JPH05101310A - Magnetic recording method - Google Patents

Abstract

PURPOSE:To record with high density equal to a perpendicular magnetic recording system by increasing more the thickness of the magnetic layer of magnetic recording medium than a value subtracting 0.2mum from the distance between edges. CONSTITUTION:The magnetic head 1 is constituted of a first core 11 and a second core 21 consisting of ferritic material and a coil 31 wound round the first core 11. The first core 11 travels ahead of the magnetic recording medium 101 forming the magnetic layer 121 on a substrate 111. Then, an edge 13 is constituted by placing an alloy film 15 consisting of Fe, Ga, Si and Ru with higher saturation magnetic flux density than ferrite on the end face of the first core 11, and the gap part of 0.5mum is constituted of the edge 13 and the edge 23 of the second core 21 opposing to the edge 13. Thus, the magnetic field strength at the time of recording of the edge 13 of the first core 11 is higher than the same of the edge 23 of the second core 21 and the recording with high density equal to the perpendicular magnetic recording system is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording method for recording information on a magnetic disk, magnetic tape or the like.

[0002]

2. Description of the Related Art Magnetic recording technology is widely used as a basic technology for large-capacity recording of external storage devices such as computers and VTRs and DATs. Almost all conventional magnetic recordings are magnetic recording media of magnetic recording media. A longitudinal recording (in-plane recording) method has been adopted in which remanent magnetization is formed in a direction parallel to the layer film surface.

With the development of the information society in recent years, there has been a great demand for a large capacity in magnetic recording, that is, a high recording density, and much research and development has been conducted. Among them, the perpendicular recording method has been proposed and is being put to practical use as a method for improving the essential defects in the high density area of the longitudinal recording method described above.

Here, the difference between the longitudinal recording method and the vertical recording method for digital recording will be briefly described as follows.

In longitudinal recording, as shown in FIG.
In the magnetization reversal region, repulsive force acts between adjacent magnetizations. This is equivalent to the maximum demagnetizing field in the medium in the magnetization reversal region, and as a result, the magnetization decreases most at the magnetization transition point. Since the demagnetizing field increases as the recording density increases, there is a limit to increase the recording density in this longitudinal recording method.

On the other hand, in the perpendicular recording method, as shown in FIG. 7B, the demagnetizing field has a minimum value in the magnetization reversal region, and an attractive force acts between adjacent magnetizations. The demagnetizing field decreases as the recording density increases, and in principle, the recording limit due to the demagnetizing field does not occur. Therefore, it is said that the recording method is essentially suitable for high density recording.

By the way, in the longitudinal recording method and the perpendicular recording method, when the reproduction is performed by using the ring type reproducing head which is generally used, the reproduction waveform is largely different.

In the longitudinal recording method, when digital recording is performed, a reproduced waveform as shown in FIG. 7A is obtained.
That is, a unimodal pulse is generated for the isolated transition of the magnetization. The peak position of this pulse almost corresponds to the magnetic transition point. Therefore, in conventional longitudinal recording, information is reproduced by electrically differentiating the reproduced waveform and detecting the zero-cross point of the obtained differentiated waveform.

When digital recording is performed by the vertical recording method, the reproduced waveform is as shown in FIG. 7B when the ring head is reproduced. That is, a bimodal pulse is generated for the isolated magnetization transition. Therefore, theoretically, the differentiation of the waveform is no longer necessary, and it suffices to simply detect the zero-cross point of the reproduced waveform. However, in reality, there is a big problem in this practical application.

That is, even if perpendicular magnetic recording is performed, in reality, only the perpendicular magnetization component is not completely formed in the medium, and the longitudinal magnetization component is mixed to some extent. ), As a result, the magnetic transition point shifts from the zero cross point of the reproduced waveform. Previous studies have reported that even if the perpendicular magnetic recording is not achieved at all, it is possible to improve the characteristics in the high density region by making the magnetic recording medium slightly susceptible to perpendicular magnetization. .. In such a recording method, the above-mentioned waveform distortion becomes considerably large, and accurate reproduction is no longer possible with either the simple zero-cross method or the differential zero-cross method in the longitudinal recording method.

