JPH1166503A - Perpendicular magnetic recording and reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize satisfactory O/W characteristics and resolution by performing recording and reproducing operations for a two-layered magnetic storage medium, in which a soft magnetic back layer of a specific thickness is provided below a magnetic recording layer having perpendicular magnetic anisotropy by using a merge-type magnetoresistance effect type magnetic head which is composed of magnetoresistance effect type devices for reproduction having specific recording gap lengths. SOLUTION: A soft magnetic back layer (having a thickness of 10 to 50 nm) is provided below a magnetic recording layer having an easily-magnetization axis along a direction perpendicular to a recording surface, thereby obtaining a two-layered magnetic recording medium. A merge-type magnetoresistance effect type magnetic head H has an MR device 1 in a reproducing section R, and an upper recording magnetic pole 8, a read gap 7 and a recording gap 10 of a length of 0.2 to 0.5 μm in a recording portion W. The upper recording magnetic pole 8 disposed in the back end side has a smaller film thickness, and thus a larger saturated magnetic flux density of magnetic pole, than those of an upper shielding layer/a lower recording magnetic pole 4b disposed in the front end side. By performing recording and reproducing operations for the two-layered magnetic storage medium using the magnetic head H, low O/W characteristics of -30 dB or less and resolution of 60% or more are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording / reproducing system, and more particularly, to a two-layer magnetic recording medium in which a soft magnetic underlayer is arranged below a magnetic recording layer having perpendicular magnetic anisotropy. And a recording / reproducing method using a merged magnetoresistive effect type magnetic head.

[0002]

2. Description of the Related Art In order to increase the density of magnetic recording, a perpendicular magnetic recording / reproducing method using a perpendicular magnetic recording medium having an easy axis of magnetization in a direction perpendicular to the recording surface has been proposed (Iwasaki, Ouchi: Eye).・ EEE Transaction on Magnetics, MGE14, 849
(1987) (S. Iwasaki and KO)
uchi: IEEE Trans. Magn. , MA
G-14, 849 (1987)). The perpendicular magnetic recording / reproducing method is different from the longitudinal recording method currently in practical use in that the self-demagnetizing effect decreases as the recording density increases. In particular, when recording is performed on a CoCr magnetic film formed on a soft magnetic underlayer using a single pole head, a reproduction output has been confirmed even in a high linear recording density region of 600 kFCI or more.

However, the Japan Society of Applied Magnetics 93
As described in “Perpendicular Magnetic Recording Using a Merge MR Head” from page 75 of the JSCE, it was designed for longitudinal recording on a double-layer magnetic recording medium with a soft magnetic underlayer. When recording / reproducing is performed using a merge type MR head, although sufficient overwrite characteristics (hereinafter sometimes abbreviated as O / W characteristics) are obtained, there is a problem that the resolution is significantly reduced. Also, JP-A-8-24
Japanese Patent Application Publication No. 9601 describes that sufficient characteristics can be obtained when recording is performed on a single-layer medium using a ring head having an increased saturation magnetic flux density on the leading edge side. In the case of a narrow track, the output is insufficient, and reproduction with a more sensitive MR head is required.

[0004]

Therefore, the present invention provides a sufficient O / W characteristic and resolution even when recording / reproducing is performed with the merged magnetoresistive magnetic head on the double-layer magnetic recording medium. It is an object of the present invention to provide a perpendicular magnetic recording / reproducing method which can be obtained.

[0005]

The above object is achieved by the following present inventions (1) to (4). (1) A double-layer magnetic recording medium in which a soft magnetic underlayer having a thickness of 10 nm or more and 50 nm or less is arranged below a magnetic recording layer having perpendicular magnetic anisotropy has a recording gap length of 0.2 μm.
A perpendicular magnetic recording / reproducing method characterized in that recording / reproducing is performed by a merge type magnetoresistive magnetic head in which a reproducing magnetoresistive element having a size of 0.5 μm or less is combined. (2) The perpendicular magnetic recording / reproducing method according to the above (1), wherein the magnetic pole thickness at the trailing edge of the magnetic head is smaller than the magnetic pole thickness at the leading edge, and the saturation magnetic flux density of the trailing edge magnetic pole is larger than the saturation magnetic flux density of the leading edge magnetic pole. (3) The perpendicular magnetic recording / reproducing method according to (1) or (2), wherein the magnetic spacing between the double-layer magnetic recording medium and the magnetic head is 60 nm or less. (4) The perpendicular magnetic recording / reproducing method according to any one of (1) to (3), wherein the coercive force in the easy axis direction of the double-layer magnetic recording medium is 1800 Oe or more.

