JP2703079B2 - Magnetic disk device 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 / reproducing information in the magnetic disk device, and particularly to a large-sized device suitable for use as an external recording device of a computer. The present invention relates to a high-capacity magnetic disk device, a thin-film magnetic head used in the magnetic disk device, and a method of writing and reading information in the magnetic disk device.

[Conventional technology]

As the storage capacity of computers has increased, the storage capacity of magnetic disk devices has tended to increase.

As a prior art relating to a magnetic disk device, for example, Japanese Patent Application Laid-Open No. 60-133501 discloses that a magnetic disk is provided with one slider so that an outer track of the magnetic disk can be stored at a high recording density in the same manner as an inner track. It describes that recording is performed at the same linear density on the outer circumference and the inner circumference using a magnetic head having a plurality of head cores. Japanese Patent Application Laid-Open No. 57-210403 describes that data is written to tracks on a magnetic disk at different frequencies, thereby optimizing the capacity of individual tracks and increasing the storage capacity as a whole. .

[Problems to be solved by the invention]

All of the above-mentioned conventional techniques relating to magnetic disk devices are intended to increase the storage capacity of the magnetic disk itself, and consider how to configure the device to increase the storage capacity of the entire magnetic disk device. It was not done.

An object of the present invention is to clarify a configuration to be provided as a magnetic disk device having a total storage capacity of 60 gigabytes or more, particularly 60 to 120 gigabytes, and to provide such a magnetic disk device.

Another object of the present invention is to provide a thin-film magnetic disk suitable for use in a magnetic disk device having a storage capacity of 60 gigabytes or more.

It is another object of the present invention to provide a thin-film magnetic head suitable for use in a magnetic disk device having a storage capacity of 60 gigabytes or more.

Still another object of the present invention is 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 includes a plurality of head disk assemblies each having a plurality of thin film magnetic disks mounted on one rotating shaft, and has a thin film magnetic head for writing and reading information on and from the thin film magnetic disk. . The thin-film magnetic disk has a track density of more than 1800 tracks per inch and a linear recording density of more than 70 kilobits, and the rotation for rotating the innermost circumference of the thin-film magnetic disk at a peripheral speed of more than 3 m per second. It has shaft driving means.

The present invention is based on the idea that in order to increase the storage capacity without significantly increasing the size of the magnetic disk device, it is necessary to increase the surface recording density of the thin-film magnetic disk and increase the data transfer speed.

The areal recording density of thin-film magnetic disks is 12 per square inch.
It has been found that the total storage capacity of the magnetic disk device can be 60 to 120 gigabytes by setting the data transfer rate to 0 to 200 megabits and the data transfer speed to 6 to 9 megabytes / second.
In order to realize these, it has been found that it is desirable to set the above-mentioned track density, linear recording density and disk peripheral speed. Pole thickness (P _T ), saturation magnetic flux density (B _S ) of magnetic head core, and recording wavelength (λ) for thin film magnetic head
And, at a recording wavelength of 0.3 to 0.97 μm, It has been found that writing and reading to and from the thin-film magnetic disk can be performed by using one satisfying the following expression.

A magnetic disk device generally used as an external storage device of a computer is usually housed on a floor having a size of 0.5 to 1.5 m square with a height not exceeding 2 m in many cases. Therefore, it is desirable that the magnetic disk device can be accommodated in the range of the space and the storage capacity can be increased.

The track density and linear recording density of the thin-film magnetic disk specified in the present invention are extremely important for achieving a storage capacity of 60 gigabytes or more in the above-mentioned space.

In the present invention, a plurality of disk-shaped thin-film magnetic disks are mounted on a single rotating shaft to form a head disk assembly, and a plurality of such head disk assemblies are provided to provide a magnetic disk device. It is desirable to constitute. It is desirable that the diameter of the thin film magnetic disk be 3.5 to 11 inches. With this size, 0.5
Eight head disk assemblies can be stored in a floor space of about 1.5m square and a storage space of about 2m height.

If the diameter of the thin-film magnetic disk is too small, the linear recording density must be increased, making recording and reproduction difficult.
On the other hand, if it is too large, the mounting density of the thin-film magnetic disk cannot be increased, and it is also difficult to increase the sliding speed of the thin-film magnetic disk. The diameter of the thin film magnetic disk of 3.5 to 11 inches is extremely effective for increasing the areal recording density of the thin film magnetic disk and increasing the data transfer speed.

