the permanent magnet film increases, and the squareness ratio 0.7 is 1680 [Å] and the squareness ratio 0.5 is 2
352 [Å] is reached. Element thickness of MR head is 500
６００600 [Å], and the step of the element portion to which the electrode for signal detection is added is 2000 when the squareness ratio is 0.7.
[Å]. This causes a distortion of 50% or more of the recording gap length in the recording magnetic pole, but a shape distortion of 50% or more significantly degrades the characteristics of O / W (overwrite) and reproduction wavelength. Is desirably 0.7 or more.

This embodiment defines the composition of the permanent magnet film 81 in the MR head according to any one of the first to fifth embodiments. The permanent magnet film 81 is C
An alloy mainly containing o, and contains at least one of Cr, Ta, Pt, and Ni as an additive element to the alloy.

In the MR head, the product Mrt of the residual magnetization / film thickness of the permanent magnet film for generating a bias magnetic field is controlled,
In order to obtain good reproduction characteristics, it is necessary to obtain a permanent magnet material exhibiting excellent magnetic characteristics in a thin film state. The thickness of the permanent magnet film of the alloy containing Co as a main component is 100 to 100.
Coercive force Hc = 1000 [Oe] or more in the range of 0 [Å],
It is possible to ensure a squareness ratio S = 0.7 or more.

A seventh embodiment will be described. In this embodiment, in the MR head according to any one of the first to sixth embodiments, a reproducing element having a magnetoresistive effect is constituted by two magnetic films stacked via a nonmagnetic metal spacer. ing. A material such as Cu or Ta can be used as the nonmagnetic metal spacer. Further, as the laminated magnetic film, NiFe, Co, Ni
FeCo, CoFe, CoTaZr, NiFe-based alloy,
A CoFe-based alloy, a CoTa-based alloy, or the like can be used, and good magnetic characteristics can be obtained.

An eighth embodiment will be described. In this embodiment, in the MR head according to any one of the first to sixth embodiments, the reproducing element can have the following form.

First Embodiment: Magnetoresistance effect film (MR film)
, Ta spacer, and S for applying a bias to the MR film.
A three-layer film is formed by laminating an AL film, and a permanent magnet film and a conductive film are provided at both ends of the three-layer film to form a reproducing element. By setting the spacer to Ta, a spacer of a metal film having high resistance can be obtained. An MR head using this reproducing element is S
This is called an AL bias type magnetic head.

Second Embodiment: A four-layer film in which a first soft magnetic film, a nonmagnetic metal spacer, a second magnetic film, and an antiferromagnetic film is laminated, and both ends of the four-layer film Is provided with a permanent magnet film and a conductive film to form a reproducing element. An MR head using this reproducing element is called a spin valve type MR head or a spin valve head. In this reproducing element, both or one of the first soft magnetic film and the second magnetic film may be used as a film in which a plurality of magnetic films are laminated, a laminated ferrilayer in which a metal layer is provided between magnetic layers, or the like. Can be replaced by Cu or the like can be used for the nonmagnetic metal spacer.

Here, a spin valve type MR head will be described with reference to FIGS. 9, 10 and 11. FIG. The above four-layered MR element 82 and the permanent magnet films 81 provided on both ends thereof
A read element composed of the first shield magnetic film 93 and the second shield magnetic film 94 is provided. The second shield magnetic film 94 is placed on a substrate 95 via an insulating film 96. The first shield magnetic film 93 is disposed above the second shield magnetic film 94 with a predetermined gap.

A recording magnetic pole 84 is arranged above the first shield magnetic film 93. The recording magnetic pole 84 extends rearward to the center of the coil 80 as shown in FIG. The recording magnetic pole 84 is covered with a protective film 97 as shown in FIG. The MR element 82 constituting the reproducing element is shown in FIG.
As shown in FIG. 1, a free layer 82a serving as a first soft magnetic film and a nonmagnetic metal layer 82 serving as a spacer are mainly provided from below.
b, a fixed layer 82c as a second magnetic layer, and an antiferromagnetic layer 82d made of an antiferromagnetic film.