[0006]

According to the present invention, the thickness of the soft magnetic backing layer of the double-layer magnetic recording medium is set to 10 to 50 nm, and the recording gap length of the merge type magnetoresistive magnetic head is set to 0.2. By setting the thickness to 0.5 μm, both high resolution of 60% or more and low O / W characteristics of -30 dB or less can be achieved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail.

The present invention relates to a perpendicular magnetic recording / reproducing system for recording / reproducing information on / from the above-mentioned two-layer magnetic recording medium by a merge-type magnetoresistive head, and has a high resolution of 60% or more, and -30 dB. In order to achieve the following low O / W characteristics, the thickness of the soft magnetic underlayer of the two-layer magnetic recording medium is set to 10 nm or more and 50 nm or less, and the recording gap length of the recording portion of the merged magnetoresistive magnetic head is reduced. 0.2
It was set to not less than μm and not more than 0.5 μm.

The O / W characteristic is obtained by first recording on a recording medium with a predetermined low-frequency signal (LF), and then overwriting it with a predetermined high-frequency signal (HF) and reproducing it. Of the LF residual reproduction signal output value and the LF reproduction signal output value before overwriting, ie, expressed by the following equation. O / W characteristic (dB) = LF residual reproduction signal output / LF reproduction signal output before overwriting

[0010] The resolution is defined as the HF reproduction between the case where information is recorded on a recording medium with a predetermined low frequency signal (LF) and the case where information recorded with a predetermined high frequency signal (HF) is reproduced separately. The ratio between the value of the signal output and the value of the LF reproduction signal output, that is, is represented by the following equation. Resolution (%) = HF reproduction signal output / LF reproduction signal output

FIG. 1 is a schematic plan view showing an example of a merge type magnetoresistive head having a preferable structure used in the perpendicular magnetic recording / reproducing system of the present invention.

In FIG. 1, a magneto-resistance effect type magnetic head H has an MR element 1 in a reproducing section R.
Are connected to electrodes 2a and 2b. M above
Non-magnetic insulating layers 3a and 3b are formed on both sides of the R element 1 and the electrodes 2a and 2b, respectively. Lower and upper shield magnetic layers 4a and 4b are formed on the non-magnetic insulating layers 3a and 3b, respectively. ing. The above playback unit R
It is formed on a substrate 6 via an underlayer 5.

On the other hand, the recording section W is configured as an inductive type thin film head, and the upper shield magnetic layer 4 of the reproducing section R is formed.
b serves as a lower magnetic pole for recording, and has an upper recording magnetic pole 8 formed on a nonmagnetic insulating layer 9 provided on the upper shield magnetic layer 4b. In the figure, reference numeral 7 indicates a read gap, and reference numeral 10 indicates a recording gap.

Since the MR element 1 may have any conventional structure, further description is omitted.
At present, those having an MR film formed of NiFeRh / Ta / NiFe are generally used. Further, a spin valve element may be used.

As the electrodes 2a and 2b, Ta, Cu
For example, a film thickness of about 500 to 2000 A is formed.

The nonmagnetic insulating layers 3a and 3b are made of A
1 ₂ O ₃ , SiO ₂ , SiN, BN, AlN, etc.
It is formed to a thickness of about 00 to 2000A.

The shield layers 4a and 4b are made of NiFe,
FeAlSi, Co-based amorphous alloy (CoZrN
b, CoZrMo, etc.) to a thickness of about 1 to 4 μm.

The underlayer 5 is formed of Al ₂ O ₃ , SiO ₂ or the like to a thickness of about 1 to 10 μm.

The substrate 6 is made of AlTiC (ceramic mainly composed of Al ₂ O ₃ and TiC).

In the recording section W, the nonmagnetic insulating layer 9 is made of Al
It is formed to a thickness of about 0.1 to 1 μm using ₂ O ₃ , SiO _2, or the like. That is, the recording gap length is set to 0.1 μm or more and 1 μm or less.

