JPH0448410A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To enable magnetic recording with high density by specifying the sum of adding the half of a magnetic gap length, the thickness of a ferromagnetic thin film and the half of intermediate layer thickness according to minimum and maximum recording intervals to be recorded onto an inner-most circumference. CONSTITUTION:An intermediate layer 2 having thickness tp is provided on one of the gap counter surfaces of magnetic cores 1 and 1' composed of ferromagnetic oxide at least, and a ferromagnetic thin film 3 having thickness (t) is provided adjacently to the intermediate layer 2. Composite magnetic heads joined through a magnetic gap 4 having thickness g1 are used and when the minimum recording interval to be recorded onto the innermost circumference of a signal recording area is defined as (b) MIN and the maximum recording interval is defined as (b) MAX, the sum of adding the half of the magnetic gap length (g1/2), the thickness (t) of the ferro-magnetic thin film 3 and the half of the thickness of the intermediate layer 2 (tp/2) is expressed by an inequality I. Thus, even when linear recording density is enlarged, enough recording ability can be obtained and energy consumption can be reduced as well.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a high-density magnetic recording device.

BACKGROUND OF THE INVENTION In recent years, there has been a remarkable demand for smaller and larger capacity magnetic disk drives. In order to achieve large capacity in magnetic disk drives, it is necessary to increase the track density (the number of tracks per unit length) and the linear recording density (the number of signal magnetizations per unit length), and to increase the recording modulation. It is necessary to optimize the method. In addition, magnetic disks with smaller diameters, ranging from 5.25 or 3.5 inches to 2.5 inches, are also being used.

In this way, when trying to increase the size and capacity, the reproduction signal decreases due to the decrease in relative speed and narrow track width (decrease in signal-to-noise ratio).
This may lead to deterioration of frequency characteristics (deterioration of resolution).

A decrease in the signal-to-noise ratio increases peak shift due to time jitter. In addition, a decrease in resolution promotes interference between reproduced signals during signal reproduction, and in the case of a certain recording pattern, increases pattern peak shift in which the peak position deviates from the reversal position of the recording current.

Therefore, metal thin film media, which have the characteristics of high coercive force, high residual magnetic flux density, and thin film, have been developed as magnetic recording media. On the other hand, in order to achieve sufficient saturation recording on this medium and obtain excellent recording and reproducing characteristics, a composite film was developed in which a ferromagnetic thin film was provided near the gap instead of the conventional magnetic core using ferromagnetic oxide. type magnetic heads have been developed and used in magnetic disk drives. By combining a composite magnetic field and a metal thin film medium in this way, it is possible to improve the S/N ratio resolution.

However, there is a limit to the resolution due to the gap length and flying height of the magnetic head, or the coercive force which is restricted by the recording capacity, and therefore there is a limit to the improvement of 7<turn peak shift.

Furthermore, in this composite magnetic head, it is known that a pseudo gap occurs at the interface between the ferromagnetic oxide and the ferromagnetic thin film, resulting in a pseudo reproduction output.

Therefore, the thickness of the ferromagnetic thin film (1), half the magnetic gap length (g 1/2), and half the thickness of the intermediate layer (t p /
2) (that is, the distance between the center of the magnetic gap and the center of the intermediate layer) is set so that the minimum recording interval is larger than the minimum recording interval recorded on the magnetic recording medium and smaller than twice that distance. It has been proposed to improve the pattern peak shift using this pseudo reproduction output by changing the thickness of the ferromagnetic thin film with a distance of 2, the magnetic gap length, and the intermediate layer (Japanese Patent Laid-Open No. 13106/1983).

Problems to be Solved by the Invention Currently, the track density is 1,700 to 18,007 PI (tracks per inch, number of tracks per inch).
Therefore, the track width is up to around 10 μm.

Therefore, in the future, higher density will require a higher recording frequency.
Alternatively, it has become impossible to achieve this unless the rotational speed is lowered or the linear recording density is increased. As the linear recording density increases, the minimum recording interval recorded on the recording medium becomes smaller.

