JP2728455B2 - Thin-film magnetic head, magnetic disk device using the same, and information recording / reproducing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device and a method of recording and reproducing information in the magnetic disk device, and more particularly to a magnetic disk device used as an external storage device of a host device such as a computer. The present invention relates to a suitable magnetic disk device, a thin-film magnetic head used in the magnetic disk device, and a method for recording and reproducing information in the magnetic disk device.

[Conventional technology]

As the storage capacity of magnetic disk devices increases, the track density of magnetic disks tends to increase.

For this reason, the track width dimension of the magnetic core of the thin-film magnetic head mounted on the magnetic disk device tends to decrease.

In the thin-film magnetic head, a magnetic circuit is formed with an upper magnetic core and a lower magnetic core exposed on a surface facing a magnetic disk with an insulating film made of a non-magnetic material constituting a magnetic gap interposed therebetween.

Thus, writing or reading on a recording medium, for example, a magnetic disk is performed.

The magnitude of the magnetic field generated in the magnetic gap affects the magnetization state of the recording medium which affects the recording density.

The shapes of the upper magnetic core and the lower magnetic core exposed on the surface of the thin-film magnetic head facing the magnetic disk are the main factors that determine the recording density of the magnetic disk device.

Many studies have been made on the shape of the magnetic core exposed on the surface facing the magnetic disk.

Of these, there are few examples focusing on the difference between the length of the upper magnetic core and the length of the lower magnetic core, and Japanese Patent Application Laid-Open No. 55-87323 and IEICE Technical Report Vol.85, No.137, MR85-22 (1985) Are only mentioned in

Japanese Patent Application Laid-Open No. 55-87323 states that by making the length of the upper magnetic core smaller than the length of the lower magnetic core, it is possible to avoid an undesired shape called an around state due to manufacturing variations. I have.

Also, IEICE Technical Report Vol.85, No.137, MR85-22 (1985) describes the difference in length between the upper magnetic core and the lower magnetic core, and the magnitude of the magnetic field oozing at the end of the magnetic core. Has been studied using computer simulation.

In addition, it is described that the difference between the lengths of the upper magnetic core and the lower magnetic core is desirably zero because the bleeding of the magnetic field adversely affects the write and read characteristics.

[Problems to be solved by the invention]

In the prior art described in Japanese Patent Application Laid-Open No. 55-87323, what is the difference between the length of the upper magnetic core and the length of the lower magnetic core in order to obtain a magnetic field distribution suitable for high recording density? There is no mention of that.

In addition, the aforementioned IEICE Technical Report Vol.85, No.137, MR85-22 (1985)
The described prior art, when the track width becomes narrow,
No mention is made that the bleeding of the magnetic field improves the write and read characteristics.

Furthermore, in both of the prior arts, in order to increase the recording density of the magnetic disk device, there is no description about the optimum relationship between the track density of the magnetic disk and the difference between the length of the upper magnetic core and the length of the lower magnetic core. It does not give new knowledge.

An object of the present invention is to clarify the relationship between the track density of the magnetic disk and the optimum value of the difference between the length of the upper magnetic core and the length of the lower magnetic core, which has not been considered in the prior art, and In view of the above, it is an object of the present invention to provide a magnetic disk device in which the S / N ratio is increased with the increase in recording density and the off-track characteristics are improved.

It is an object of the present invention to achieve a track density of 18
Clarify the conditions of the thin-film magnetic head used for the magnetic disk device having a track length of 00 or more and the shape of the magnetic core exposed on the surface facing the recording medium, and provide a magnetic disk device equipped with such a thin-film magnetic head. Is to provide.

Another object of the invention is to provide a track density of 18 / inch.
It is an object of the present invention to clarify a thin-film magnetic head and a configuration provided in a magnetic disk used for a magnetic disk device having a track or more, and to provide such a thin-film magnetic head and a magnetic disk.

Still another object of the present invention is to provide a magnetic disk device using a magnetic disk device having a track density of 1800 or more tracks per inch.

It is still another object of the present invention to provide a method for recording and reproducing information in such a magnetic disk device.

[Means for solving the problem]

The magnetic disk device of the present invention has a magnetic disk for recording information, a thin-film magnetic head for writing and reading information to and from the magnetic disk, a means for rotating the magnetic disk, and a means for positioning the thin-film magnetic head. .