With eight head disk assemblies, the storage capacity per head disk assembly would need to be about 7.5 gigabytes or more. If both sides of the thin-film magnetic disk are used for writing information and the entire 15 sides are used, the storage capacity per side is about 0.5 GB or more. The portion of the thin-film magnetic disk that is actually used for writing information is at most about 4 cm from the outer periphery. In order to realize the above-mentioned 0.5 GB using such a thin-film magnetic disk, it is necessary to have a track density of 1800 tracks or more per inch and a linear recording density of 70 kilobits or more per inch.

Even if the storage capacity of the magnetic disk device is increased, if much time is required for writing and reading information, there is little or no advantage in increasing the storage capacity. In parallel with the increase in capacity, it is necessary to increase the speed of writing and reading information, that is, the speed of data transfer. To achieve a storage capacity of 60 to 120 gigabytes in a magnetic disk device having a thin-film magnetic disk with an areal recording density of 120 to 200 megabits per square inch, the data transfer rate should be 6 to 9 megabytes / second. desirable. This makes it possible to increase the storage capacity without reducing the information processing speed.

The surface recording density can be represented by the product of the track density and the linear recording density, and the data transfer speed can be represented by the product of the linear recording density and the peripheral speed of the thin-film magnetic disk.

Using a thin film magnetic disk with a diameter of 3.5 to 11 inches,
To achieve a track density of 1800 or more tracks per inch, the pitch between tracks must be 14.1 μm or less, and a guard band of about 1 to 4 μm is provided to avoid mutual interference between tracks. Therefore, the track width is desirably 11 μm or less.

The data access time (predetermined time) needs to be reduced as the data transfer rate increases, and in the present invention, it is desirable that the average be 10 ms or less. The disk rotation speed and the rotation waiting time of the thin-film magnetic head are desirably 3500 rpm or more and the rotation waiting time is 10 ms or less on average from the viewpoint of the data transfer speed. Here, the rotation waiting time means that the thin-film magnetic head that has moved to a predetermined track position is stationary in order to write information at a predetermined position on the track or read information from the predetermined position. Means the time you are waiting for.

To realize the large-capacity magnetic disk device of the present invention, the configuration of the thin-film magnetic disk is extremely important.

The thin-film magnetic disk is formed by manufacturing a magnetic film on at least one surface of a non-magnetic substrate such as aluminum by other means such as a sputter or plating. Coercivity becomes important.

Specifically, a linear recording density of 60 kilobits or more per inch is about 0.97 μm or less at a recording wavelength. In the case of a thin-film magnetic disk, the magnetization reversal width is approximately a∝t _mag · Mr
/ Hc. Here, a is the magnetization reversal width, t _mag is the magnetic film thickness, Mr is the residual magnetization of the magnetic film, and Hc is the coercive force of the magnetic film. To increase the linear recording density, it is essential to reduce the width of the magnetization reversal. As can be seen from the above equation, the magnetization reversal width can be reduced by reducing the residual magnetization of the magnetic film and increasing the coercive force of the magnetic film. If the residual magnetization of the magnetic film is reduced, the head output is reduced, so that it cannot be reduced too much. Further, it is desirable that the magnetic film thickness is made thinner, and the lower limit is 0.04 to 0.06 μm from the viewpoint of film production. Therefore, the coercive force of the magnetic film must be increased. The coercive force of the magnetic film is at least 1.8 kE and the magnetic magnetization of the magnetic film is about 15 kGauss, so that the recording wavelength is 0.97μ.
m or less.

It is desirable to provide a lubricating film on the surface of the magnetic film of the thin-film magnetic disk in order to prevent abrasion damage due to contact with the magnetic head and sticking during operation of the apparatus. If the lubrication film thickness is too thick, this thickness becomes a substantial space,
Since it is a cause of deteriorating the recording / reproducing characteristics, it is preferable that the thickness be 0.05 μm or less.

In a magnetic disk device, the floating space of the thin-film magnetic head also affects the recording density. In order to increase the recording density, it is desirable to reduce the flying space, and in the present invention, it is desirable that the flying space is 0.15 μm or less.

The magnetic disk device of the present invention can write and read information using a general inductive thin film magnetic head. However, more preferably,
It is desirable to overwrite using a thin-film magnetic head capable of overwriting, particularly a magnetic head capable of overwriting less than -22 dB. When writing at the minimum frequency ₁ and overwriting at the maximum frequency ₂ , it is desirable that the ratio of the output of the remaining erased ₁ is −22 dB or less.
If it is larger than this, the effect of the unerased portion overwritten on the reproduced waveform appears strongly, and the error increases rapidly. Improving the reproduction characteristics of the magnetic disk device can be achieved by providing a waveform improving circuit to shape the reproduced waveform and sharpen the waveform. By doing so, the phase margin can be widened and errors can be reduced.

