JP2958187B2 - Magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive equipped with a composite type thin film magnetic head in which a recording head and a reproducing head are separated and integrally formed, and more particularly to a high-performance composite disk capable of industrial production. The present invention relates to a magnetic disk drive equipped with a thin-film magnetic head.

[0002]

2. Description of the Related Art A recent magnetic disk drive uses a magnetic disk having a high coercive force in order to achieve a high recording density with an increase in storage capacity, and a magnetic head for efficiently recording and reproducing data on the magnetic disk having a high coercive force. Is required. As a magnetic head for meeting such demands, a thin-film magnetic head having a small inductance and capable of obtaining a large reproduction output even at a high frequency is preferable. Particularly, recently, a recording head and a reproduction head are separated from each other. An integrated composite thin film magnetic head is employed. The composite thin-film magnetic head can be designed so that the recording head and the reproducing head exhibit their respective capabilities to the maximum. For example, the recording head can be designed without compromising the reproducing capability by (1) the magnetic core of the head. And (2) shortening the magnetic gap depth, (3) using a material having a high saturation magnetic flux density for the magnetic core, etc., to improve the recording performance, and the reproducing head has a magnetic resistance. By employing the effect type magnetic head, it is possible to obtain higher output sensitivity than the conventional inductive type head regardless of the peripheral speed of the magnetic disk. Incidentally, a composite type thin film magnetic head according to the prior art is disclosed in, for example, JP-A-59-30223,
JP-A-59-121617, JP-A-61-145
No. 718 and Nikkei Electronics, September 30, 1990 (No. 537), pp. 88-89, entitled "Structure of MR Inductive Composite Thin Film Magnetic Head".

[0003]

The composite type thin film magnetic head according to the prior art described above is difficult to produce industrially unless the individual recording and reproducing heads have the simplest structure and the manufacturing process is simplified. For this reason, it is necessary to consider the constraints of the manufacturing process more than the conventional mutual constraints on the design of each head. In particular, in the case of a recording head, (1) increasing the thickness of the magnetic core of the head remarkably requires precision of narrow track width processing.
(2) Since shortening the magnetic gap depth requires alignment accuracy with the reproducing head, there is a problem that the constraint from the manufacturing process is extremely large.

It is an object of the present invention to provide a magnetic disk drive capable of recording and reproducing data at a high recording density on a high coercive force medium while sufficiently increasing the allowable dimensional variation of each part of the recording head.

[0005]

In order to achieve the above object, the present invention provides a recording head and a reproducing head which are separated from each other.
Type thin film magnetic head integrally formed by
Data recording / reproduction for recording / reproducing data on / from magnetic disk
In a magnetic disk drive having a raw circuit,
The head has a lower magnetic core and a magnetic gap with the lower magnetic core.
An upper magnetic core having a stepped portion facing each other with a step layer therebetween.
The data recording / reproducing circuit causes the step to be magnetic.
Magnetic saturation occurs before the upper magnetic core near the disk facing part.
The first characteristic is that data recording is performed with a recording current value within a certain range.
Sign.

The present invention also relates to a recording head and a reproducing head.
Composite thin-film magnetic head and magnetic
A magnetic disk device comprising:
The recording head includes a lower magnetic core and the lower magnetic core.
The upper magnetic core opposing the magnetic gap layer at the end
And the thickness of the upper and lower magnetic cores at the opposed portions of the magnetic disk.
A pole length and the total thickness of the magnetic gap layer (T
t) and the magnetic gap opposing portions of the upper and lower magnetic cores
The gap depth (Gd), which is the length, and the saturation of the magnetic core.
The total magnetic flux density (Bs)
The thickness (tm) of the magnetic recording medium and its holding force (Hc)
On the other hand, the reference value Bso of the saturation magnetic flux density of the head magnetic core
Is 1.0T, and the reference value tmo of the thickness of the magnetic recording medium is
25 nm, the reference value Hco of the magnetic recording medium holding force is set to 1
When 200 Oc is satisfied, the following expression is satisfied.
The feature of. Gd · tm ′ ≦ 0.7 · Tt · Bs ′ / Hc′−1.0 tm ′ = tm / tmo Bs ′ = Bs / Bso Hc ′ = Hc / Hco

Further, according to the present invention, there is provided a magnetic disk according to the first or second aspect.
In the disk apparatus, the recording head is a lower magnetic core.
And the lower magnetic core faces the lower magnetic core with the magnetic gap layer interposed therebetween.
And an upper magnetic core having a step portion, wherein the upper and lower portions
The magnetic core has a saturation magnetic flux density of 1.3 T or more and a magnetic permeability of 100
Magnetic recording of magnetic disk
The thickness (tm) of the surface is 25 ± 10 nm, and its holding power (H
c) is 1200 ± 400 Oe, the upper and lower magnetic cores
The thickness of the magnetic disk facing portion and the magnetic gap layer.
That the thickness Tt is not less than 1.5 μm and not more than 6.5 μm.
This is the third feature.