FIG. 9 shows an example of an enlarged view of the magnetic core and the magnetic gap portion of the thin-film magnetic head used in the magnetic disk device, which are exposed on the surface facing the recording medium.

The length of the side of the upper magnetic core 21 facing the magnetic gap 22 is CW
U (μm), and the length of the side of the lower magnetic core 23 facing the magnetic gap 22 is CWD (μm).

In the present invention, the track density (Tr) of the magnetic disk is 1800.
(Track / inch) The difference between CWU and CWD (Δ
CW) is such that 0 <ΔCW ≦ 5000 / Tr (μm), preferably 0.2 ≦ ΔCW ≦ 5000 / Tr (μm).

Further, the longer one of CWU and CWD is shorter than the track pitch of the magnetic disk and longer than the track width.

FIG. 10 shows the relationship between the track pitch and the track width of the magnetic disk in the case where the CWU is shortened.

The track width 50 refers to the width in which information is recorded on the magnetic disk, and the shorter width of CWU or CWD is determined.

The track pitch 51 of the magnetic disk is a width obtained by adding the guide band 55 to the track width 50, and is a protection band provided so that adjacent information does not overlap.

Reference numeral 52 denotes an upper magnetic core, reference numeral 53 denotes a lower magnetic core, and reference numeral 54 denotes a magnetic gap.

As a result, it has been found that the S / N ratio can be increased and the off-track characteristics can be improved.

In other words, the present invention responds to the increase in track density.
Based on the idea that in order to increase the S / N ratio and improve the off-track characteristics, it is necessary to control the shape of the magnetic core with high accuracy in accordance with the track density.

The optimum range of ΔCW satisfying the above relational expression is satisfied even when the track density of the magnetic disk is less than 1800 (track / inch).

If the track density is low, the S / N of the magnetic disk
Since the ratio is greatly affected by factors other than ΔCW, it is not necessary to substantially define the value of ΔCW.

However, it has been found that when the track density is 1800 (track / inch) or more, the value of ΔCW greatly affects the S / N ratio of the magnetic disk device.

That is, in a magnetic disk device having a high recording density such as a track density of 1800 (track / inch) or more, the track pitch of the magnetic disk is about 14 μm.

Correspondingly, the shape of the magnetic core exposed on the surface of the thin-film magnetic head for recording information that faces the magnetic disk also becomes smaller.

Otherwise, the adjacent information will be read, the S / N ratio will deteriorate, and the information cannot be reproduced with high accuracy.

In addition, CWU or CWD, which is an important factor in writing information,
Is smaller than the track pitch of the magnetic disk in consideration of the guide band.

However, the magnetic core cannot be made small in consideration of the manufacturing process, and if it is too small, effective information cannot be read.

Under these circumstances, the shape and dimensions of the magnetic core are important, and in consideration of the positioning accuracy of the magnetic disk device, the difference between CWU and CWD is made rather than zero, and bleeding occurs there. It has been found that the magnetic field should be used effectively.

In order to control the oozing magnetic field, it is necessary to strictly define the CWU and CWD. The oozing magnetic field generated by the difference between CWU and CWD is used for reading information, and information is widely read to improve off-track characteristics.

Further, since the effect of the present invention is obtained by oozing out the magnetic field at the left and right ends of the magnetic core portion, the length of the side of the upper magnetic core facing the magnetic gap (CW
U) and the length of the side facing the magnetic gap of the lower magnetic core (CW
The difference (ΔCW ′) between the left and right ends of the magnetic core is 0 <ΔCW ′ ≦ 2500 / Tr (μm), preferably 0.1 ≦ ΔCW ′ ≦ 2500 / Tr (μm). Satisfies the relationship.

As a result, as in the case described above, the S / N ratio is increased,
In addition, they have found that off-track characteristics can be improved.

Furthermore, considering the actual manufacturing process, the lower limit of ΔCW is
Preferably, the lower limit of ΔCW ′ is 0.1 μm.

Also, in order to keep the bleeding of the magnetic field at the left and right ends of the magnetic core uniform and to improve the off-track characteristics, the upper magnetic core is arranged substantially symmetrically with respect to the central symmetry axis in the writing and reading directions of the lower magnetic core. It is found that it is desirable to be.

On the other hand, in order to increase the recording density of the magnetic disk device, it is necessary to increase not only the track density but also the linear recording density.