In the present invention, it is particularly desirable to use a thin film magnetic head having the following structure. That is, the lower magnetic film is formed on the lower magnetic film, and one end is in contact with one end of the lower magnetic film, and the other end is opposed to the other end of the lower magnetic film via the magnetic gap, and thereby, together with the lower magnetic film. An upper magnetic film forming a magnetic circuit having a magnetic gap in part;
With a conductor coil passing between both magnetic films and crossing the magnetic circuit, and at a recording wavelength of 0.3 to 0.97 μm, A thin film magnetic head having a pole thickness satisfying the following condition is used.

The present inventors have shown that the overwrite characteristics are significantly affected by the product of the pole thickness of the thin-film magnetic head and the saturation magnetic flux density of the magnetic core material. Then, in order to improve the overwrite characteristics, it has been clarified that the product of the pole thickness and the saturation magnetic flux density of the magnetic core material desirably has a predetermined relationship as shown in the above equation. The above equation is derived based on measurements of overwrite characteristics using dozens of types of thin film magnetic heads having different pole thicknesses and saturation magnetic flux densities of the magnetic core material.

If the track width of the thin-film magnetic head is reduced to increase the track density, the output will decrease in proportion to it. To compensate for this, it is desirable to increase the number of coil turns of the thin-film magnetic head to increase the output, and more specifically, it is desirable that the number of turns is 17 or more.

Thin-film magnetic heads produce a magnetic film on a non-magnetic substrate,
Finally, it is processed into a slider shape and used. In this case, as a substrate material, it is desirable to use ceramics such as alumina, zirconia, silicon carbide, and an oxide having a spinel structure such as MgAl ₂ O ₃ .

The load for pressing the thin-film magnetic head against the disk should be lighter for better slidability, especially 10g.
It is desirable to make the following.

It is desirable that one end surface of the slider of the thin-film magnetic head, especially one of the surfaces facing the thin-film magnetic disk be provided with a crown. This makes it possible to levitate the thin-film magnetic head by utilizing the entrainment of air into the crown portion.

The shape of the slider of the thin-film magnetic head can be used as a positive pressure slider shape in which the levitation force on the side close to the head core tip is weakened or a negative pressure slider shape in reverse.

As a magnetic core material of the thin film magnetic head, a magnetic material having a high saturation magnetic flux density, particularly
It is desirable to use a material having a saturation magnetic flux density higher than Tesla. Examples of such a magnetic material include nickel-iron crystalline, cobalt-based amorphous and crystalline, and iron-based crystalline alloys represented by Permalloy. Each of the upper and lower magnetic films may have a multilayer structure. In this case, a magnetic film and a nonmagnetic layer are alternately laminated to form a multilayer film. As the nonmagnetic film, an insulating film such as alumina or silicon oxide is desirable. When a non-magnetic film and a magnetic film are alternately laminated, it is desirable that the magnetic film thickness of each layer be the same. Of course, the magnetic film thickness of each layer may be changed. The total number of layers of the multilayer film is two or more, that is, a minimum, and two or more layers of one magnetic film and one nonmagnetic film. Magnetic films and non-magnetic films are alternately laminated to form a multilayer film, which not only improves the high-frequency permeability by reducing eddy currents, but also becomes close to a single magnetic domain, and reproduces output by suppressing domain wall movement. It is also effective for stabilization. Further, by using a magnetic material having a high saturation magnetic flux density, a high magnetic flux density and a strong magnetic field can be generated to improve the overwrite characteristics. As a means for forming the multilayer film, a spatter method, a plating method, or the like can be used.

In the magnetic disk device of the present invention, it is possible to write with an inductive thin-film magnetic head having a thick pole and use a thin-film magnetic head having a high-permeability magnetic core, using two types of read head and write head. It is. By doing so, the overwrite characteristics can be improved and the read performance can be improved. Also, by using an MR element for the read head, it is possible to increase the ratio S / N between the value N of the remaining erased signal after overwriting and the value S of the newly written signal.

The thin-film magnetic head may be brought into contact with the thin-film magnetic disk when the operation of the magnetic disk device is stopped, and levitated with the rotation of the thin-film magnetic disk. The flying height may be controlled after reaching the number of rotations. In particular, the latter method is suitable for suppressing wear of the thin-film magnetic disk surface or wear of the head, and is a desirable method.