The upper recording magnetic pole 8 is made of NiFe,
Co-based amorphous alloys (CoTaZr, CoZrNb
), And a film thickness of about 0.5 to 4 μm made of FeTaN or the like.

The upper recording magnetic pole 8 and the upper shield layer (common pole) 4b may have the same film thickness, but the magnetic pole on the trailing edge side (trailing side) with respect to the moving direction of the recording medium, that is, the upper pole. It is preferable that the recording magnetic pole 8 has a smaller film thickness than the magnetic pole on the front edge side (leading side), that is, the upper shield layer (common pole) 4b. Assuming that the thickness of the magnetic pole on the trailing edge side (trailing side) is 1, the thickness of the magnetic pole on the leading edge side (leading side) is preferably about 1 to 5. Further, the saturation magnetic flux density Bs of the magnetic pole on the trailing edge side (trailing side), ie, the upper recording magnetic pole 8 is preferably larger than the magnetic flux density Bs of the magnetic pole on the leading edge side (leading side), ie, 4b. The saturation magnetic flux density Bs of the magnetic pole on the edge side (trailing side) is 0.8T to 1.8.
T is about T, the saturation magnetic flux density Bs of the magnetic pole on the leading edge side (leading side) is about 0.5T to 0.8T, and the saturation magnetic flux density Bs of the magnetic pole on the trailing edge side (trailing side) is 1, Saturation magnetic flux density of the magnetic pole on the leading edge side (leading side)
Bs is preferably about 0.4 to 1. If the above conditions are not satisfied, the resolution and O / W characteristics tend to deteriorate.

The length of the recording gap 10 of the merged magnetoresistive head H of the present invention is 0.2
It is set to be not less than μm and not more than 0.5 μm. If the recording gap length is smaller than the above range, the O / W characteristics deteriorate, and if it is larger than the above range, the resolution deteriorates.

The double-layer magnetic recording medium has a thickness of 0.5 to 0.5.
A soft magnetic underlayer and a magnetic recording layer are sequentially formed on a glass or aluminum substrate of about 2 mm.

The magnetic recording layer is a magnetic recording layer having an easy axis of magnetization perpendicular to the recording surface, such as a CoCr magnetic layer, a Ba ferrite magnetic layer, or Co-γFe ₂ O _3.
Preferably, it is set to about 0 to 200 nm. In addition,
The coercive force in the easy axis direction of this double-layer magnetic recording medium is 1
It is preferably at least 800 Oe. This coercive force is 18
If it is less than 00 Oe, the resolution tends to deteriorate.

The soft magnetic underlayer is made of NiFe (permalloy), CoZrNb, or the like, and has a thickness of 10 nm or more and 50 nm or less. When the thickness of the soft magnetic backing layer is
If the value is smaller than the above range, the O / W characteristics deteriorate, and if the value is larger than the above range, the resolution deteriorates.

In the perpendicular magnetic recording / reproducing method of the present invention, information is recorded / reproduced on / from the above-described double-layer magnetic recording medium by using the above-mentioned merge type magnetoresistive head. The magnetic head, during the recording and reproduction,
In this case, the magnetic spacing between the double-layer magnetic recording medium and the merge-type magnetoresistive magnetic head is preferably 60 nm or less. If the magnetic spacing exceeds 60 nm, both resolution and O / W characteristics tend to deteriorate. When a protective film is formed on the surface of the medium facing the magnetic head, the magnetic spacing is a value obtained by adding the thickness of the protective film to the flying height of the head.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail.

Example 1 A film was formed on a 2.5 inch glass disk substrate of a perpendicular magnetic recording medium.
= 2400 Oe and a magnetic recording layer which is a CrCo magnetic layer with a film thickness of 100 nm. Under this magnetic recording layer, Ni
The soft magnetic backing layer of the Fe film is set to 0, 10, 20, 30, 4
0, 50, 60 and 100 nm, respectively, and sample Nos. M-1, M-2 and M-
3, M-4, M-5, M-6, M-7 and M-8.

Merge type magnetoresistive head This merge type magnetoresistive head has an upper magnetic pole (corresponding to 8 in FIG. 1) and a lower magnetic pole (corresponding to 8 in FIG. 1).
4b) and NiF whose saturation magnetic flux density Bs is 0.8T
An e-film was used. Other specifications of this magnetic head were as follows.