According to the present invention, there is provided a magnetic disk drive having the above characteristics.
The material of the upper and lower magnetic cores is Co-Ni-F
e or Co-Ni-Fe-Pd alloy
Features.

Further, according to the present invention, the recording head may include a lower part.
With the magnetic core and the lower magnetic core sandwiched by the magnetic gap layer
An upper magnetic core having an opposing and stepped portion,
The upper and lower magnetic cores have a saturation magnetic flux density of about 1.0T and a magnetic permeability of 1.
About 000 magnetic alloy, magnetic recording of magnetic disk
The thickness (tm) of the surface is 25 ± 10 nm, and its holding power (H
c) is 1200 ± 400 Oe, the upper and lower magnetic cores
The thickness of the magnetic disk facing portion and the magnetic gap layer.
The total thickness (Tt) is 2.0 μm or more and 8.0 μm or less
The fifth feature is that the material of the upper and lower magnetic cores is
A sixth feature is that it is a Ni-Fe alloy.

[0010]

[0011]

[0012]

The magnetic disk drive according to the first aspect has the following features.
The magnetic core near the write gap of the recording head is magnetically saturated
Overwrite to write data so that it does not
The value can be monotonously decreased with the recording current value . Ma
The magnetic disk drive according to the second amnesty is the material of the magnetic core.
Select a material having a saturation magnetic flux density and magnetic permeability within the specified range.
As a result, the magnetic saturation of the magnetic core can be suppressed.
it can. Further, the magnetic disk drive according to the third feature is
Of the magnetic recording surface of the magnetic disk and the components of the magnetic head
By selecting the dimensions etc. within a predetermined range, the magnetic core
Magnetic saturation can be suppressed. According to the fourth aspect,
Magnetic disk drives select the material of the upper and lower magnetic cores.
Can reduce the magnetic saturation of the magnetic core.
it can.

A magnetic disk drive according to the fifth aspect.
Changes the material of the magnetic core of the recording head
Select the material of the degree and permeability, and the magnetic of the upper and lower magnetic cores
Keep the thickness of the disk facing part or the magnetic gap layer within the specified range
The selection reduces the magnetic saturation of the magnetic core.
Can be. Further, a magnetic disk drive according to the sixth aspect.
By selecting the material of the upper and lower magnetic cores,
Magnetic saturation of the air core can be suppressed. These magnetic
The disk drive can expand the degree of freedom in selecting the magnetic material.
And the allowable dimensional variation of each part of the recording head is
Data with high recording density on a high coercive force medium
Provide a magnetic disk drive capable of recording and reproducing
be able to.

[0014]

【Example】

<Principle of the Present Invention> A magnetic disk drive equipped with a composite thin-film magnetic head according to an embodiment of the present invention will be described below. First, the principle of the present invention will be described with reference to FIGS. In general, the recording performance of the recording head is determined by the unerasable ratio of the first recorded signal (overwrite value [overwrite value [when the signal recorded first by the head is subsequently overwritten with a signal having a shorter wavelength than that of the previous signal). Over Wr
item Modulation]: Also referred to as an overwrite characteristic or a past characteristic. If data recording on the magnetic disk is insufficient (for example, the overwrite value is -20 dB or more) in the magnetic disk device, even if a high-sensitivity reproducing head is used, a sufficient data reproduction signal / noise can be obtained. The ratio (S / N value) cannot be obtained, and an error occurs in data reproduction. The inventors of the present application have considered the deterioration of the overwrite value as follows based on experimental results.

[Cause 1 of Overwrite Characteristics Failure] The inventors of the present invention have reported that the overwrite characteristics are the magnetic characteristics of the magnetic disk on the recording side, the flying spacing between the magnetic disk and the magnetic head, and the recording wavelength. It was clarified by experiments etc. that it also changed. That is, in an experiment for magnetic heads H1 and H2 having different characteristics, as shown in FIG. 7, the overwrite value OW increases as the coercive force Hc of the recording medium increases, and the film thickness tm increases as shown in FIG. As the overlight value OW increases, the flying space increases as shown in FIG.
The overlight value OW decreases as the singing amount hf decreases,
As shown in FIG. 10, it has been clarified that the overwrite value OW increases as the recording wavelength λ decreases and the recording density increases.

FIG. 11 shows a calculation of the recording magnetic field of the head used in the above-mentioned experiment, and the actual measured values (OW) and the recording magnetic field / medium coercivity ratio (Hx / Hc).
And the thickness of magnetic disk media (tm)
The singing amount (hf) is arranged and shown as a parameter. When the broken line is 0.08 μm, the solid line is 0.12 μm.
Is the case. From the figure, it is understood that the smaller the thickness (tm) of the medium and the smaller the flying spacing (hf), the smaller the recording magnetic field for obtaining the same overwrite value. For example, in each head, when the film thickness of the medium is reduced from case C3 (tm = 40 nm) to case C1 (tm = 20 nm), the overwrite value is reduced, and the flying height is reduced from 0.12 μm (solid line) to 0.1%. It can be seen that the overwrite value decreases even if it decreases to 08 μm (broken line). These phenomena are caused by reducing the thickness of the medium and by reducing the spacing, the demagnetizing field from the medium decreases,
It can be understood that a sufficient overwrite performance can be obtained with a smaller recording magnetic field as compared with a case where the coercive force of the medium is simply reduced.