Third Embodiment: A three-layer film in which a first soft magnetic film, a spacer made of an insulating material, and a second soft magnetic film are laminated, and a conductive film is provided on the three-layer film to form a read element And An MR head using this reproducing element is called a tunnel junction type magnetic head. Fourth Embodiment: A reproducing element that produces a giant magnetoresistance effect is used.

[0076]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An MR head according to the present invention is manufactured by the following steps to demonstrate the effects of the present invention. First,
A lower shield film made of a soft magnetic material having a thickness of 1 to 2 [μm] was formed on a ceramic substrate on which an insulating film such as Al ₂ O ₃ was formed. After shaping the lower shield film into a shape required for a magnetic head, a lower read gap using an insulating film such as Al ₂ O ₃ was formed. A laminated thin film for a reproducing element was formed on the insulating film by using a method such as sputtering in the order of a soft magnetic film, a non-magnetic spacer film, and a magnetic film. At this time, these films need to be thin films of about 100 to 200 [Å]. The formed laminated thin film is shaped into a required element shape by a method such as milling (also called ion milling).

Next, an electrode for detecting a change in resistance of the reproducing element is manufactured. Since the reproduction track width w is determined by the distance between the two electrodes in contact with the reproduction element, a stencil for controlling the electrode distance is first formed on the reproduction element by using the photolithography technique. .
At this time, since the electrode material to be formed needs to be electrically connected well to the reproducing element as described later, the portion of the stencil in contact with the reproducing element is 0.1 mm wider than the element width formed by milling. It was necessary to reduce the width by about 2 to 0.3 [μm]. At this time, the reproduction track width regulated by the width of the stencil was set to 0.7 to 1.5 [μm]. Among the films constituting the electrodes, first, as a permanent magnet film for generating a bias magnetic field, a CoCrPt alloy is formed by adjusting the film thickness so as to obtain a product Mrt of a required residual magnetization and film thickness, and then formed. Thus, a Ta film and a Cu film, which are electrically good conductors, were formed.

At this time, the film was formed under the condition that the product Mrt of the residual magnetization and the film thickness of the permanent magnet film was 0.8 to 3.9 [memu / cm ² ]. The permanent magnet film and the conductive film were formed using a sputtering method. After the film forming operation by sputtering was completed, the stencil and the film adhered on the stencil were removed, and an insulating film made of Al ₂ O ₃ or the like was formed again on the completed reproducing element. This insulating film forms a reproducing gap together with the insulating film below the reproducing element. Further, an upper shield film having a thickness of 3 to 4 [μm] was formed on the reproducing gap. A recording coil and a recording magnetic pole were laminated on the upper portion of the completed reproducing head, and a protective film and a conductive pad were attached on the upper portion, thereby completing all the head manufacturing steps.

When the reproduction track width w is 0.7 to 1.5 [μ
m], and the Mrt of the permanent magnet film is 0.8 to 3.9 [memu].
/ Cm ² ], the reproduced waveform asymmetry of the prototype MR head,
The measurement results of the reproduction output and the hysteresis are as shown in FIGS. 1, 3 and 5, respectively.

[0080]

By using the MR head according to the present invention, it is possible to obtain good reproduction characteristics with asymmetry of the reproduction waveform, reproduction output, and little variation in the reproduction output even when the reproduction track width becomes narrow in accordance with the high track density. It becomes possible. Further, since the relationship between the magnet film and the reproduction track width that can effectively remove Barkhausen noise can be used, a high-performance MR head can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing a reproduction waveform asymmetry with respect to a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 2 is a graph showing a relationship between a reproduction track width w for regulating reproduction waveform asymmetry and a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 3 is a graph showing a reproduction output with respect to a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 4 is a reproduction track width w for defining a reproduction output.
5 is a graph showing the relationship between the residual magnetization of the permanent magnet film and the product Mrt of the film thickness.

FIG. 5 is a graph showing hysteresis with respect to a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 6 is a graph showing a relationship between a reproduction track width w for controlling hysteresis and a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 7 is a graph showing a relationship between a reproduction track width w for restricting a reproduction output and hysteresis, and a product Mrt of a residual magnetization and a film thickness of a permanent magnet film.