Upper recording magnetic pole width 3.2 μm Effective MR track width 2.2 μm

Upper recording magnetic pole thickness 3.5 μm Recording gap length 0.45 μm Upper shield (common pole) thickness 3.5 μm Read gap length 0.27 μm Lower shield thickness 1.0 μm

Slider shape Negative pressure / positive pressure combined type Head floating amount 30 nm Magnetic spacing amount 50 nm

Under the above conditions, LF (16.7 kF
CI) and HF (100 kFCI) are applied to the recording portion of the merged magnetoresistive magnetic head, and the resolution and O
/ W characteristics were measured. The resolution and the O / W characteristics were determined by the above equations. The results are shown in Table 1.

[0035]

[Table 1]

Next, the thickness of the soft magnetic backing layer of the double-layer magnetic recording medium was fixed at 20 nm, the recording gap length was 0.1, and
0.2, 0.3, 0.4, 0.5 and 0.6 μm (sample Nos. H-1, H-2, H-3, H-4,
H-5 and H-6), and the resolution and O / W characteristics were determined by the above equations. The results are shown in Table 2.

[0037]

[Table 2]

The effects of the present invention are apparent from the above results.

Example 2 The resolution and O / W characteristics were measured in the same manner as in Example 1 except that the film thickness and the saturation magnetic flux density of the trailing edge magnetic pole and the leading edge magnetic pole of the magnetic head were variously changed. Only when the trailing edge magnetic pole thickness of the magnetic head is thinner than the leading edge magnetic pole thickness and the saturation magnetic flux density of the trailing edge magnetic pole is larger than the saturation magnetic flux density of the leading edge magnetic pole, both the resolution and the O / W characteristics tend to be improved. Obtained.

Example 3 In Example 1, the resolution and O / W characteristics were measured by varying only the value of the magnetic spacing between the double-layer magnetic recording medium and the magnetic head. When the spacing is 60 nm or less, the resolution and O / W
A tendency to improve both characteristics was obtained.

Example 4 The resolution and O / W were the same as in Example 1 except that the coercive force in the easy axis direction of the double-layer magnetic recording medium was changed variously.
When the characteristics were measured, the magnetic spacing was 60
At nm or less, both resolution and O / W characteristics tended to be improved.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an example of a layer configuration of a magnetoresistive head according to the present invention.

[Explanation of symbols]

H Magnetoresistive magnetic head 1 MR element 2a Electrode 2b Electrode 3a Non-magnetic insulating layer 3b Non-magnetic insulating layer 4a Lower shield magnetic layer 4b Upper shield magnetic layer / lower recording magnetic pole (common pole) 7 Read gap 8 Upper recording magnetic pole 9 Non-magnetic layer 10 Recording gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutake Sato 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Kazuhiro Ouchi 4-Sunanu, Shinyacho, Akita City, Akita Prefecture 21 Within the Akita Prefectural Advanced Technology Research Institute (72) Inventor Naoki Honda 4-21, Sanda-Yoro, Niiyacho, Akita-shi, Akita Pref.

Claims (4)

[Claims] 1. A two-layer magnetic recording medium in which a soft magnetic underlayer having a thickness of 10 nm or more and 50 nm or less is disposed below a magnetic recording layer having perpendicular magnetic anisotropy, has a recording gap length of 0.1 mm.
A perpendicular magnetic recording / reproducing method characterized in that recording / reproducing is performed by a merged magnetoresistive magnetic head in which a reproducing magnetoresistive element of 2 μm or more and 0.5 μm or less is combined. 2. The perpendicular magnetic recording / reproducing method according to claim 1, wherein the thickness of the trailing edge magnetic pole of the magnetic head is smaller than the thickness of the leading edge magnetic pole, and the saturation magnetic flux density of the trailing edge magnetic pole is larger than the saturation magnetic flux density of the leading edge magnetic pole. 3. The perpendicular magnetic recording / reproducing method according to claim 1, wherein a magnetic spacing between the double-layer magnetic recording medium and the magnetic head is 60 nm or less. 4. The perpendicular magnetic recording / reproducing method according to claim 1, wherein the coercive force in the easy axis direction of the double-layer magnetic recording medium is 1800 Oe or more.