Since the S / N ratio decreases as the linear recording density increases, the control of the value of ΔCW or ΔCW ′ specified by the present invention becomes more important.

Therefore, as a result of the study, it is desirable that the linear recording density be 30 kilobits per inch or more.

Further, as a result of a similar study on the areal recording density, it is desirable that the areal recording density be 54 megabits per square inch or more.

As described above, the difference between the length of the side facing the magnetic gap of the upper magnetic core and the length of the side facing the magnetic gap of the lower magnetic core is controlled with high precision, and is set within an optimum range, so that the magnetic disk can be set. High recording density of the device becomes possible,
The S / N ratio can be increased and the off-track characteristics can be improved.

An upper magnetic core of the thin-film magnetic head according to the present invention, which is exposed on a surface facing the magnetic disk, has a central portion substantially parallel to the lower magnetic core, and left and right ends extending in a direction away from the lower magnetic core. The upper magnetic core exposed on the surface of the thin-film magnetic head facing the magnetic disk has a central portion substantially parallel to the lower magnetic core, and extends in a direction away from the lower magnetic core. Upper and lower cores exposed on the surface of the thin-film magnetic head facing the magnetic disk, with respect to the central symmetry axis in the write and read directions of the magnetic core. The length of the side facing the magnetic gap of the upper magnetic core exposed on the surface of the thin-film magnetic head facing the magnetic disk is substantially symmetrical. It is preferably shorter than the length of the side facing the magnetic gap of the core.

In addition, the magnetic disk according to the present invention
Preferably, the magnetic disk has a linear recording density of 30 kilobits or more, and the magnetic disk has a magnetic material having a coercive force of 600 Oe or more and a thickness of 0.35 μm or less on the surface of the magnetic disk.

On the other hand, not only the length of the side of the magnetic core but also the angle of the end portion on the side of the magnetic core changes the manner of bleeding of the magnetic field.

As a result, in order to form an effective magnetic field oozing area, the length of the side where the magnetic core faces the magnetic gap (CWU) or the length of the side where the lower magnetic core faces the magnetic gap (CWD) is determined. For the shorter magnetic core, the angle (θ _S ) between the side end of the magnetic core and the side of the magnetic core facing the magnetic gap (θ _S ) Length of the side facing the magnetic gap of the upper magnetic core (CWU) or lower magnetic core The angle (θ _L ) between the side end of the magnetic core facing the magnetic gap and the side of the magnetic core facing the magnetic gap, whichever is the longer of the length of the side facing the magnetic gap (CWD), is 45 It is desirable to control within the range of {≦ θ _S ≦ 150}.

When θ _S <45 °, the end of the magnetic core is in a magnetically saturated state, the noise at the time of writing or reading increases, and an effective magnetic field cannot be obtained.

If θ _S > 150 °, the track width becomes substantially large, and an effective magnetic field cannot be obtained.

On the other hand, in order to form an effective magnetic field bleeding area, the angle (θ _L) between the side edge of the magnetic core and the side of the magnetic core facing the magnetic gap for the longer magnetic core of CWU or CWD. ) Is desirably controlled within the range of 91 ° ≦ θ _L ≦ 150 °.

Furthermore, it has been found that a greater effect can be obtained if the structure is such that the above-mentioned θ _S and θ _L satisfy the respective optimum ranges simultaneously.

This forms an effective magnetic field bleed area,
It is possible to maintain good off-track characteristics and crosstalk characteristics during reading.

On the other hand, FIG. 9 shows an example of the shape of the magnetic core when the CWU is shorter than the CWD. However, even when the CWU is longer than the CWD, the effect of the present invention is not impaired at all.

However, considering the actual magnetic head manufacturing process, CW
When U is longer than CWD, it is necessary to provide a nonmagnetic planarizing material having the same thickness as the lower magnetic core on the side of the lower magnetic core in order to avoid a wraparound state.

In order to accurately form the film thickness of the non-magnetic insulating material, a complicated process is required.

When processing the length of the side (CWU) of the upper magnetic core facing the magnetic gap, the conventional thin-film magnetic head has a lower part of a step portion having a height of about 10 to 20 μm formed by a conductor coil and an insulating film. And a pattern of the upper magnetic core.

Even if the value of CWU is controlled with respect to the value of the length of the side facing the magnetic gap (CWD) of the lower magnetic core using such a pattern forming method, the effect of the present invention can be obtained, but the actual manufacturing Considering the process, it is difficult to process the dimensions of the magnetic core with high precision below the step.