FIG. 12 shows the measured overwrite value (OW) and the recording magnetic field / medium coercive force ratio (Hx) as in FIG.
/ Hc) is arranged using the recording wavelength λ as a parameter. As can be seen from the figure, comparing case C4 with a recording wavelength of 0.5 μm and case C5 with a recording wavelength of 0.3 μm, the higher the recording density, the larger the recording magnetic field that obtains the same overlite value (for example, −30 dB). It turns out that it is necessary. It is considered that the influence of the recording wavelength can be explained by the demagnetizing field.

[Overwrite defect cause 2] However, the present inventors show in FIG. 13 and FIG. 14 that such an overwrite characteristic sometimes shows a change that cannot be explained only by the maximum value of the recording magnetic field. Experiment revealed.
FIG. 13 shows three types of heads a and b for the relationship between the overwrite value and the magnetomotive force mmf due to the recording current of the magnetic head.
FIG. 14 shows the experimental results of the relationship between the S / N and the magnetomotive force mmf for the heads a and c.

The present inventors have arranged such experimental facts. As a result, when the magnetomotive force is increased, the head a (see FIG. 13) in which the overlite value decreases almost monotonously is almost equal to the overlite value. Corresponds to the maximum value of the recording magnetic field, and the S / N ratio increases as the magnetomotive force increases (see FIG. 14).
On the other hand, the overwrite value increases with an increase in the magnetomotive force (see FIG. 13).
It has been clarified that there is a characteristic that the / N ratio decreases. Due to this phenomenon, the inventors considered that the overwrite characteristics did not correspond to the maximum value of the recording magnetic field and changed due to another factor, and further promoted the experimental facts. The overlite value increases because
In most cases, it was found that this was linked to the phenomenon that the reproduction output decreased with increasing magnetomotive force. As I will explain later,
If the reproduction output decreases with an increase in the magnetomotive force, the disk noise also increases, so that the total S / N ratio also decreases with the increase in the magnetomotive force.

FIGS. 13 and 14 illustrate such a situation. In other words, the head a in which the overlite value decreases almost monotonically with the increase in the magnetomotive force is S / S with respect to the increase in the magnetomotive force.
In the head c in which the N ratio increases almost monotonically and the overwrite increases in the middle with the increase in the magnetomotive force, the S / N decreases in the middle with the increase in the magnetomotive force.

Therefore, in order to stably secure the performance that can be sufficiently operated as the magnetic disk device, the S / N ratio increases almost monotonically and the overwrite decreases almost monotonously with the increase of the magnetomotive force. It is desirable to use a combination of a magnetic head and a magnetic disk. Therefore, according to FIG. 13, overwrite-20d, which is a measure of the performance of the magnetic disk drive, is used.
B is less than B and the magnetomotive force range Δmmf in which the overwrite decreases with increasing magnetomotive force is the largest for the head a that only decreases monotonically (Δmmfa>Δmmfb> Δm).
mfc), which indicates that the magnetic disk drive is suitable for high performance and mass production. According to FIG. 14, the magnetomotive force range Δmmf in which the S / N ratio is 30 dB or more, which is also a measure of the performance of the magnetic disk device, and in which the S / N ratio increases as the magnetomotive force increases, is monotonous. Head a that only decreases
Is larger (Δmmfa ′> Δmmfc ′), which indicates that the magnetic disk drive is suitable for high performance and mass production.

The inventor of the present invention has found that the cause of the decrease in the reproduction output in response to the increase in the magnetomotive force is mainly due to an increase in the transition width of the medium magnetization due to the distribution of the recording magnetic field leaking from the tip of the head magnetic gap becoming broad. It is considered that this corresponds well to the gradient of the recording magnetic field. When the reproduction output decreases with an increase in the magnetomotive force, the overwrite value is closely related to not only the maximum value of the recording magnetic field but also the gradient of the magnetic field, particularly the magnetic field gradient near the medium coercive force. Thought it was possible.

As a result of studying the magnetic field gradient, the inventors have found that when the magnetic head is excited, the location where magnetic saturation starts moves from the step of the upper magnetic core to the magnetic gap opposing portion at the tip of the upper magnetic core. It was considered that the magnetic field gradient on the upper magnetic core side of the expanding recording magnetic field distribution tends to become gentle as the recording current increases. That is, in general, when the magnetic characteristics of the medium are constant, the steepness of the magnetization reversal becomes worse as the recording magnetic field gradient on the upper magnetic core side becomes gentler, and when such a recording magnetization signal is reproduced, it is obtained corresponding to the magnetization reversal. The half-width of the output waveform to be expanded is widened, and particularly when the recording is performed at a high recording density, a remarkable decrease in the reproduction output is caused. In the case of a thin-film magnetic head with a reduced length, when the magnetic head is excited, the magnetic field gradient on the upper magnetic core side of the recording magnetic field distribution that spreads to the head end becomes gentler with an increase in the recording current. It was thought that it would decrease with the increase.