In order to solve the above-mentioned problems in the perpendicular magnetic recording system, various signal processing systems have been proposed.
For example, a method using a Hilbert filter (reference: BJ
Langland and MGLarimore, "Processing of Signals
from Media with Perpendicular Magnetic Anisotrop
y ", IEEE Trans. on Magn. vol.MAG-16, No.5, 1980B.J.
Langland, "Phase Equilization for Perpendicular Re
cording ", IEEE Trans. on Magn. vol. MAG-18, No. 5,
1982) and double differential method (reference: N. Aoyama et al., "Bit
Error Rate Characteristics for a Co-Cr-Ta Single
Layer Perpendicular Recording Medium ", J. of Mag
n.Soc. of Japan vol.13, Supplement No.S1, 198
9), delayed signal superposition method (reference: T.Okuwaki et al, "5.25
INCH FLOPPY DISK DRIVE USING PERPENDICULAR MAGNET
IC RECORDING ", IEEE Trans. On Magn. Vol.MAG-21, N
o.5, 1985) and so on.

However, none of these methods touches on the essential remanent magnetization state, and
It was only trying to fix the reproduced waveform to a waveform that is easy to demodulate, and it was not one that could be used accurately over a high band. Moreover, many of these are expensive for signal processing,
Moreover, it uses a delay line that is difficult to miniaturize,
There was a practical inconvenience. In theory, an infinite number of delay lines are required in the method using the Hilbert filter, and when a finite number of practically designed delay lines are designed, an error is apt to occur.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is capable of excellent high-density recording and simple reproduction processing.
It is an object of the present invention to provide a novel magnetic recording method for generating an ideal symmetric unimodal reproduction waveform for one isolated magnetization transition.

[0014]

According to the magnetic recording method of the present invention, the first edge having the first magnetic field strength is more than the second edge having the second magnetic field strength smaller than the first magnetic field strength. A magnetic recording method for recording on a magnetic recording medium between edges in advance, characterized in that the magnetic layer as a magnetic recording medium is thicker than at least the distance between edges minus 0.2 micron. It is a thing.

[0015]

According to the above-mentioned magnetic recording method, the inventors have been able to control the reproduced waveform by the recording current within a range that does not affect the output characteristics. It was found that a more symmetric and sharp unimodal waveform can be realized than can be obtained.

Even if a vertically oriented medium is used as the recording medium,
This steep unimodal waveform was obtained, and in this case, the waveform was sharper than the unimodal waveform obtained by Hilbert filtering the reproduced waveform when the same medium was conventionally recorded.

Moreover, in this case, although the reproduced waveform is a so-called in-plane waveform having a single peak, the recording density characteristic is
It was no better than recording with a conventional head.

The present invention is qualitatively expected to have the following effects.

That is, it is considered that the magnetic recording method of the present invention has a completely different magnetization state from the conventionally considered perpendicular recording or in-plane recording.

In conventional magnetic recording, the remanent magnetization of the medium is determined near the trailing edge of the head gap (the edge on the side that acts later with respect to the relative running of the medium). On the other hand, in the head of the present invention, the magnetic field strength in the vicinity of the leading edge (the leading edge) is larger than the magnetic field strength on the trailing edge side. Is expected to work only to modify the magnetization.

When the recording current (i) is applied to the coil (31) as shown in FIG. 1A, the edge (1) of the first core (11) is
3) That is, a large magnetic field (HL) is generated on the leading side of the head gap, and when the magnetic recording medium (101) passes this point, it has not only a longitudinal component but also a vertical component as shown in FIG. 2 (a). Remanent magnetization is formed. Magnetic recording medium
As the (101) travels, this magnetization is again affected by the relatively large magnetic field (HT) at the edge (23) of the second core (21), the trailing edge. The longitudinal component (HTh) of the magnetic field at the trailing edge is the same as on the leading side,
The vertical component (HTv) is in antiphase.

In the magnetic head (1) used in the present invention, the magnetic field (HT) on the trailing side is smaller than the magnetic field (HL) on the leading side. The magnetization is not determined, but rather it only slightly modifies the magnetization determined by the leading magnetic field (HL). That is, the perpendicular component of the residual magnetization is attenuated on the trailing side, and the longitudinal magnetization component remains strong.

As described above, the magnetic head (1) is moved in a fixed direction.
At the moment when is excited, the trailing magnetic field (HT) acts so as to cancel the perpendicular component of the remanent magnetization in the medium due to the reading magnetic field (HL).

However, this does not occur at the moment of the most important magnetization transition in digital recording. That is,
Remanent magnetization (HL) formed near the leading edge
However, the direction of the head exciting current is reversed by the time the trailing edge is reached. That is, the magnetic field at the trailing edge (HT) is opposite in phase to the magnetic field at the leading edge (HL) before reversal, as shown in FIG. It changes to the same phase. Therefore, it is expected that large perpendicular magnetization is formed at the transition point.