As a specific problem when reading information using a thin-film magnetic head, there is a “Uyghur”, which is also described in JP-A-58-194125. This is a phenomenon that the reproduction output fluctuates irregularly, and causes a reading error. In order to suppress this Uyggle phenomenon, it is desirable that the intensity of the external magnetic field be 3 Oersted or less.

In addition, since the track width of the thin-film magnetic head is reduced in order to increase the recording density, it is desirable to use an embedded servo system in which servo information is also written on the data surface instead of being aligned on the servo surface.

[Action]

An object of the present invention is to clarify conditions to be provided as a magnetic disk device having a recording capacity of 60 gigabytes or more, particularly a magnetic disk device having a recording capacity of 60 to 120 gigabytes. That is, assuming that the areal recording density is 120 to 900 megabits per square inch, the pole thickness (P _T ), the saturation magnetic flux density (B _S ) of the magnetic head core, and the recording wavelength (λ) are 0.3 to 0.97.
In μm, It is necessary to write or read with a thin film magnetic head that satisfies the following equation, and furthermore, to make the data transfer rate 6 to 9 megabytes / second in order to put a magnetic disk device having a storage capacity of 60 to 120 gigabytes to practical use. It is clear.

In addition, in order to increase the capacity, the linear recording density, the track density, and the disk rotation speed of the thin-film magnetic disk are important in order not to increase the diameter of the thin-film magnetic disk, and the relationship between them was clarified. Things.

The present invention is probably the first to examine and clarify what configuration must be provided for a large-capacity magnetic disk device having a storage capacity of 60 to 120 gigabytes.

In order to increase the storage capacity without increasing the size of the magnetic disk device, it is desirable to increase the storage density of the thin-film magnetic disk.

In order to increase the storage density of the thin-film magnetic disk, the configuration of the thin-film magnetic head for writing or reading information to or from the thin-film magnetic disk becomes extremely important. Specifically, in order to reduce the recording wavelength, it is necessary to use a thin film magnetic disk having a high coercive force, and it is required to increase the strength of the magnetic field emitted from the tip of the thin film magnetic head.
However, when the pole thickness is too large, there is a problem that the track width processing accuracy is deteriorated.

The present inventors have found that as a thin-film magnetic head, the pole thickness (P _T , unit: μm) and the saturation magnetic flux density (B _S , unit: Tesla) of the head core have a recording wavelength (λ, unit: μm) of 0.3 or more. , 0.97 or less, it has been found that writing and reading of a high recording density thin film magnetic disk can be achieved by using the one having the following relational expression.

By using a high saturation magnetic flux density material for the magnetic core so as to satisfy the above relational expression, the pole thickness can be reduced and the track width processing accuracy can be improved. As a result, a high recording density of the thin-film magnetic disk can be achieved.

When the recording wavelength is reduced, it is effective to reduce the flying height of the thin-film magnetic head relative to the thin-film magnetic disk surface so as to approach the thin-film magnetic disk surface, and to reduce the magnetic film thickness of the thin-film magnetic disk. It is effective to do.

In this way, even if the storage capacity of the magnetic disk device is increased, if the access time to data is slow,
The advantage of large capacity is small. Therefore, it is necessary to increase the data transfer speed, and the peripheral speed of the thin-film magnetic disk becomes important.

〔Example〕

FIG. 1 is a schematic perspective view of a magnetic disk device according to one embodiment of the present invention, showing a state where the magnetic disk device is housed in a predetermined space.

The head disk assembly (H
A head disk assembly unit (HDU) 103 is formed by the DA) 101 and the electronic circuit unit 102, and is housed inside the container 100. Further, an interface (not shown) with the computer is housed inside the container 100. HDU10
There are eight 3 and these are stored two by two in four steps. The length of one side of the bottom of the container 100 is 0.5 to 1.5 m, and the height is about
2m.

In FIG. 1, A and B show the flow of air for supplying clean air to the magnetic head and the magnetic disk.

FIG. 2 is a schematic diagram showing one embodiment of the present invention. FIG. 3 is an enlarged perspective view of the vicinity of the thin-film magnetic head 5 in FIG.

Reference numeral 1 is a base and 2 is a spindle. As shown in the figure, a plurality of disk-shaped thin-film magnetic disks 4 are mounted on one spindle.
Is attached. As shown in FIG. 3, the thin-film magnetic disk 4 has a magnetic film 4b provided on one or both surfaces of a non-magnetic disk 4a made of alumina or the like. The magnetic film 4b has a large number of track grooves. The areal recording density of the thin film magnetic disk 4 is 120 to 900 megabits per square inch.
The track density is desirably at least 1,800 tracks per inch, and the linear recording density is desirably at least 70 kilobits per inch. Then, within the range of the linear recording density and the track density, it is desirable that the surface recording density, which is the product of the two, be 120 to 900 megabits per square inch as described above.