Therefore, the inventors of the present application consider that in order to prevent the reproduction output from lowering when the magnetomotive force is increased, it is only necessary to suppress the magnetic saturation at the magnetic gap opposing portion at the tip of the upper magnetic core. Has optimized the combination of the magnetic head and the magnetic disk so that the recording current value can be set in a range that monotonously decreases with the recording current value.

As described above, the present inventors have found that the cause of the deterioration of the overwrite value in the magnetic disk drive is the above [Cause 1].
In addition, to clarify the cause of the phenomenon that the magnetic field gradient on the upper magnetic core side of the magnetic head becomes gentle, and to prevent this magnetic field gradient deterioration, the film thickness of the magnetic disk medium is reduced by reducing the thickness of the medium. And the total thickness of the upper and lower magnetic cores and the magnetic gap is reduced for the head.
By increasing the gap depth, the location where magnetic saturation begins when the head is excited returns from the magnetic gap opposing portion at the tip of the upper magnetic core to the step of the upper magnetic core. A magnetic disk drive has been invented in which the phenomenon that the magnetic field gradient on the core side becomes gentle is prevented. As a result, the magnetic disk drive according to the present invention can prevent a decrease in reproduction output and an increase in overwrite without significant or special improvement of the head structure, and is suitable for mass production.

Incidentally, in the case of the conventional recording / reproducing head, it is difficult to prevent magnetic saturation at the tip of the upper magnetic core due to the restriction of maintaining or improving the reproducing performance. For example, only this portion is made of Co-Ni-Fe-Pd. It is considered necessary to greatly improve the head structure, for example, by increasing the saturation magnetic flux density by applying a system crystalline material or the like, or by easily concentrating the magnetic flux at the lower end.

<Overview of the Entire Magnetic Disk Device> A magnetic disk device according to an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram for explaining the configuration of a magnetic disk drive equipped with a thin-film magnetic head to which the present invention is applied. The magnetic disk device includes a magnetic disk corresponding to a magnetic recording medium on which data is recorded and reproduced, a spindle motor holding the disk 2 and rotating at a high speed, a magnetic head assembly 400 recording and reproducing data on the disk 2, An HDA (head disk assembly) 1 comprising an accessor 7 for moving the assembly 400 in the radial direction of the disk 2 via a head arm 6, a disk rotation control circuit 8 for controlling the rotation of the spindle motor 3, A head positioning circuit 9 for instructing the accessor 7 to move the magnetic head assembly 400, and a magnetic head assembly 400
And a data recording / reproducing circuit 10 for instructing data recording / reproducing by the data recording / reproducing apparatus.

The magnetic disk device configured as above is
After the head positioning circuit 9 positions the magnetic head assembly 400 on the target track of the magnetic disk 2 by the accessor 7 while the disk rotation control circuit 8 holds the magnetic disk 2 at a predetermined rotation speed, the data recording / reproducing circuit 10 The assembly 400 operates so as to record and reproduce data on the disk 2 according to the instruction.

The magnetic disk drive to which the present invention is applied
The present invention can also be applied to a small to large-capacity large magnetic disk device. For example, as shown in FIG. 2, a small magnetic disk drive includes a magnetic disk 12 having a small diameter, for example, a 3-inch diameter.
A magnetic head assembly 13 for recording and reproducing data on and from the disk 12, a rotary accessor 14 for rotatably moving the head assembly 13, and a spindle motor and circuits (not shown) are integrally housed in the HDA 11. Is done. In a large-capacity magnetic disk drive, as shown in FIG. 3, a plurality of magnetic disks 22 having a medium diameter, for example, 8 inches, and a plurality of magnetic head assemblies 2 for recording and reproducing data on and from the plurality of magnetic disks 22.
6 and a voice coil motor 27 that integrally moves the plurality of magnetic head assemblies 26 are housed in the HDA 21.

As shown in FIG. 4A, a magnetic head assembly used in the above-mentioned large-capacity magnetic disk drive is provided with an elastic magnetic head slider 4 having a magnetic head 40 formed by a thin film technique. The gimbal 5 has a structure in which the gimbal 5 is supported so as to be orthogonal to the rotation direction of the magnetic disk. A magnetic head assembly used in a small-sized magnetic disk device is a magnetic head formed by a thin film technique as shown in FIG. This structure supports the magnetic head slider 4 having the elastic gimbal 5 substantially parallel to the rotation direction of the magnetic disk. The differences in the support directions of these magnetic head sliders are as follows. That is, a large-sized magnetic disk drive employs a linear voice coil motor in order to respond to a demand for high-speed positioning of a magnetic head, and supports the magnetic head slider at right angles to a track to linearly move the slider in the disk radial direction. The small magnetic disk drive is a so-called straight type in which the magnetic head slider is moved in an arc shape in the disk radial direction by a linear motor that is rotationally driven for miniaturization, and the slider is supported in parallel with the track. is there.