That is, as shown in FIG. 2, in the magnetic recording according to the present method, the surface layer portion and the deep layer portion are recorded on the magnetic layer (121), and as a result, the residual magnetization is as shown in FIG. It is considered to be close to the ideal horseshoe-shaped magnetization.

As described above, according to the present method, the recording of the surface layer portion and the recording of the deep layer portion of the magnetic layer are well controlled to strengthen each other and cancel each other to form an ideal horseshoe-shaped magnetization. Therefore, if the thickness of the magnetic layer is smaller than the predetermined range, it becomes difficult to control the reproduction waveform.

Therefore, the inventors of the present invention have found from various experiments that the thickness of the magnetic layer is larger than the value obtained by subtracting 0.2 μm from the distance between the leading edge and the trailing edge in such a recording method. Will be needed.

[0028]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a schematic block diagram for explaining a magnetic recording method according to an embodiment of the present invention.

The magnetic head (1) is composed of a first core (11) and a second core (21) made of a ferrite material, and a coil (31) wound around the first core. ) The first core (11) is arranged so as to run ahead of the magnetic recording medium (101) on which the magnetic layer (121) is formed.

Then, on the end face of the first core (11), Fe, Ga, Si, R having a saturation magnetic flux density larger than that of ferrite is used.
An alloy film (15) made of u is installed to form an edge (13), and an edge of the second core (21) facing the edge (13)
(23) forms a gap of 0.5 micron. By constructing the magnetic head (1) in this way, the edge (13) of the first core (11) becomes the second core (2).
The magnetic field strength during recording is larger than that of the edge (23) of 1).

Recording according to the embodiment of the present invention will be described using the magnetic recording apparatus thus constructed.

The magnetic recording medium (101) is a 1.0 μm thick magnetic layer formed by dispersing plate-shaped barium ferrite magnetic powder, which is one of hexagonal magnetic powder, in a binder resin.
A 3.5-inch size magnetic disk having (121) on a support (111) made of polyester was used. The perpendicular squareness ratio (hereinafter referred to as the perpendicular squareness ratio) after demagnetizing field correction of this magnetic disk (101) was 0.75, and the coercive force (Hc) was 1400 Oe.

In FIG. 4, the vertical axis represents the reproduced waveform parameter (θ).
Shows the recording current (I) on the horizontal axis, and the curve (a) in the figure shows the case where recording is performed at a recording density of 5 kFRPI on a magnetic disk having a magnetic layer of 1.0 μm thick by the above method. The curve (b) in the figure shows a conventional case in which the running direction of the magnetic head is reversed at a recording density of 5 kFRPI and recording is performed on a magnetic disk having a magnetic layer of 1.0 μm thick.

The reproduction waveform parameter (θ) in this specification means the obtained reproduction waveform after Fourier transformation,
It shows the phase shift when the time axis is determined so that the sine wave term of the fundamental wave becomes zero, and Fourier transform is performed again to expand it into a cosine wave. Generally, the (2n-1) th order term
It has been confirmed that a phase shift approximating n-2) · θ is included. At this time, if θ is zero, the obtained waveform is an ideal unimodal in-plane waveform, and if θ is 90, the obtained waveform is an ideal bimodal vertical waveform.
Further, if θ takes a value in between, it is known that the waveform is a mixture of an in-plane waveform and a vertical waveform. (Yamamori, Tanaka, et al. Magnetic Recording Research Society of Japan Institute of Electronics, Information and Communication, MR89-5 “Electromagnetic conversion characteristics of highly oriented Ba ferrite media”) While the waveform parameter (θ) is almost constant, it can be understood that the reproducing waveform parameter (θ) can be freely selected by the recording current (I) according to the present embodiment.

That is, as shown by the curve (a) in the figure, according to the method of this embodiment, a single-peak in-plane waveform could be obtained by setting the recording current (I) to 20 mA.

FIG. 5 shows the reproduced waveform when the isolated magnetization transition is recorded, with the output (E) on the vertical axis and the time (t) on the horizontal axis. Here, the curve (a) in the figure shows the reproduction waveform when recording is performed at the recording current (I) at which the reproduction waveform parameter (θ) becomes 0, that is, 20 mA, by this apparatus. Further, (b) in the figure shows a reproduced waveform when recording is performed by the conventional method, and (c) in the figure, the reproduced waveform when recorded by the conventional method is converted into an in-plane waveform by using a Hilbert filter. It shows a waveform at the time.