By doing so, it is possible to increase the recording density without significantly increasing the diameter of the thin-film magnetic disk.

Even if the recording density is increased and the recording capacity of information is increased, if the data transfer speed is reduced by that amount, the usefulness is small. If the data transfer speed is 6 to 9 megabytes / second, data can be transferred in and out quickly. This data transfer speed is determined by the product of the peripheral speed of the thin-film magnetic disk and the linear recording density. Since the linear recording density is 70 kilobits per inch, a data transfer rate of 6 to 9 megabytes / second can be realized by setting the rotational speed of the disk to 3500 rpm or more in the case of a thin film magnetic disk having a diameter of 3.5 to 11 inches. The rotation speed of 3500 rpm is a general rotation speed employed in a normal magnetic disk device, and is very easy to realize.

FIG. 2 shows an example in which five thin-film magnetic disks are provided on one spindle, but the number is not limited to five. A plurality of thin-film magnetic disks provided on one spindle as described above may be provided.

Reference numeral 3 denotes a motor for driving the spindle 2 and rotating the thin-film 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, and reference numeral 8 denotes a magnet. The voice coil motor is constituted by the voice coil 7 and the magnet 8. The heads are positioned by the elements denoted by reference numerals 6, 7, and 8. The voice coil and the magnetic heads 5, 5a are connected via a voice coil motor control circuit. In FIG. 2, the host device indicates, for example, a computer system.

The read / write circuit identifies write and read information and sends a signal to the magnetic disk device. The interface section connects the host device and the magnetic disk device. A system having the host device and the magnetic disk device is an information processing system.

FIG. 3 is an enlarged view of the thin-film magnetic head and the thin-film magnetic disk. Reference numeral 11 is a slider, reference numeral 9 is a recording wavelength,
Reference numeral 10 indicates a disk rotation direction. t represents the flying height of the thin-film magnetic head, and Tp represents the track pitch.

In a magnetic disk device, new information is written and used on a recording medium on which information has already been written. This is called overwriting. At that time, the previously written information is detected as noise with respect to the newly written information. Therefore, in order to write new information on a medium, it is required to generate a magnetic field necessary for magnetizing the thin-film magnetic disk from the tip of the thin-film magnetic head. In particular, in a large-capacity magnetic disk device, this overwrite characteristic becomes important.

The strength of the magnetic field emitted from the tip of the thin-film magnetic head needs to be increased as the coercive force of the magnetic film of the thin-film magnetic disk increases. Therefore, using a thin-film magnetic disk having several coercive forces, the relationship between the noise characteristic of an overwrite required for a magnetic disk device and the magnetic field intensity generated from a magnetic head was investigated, and the magnetic disk device malfunctioned. Not examined the relational expression.

FIG. 10 schematically shows the structure of the tip of the magnetic core of the thin-film magnetic head used in the magnetic disk device of the present invention.
Reference numeral 36 denotes a pole thickness, and a length at which the lower magnetic film 31 and the upper magnetic film 32 are parallel to each other at the head end is a magnetic gap depth 38. Numeral 34 is the thickness of the disk-facing surface of the lower magnetic film, numeral 35 is the thickness of the upper magnetic film, and numeral 33 is the magnetic gap length. 37 is a conductor coil. In a large-capacity magnetic disk device, an overwrite method of directly writing new information on already written information is important. At the time of new writing, information already written remains as noise for new information, but its value is required to be a small value of -22 dB or less.

Therefore, recording wavelength 0.68 μm, flying height 0.1 μm, magnetic film thickness 0.0
6μm thin-film magnetic disk medium (film production by spatter method)
The relationship between the coercive force of the thin-film magnetic disk and the magnetic field strength generated from the thin-film magnetic head was examined. The results obtained are shown in FIG. From these results, it has been found that the relational expression of H _X ≧ H _C +800 must be satisfied in order to obtain the required overwrite characteristics. Here, X _X magnetic field strength generated from the magnetic head, H _C is the coercivity of the thin film magnetic disk. It has been found that it is important to increase the pole thickness in order to increase the magnetic field intensity generated from the thin-film magnetic head so as to satisfy the above relational expression. This is because, as shown in FIGS. 5 (a) and 5 (b), the thicker the pole,
This is because the magnetic flux emitted from the tip of the magnetic core toward the thin-film magnetic disk becomes stronger.