<Magnetic Head According to the Present Embodiment> As shown in FIG. 5, the magnetic head slider has a thin film on the side of the air outflow end of the head slider rail 44 provided on the slider surface floating on the disk surface for generating a negative pressure. The recording / reproducing separation / composite thin film magnetic head 4 which is a feature of this embodiment by the technology
0 is formed. As shown in FIG. 6, the recording / reproducing separation / combination type thin film magnetic head has the head slider 40 shown in FIG.
The reproducing head 102 and the recording head 101 are sequentially formed on the substrate 100 via an insulating member such as alumina to separate and composite the two heads.

The reproducing head 102 is a high-sensitivity magneto-resistive magnetic head utilizing the magneto-resistive effect, and has an upper shield film 107 and a lower shield 107 for shielding an external magnetic field other than the data magnetization of the magnetic disk. Magneto-resistance effect detecting portion (MR film, bias film, magnetic domain control film, etc.) formed between the upper and lower shield films 106 and 107
108 and the magnetoresistive effect detecting unit 10 comprising the MR film or the like
It basically comprises an electrode terminal 109 for electrically extracting a resistance change corresponding to the data magnetization of the magnetic disk detected at 8 to a voltage signal externally. The area from which data is read by the magnetoresistance effect is defined by the depth dimension (MR height) 111 of the magnetoresistance effect detection unit 108 and the interval (track width) 112 between the two electrode terminals 109.

The recording head 101 is an inductive head formed above the reproducing head 102 with an insulating member such as alumina interposed therebetween.
An upper magnetic core 103, a nonmagnetic insulating layer 110 made of an organic material such as a photoresist filled between the upper and lower magnetic cores 103 and 104, and a metal conductor such as Cu for exciting the thin film magnetic head. Basically formed by the coil 105. Further, each tip of the upper magnetic core 103 and the lower magnetic core 104 provided at the medium facing portion at the tip of the thin film magnetic head, that is, the upper pole 11
The third and lower poles 114 are magnetic gaps 115 formed of a non-magnetic insulating layer made of a ceramic material such as alumina.
Are opposed to each other. FIG. 15 shows the recording head 101.
FIG. In the drawing, Tt is the total thickness of each layer of the upper pole 113, the lower pole 114 and the magnetic gap 115, and Gd is the length of the magnetic gap opposing portions of the upper and lower poles, that is, the gap depth. , Hw are the facing distance (window height) between the upper and lower magnetic cores.

The recording head 101 has a Tt of about 3 to 6 μm and a window height Hw of about 3 so that the track width processing accuracy of the pole is about ± 0.5 μm.
７7 μm. Further, considering the processing accuracy of the reproducing head formed below the recording head with respect to the magnetoresistive effect portion depth (MR height) 111 and the margin of the gap depth Gd itself, the variation width of Gd is roughly determined. 1 to
Desirably, it is allowable to 3 μm.

The reproducing head 102 and the recording head 101 configured as described above are arranged on the side of the air outflow end of the head slider rail 44 shown in FIG. 5 so that the front in FIG. Is what you do.

[Points of Magnetic Head According to the Present Embodiment]
In the recording / reproducing separation / composite thin film magnetic head according to the present embodiment, a magnetic material having a saturation magnetic flux density of 1.3 T or more and a magnetic permeability of 100 or more and 1000 or less is used as the magnetic core. As a specific example, the recording head 10
1 is that the material of the upper and lower magnetic cores 103 and 104 is C
a ternary or quaternary alloy having a saturation magnetic flux density of 1.3 T or more, such as o-Ni-Fe or Co-Ni-Fe-Pd;
When the thickness (tm) of the recording surface of the magnetic disk is 25 ± 10 nm,
When the coercive force (Hc) is 1200 ± 400 Oe, the total thickness Tt of the magnetic disk opposing portions of the upper and lower magnetic cores and the total thickness Tt of the magnetic gap layer are set to 1.5 μm or more and 6.5 μm or less.

The material and the like are such that the material of the upper and lower magnetic cores 103 and 104 is Ni-Fe, and the thickness of the magnetic medium (t
m) is 25 ± 10 nm and the coercive force (Hc) is 1200 ± 4.
In the case of 00 Oe, the total thickness Tt of the magnetic gap layers and the total thickness Tt of the magnetic disk opposing portions of the upper and lower magnetic cores is set to 2.
It may be 0 μm or more and 8.0 μm or less. The reason for defining the saturation magnetic flux density and the magnetic permeability for the magnetic core is to facilitate setting of a recording current described later.