Therefore, in order to further improve the track density, a magnetic core having a shape as shown in FIG. 3 has been found as an example for easily realizing a highly accurate track width of the magnetic core.

This is because the upper magnetic core 31 has a side (CWU) shorter by ΔCW than the side (CWD) of the lower magnetic core 33 facing the magnetic gap 32.
, And two end portions (shown in the figure) extending in a direction away from the lower magnetic core as compared with the center portion. .

Further, a method of manufacturing a thin-film magnetic head having the shape shown in FIG. 3 will be described.

After forming the lower magnetic core, a non-magnetic insulating layer is deposited on the side and upper ends of the lower magnetic core, and a groove is formed above the lower magnetic core.

Thereafter, a magnetic gap film is formed, and an upper magnetic core is deposited.

Thus, in the thin-film magnetic head having the shape shown in FIG. 3, the track width of the magnetic core is determined by the value of CWU, so that it is possible to control the processing of the high-precision CWU dimension with a small step.

As a result of the study, the thin film magnetic head having the shape shown in FIG. 3 has a track density of 1800 (track / inch) or more, as described for the thin film magnetic head having the shape shown in FIG. It has been found that the value of ΔCW needs to be determined so as to satisfy the following expression: 0 <ΔCW ≦ 5000 / Tr (μm).

Further, it is preferable that the difference (ΔCW ′) between the center of the upper magnetic core 31 and the left and right ends of the lower magnetic core 33 satisfies the following expression: 0 <ΔCW ′ ≦ 2500 / Tr (μm) Was found.

Furthermore, considering the actual manufacturing process, the lower limit of ΔCW is
Preferably, the lower limit of ΔCW ′ is 0.1 μm.

Further, it is desirable that the upper magnetic core 31 and the lower magnetic core 33 be disposed substantially symmetrically with respect to the same axis in the writing and reading directions.
It is desirable to Kirobitsuto more and areal recording density is 54 Megabitsuto or more per square inch and side edge angle of the upper magnetic core (Fig. 3 in indicated by theta _S) and the side end portion angle of the lower magnetic core ( (Indicated by θ _L in FIG. 3)
It has also been found that it is preferable to satisfy 45 ° ≦ θ _S ≦ 150 ° and 91 ° ≦ θ _L ≦ 150 °, respectively.

That is, in order to achieve the high recording density described above,
It is necessary to increase the coercive force of the magnetic material serving as the recording medium on the magnetic disk and to reduce the film thickness.

In order to achieve the effects of the present invention, it is desirable to use a magnetic material having a coercive force of at least 600 Oe and a film thickness of at most 0.35 μm.

In order to generate a sufficiently large effective magnetic field from the magnetic core, a single-layer film or a single-layer film having a saturation magnetic flux density of 1 Tesla or more is used.
It is desirable to use a magnetic core composed of a multilayer film having at least two non-magnetic films interposed, and it is desirable that the number of turns of the conductor coil be 18 turns or more.

In order to increase the read / write efficiency of the magnetic disk and achieve a higher recording density, it is necessary to reduce the flying height of the magnetic head. In the present invention, it is desirable that the flying height is 0.25 μm or less.

The thin-film magnetic head described in the present invention achieves the optimum combination of the bleeding of the write magnetic field and the area of low noise at the time of reading by optimizing the difference in width between the upper magnetic core and the lower magnetic core. Therefore, the S / N ratio of the magnetic disk device is increased to improve the off-track characteristics.

Therefore, the effect of the present invention is greater when the thin-film magnetic head is an inductive type in which writing and reading of information are performed by the same head.

However, for example, even in the case of a composite type thin film magnetic head in which writing is performed by an inductive type and reading is performed by an MR type using a magnetoresistive effect, the present invention is applied to at least the thin film magnetic head used for writing. By applying, the effect of the present invention is achieved.

The present invention is based on the relationship between the shape of the magnetic core of the thin-film magnetic head and the recording density of a magnetic disk device using the same, and therefore does not limit the method of manufacturing the thin-film magnetic head.

However, as a pattern forming method for determining the end position of the magnetic core with high accuracy, it is desirable to use a method of forming a pattern by dry or wet etching a magnetic material produced by a sputtering method, or a photoresist. It is preferable to use a method of forming a pattern by using a selective plating method with a mask material.