Currently, the minimum recording interval for a 3.5-inch hard disk is about 1.0 μm, and the appropriate value according to Japanese Patent Application Laid-Open No. 6313106 is 1.0 to 2.0 μm. However, if you aim for even higher density recording, the minimum recording interval is 1 μm.
It becomes the following. For example, 3.5 inch innermost circumference 22
The minimum recording interval when recording a frequency of 7MHz on the drum is
The value is approximately 0.59 μm (42.9 kFRPI: number of signal magnetizations per inch), and the appropriate value in this case is 0.59 μm.
It becomes 59-1.18 μm.

Here, Fig. 9 shows the thickness of the ferromagnetic thin film and the magnetomotive force NT90, which is a parameter indicating the writing ability of the magnetic/magnetic head (at the time of recording when the reproduction output reaches 90% of the maximum value with respect to the recording current in the input/output characteristics). (magnetomotive force). The smaller the value of Nl 90, the better the recording efficiency and the ability to write with a small recording current, which has the advantage of reducing power consumption as a magnetic disk device.

As described above, when the minimum recording interval is made small with the aim of high-density recording, there is a problem that the recording efficiency deteriorates when the thickness of the ferromagnetic thin film of the head becomes 1 μm or less. Also,
As a ferromagnetic thin film becomes thinner, magnetic saturation of the ferromagnetic thin film occurs faster, and the number of layers with poor initial magnetic properties increases relative to the total thickness of the ferromagnetic thin film.
There is also the problem that the magnetic characteristics deteriorate, impairing the reliability of the magnetic disk drive. Additionally, this phenomenon becomes more pronounced as the coercive force of the recording medium increases, that is, the higher the linear recording density is aimed at.
This becomes noticeable and if the thickness of the ferromagnetic thin film is too thin, it becomes unsuitable for high-density recording.

It has also been revealed that the thickness of the ferromagnetic thin film, the magnetic gap length, and the appropriate values of the intermediate layer for the minimum recording interval vary depending on the recording modulation method, which is a condition for achieving high density.

The present invention aims to solve the above-mentioned conventional problems and provide a magnetic disk device capable of high-density magnetic recording.

Means for Solving the Problems In order to achieve the above object, the present invention has an intermediate layer having a thickness of [p] on at least one of the gap-opposing surfaces of a magnetic core made of a ferromagnetic oxide, and is adjacent to the intermediate layer. A composite magnetic head is used in which a ferromagnetic thin film with a thickness t is provided and joined through a magnetic gap with a thickness gl, and half of the magnetic gap length (gl/2) and the thickness (1) of the ferromagnetic thin film are The sum of half the thickness of the intermediate layer (t p/2) is the minimum recording interval recorded on the innermost circumference of the signal recording area of the magnetic recording medium.
MIN, the maximum recording interval is b MAX, and b MIN+
nx(b MrN+ b MAX)≦(gl/2+t+
tp/2)≦b MAX+nx(b MIN+ b M
AX) (n=0.1.2.3...) The magnetic disk device is configured so that

Even if the linear recording density is increased using a magnetic disk device with a configuration that exceeds the function, it has sufficient recording capacity and can improve pattern peak shift, achieving high-density recording and low power consumption. magnetic disk devices.

Embodiment FIG. 10 shows an example of a composite magnetic head used in the magnetic disk device of the present invention. M n which is a ferromagnetic oxide
- Zn ferrite or NiZn ferrite, one side 1 of the magnetic core is coated with S having a thickness tp as an intermediate layer 2.
iO2, Cr, SiN.

Ti, Al2O3, Mo, Ir, etc. are deposited by sputter link vapor deposition, etc., and then Fe-Aj+Si alloy 3 is deposited to a thickness t by sputtering, vapor deposition, etc., and then a non-magnetic material such as 5i02 is deposited. A composite magnetic head is formed by joining the other magnetic core 1° through a magnetic gap 4 having a thickness GL, and a winding 5 is provided. In this case, 5i02. Cr was provided for the purpose of improving the characteristics of the Fe-Aj'-8i alloy, which is a ferromagnetic thin film, and preventing diffusion from the ferromagnetic thin film to the ferromagnetic oxide. 03
Mo and Ir are provided for the purpose of preventing diffusion from the ferromagnetic thin film to the ferromagnetic oxide. Further, the ferromagnetic thin film 3 is made of permalloy, amorphous apricot, Fe-Ga-3i.
-Ru alloy or the like may also be used.