<Magnetic Disk and Data Recording / Reproducing Wavelength According to the Present Embodiment> The magnetic disk according to the present embodiment has a track density (200
0 TPI) and a linear recording density of 45 kilobits per inch or more (45 kiloBPI). The thickness of the magnetic film is set to a predetermined range described later, and the magnetic film has a predetermined range of coercive force. Is set. The thickness of the magnetic film and the range of the coercive force differ depending on the structure and material of the magnetic head described later. When data is recorded on a magnetic disk configured as described above using a thin-film magnetic head, the magnetic disk device according to the present embodiment performs high-density recording at a recording wavelength of 1.5 μm or less by a data recording / reproducing circuit. The recording current value according to the recording wavelength is determined by calculating a remaining ratio (overwrite value) of the first recording signal when a signal recorded first by the recording head is overwritten with a signal having a shorter wavelength. Is not more than -20 dB, the overwrite value falls within a range in which the overwrite value monotonously decreases with the recording current value, and the ratio of the reproduction output to the noise (S /
N) is driven in a range where the recording current value monotonously increases with the recording current value. The current setting range may be a recording current range in which the magnetic disk facing portion of the upper magnetic core 103 is not magnetically saturated, or the upper magnetic core stepped portion may be closer to the magnetic disk of the upper magnetic core 103 in the process of increasing the recording current value. This is the recording current range where the magnetic saturation occurs before the opposing portion.

<Combination of magnetic head, magnetic disk, and recording current according to the present embodiment> Thus, in the magnetic disk device according to the present embodiment, the material of the magnetic head for recording is specified, and the overwrite value is changed to the recording current value. In addition to controlling the recording current range to a monotonically decreasing range with the use of a magnetic disk suitable for the magnetic head, recording and reproduction can be performed sufficiently on a high coercive force medium, and the reproduction output decreases when the magnetomotive force increases. It is possible to ensure a small and sufficiently large dimensional variation tolerance of each part of the recording head.

<Other Embodiments> The dimensions and the like of the recording head and the magnetic disk described above are not limited to those in the above-described embodiment, and the thickness (pole length) of the magnetic disk facing portions of the upper and lower magnetic cores. ), The total thickness Tt of the magnetic gap layers, the length (gap depth) Gd of the magnetic gap opposing portions of the upper and lower magnetic cores, and the saturation magnetic flux density Bs of the magnetic cores, on the magnetic disk surface. Medium thickness tm,
As long as the following equation is satisfied with respect to the coercive force Hc and the coercive force Hc, more application examples can be considered. FIG. 16 schematically shows such a situation.

[0041]

(Equation 1)

In the recording head, it is preferable that the product (magnetomotive force) of the number of coil turns and the recording current value be set to 1.0 AT or less in order to suppress the power consumption of the disk drive. This is quite possible for the configuration.

In the above-described embodiment, the current setting range may be the recording current range in which the magnetic disk facing portion of the upper magnetic core 103 is not magnetically saturated, or the upper magnetic core stepped portion may be larger in the process of increasing the recording current value. It has been described that the upper magnetic core 103 is set to a range where the magnetic saturation occurs before the magnetic disk opposing portion, in other words, the saturation of the magnetic core is made insufficient. It is suitable for. Next, this will be described with reference to FIG. FIG. 17 shows the relationship between the head recording magnetic field (maximum value) Hx / Hc and the magnetomotive force mmf when the saturation magnetic flux density Bs and the magnetic permeability μ of the head magnetic core are different. Case A has Bs = 1.7 Bso, μ = 500, case B has Bs = 1.3 Bso, μ = 1000, and case C has Bs.
s = Bso, μ = 1000, and Bso is 1.0T. If 1.5 is selected as a standard of Hx / Hc, which is almost equivalent to the saturation level of the magnetic core of case C. In case B having a larger Bs than case C, case C
It reaches even when the magnetomotive force is smaller (mmfB <mmfC) and the magnetic core is not sufficiently saturated. Furthermore, in case A, which has a large Bs but a small magnetic permeability, the Hx
Although the magnetomotive force is slightly larger than Case B (mmfA> mmfB), it can be sufficiently reached even when the magnetic core is not saturated. Therefore, from this comparison result, in the case of a normal inductive head, it is common to use under conditions where the magnetic core is sufficiently saturated without being affected by the magnetic permeability of the core, but the output reduction phenomenon described above may occur. In some cases, it can be said that it is more desirable if the required Hx / Hc can be obtained, even if the saturation of the magnetic core is insufficient and the influence of the dimensional fluctuation of each part of the head is small. Figure 1 shows this situation.
8 to 24, the relationship between Hx / Hc and the size of the main part of the head becomes more apparent.

FIG. 18 shows the relationship between Hx / Hc and the magnetomotive force mmf using the total thickness of the head tip as a parameter. In the same figure, the variation width of Hx / Hc for the thickness Tt1 <Tt2 <Tt3 decreases as the magnetomotive force decreases (mm
f1 <mmf2 <mmf3) It turns out that it is small. FIG.
9 shows the magnetomotive force mmf1 <mmf2 <mmf
3, the relationship between Hx / Hc and the total thickness of the head tip is rewritten. From the figure, the relationship between the variation width of Hx / Hc due to Tt and the magnetomotive force is clearer.