The storage capacity of a magnetic disk device has been increasing as the performance of electronic computers has increased. One means of achieving higher performance of this magnetic disk device is to shorten the recording wavelength.

Therefore, first, for a recording wavelength of 0.68 μm, a permalloy having a saturation magnetic flux density of 1 Tesla was used as the magnetic core material of the thin-film magnetic head, and the sum of the upper magnetic film, the lower magnetic film, and the magnetic gap length (pole thickness). ) And overwrite characteristics. The obtained result is the sixth
Shown in the figure. From FIG. 6, it was found that a higher value was obtained for the overwrite characteristic as the pole thickness increased. As described above, since the overwrite characteristic is required to be −22 dB or less, it has been found that the pole thickness needs to be 5.5 μm or more. Based on this result, considering the variation of the coercive force of the magnetic film and the pole thickness of the thin film magnetic disk, the write and read characteristics are satisfied and the pole length is used as a thin film magnetic head for a magnetic disk device with a recording wavelength of 0.68 μm. 8.6 μm was adopted.

Next, it was studied to further shorten the recording wavelength and improve the recording density.

To sharpen the write magnetic field emerging from the tip of the thin-film magnetic head, decrease the magnetic gap depth,
It turned out that it was necessary to reduce the gap length. However, as a result of studying in accordance with this policy, it is difficult in terms of processing technology to control the magnetic gap depth to about 1 μm or less. If it is attempted to cover that amount with the pole thickness, it takes time to prepare the film and the track width processing accuracy deteriorates. That is, when the recording wavelength is small, it is practically difficult to secure the overwrite characteristics. Therefore, in order to secure the overwrite characteristics and allow a margin in the dimensional accuracy of the magnetic gap depth, the application of a saturated magnetic flux density magnetic material for the magnetic core material was studied.

As a result, the effect of the high saturation magnetic flux density magnetic material effectively increases the pole thickness (P _T ) described above, which results in a saturation flux density of 1 Tesla compared to Permalloy. It was found that the value of Therefore, the recording wavelength is 1 μm
In order to secure the overwrite characteristics in the following, it has been found that the pole thickness can be reduced by the ratio of the above relational expression by using a high saturation magnetic flux density magnetic material for the magnetic core.

Next, it was studied to keep the above-mentioned _PT constant at 8.6 μm and to further narrow the magnetic gap length which is considered necessary for improving the recording density. As a result, when the magnetic gap length is made smaller, the magnetic field distribution to the medium becomes steeper, but the magnetic field strength decreases. Therefore, in order to keep the gap depth large while keeping the overwrite characteristic at -22 dB or less, it is effective to keep the gap length of 0.2 to 0.4 μm which has been studied so far.

The situation of magnetic recording is determined by the total of the magnetic medium and the magnetic head. Therefore, using a thin-film magnetic head with a pole thickness of 8.6 μm, overlooking the future improvement in recording density, the recording wavelength and the magnetic film thickness of the thin-film magnetic disk with overwrite characteristics of -22 dB or less, and the thin-film magnetic disk and thin-film magnetic The relationship with the distance from the head (flying height) was examined.

The obtained results are shown in FIGS. 7 and 8. FIG. 7 shows the relationship between the recording wavelength and the magnetic film thickness of the thin-film magnetic disk, and FIG. 8 shows the relationship between the recording wavelength and the distance (flying height) between the thin-film magnetic disk and the thin-film magnetic head. From these figures, it can be seen that it is better to reduce the magnetic film thickness of the thin-film magnetic disk and to reduce the flying height of the thin-film magnetic head in order to cope with higher density. However, the magnetic film thickness is 0.04 to 0.06 μm in consideration of the fluctuation at the time of film production. The lower limit is about 0.05 μm from the viewpoint of sliding resistance of the flying height.
As shown in the figure, the minimum recording wavelength is 0.3 μm.

Here, the flying height hg, magnetic film thickness t _mag of the thin film magnetic disk
The recording wavelength dependence was determined based on the values of 0.68 μm, the flying height of 0.1 μm, the magnetic film thickness of the thin-film magnetic disk of 0.04 μm, and the coercive force of 2500 Oersteds, which are one of the recording wavelengths studied so far.

Flying height hg is defined as hgo Magnetic film thickness t _mag of the thin film magnetic disk is Indicated by Here, lambda is the recording wavelength, the lambda _b is the reference recording wavelength. Further, the magnetic field intensity H _X required a thin film magnetic head to realize the following overwrite characteristic -22dB I understood what was shown.