FIG. 8 shows an isolated reproduction waveform of a composite magnetic head having such a configuration. The interval between the peak of the reproduction signal and the peak of the pseudo output is (gl/2+t+tp/2).

Furthermore, the magnitude of the pseudo output varies depending on the thickness tp of the intermediate layer.

When recording signals on a magnetic disk, the relative speed is the slowest and the linear recording density is the highest at the innermost circumference, so the resolution per output is the lowest.

Therefore, the pattern peak shift is also largest at the innermost circumference. Therefore, it can be seen that the magnetic disk device should be configured so that the pattern peak shift can be improved at the innermost circumference and adjacent signals can be discriminated.

Now, the minimum recording interval of the signal on the innermost circumference is b MIN,
Assuming that the maximum recording interval is b MAX, the magnetic disk device of the present invention can be summarized as b MIN + nx (b
MIN+ b MAX)≦(gl/2+t+tp/2)
≦b MAX+nx(b MIN+ b MAX) −
-(11 (n=0.1.2, 3...) The minimum recording interval 1 ferromagnetic thin film, magnetic gap, and intermediate layer are formed (the maximum recording interval depends on the modulation method). (determined to be a certain ratio to the minimum recording interval).

Here, based on FIGS. 2 to 7, pattern peak shifts in magnetic disk drives will be considered by retracing the process that led to such a result.

In Figure 2, the recording modulation method is MFM (ilodif
iedFrequency ) [odulation)
This is the worst pattern for the method...110
The results of calculating the pattern peak shift of 110... by simulation are shown. It is expressed as a percentage based on the value without the ferromagnetic thin film. The pseudo output was set to -21 dB with respect to the reproduced output. The pattern peak shift is improved with respect to the ratio of the sum of the thickness of the ferromagnetic thin film (1), half the magnetic gap length (g 1/2), and half the thickness of the intermediate layer (tp/2) and the minimum recording interval. It can be seen that there are cases where the situation is affected and cases where it gets worse.

In the case of the MFM method, bMAX=2bMIN (
1) By transforming the equation, the following equation is obtained.

(1+3n)≦(gl/2+t+tp/2)/b
MIN≦(2+3n)・・・・・・
・(2) (n=o, 1.2.3...) When pattern peak shift is improved ・When n=o, 1≦(gl/2+t+tp/2)/b MIN≦2・
...Area A in Figure 2 ・When n=1, 4≦(gl/2+t+tp/2)/b MIN≦5・
...Region B in Figure 2 ・When n=2, 7≦(gl/2+t+tp/2)/b MIN≦8・
...It can be seen that this is the middle head area C in Figure 2. Items where n is 3 or more are omitted.

Further, FIG. 3 shows an area where the pattern peak shift is improved with respect to the minimum recording interval.

For example, if the minimum recording interval is 0.59 μm, the gap length is 0.3 μm, and the intermediate layer is 0.02 μm, then the thickness t of the ferromagnetic thin film is n=o (when D is 0.59 μm to 1.18 μm n=1
When 2.36μm~2.95μm When n=2
4.13 μm to 4.72 μm When n=3 5.9
It can be seen that it is sufficient to set the thickness to 6.49 μm.

In this case, when n=0, the ferromagnetic thin film becomes too thin, resulting in poor writing efficiency and poor magnetic head characteristics as described above. Further, when n=3.4.5, the thickness of the ferromagnetic thin film becomes large, which causes a problem in terms of productivity, and the preferable case is n=1.2.

Thus, it can be seen that by selecting the value of the coefficient n depending on the minimum recording interval to be used and selecting an appropriate thickness of the ferromagnetic thin film, sufficient recording ability can be obtained and pattern peak shift can be improved.

Next, consider recording modulation methods other than the MFM method.