FIGS. 20 to 24 summarize the relationship between Hx / Hc and the dimensions of each part of the head in the same manner as in FIG. 20 shows the gap depth, FIG. 21 shows the step coverage factor, FIG. 22 shows the pole height, FIG. 23 shows the window height, and FIG. 24 shows the step taper angle with the head dimensions. Show the relationship. The variation width of Hx / Hc depending on the dimensions of each part of the head is smaller as the magnetomotive force is smaller (mmf1 <mmf2 <mm
f3) It is clear from each figure that it is small. Note that FIG.
If Hw is further reduced from about 5 μm, Hx / Hc
Is rapidly reduced, and 5 ± 2μ
It is understood that it is desirable to be at least m.

In each of the above embodiments, the saturation magnetic flux density Bs of Ni—Fe, which is well known as the magnetic core material of the thin film magnetic head, is about 1 Tesla,
The material having s is, for example, Co-N described in the text.
i-Fe-Pd crystalline material is about 1.3 Tesla, Co-N
The i-Fe crystalline material shows Bs of about 1.7 Tesla.
Some Fe-Ta-C crystalline materials exhibit a Bs of about 1.7 Tesla. Although some examples other than the magnetic core have been disclosed, the materials of these parts are not limited to those described in the above embodiments.

According to each of the above embodiments, the magnetic disk opposing portion of the upper magnetic core of the recording head does not become magnetically saturated in the process of increasing the recording current value, or the upper magnetic core step portion is more likely to be the upper magnetic core. A range in which the core is magnetically saturated prior to the magnetic disk facing portion, that is, a range in which the overwrite value monotonously decreases with the recording current value, and S / N
And the total thickness Tt of the magnetic gap layer and the thickness (pole length) of the magnetic disk facing portions of the upper and lower magnetic cores so that the recording current value can be set within a range that monotonically increases with the recording current value. The length (gap depth) Gd of the magnetic gap opposing portion of the upper and lower magnetic cores, the height Hw of the step portion of the upper magnetic core, the saturation magnetic flux density Bs of the magnetic core, the number of coil turns,
The thickness t of the magnetic medium formed on the magnetic disk surface
Since the head-medium can be optimized for each parameter such as m and coercive force Hc, a thin film magnetic material, a thin film coil and a non-magnetic insulating layer are sequentially laminated to separate a recording head and a reproducing head. Composite thin-film magnetic heads formed integrally with each other, especially those capable of sufficiently recording / reproducing on high coercivity media, having a sufficiently small reduction in reproduction output when the magnetomotive force is increased, and ensuring a sufficiently large dimensional variation tolerance of each part of the recording head. A magnetic disk device equipped with a thin-film magnetic head can be realized.

Further, since a magnetic material having a high magnetic flux density and a low magnetic permeability among the magnetic materials having a high saturation magnetic flux density can be applied to the recording head core, the degree of freedom in selecting the magnetic material can be increased, and the head and the magnetic medium can be used. It is possible to realize a magnetic disk drive equipped with a composite type thin-film magnetic head that can be mass-produced industrially by enabling an appropriate combination of the above and an appropriate setting of the recording current value.

[0049]

As described above, the write current value / wavelength by the data recording / reproducing circuit, the TPI / BP of the magnetic disk,
I, recording / reproducing data with high recording density on a high coercive force medium by making the appropriate combination of I, magnetic recording surface thickness, size and material of magnetic head, while sufficiently increasing the dimensional variation tolerance of each part of the recording head. A magnetic disk device capable of performing the above-mentioned operations can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a magnetic disk drive to which the present invention is applied.

FIG. 2 is a schematic external view of a small magnetic disk drive.

FIG. 3 is a schematic diagram of a head disk assembly for a large-capacity magnetic disk device.

FIG. 4 is a schematic view of a head assembly.

FIG. 5 is a schematic diagram of a head slider on which a thin-film magnetic head is formed.

FIG. 6 is a schematic diagram of a recording / reproducing separation / composite thin film magnetic head.

FIG. 7 is a diagram showing a relationship between overwriting and a medium coercive force.

FIG. 8 is a diagram showing a relationship between overwriting and a medium thickness.

FIG. 9 is a diagram showing a relationship between overwriting and a flying height of a head.

FIG. 10 is a diagram showing a relationship between overwriting and a recording wavelength.

FIG. 11 is a diagram showing a relationship between overwriting and a head magnetic field / medium coercive force.

FIG. 12 is a diagram showing a relationship between overwriting and a head magnetic field / medium coercive force.

FIG. 13 is a diagram showing the relationship between overwriting and head magnetomotive force.

FIG. 14 is a view showing characteristics of the S / N ratio and the magnetomotive force.

FIG. 15 is a schematic sectional view of a recording head.

FIG. 16 is a diagram showing the relationship between the gap depth and the total thickness of the tip of the recording head according to the present invention.

