JPH05101318A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To record with high density equal to a perpendicular magnetic recording system by travelling the edge of a core with high density of two cores with different saturation magnetic flux density ahead of the other edge. CONSTITUTION:A magnetic head is constituted of the first core 11 with the first saturation magnetic flux density and the second core 21 with the magnetic flux density lower than the first core. The edge of the first core 11 is arranged so as to travel ahead of the edge of the second core 21. Thus, a regenerative waveform is controlled with recording current within the range of unaffecting to an output characteristic, and also, as the controlled result, a single peak waveform being more symetrical and sharper than the waveform obtained by conventional longitudinal recording is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording device 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. 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, only the perpendicular magnetization component is not completely formed in the medium, and the longitudinal magnetization component is mixed to some extent, so that the reproduced waveform is shown in FIG. 7C. As shown in (4), the result is that the magnetization transition point deviates from the zero cross point of the reproduction waveform. From previous studies, even if perfect perpendicular magnetic recording is not achieved,
It has been reported that even if the magnetic recording medium is made slightly susceptible to perpendicular magnetization, the characteristics in the high density region are significantly improved. In such a recording method that should be called a quasi-vertical recording method, the above-mentioned distortion of the waveform becomes considerably large,
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 device that generates an ideal symmetrical unimodal reproduction waveform with respect to one isolated magnetization transition.

[0014]

The magnetic recording apparatus of the present invention comprises a first core having a first saturation magnetic flux density and a second core having a second saturation magnetic flux density smaller than the first saturation magnetic flux density. A magnetic recording device including a magnetic head composed of a core of the first core and an edge of the first core. It is a shimizu.

[0015]

According to various experiments, the inventors of the present invention can control the reproduced waveform by the recording current in the range that does not affect the output characteristics, and as a result of the control, It was found that a symmetric and sharp unimodal waveform can be realized more than that obtained by conventional longitudinal recording.

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 was a so-called in-plane waveform having a single peak, the recording density characteristics were no different from those recorded by the conventional head.

According to the magnetic recording by the magnetic recording apparatus of the present invention, the following actions are expected to occur.

That is, it is considered that the magnetic state of the magnetic recording of the present invention is completely different 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 that acts later in time 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, the magnetic field (HL) affects the longitudinal component (HL).
Remanent magnetization having a vertical component (HLv) as well as h) is formed. As the magnetic recording medium (101) runs, this magnetization is then again affected by a relatively large magnetic field (HT) at the edge (23), or trailing edge, of the second core (21). Longitudinal component (HTh) of the magnetic field at the trailing edge is in the same direction as the leading side, but vertical component (HTv)
Is the opposite phase.

In the magnetic head (1) used in the present invention, the magnetic field (HT) on the trailing side is the magnetic field (H) on the leading side.
Since it is smaller than L), the trailing magnetic field (HL) does not generally determine the residual magnetization as in the conventional case, but rather, the magnetization determined by the leading magnetic field (HL) is only slightly modified. is there.

As described above, when the medium is viewed from the magnetic head, at the moment when the magnetic head (1) is excited in a fixed direction, the trailing magnetic field (HT) is generated by the leading magnetic field (HL) in the medium. Vertical component of remanent magnetization (HL
v) acts to cancel.

However, this does not occur at the moment of the most important magnetization transition in digital recording. That is,
As shown in FIG. 1B, the direction of the head exciting current is reversed by the time the residual magnetization (HL) formed near the leading edge reaches the trailing edge. That is, in the trailing edge magnetic field (HT), the longitudinal component (HTh) is in antiphase and the vertical component (HTv) is in phase with the leading edge magnetic field (HL) before reversal. Therefore, it is expected that large perpendicular magnetization is formed at the transition point.

What is predicted from the above is that the remanent magnetization produced by the present invention is close to the ideal horseshoe-shaped magnetization as shown in FIG.

[0025]

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

FIG. 1 is a schematic sectional perspective view of a magnetic recording apparatus according to an embodiment of the present invention.