From the curve (a) in the figure, in the recording by this method, even when a medium having a large vertical squareness ratio is used,
It can be understood that the reproduced waveform has an in-plane waveform as in the case where the harmonic component is converted to an in-plane waveform by using a Hilbert filter. Further, according to the present apparatus, it can be seen that the reproduced waveform is excellent in symmetry and the half width is very small.

Therefore, according to this embodiment, since the in-plane waveform can be recorded on the magnetic recording medium, there is no need for a complicated waveform processing system and reproduction is performed by a simple waveform processing system similar to the conventional one. can do.

In FIG. 6, the vertical axis represents the reproduction output (E) and the horizontal axis represents the recording density (D).
It shows the dependence of the reproduction output (E) on the recording density (D) at 0 mA. The curve (a) in the figure shows the present method, and the curve (b) in the figure shows the conventional method. ..

As is apparent from this figure, it can be understood that a high reproduction output is secured in the short wavelength region.

Generally, in the in-plane magnetic recording method, when high density recording is performed, a high reproduction output cannot be obtained because of a large influence of the demagnetizing field. However, according to the present embodiment, as described above. Although the reproduced waveform showed an in-plane waveform, the reproduced output was not significantly reduced in the high density region.

Instead of the magnetic recording medium of the above embodiment,
When a magnetic recording medium having a magnetic layer thickness (M) of 0.25 μm was used, the optimum recording current value (I) and the reproduction waveform parameter (θ) were −10 or more and +10 as compared with the above-described examples.
The following current values (I) did not match.

The margin of the reproduced waveform parameter (θ) in the actual recording is preferably −10 or more and +10.
It is easy to design the system if it is below. Therefore, if the magnetic recording medium has a magnetic layer thickness larger than a value obtained by subtracting 0.2 μm from the gap length,
It can be understood that the effects of the present invention can be sufficiently obtained.

As described above, according to the magnetic recording method of the present invention, high-density recording equivalent to that of the perpendicular magnetic recording method is possible, and the phase can be adjusted only by adjusting the recording current (I). Therefore, the form of the reproduced waveform can be appropriately selected. Then, particularly by adjusting the recording current (I) so that the reproduction waveform parameter (θ) becomes substantially zero and recording, a reproduction waveform can be obtained as a single-peak in-plane waveform, and reproduction is performed by a simple reproduction system. can do.

In particular, by making the thickness of the magnetic layer thicker than the value obtained by subtracting 0.2 μm from the gap length, it is possible to control the reproducing waveform parameter (θ) with a recording current value that can obtain a high output. Produce an effect.

[0047]

As described above, according to the magnetic recording method of the present invention, high density recording equivalent to that of the perpendicular magnetic recording system is possible, and the phase is adjusted only by adjusting the recording current (I). It is possible to appropriately select the form of the reproduced waveform. Then, particularly by adjusting the recording current (I) so that the reproduction waveform parameter (θ) becomes substantially zero and recording, a reproduction waveform can be obtained as a single-peak in-plane waveform, and reproduction is performed by a simple reproduction system. can do.

In each of the embodiments, magnetic recording on a floppy disk has been shown, but the present invention can be applied to various magnetic recording media other than this, and has a unique effect.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a magnetic recording method according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a magnetic recording method according to an embodiment of the present invention.

FIG. 3 is a diagram showing a magnetization state of a magnetic recording medium according to the present invention.

FIG. 4 is a graph in which the vertical axis represents the reproduced waveform parameter (θ),
FIG. 6 is a diagram showing a recording current (I) -reproduction waveform parameter (θ) characteristic with a recording current (I) on the horizontal axis.

FIG. 5 is a diagram showing a reproduction waveform with the reproduction output (E) on the vertical axis and the time (T) on the horizontal axis.

FIG. 6 is a diagram showing the reproduction output (E) on the vertical axis and the recording density (D) on the horizontal axis, showing the dependence of the reproduction output (E) on the recording density (D).

FIG. 7 is a diagram for explaining various reproduction waveforms.

[Explanation of symbols]

 (1), (51) ... Magnetic head (11), (61) ... First core (21), (71) ... Second core (101) ... Magnetic recording medium

Claims (1)

[Claims] 1. A magnetic recording medium having a first edge having a first magnetic field strength preceded by a second edge having a second magnetic field strength smaller than the first magnetic field strength, between the respective edges. In the magnetic recording method, the thickness of the magnetic layer of the magnetic recording medium is 0.
A magnetic recording method characterized by being thicker than the one obtained by subtracting 2 microns.