Figure 4 shows the (2,7) RLL method (1?UN LENG
THLIMITED) is the worst pattern...
...100100000001001...
The results of calculating the pattern peak shift of `` by simulation are shown below.The conditions are the same as in the case of the MFM method.

(2,7) In the case of RLL method, b'MAX=8/3b
Since it is MIN, the following equation can be obtained from equation 1.

(1+nX11/3)≦(gl/2+t+tp/2)/
b MIN≦(8/3+nxll/3)
+++ =-(31 (n=012, 3...) When pattern peak shift is improved - When n=o, 1≦(gl/2+t+tp/2)/b MIN≦8
/3... Area A in Figure 4 ・When n=1, 14/3≦(gl/2+t+tp/2)/b MI
N≦19/3・・・Region B in Figure 4 ・When n=2, 25/3≦(gl/2+t+tp/2)/b WIN
It can be seen that ≦lO...Area C in FIG. 4. Items where n is 3 or more are omitted.

FIG. 5 shows an area where the pattern peak shift is improved with respect to the minimum recording interval. Similar to the MFM method, if the minimum recording interval is 0.59 μm, the gap length is 0.3 μm, and the intermediate layer is 0.02 μm, the thickness of the ferromagnetic thin film is 0.59 μm to 1.57 μm when n=0 and n=1. When 2.75μm to 3.74μmn=2
4.92 μm to 5.9 μm When n=3 7.0
It can be seen that the thickness should be 8 μm to 8.06 pm.

In this case, even when n=o, a sufficient value can be selected as the thickness of the ferromagnetic thin film. Further, as in the case of the MFM method, it is preferable that n=0.1.2.

In Fig. 6, the worst pattern for the (1,7) RLL method is “...1010000000101...
. . ” is the result of calculating the pattern peak shift by simulation.The conditions are the same as in the case of the MFM method.

(1,7) In the case of RLL method, b MAX = 4b II
Since it is IN, the following equation is obtained from equation (1).

(1+5n)≦(gl/2+t+tp/2)/ b M
IN≦(4+5n) ・・・・・・
(4) (n=0.1.2.3...) When the pattern peak shift is improved - When n=0, 1≦(gl/2+t+tp/2)/b i[IN≦ 4
... Area A in Figure 6 ・When n=1, 6≦(gl/2+t+tp/2)/b MIN≦9・
... Area B in Figure 6 ・When n=2, 11≦(gl/2+t+tp/2)/b Lid IN≦1
4... It can be seen that this is region C in Fig. 6. Items where n is 3 or more are omitted.

FIG. 7 shows an area where the pattern peak shift is improved with respect to the minimum recording interval. As with the MFM method, assuming that the minimum recording interval is 0.59 μm, the gear lug length is 0.3 μm, and the intermediate layer is 0.02 μm, the thickness of the ferromagnetic thin film is 059 μm to 236 μm when n=0 and 059 μm to 236 μm when n=1. .54 μm to 531 μm When n=2 6.4
9μm~8.26μm When n=3 944μm~1
It can be seen that 1.21 μm is sufficient.

In this case, preferably n=0.1.

Depending on the recording modulation method used in this way, the thickness of the ferromagnetic thin film, the thickness of the intermediate layer, and the magnetic gap length that improve the pattern peak shift with respect to the minimum recording interval can be calculated using equations (2) and (3).
) and (4), the value of the coefficient n may be selected depending on the minimum recording interval.

Furthermore, when the intermediate layer (tp) is eliminated, a pseudo output occurs at the interface between the ferromagnetic oxide and the ferromagnetic thin film. Since no measures are taken to prevent diffusion, the spurious output will be large. In this case, it is expressed by the case where tp=0 in the above-mentioned equation (1), and the same effect as when using the intermediate layer can be obtained.