FIG. 17 is a diagram showing a relationship between a head magnetic field / medium coercive force and Hx / Hc.

FIG. 18 is a diagram showing a relationship between a head tip thickness, a magnetomotive force, and Hx / Hc.

FIG. 19 is a diagram showing the relationship between Hx / Hc and the total thickness of the head tip.

FIG. 20 is a diagram showing a relationship between Hx / Hc and a gap depth.

FIG. 21 is a diagram showing a relationship between Hx / Hc and a head step coverage factor.

FIG. 22 is a diagram showing a relationship between Hx / Hc and head pole height.

FIG. 23 is a diagram showing a relationship between Hx / Hc and head window height.

FIG. 24 is a diagram showing a relationship between Hx / Hc and a taper of a head step portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... HDA, 2 ... Magnetic disk, 4 ... Magnetic head slider, 40 ... Thin film magnetic head, 400 ... Magnetic head assembly, 101 ... Recording head, 102 ... Reproduction head, 103 ... Upper magnetic core, 104 ... Lower magnetic core , 1
05: Conductor coil, 110: Non-magnetic insulating layer, 113: Upper pole, 114: Lower pole, 115: Magnetic gap.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuo Suda 2880 Kozu, Kozuhara-shi, Odawara-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Odawara Plant 72) Inventor Miyafumi Shobun 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Inside Hitachi Research Laboratory (56) References JP-A-3-185601 (JP, A) JP-A-3-276408 (JP, A) Kaihei 3-29104 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5 / 02,5 / 09 G11B 5 / 127,5 / 31

Claims (6)

(57) [Claims] 1. A recording head and a reproducing head are separated from each other.
An integrated composite thin film magnetic head and the magnetic head
Data recording / reproduction for recording / reproducing data on / from magnetic disks
In a magnetic disk drive provided with a circuit,
Is a lower magnetic core and a magnetic gap between the lower magnetic core and the lower magnetic core.
And an upper magnetic core having a step and facing each other with the layer interposed therebetween.
And the data recording / reproducing circuit causes a step
Saturates magnetically before the upper magnetic core near the disk opposing part
A magnetic disk device for performing data recording with a recording current value in a range . 2. The recording head and the reproducing head are separated from each other.
Integrated thin film magnetic head and magnetic disk
The recording head, wherein
Is a lower magnetic core and a magnetic gap at one end with the lower magnetic core.
And an upper magnetic core opposed to the top layer.
Length, which is the thickness of the magnetic disk facing part of the magnetic core
The total thickness of the magnetic gap layer (Tt);
A gap that is the length of the lower magnetic core facing the magnetic gap.
The tip depth (Gd) and the saturation magnetic flux density (B
s) corresponds to the magnetic recording medium formed on the magnetic disk.
For the thickness (tm) and its holding force (Hc),
The reference value Bso of the magnetic core saturation magnetic flux density is 1.0T,
The reference value tmo of the thickness of the magnetic recording medium is 25 nm,
The reference value Hco of the magnetic recording medium holding force is set to 1200 Oc.
When the magnetic recording device satisfies the following expression,
Disk device. Gd · tm ′ ≦ 0.7 · Tt · Bs ′ / Hc′−1.0 tm ′ = tm / tmo Bs ′ = Bs / Bso Hc ′ = Hc / Hco 3. The recording head according to claim 1, wherein the lower magnetic core is
The lower magnetic core is opposed to the magnetic gap layer with
An upper magnetic core having a difference portion, wherein the upper and lower magnetic cores are provided.
The saturation magnetic flux density is 1.3T or more, and the magnetic permeability is 100 to 10
The thickness of the magnetic recording surface of the magnetic disk.
(Tm) is 25 ± 10 nm and its holding power (Hc) is 1
For 200 ± 400 Oe, the magnetic
The thickness of the disk facing portion and the thickness Tt of the magnetic gap layer
It is characterized in that but a 6.5μm hereinafter more 1.5μm
The magnetic disk drive according to claim 2. 4. The material of the upper and lower magnetic cores is Co-N.
i-Fe or Co-Ni-Fe-Pd alloy
4. The magnetic disk drive according to claim 3, wherein: 5. A recording head comprising : a lower magnetic core;
The lower magnetic core is opposed to the magnetic gap layer with
An upper magnetic core having a difference portion, wherein the upper and lower magnetic cores are provided.
Has a saturation magnetic flux density of about 1.0T and a magnetic permeability of about 1000
A magnetic alloy, and the thickness of the magnetic recording surface of the magnetic disk (t
m) is 25 ± 10 nm, and its holding power (Hc) is 1200.
The magnetic disc of the upper and lower magnetic cores
The total thickness of the magnetic gap layer (T
t) is 2.0 μm or more and 8.0 μm or less
3. The magnetic disk drive according to claim 2, wherein: 6. The material of said upper and lower magnetic cores is Ni-Fe.
6. The magnetic disk drive according to claim 5, wherein the magnetic disk drive is an alloy .