Actually, using the above relational expression and the relational expression between H _X and H _C ,
The G _d and 1 [mu] m, the _{hg b,} t magb, Paul thickness P _T at the reference value of lambda _b is 8.6 [mu] m, the B _S is calculated using the 1 Tesla A relationship is obtained.

Based on this result, the relationship between the recording wavelength at which an overwrite of -22 dB or less was obtained, the pole thickness, and the product of the saturation magnetic flux density of the magnetic core material was determined. The results obtained are shown in FIG.
Above this line, it was found that high-performance recording with an overwrite characteristic of -22 dB or less could be performed.

〔The invention's effect〕

According to the present invention, an extremely large-capacity magnetic disk device having a storage capacity of 60 to 120 gigabytes can be realized.

Further, a thin-film magnetic head and a thin-film magnetic disk used in such a large-capacity magnetic disk device have been clarified.

[Brief description of the drawings]

1 is a schematic perspective view showing one embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing one embodiment of a magnetic disk device of the present invention, and FIG. 3 is a vicinity of the thin-film magnetic head of FIG. It is the perspective view which expanded. FIG. 4 is a characteristic diagram showing the strength of a head magnetic field required to overwrite the coercive force of the magnetic film of the thin-film magnetic disk, and FIGS. 5 (a) and (b) show the flow of magnetic flux at the tip of the head. FIG. 6 is a characteristic diagram showing the dependence of the overwrite and the resolution characteristic on the pole thickness, FIG. 7 is a characteristic diagram showing the relationship between the magnetic film thickness of the thin-film magnetic disk and the recording wavelength, and FIG. FIG. 9 is a characteristic diagram showing the relationship between the flying height and the recording wavelength, FIG. 9 is a characteristic diagram showing the relationship between the product of the pole thickness of the thin-film magnetic head and the saturation magnetic flux density of the magnetic core material, and the recording wavelength, and FIG. 10 is the tip of the thin-film magnetic head. It is sectional drawing of a part. 2 ... Spindle, 3 ... Motor, 4 ... Thin film magnetic disk, 5,5a ... Thin film magnetic head, 101 ... Head disk assembly.

Continued on the front page (72) Inventor Masanori Tanabe 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory, Ltd. (72) Inventor Moriaki Fuyama 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd. 72) Inventor Shinji Narushige 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd.Hitachi Research Laboratories Co., Ltd. (72) Inventor Sugita Shin Ibaraki Prefecture, Hitachi City 4026 Kuji-cho, Hitachi City Co., Ltd. Hitachi, Ltd. Hitachi Research Laboratory Co., Ltd. Yoshihiro 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Motoi Aoi 1-1280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Tsubasa Saito Kanagawa 2880 Kozu, Kodahara, Hitachi, Ltd.Odawara Plant, Hitachi, Ltd. (72) Inventor Hiroharu Kawakami 2880 Kozu, Kozuhara, Odawara, Kanagawa, Japan Inside Odawara Plant, Hitachi, Ltd. (72) Inventor Yoshikazu Tsuji 2880 Kokuzu, Odawara, Japan Stock Company, Ltd.Odawara Plant, Hitachi, Ltd. Inside the Odawara Plant of Hitachi, Ltd.

Claims (20)