Effects of the Invention As shown in the above embodiments, the present invention provides at least one gap-opposing surface of a magnetic core made of a ferromagnetic oxide.
A composite magnetic head is used, which has an intermediate layer with a thickness tp, a ferromagnetic thin film with a thickness t adjacent to the intermediate layer, and is joined through a magnetic gap with a thickness gl. gl/2), the thickness (1) of the ferromagnetic thin film, and half the thickness of the intermediate layer (tp/2) is the minimum recording interval recorded on the innermost circumference of the signal recording area of the magnetic recording medium. Let b MIN and the maximum recording interval be b MAX, then b MIN
+nx(b MIN+ b MAX)≦(gl/2+t
+tp/2)≦b MAX+nx(b MIN+b
MAX) (n=o, 1.2.3...) by configuring the magnetic disk drive and selecting an appropriate coefficient n depending on the minimum recording interval and recording modulation method to be used. We are developing a compact, high-capacity magnetic disk device that can improve pattern peak shift even when the linear recording density is increased, has sufficient recording capacity, can achieve high-density recording, and has low power consumption. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a composite magnetic head used in a magnetic disk drive according to an embodiment of the present invention, and FIG. 2 shows the results of pattern peak shift staining in the case of the same <MFM method. The characteristic diagram and Figure 3 are the same <MFM
Figure 4 is a characteristic diagram showing the area where the pattern peak shift improves with respect to the minimum recording interval in the case of the method.
2,7) Figure 5, a characteristic diagram showing the simulation results of pattern peak shift in the case of the RLL method, is the same < (
2, 7) Characteristic diagram showing the area where the pattern peak shift improves with respect to the minimum recording interval in the case of the RLL method, No. 6
The figure is the same < (1, 7) Characteristic diagram showing the simulation results of pattern peak shift in RLL method, Figure 7 is the same (1, 7) Improvement in pattern peak shift with respect to the minimum recording interval in RLL method FIG. 8 is a characteristic diagram showing the isolated reproduction waveform of the composite magnetic head shown in FIG. It is a characteristic diagram showing a relationship. 1.1'...Magnetic core of ferromagnetic oxide, 2...
...Intermediate layer, 3...Ferromagnetic thin film, 4...
...Magnetic gear, 5...Winding. Name of agent: Patent attorney Shigetaka Awano and one other person & Figure Figure bM+s (pml batN (胛) Loading part-2) to the saw, μ9-ξS +: Akebono-,) To the T saw,) Hess 9 breaking Jimi, Figure 1N (pml Diagram Diagram Diagram 5 Mu Book X Training Ring 2wo(i)

Claims (5)

[Claims] (1) An intermediate layer with a thickness tp is provided on at least one of the gap-opposing surfaces of a magnetic core made of a ferromagnetic oxide, a ferromagnetic thin film is provided adjacent to this intermediate layer, and a ferromagnetic thin film is provided through a magnetic gap with a thickness gl. Using a composite magnetic head joined to the other magnetic core, half of the magnetic gap length (gl/2), the thickness of the ferromagnetic thin film (t), and half the thickness of the intermediate layer (
bMIN+nx(bMIN+bMAX)≦(gl/2+
t+tp/2)≦bMAX+nx(bMIN+bMAX
) (n=0, 1, 2, 3...) A magnetic disk device configured so that: (2) The magnetic disk device according to claim 1, wherein the intermediate layer uses a material that prevents diffusion from the ferromagnetic thin film to the ferromagnetic oxide. (3) The magnetic disk device according to claim 1, wherein the intermediate layer is made of a material that improves the characteristics of the ferromagnetic thin film. (4) Using a composite magnetic head in which a ferromagnetic thin film is provided on at least one of the gap-opposing surfaces of a magnetic core made of a ferromagnetic oxide and is joined to the other magnetic core via a magnetic gap of thickness GL, the magnetic Half the gap length (gl/2)
and the thickness (t) of the ferromagnetic thin film is the minimum recording interval recorded on the innermost circumference of the signal recording area of the magnetic recording medium.
MIN, maximum recording interval is bMAX, bMIN+nx (bMIN+bMAX)≦(gl/2+
t)≦bMAX+nx(bMIN+bMAX) (n=0, 1, 2, 3...). (5) The magnetic disk device according to claim 1, 2, 3 or 4, wherein the ferromagnetic thin film has a thickness of 1 μm or more.