Further, the thin-film magnetic head used in such a magnetic disk device also needs to satisfy the relationship of ΔCW of 0 <ΔCW ≦ 5000 / Tr (Tr indicates the track density of the magnetic disk).

Further, a recording system using such a magnetic disk device can be connected to a computer system or the like as a higher-level device, and a system having a large storage capacity can be obtained.

The thin-film magnetic head according to the present invention has a non-magnetic insulating layer on both sides and upper ends of the lower magnetic core, and has the shortest magnetic gap at the bottom of the groove in the lower magnetic core formed by the non-magnetic insulating layer. It is preferred to form a part.

[Action]

The present invention relates to a magnetic core exposed on a surface facing a recording medium of a thin-film magnetic head used for a high recording density magnetic disk apparatus having a magnetic disk having a track density of 1800 tracks or more per inch. This clarifies the requirements that the shape should have.

That is, the difference between the length of the upper magnetic core facing the magnetic gap (hereinafter referred to as “CWU”) and the length of the lower magnetic core facing the magnetic gap (hereinafter referred to as “CWD”) is determined by the magnetic disk device. By optimizing according to the track density of the magnetic disk possessed by, for high recording density,
The S / N ratio is increased to improve the off-track characteristics.

The present inventors studied the magnitude of the magnetic field generated from the magnetic core by using a thin-film magnetic head having a magnetic core having a shape as shown in FIG.

As a result, as shown in FIG. 4 (1), the flying height of the thin-film magnetic head is on an extension of the magnetic gap, that is, in the Z direction in the figure, in a direction perpendicular to the recording medium facing surface (FIG. 4 (2)). )
It has been found that the magnetic field strength in the longitudinal direction of the recording medium at a point farther away decreases as the distance in the Z direction on the extension of the magnetic gap increases.

When the difference between CWU and CWD (hereinafter referred to as “ΔCW”) increases, the distances W ₀ , W ₁ , and W ₂ in the Z direction at which _a certain magnetic field strength Ha is obtained increase, but gradually increase by W. _It was found from FIG. 4 (3) that it approached ₂₀₀ .

The subscripts 0, 1, 2, and 200 indicate the value of ΔCW, and
It can be seen that there is a limit to the oozing magnetic field even if the difference in ΔCW is large.

The values of the distances W ₀ , W ₁ , and W ₂₀₀ correspond to the oozing width of the magnetic field generated from the magnetic core, respectively.

Accordingly, the relationship between the value of ΔCW and the bleeding width of the magnetic field is determined, and accordingly, the relationship between the signal intensity and ΔCW when a thin film magnetic head having a constant track width is used is determined.

 The result is shown as a curve S in FIG.

On the other hand, as a result of examining the noise intensity at the time of reading,
As the value of ΔCW increases, crosstalk noise and off-track noise from adjacent tracks increase, and the fifth
It has the relationship shown in the curve N in the figure.

Accordingly, the relationship between the signal-to-noise ratio (S / N ratio) representing the performance of the magnetic disk device and ΔCW is as shown in FIG. 6, and in the range of 0 <ΔCW <ΔCW _lim , ΔCW = 0. It has been found that the S / N ratio can be increased as compared with the case.

Furthermore, when the track density of the magnetic disk is increased,
As also shown in FIG. 6, the S / N ratio decreased, and
The value of ΔCW _lim was also found to be reduced to ΔCW _lim '.

Therefore, the track density (Tr) of the magnetic disk and ΔCW _lim
As a result, as shown in FIG. 7, the value of ΔCW _lim was almost proportional to the reciprocal of the track density (1 / Tr), and the proportional coefficient was almost 5,000.

Also, considering the value of ΔCW _lim for the left and right ends, CWU and
Each difference at the left and right ends from CWD (hereinafter “ΔC
Examining the relationship between W ′ ”) and the reciprocal of the track density (1 / Tr), we found that the proportional function was approximately 2500.

Therefore, in a magnetic disk device having a high recording density of 1800 or more tracks per inch, the magnetic disk must satisfy the condition of 0 <ΔCW ≦ 5000 / Tr or 0 <ΔCW ′ ≦ 2500 / Tr. , ΔCW = 0 or ΔCW ′ = 0, it is considered that the S / N ratio can be increased.

〔Example〕

FIG. 1 is a schematic view of a magnetic disk device showing one embodiment of the present invention.