(57) [Claims] 1. A magnetic disk drive comprising a thin-film magnetic head for writing and / or reading information to and from a thin-film magnetic disk for recording information, wherein said thin-film magnetic head forms a magnetic circuit across a magnetic gap. An upper magnetic film, a lower magnetic film, and a conductor coil intersecting the magnetic circuit. The pole thickness (P _T ) of the magnetic gap portion, the saturation magnetic flux density (B _S ) of the upper magnetic film and the lower magnetic film ), And the recording wavelength (λ) satisfies the following equation: [However, P _T is [mu] m, B _S Tesla, lambda is a is [mu] m] The magnetic disk apparatus characterized by said recording wavelength is 0.3～0.97Myuemu. 2. The recording medium according to claim 1, wherein the track density is 1.8 to 10 kilotracks per inch, the linear recording density is 70 to 220 kilobits per inch, and the area recording density is 120 to 900 megabits per square inch. A magnetic disk drive, comprising: a head disk assembly having a plurality of the thin film magnetic disks having at least one of the following on a single rotating shaft; and rotating means for rotating the magnetic disk. 3. A magnetic disk drive according to claim 1, wherein said thin-film magnetic disk has a diameter of 3.5 to 11 inches. 4. The magnetic disk drive according to claim 3, wherein the storage capacity of said thin-film magnetic disk is 7.5 to 60 gigabytes. 5. A magnetic disk drive according to claim 4, wherein said magnetic disk drive is housed in a container having a length and width of 0.5 to 1.5 m and a height of 2 m or less. 6. A magnetic disk drive according to claim 1, wherein both surfaces of said thin-film magnetic disk are recording surfaces. 7. A head disk assembly according to claim 3, wherein said thin-film magnetic disk comprises nine thin-film magnetic disks per head disk assembly, excluding an uppermost surface and a lowermost surface of said nine thin-film magnetic disks. A magnetic disk drive characterized in that at least 15 out of a total of 16 surfaces on both sides are used as recording surfaces. 8. The magnetic disk drive according to claim 4, wherein a total of eight head disk assemblies are provided. 9. A magnetic disk drive according to claim 1, wherein a floating space of said thin film magnetic head with respect to said thin film magnetic disk is 0.15 μm or less. 10. A magnetic disk drive according to claim 1, further comprising a thin-film magnetic head having an overwrite of -22 dB or less. 11. A magnetic disk drive according to any one of claims 1 to 10, further comprising a waveform improving rotation means for shaping a reproduction wavelength. 12. The magnetic disk drive according to claim 1, wherein in the thin-film magnetic head, the number of turns of the conductor coil is 17 or more. 13. The magnetic disk drive according to claim 1, wherein the weight of the thin-film magnetic head is 10 g or less. 14. The method according to claim 1, wherein at least one of the lower magnetic film and the upper magnetic film is formed of a multilayer film in which a total of two or more magnetic films and nonmagnetic films are alternately laminated. Characteristic magnetic disk drive. 15. The magnetic disk drive according to claim 1, wherein the saturation magnetic flux density of at least one of the lower magnetic film and the upper magnetic film is 1 Tesla or more. 16. A magnetic disk drive according to claim 1, wherein said read-only head is an MR head. 17. A magnetic disk drive according to claim 1, wherein said write-only head is an inductive type magnetic head comprising a high-permeability magnetic core. 18. A method for writing information on a thin-film magnetic disk for recording information by a thin-film magnetic head, wherein the thin-film magnetic head includes an upper magnetic film and a lower magnetic film forming a magnetic circuit across a magnetic gap; A conductor coil crossing the magnetic circuit, wherein a pole thickness (P _T ) of the magnetic gap portion, a saturation magnetic flux density (B _S ) of the upper magnetic film and the lower magnetic film, and a recording wavelength (λ) are as follows: Satisfy the formula of [However, _PT is μm, _BS is Tesla, and λ is μm] Track density of 1800 tracks or more per inch, linear recording density of 70 kilobits or more per inch and recording wavelength of 0.3
A method for writing information on a thin-film magnetic disk, characterized in that information is written with a thickness of 0.97 μm. 19. A recording / reproducing method for a magnetic disk device for writing and reading information on a thin film magnetic disk for recording information by a thin film magnetic head, wherein the thin film magnetic head forms a magnetic circuit across a magnetic gap. An upper magnetic film, a lower magnetic film, and a conductor coil intersecting the magnetic circuit; a pole thickness (P _T ) of the magnetic gap portion; and a saturation magnetic flux density (B _S ) of the upper magnetic film and the lower magnetic film. , And the recording wavelength (λ) satisfy the following equation: [However, P _T is [mu] m, B _S Tesla, lambda is [mu] m a is] the thin film magnetic disk is 3.5 to 11 inches in diameter,
A head disk assembly comprising a plurality of the thin film magnetic disks on one rotating shaft, a positioning means for the thin film magnetic head and an interface with a host device, and the thin film magnetic head based on a command from the host device. A magnetic disk drive, wherein the head is positioned and the information is written and read at a recording wavelength of 120 to 900 megabits / square inch and a recording wavelength of 0.3 to 0.97 μm while rotating the thin-film magnetic disk at 3500 rpm or more. Recording and playback method. 20. A thin film magnetic head comprising an upper magnetic film and a lower magnetic film forming a magnetic circuit across a magnetic gap, and a conductor coil intersecting the magnetic circuit, wherein a pole thickness of the magnetic gap portion ( P _T ), the saturation magnetic flux density (B _S ) of the upper magnetic film and the lower magnetic film, and the recording wavelength (λ) satisfy the following expressions: [However, P _T is [mu] m, B _S Tesla, lambda is the [mu] m] thin film magnetic head, wherein the recording wavelength is 0.3～0.97Myuemu.