FIG. 8 is a schematic diagram of a magnetic pole portion of the MR head viewed from the air bearing surface.

FIG. 9 is a perspective view of a spin-valve MR head to which the present invention is applied.
A part of the R head is shown in a sectional view.

FIG. 10 is a front view of the MR head of FIG. 9;

FIG. 11 is an enlarged view of a reproducing element in the MR head of FIG. 10;

FIG. 12 is a perspective view showing a configuration of a conventional MR head.

[Explanation of symbols]

80 coil, 81 permanent magnet film, 82 magnetoresistive effect element (MR element), 82a free layer, 82b spacer, 82c fixed layer, 82d antiferromagnetic layer, 8
3 electrodes, 84 recording magnetic pole, 85 lower shield film,
86 upper shield film, 87 reproduction gap, 91
Magnetoresistance effect element, 92 reproduction gap, 93 shield magnetic film (lower magnetic pole) 94 shield magnetic film, 9
5 substrate, 96 insulating film, 97 protective film.

Claims (12)

[Claims] 1. A magneto-resistance effect type magnetic head comprising: a magneto-resistance effect element having a thin film having a magneto-resistance effect; and a permanent magnet film for applying a magnetic bias magnetic field to said magneto-resistance effect element. The product Mrt [memu / cm ² ] of the residual magnetization Mr and its film thickness t is as follows: when the reproduction track width w [μm], Mrt ≧ 1.0 × w + 0.5 Mrt ≦ 3.6 × w−0.4 And the reproduction track width w
Is 1.5 μm or less. 2. The reproduction track width w [μm] and the product Mrt [memu of the film thickness t and the residual magnetization Mr of the permanent magnet film.
/ Cm ² ], the relation: Mrt ≦ 4.5 × w−2.0 is satisfied. 3. The product Mrt [memu / c of the reproduction track width w [μm], the residual magnetization Mr of the permanent magnet film and the film thickness t.
The magnetoresistance effect type magnetic head according to claim 1, wherein the relationship of m ² satisfies the following condition: Mrt ≧ 3.7 × w−1.2. 4. The product Mrt [memu / c of the reproduction track width w [μm], the residual magnetization Mr of the permanent magnet film and the film thickness t.
relationship m ^2] A magnetic resistance according to any one of claims 1 to 3, characterized by satisfying the Mrt ≦ 4.5 × w-2.0 Mrt ≧ 3.1 × w-1.9 Effect type magnetic head. 5. When the squareness ratio S given by the ratio between the residual magnetization Mr and the saturation magnetization Ms of the permanent magnet film is given by the following equation: S = Mr / Ms, the squareness ratio S is 0.7 to 1.0. 5. The magnetoresistive head according to claim 1, wherein the value is in the range of zero. 6. The permanent magnet film is made of an alloy containing Co as a main component, or contains Cr,
6. The magnetoresistive head according to claim 5, comprising at least one of Ta, Pt, and Ni. 7. The magnetoresistive head according to claim 6, wherein the magnetoresistive element is constituted by two magnetic films stacked via a nonmagnetic metal spacer. 8. The magnetoresistive head according to claim 1, wherein the asymmetry of the reproduction output of the magnetoresistive element is within ± 10%. 9. The magnetoresistance effect type magnetic device according to claim 2, wherein the reproduction output of the magnetoresistance effect element has an asymmetry within ± 10% and a reproduction output of 0.4 mV or more. head. 10. The reproduction output of the magnetoresistive element has an asymmetry of ± 10% or less and a reproduction output variation of 1%.
4. The magneto-resistance effect type magnetic head according to claim 3, wherein said magnetic head is 0% or less. 11. The apparatus according to claim 4, wherein the asymmetry of the reproduction output of the magnetoresistive effect element is within ± 10%, the reproduction output is 0.4 mV or more, and the variation is 10% or less. Magnetoresistive magnetic head. 12. A product of a remanent magnetization Mr of the permanent magnet film and a thickness t thereof, Mrt [memu / cm ² ], and a reproduction track width w have a relationship of Mrt = 1.6 × w + 0.4. 2. The magnetoresistive head according to claim 1, wherein the reproduced waveform does not substantially include asymmetry.