The magnetic disk device has components indicated by reference numerals 1 to 8 shown in FIG. 1 and a voice coil motor control circuit.

 Reference numeral 1 denotes a base, and reference numeral 2 denotes a spindle.

A plurality of disk-shaped magnetic disks 4 are attached to one spindle as shown in the figure.

FIG. 1 shows an example in which five magnetic disks are provided on one spindle, but the number is not limited to five.

Further, a plurality of magnetic disks provided with a plurality of magnetic disks on one spindle may be provided.

Reference numeral 3 denotes a motor for driving the spindle 2 and rotating the magnetic disk.

Reference numeral 5 denotes a magnetic head for data, and reference numeral 5a denotes a magnetic head for positioning.

Reference numeral 6 denotes a carriage, reference numeral 7 denotes a voice coil, reference numeral 8
Is a magnet.

The voice coil motor is constituted by the voice coil 7 and the magnet 8.

The head is positioned by the elements denoted by reference numerals 6, 7, and 8.

The voice coil 7 and the magnetic heads 5 and 5a are connected via a voice coil motor control circuit.

In FIG. 1, the host device indicates, for example, a computer system.

FIG. 2 is an enlarged view of a magnetic core exposed on the surface of the thin-film magnetic head 5 facing the magnetic disk 7 in FIG.

 FIG. 11 shows a configuration diagram of the thin-film magnetic head.

Reference numeral 1 denotes a substrate, and reference numeral 2 denotes a base film for forming a flat surface.

An upper magnetic core 4 is deposited on a base film 2 via a lower magnetic core 3 made of a magnetic material and an insulating film 6 constituting a magnetic gap G.

A conductor coil 5 is formed inside the insulating film 6 to electrically induce a magnetic field.

Reference numeral 7 denotes a protective film, which is deposited on the upper magnetic core 4.

The magnetic core shown in FIG. 2 shows a hatched portion in FIG.

FIG. 2 shows the shape of the magnetic core of the portion of the thin film magnetic head exposed to the recording medium facing surface used in a magnetic disk device having a track density of 2500 tracks per inch to which the present invention is applied.

FIG. 2 (a) shows a magnetic core made of a magnetron sputtering method as a magnetic core and exposed on a surface facing a thin-film magnetic head magnetic disk made by patterning the magnetic material with an ion beam etching method. It shows the shape of the magnetic core in the portion indicated by the dotted line.

In FIG. 2, the length (CWU) of the side of the upper magnetic core 11 facing the magnetic gap 12 is 6.9 μm, and the length of the side of the lower magnetic core 13 facing the magnetic gap 12 (CWD) is 8.7 μm.

The upper magnetic core 11 and the lower magnetic core 13 are arranged so as to be symmetric about the same axis in the writing and reading directions with respect to the magnetic disk facing surface.

Using this thin-film magnetic head, we examined the write and read characteristics for a magnetic disk device.
= 6.9 μm, the S / N ratio increased by 4.3% as compared with the case of using a magnetic head with CWD = 9.1 μm.

On the other hand, FIG. 2 (b) shows that the lower magnetic core 16 is made of a magnetic material manufactured by a magnetron sputter method, is patterned by an ion beam etching method, and the upper magnetic core 14 is formed by using a photoresist as a mask material. This figure shows the formation of a thin-film magnetic head formed by pattern formation by the plating method.

Length of the side of the upper magnetic core 14 facing the magnetic gap 15 (CW
U) is 7.0 μm, and the magnetic gap 15 of the lower magnetic core 16 is
Is 8.6 μm.

The difference between the left and right ends of the magnetic core is
They were 0.9 μm and 0.7 μm.

Using this thin-film magnetic head, we examined the write and read characteristics for a magnetic disk device.
The S / N ratio was increased by 8.6% as compared with the case of using a magnetic head having a CWD = 7.0 μm and CWD = 9.5 μm.

FIG. 8 shows the shape of the magnetic core of the portion of the thin film magnetic head exposed to the recording medium facing surface using a magnetic disk device having a track density of 3000 tracks per inch to which the present invention is applied.

This figure shows the shape of a thin-film magnetic head produced by using a magnetic material produced by a magnetron sputter method as a magnetic core and forming a pattern by ion beam etching.