The magnetic head (1) comprises a first core (11) made of sendust material and a second core (2) made of ferrite material.
1) and a coil (31) wound around a second core, and the first core (101) with respect to the magnetic recording medium (101) having the magnetic layer (121) formed on the support (111). 11) is arranged so that it will be driven first.

Then, the edge (13) of the first core (11) having a depth of 10 μm and the edge (23) of the second core (21) facing the edge (13) have a depth of 0.4 μm. The gap is made up. In this way the magnetic head
By configuring (1), the edge (1
In 3), the magnetic field strength at the time of recording is larger than that of the edge (23) of the second core (21).

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

As the magnetic recording medium (101), a magnetic layer (121) in which a plate-shaped barium ferrite magnetic powder which is one of hexagonal magnetic powder is dispersed in a binder resin is used as a support made of polyester. A 3.5-inch magnetic disk prepared on (111) was used. And this magnetic disk
The vertical squareness ratio (hereinafter referred to as vertical squareness ratio) after demagnetizing field correction of (101) is 0.75, and the coercive force (Hc) is 1
It was 400 Oe.

In FIG. 3, the vertical axis represents the reproduced waveform parameter (θ).
The recording current (I) is plotted on the horizontal axis. The curve (a) in the figure shows the case where recording is performed at the recording density of 5 kFRPI by the above method, and the curve (b) in the figure shows the recording density of 5 kFRPI. A conventional case is shown in which recording is performed by reversing the running direction of the magnetic head.

The reproduction waveform parameter (θ) in this specification means that after the obtained reproduction waveform is Fourier transformed,
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. Electromagnetic Recording Characteristics of the Institute of Electronics, Information and Communication Engineers, Magnetic Recording Study Group, 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, 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.

Of course, it is preferable that the setting of the recording current (I) is set to zero as the reproduction waveform parameter (θ), but in practice, the reproduction waveform parameter (θ) is ± 2.
It should be 0 or less.

FIG. 4 shows the reproduced waveform when recording is performed at the recording frequency of 5 kFRPI, with the output (E) on the vertical axis and the time (t) on the horizontal axis. Curve (a) in the figure
Shows the recording waveform (I) at which the reproduction waveform parameter (θ) becomes 0, that is, the reproduction waveform when recording is performed at 20 mA. 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 recording by this apparatus, even when using a medium having a large vertical squareness ratio,
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 the present 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. 5, 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 clear from this figure, it can be understood that according to the present embodiment, a high reproduction output in the short wavelength region is secured to the same extent as in the conventional case.

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 this 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.

As described above, according to the magnetic recording apparatus of the present embodiment, it is possible to perform high-density recording, and it is possible to perform the reproduction by the reproduction system similar to the conventional one, which is a particular effect.

Further, as to the squareness ratio of the magnetic recording medium after the correction of the demagnetizing field in the vertical direction, various experiments other than the above have shown that a sufficient effect can be obtained if it is preferably 0.5 or more. confirmed.

Furthermore, since the magnetic head of each of the magnetic recording devices described above, especially the magnetic head, is made of an inexpensive material such as ferrite and sendust, the magnetic recording device can be manufactured at low cost.

According to the above-mentioned embodiment, the first core is composed of sendust and the second core is composed of ferrite.
Various metal materials such as permalloy, nimalloy, hard palm, alperm, etc. can be used as the first core, and single crystal ferrite, polycrystalline ferrite, etc. can be used as the second core.

[0045]

As described above, according to the magnetic recording apparatus 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 is shown, but the present invention can be applied to various magnetic recording devices other than this, and has a unique effect.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a magnetization state of a magnetic recording medium according to the present invention.

FIG. 3 is a graph in which a vertical axis represents a reproduction 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. 4 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. 5 is a schematic configuration diagram for explaining a magnetic recording device according to another embodiment of the present invention.

FIG. 6 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 head comprising a first core having a first saturation magnetic flux density and a second core having a second saturation magnetic flux density smaller than the first saturation magnetic flux density. In the magnetic recording device, the edge of the first core is arranged so as to run ahead of the edge of the second core.