After the lower magnetic core 83 was manufactured, a nonmagnetic insulating material 84 was deposited on the side and upper ends thereof, and a groove 85 was formed on the lower magnetic core 83 to form a magnetic gap film 82.

By using this method, the CWU dimensions could be controlled with high accuracy.

Length of the side of the upper magnetic core 81 facing the magnetic gap (CW
U) is 6.0 μm, and the length (CWD) of the lower magnetic core 83 facing the magnetic gap is 7.2 μm.

Using this thin-film magnetic head, we examined the write and read characteristics for a magnetic disk device.
The S / N ratio was increased by 8.6% as compared with the case of using a magnetic head having a CWD = 6.0 μm and CWD = 8.0 μm.

〔The invention's effect〕

According to the present invention, for a magnetic disk device having a track density of 1800 or more tracks per inch, a high S /
Since a thin-film magnetic head exhibiting an N ratio can be achieved, a magnetic disk device having a high recording density can be realized.

Further, the requirements to be provided, such as the shape of the magnetic core of the thin-film magnetic head used in such a high-recording-density magnetic disk device, were clarified.

Further, a thin-film magnetic head and a magnetic disk used in such a high-recording-density magnetic disk device have been clarified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an embodiment of a magnetic disk device according to the present invention, and FIGS. 2, 3 and 8 are thin films showing an embodiment of the present invention. FIG. 4 is a front view showing the shape of the magnetic core on the surface of the magnetic head facing the magnetic disk, FIG. 4 is a characteristic diagram showing the relationship between the extension distance of the magnetic gap and the magnetic field strength, and FIG. FIG. 6 is a characteristic diagram showing the relationship between the difference between the core and the signal and noise intensity, FIG. 6 is a characteristic diagram showing the relationship between the difference between the upper magnetic core and the lower magnetic core, and the S / N ratio, and FIG. FIG. 9 is a characteristic diagram showing the relationship between the reciprocal of the track density and the limit value of the difference between the upper magnetic core and the lower magnetic core of the thin-film magnetic head. FIG. Fig. 10 shows the relationship between tracks on magnetic disks and thin-film magnetic heads. , FIG. 11 is a configuration view of a thin film magnetic head. 11,14: Upper magnetic core, 12,15: Magnetic gap, 13,1
6 ... Lower magnetic core.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatoshi Tsuchiya 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory Co., Ltd. (72) Inventor Eiji Ashida 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research, Ltd. In-house (72) Inventor Makoto Morishiri 4026 Kuji-cho, Hitachi City, Ibaraki Pref.Hitachi, Ltd.Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Hideki Yamazaki 4026 Kuji-cho, Hitachi City, Ibaraki Pref.Hitachi, Ltd. Sugita Sen 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd.Hitachi Laboratory, Hitachi, Ltd. (72) Inventor Hiroshi Fukui 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd.Hitachi Laboratory, Hitachi, Ltd. 4026 Kuji-cho Hitachi Research Laboratory, Ltd.Hitachi Laboratory (72) Inventor Makoto Aihara 4026 Kuji-cho, Hitachi, Japan Hitachi, Ltd.Hitachi Research Laboratory, Ltd. (72) Inventor Makoto Saito 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside, Hitachi, Ltd.Central Research Laboratory, Inc. (72) Inventor Shun-ichiro Kuezuka, Kanagawa Prefecture 2880 Kozu, Hitachi, Ltd.Odawara Plant, Hitachi, Ltd. (72) Inventor Hiroshi Ikeda 2880 Kofu, Odawara, Kanagawa Prefecture, Ltd.Odawara Plant, Hitachi, Ltd. (72) Tsubasa Saito 2880, Kozu, Kozuhara, Odawara, Kanagawa Prefecture Odawara factory

Claims (7)

(57) [Claims] A lower magnetic core; and an upper magnetic core formed on the lower magnetic core, one end of which contacts one end of the lower magnetic core and the other end of which faces the other end of the lower magnetic core via a magnetic gap. A conductor coil wound between the two magnetic cores so as to intersect with the magnetic circuit, and an insulating layer interposed between the upper magnetic core and the lower magnetic core;
In a thin-film magnetic head provided in a magnetic disk drive having a magnetic disk of 1800 TPI or more, the length of the side of the magnetic core facing the magnetic gap of the thin-film magnetic head exposed on the surface facing the magnetic disk has an upper side. Difference between magnetic core and lower magnetic core, difference between both sides (ΔCW, unit μm)
Satisfies the relationship of 0 <ΔCW ≦ 5000 / Tr. 2. A magnetic disk for recording information, a thin-film magnetic head for writing and reading information to and from the magnetic disk, a unit for rotating the magnetic disk, and a unit for positioning the thin-film magnetic head. In the magnetic disk drive, the length of the side of the magnetic core facing the magnetic gap of the thin-film magnetic head exposed on the surface facing the magnetic disk differs between the upper magnetic core and the lower magnetic core, and the difference between the two sides is different. (ΔC
W, unit μm) is magnetic disk track density (Tr) 1800TP
A magnetic disk drive, which satisfies the relationship of 0 <ΔCW ≦ 5000 / Tr. 3. A magnetic disk for recording information, a thin-film magnetic head for writing and reading information to and from the magnetic disk, a unit for rotating the magnetic disk, and a unit for positioning the thin-film magnetic head. In the magnetic disk drive provided, the magnetic disk has a track density (Tr) of 1800 tracks or more per inch, and the thin-film magnetic head has an upper portion exposed on a surface facing the magnetic disk. The difference (ΔCW ′, unit μm) at the left and right ends of the length (CWU) of the side facing the magnetic gap of the magnetic core and the length (CWD) of the lower magnetic core facing the magnetic gap is 0 < A magnetic disk drive characterized by satisfying a relationship of ΔCW ′ ≦ 2500 / Tr. 4. A magnetic disk for recording information, a thin-film magnetic head for writing information to the magnetic disk, a magnetic head for reading written information, means for rotating the magnetic disk, and the thin film A magnetic head positioning means, comprising: a magnetic disk having a track density (Tr) of not less than 1800 tracks per inch, and The difference (ΔCW, unit) between the length of the side facing the magnetic gap of the upper magnetic core (CWU) exposed on the surface facing the disk and the length of the side facing the magnetic gap of the lower magnetic core (CWD) μm) satisfies the relationship of 0 <ΔCW ≦ 5000 / Tr. 5. A track density (Tr) of 1800 for recording information.
A magnetic disk device comprising: a magnetic disk having TPI or more; a thin-film magnetic head for writing and reading information to and from the magnetic disk; a unit for rotating the magnetic disk; and a unit for positioning the thin-film magnetic head In the thin-film magnetic head, the length of the side facing the magnetic gap of the magnetic core exposed on the surface facing the magnetic disk differs between the upper magnetic core and the lower magnetic core, and the difference between both sides (ΔCW,
A magnetic disk device characterized by satisfying the following relationship: 0 <ΔCW ≦ 5000 / Tr. 6. A head disk assembly (HDA) for magnetically writing or reading, a W / R circuit for switching between writing and reading, and joining the HDA to a host device via the W / R circuit. A magnetic disk device comprising: a magnetic disk for recording information; a thin-film magnetic head for writing or reading information to and from the magnetic disk; and means for rotating the magnetic disk. And a positioning means for the thin-film magnetic head, wherein the magnetic disk has a track density (Tr) of 1800 tracks or more per inch, and the thin-film magnetic head faces the magnetic disk. Length of the side facing the magnetic gap of the upper magnetic core (CWU) exposed on the surface and the length of the side facing the magnetic gap of the lower magnetic core The difference between the CWU) (ΔCW, the unit [mu] m) magnetic disk device characterized by satisfying the relationship of 0 <ΔCW ≦ 5000 / Tr. 7. A method for recording and reproducing information using a magnetic disk device, comprising: rotating a magnetic disk having a track density (Tr) of 1800 tracks or more per inch; and writing information to the magnetic disk. Alternatively, a thin-film magnetic head for reading is accessed to the magnetic disk, and the thin-film magnetic head is exposed on the surface of the thin-film magnetic head facing the magnetic disk. Information is magnetically written in the shorter width (track width) of the length of the upper magnetic core facing the magnetic gap (CWU) or the length of the lower magnetic core facing the magnetic gap (CWD). Again, a thin-film magnetic head for writing or reading information to or from the magnetic disk is accessed by accessing the disk, and the information written to the magnetic disk at the track width is compared with the difference between CWU and CWD ( (CW) 0 <ΔCW ≦ 5000 / Tr, using a thin-film magnetic head, and reading out a wide area by the amount of the magnetic field bleeding in ΔCW.