JPH06139542A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent reduction of reproducing efficiency by forming a soft magnetic backing layer having specified characteristics and a perpendicular recording layer on a nonmagnetic substrate to constitute a perpendicular magnetic recording medium. CONSTITUTION:This magnetic recording medium consists of a soft magnetic backing layer 12 and a perpendicular recording layer 13 formed on a nonmagnetic substrate 11. This soft magnetic backing layer 12 has 20-1000 relative magnetic permeability and >10kG saturation magnetic flux density. Further, film thickness deltaumum and relative magnetic permeability muu of the soft magnetic backing layer satisfy the relation of muuXdeltau (mum)>200. By this method, no magnetic saturation is caused in the top end of a head main pole or in the soft magnetic backing layer facing to the top end of the main magnetic pole by external floating magnetic field. The magnetic resistance of the backing layer can be decreased because its film thickness is controlled considering the relation with the low relative magnetic permeability, which prevents reduction of the reproducing efficiency.

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 medium used in a magnetic disk device of a perpendicular magnetization recording system, and more particularly to a perpendicular magnetic recording medium having improved reliability.

In recent years, as the amount of information processing in computer systems has increased, the amount of recorded information in magnetic disk devices has also increased, and there has been a demand for smaller size, larger capacity, and higher density recording. Along with this, a perpendicular magnetization recording method has been developed that enables much higher density recording than the conventional horizontal magnetization recording method. As a medium of the perpendicular magnetization recording method, a perpendicular recording layer is formed on a soft magnetic backing layer with high relative permeability. A perpendicular magnetic recording medium having a double-layered film structure in which magnetic layers are stacked has been proposed and put into practical use.

In the perpendicular magnetic recording medium having such a two-layer film structure, due to the presence of the soft magnetic backing layer having a high relative magnetic permeability, the stray magnetic field leaking from the outside is easily absorbed in the soft magnetic backing layer, and the absorption thereof. The generated stray magnetic field concentrates on the main magnetic pole of the corresponding perpendicular magnetic head, and the magnetic field concentration tends to hinder recording / reproduction. Therefore, the reliability of the stray magnetic field from the outside is prevented. A good media structure is needed.

[0004]

2. Description of the Related Art A conventional perpendicular magnetic recording medium 1 having a double-layer film structure.
As shown in FIG. 12, a high relative magnetic permeability (μ) of, for example, a NiFe film with a thickness of 1 μm is formed on a non-magnetic substrate 2 made of aluminum or glass whose surface is subjected to NiP plating or alumite treatment. = 1500 or more), and a perpendicular recording layer 4 made of a CoCr film having a thickness of 0.1 μm and having an easy axis of magnetization perpendicular to the thickness direction of the soft magnetic backing layer 3 was sequentially laminated. It consists of a composition.

The recording magnetic field from the perpendicular magnetic head 5 for recording / reproducing information on / from the perpendicular magnetic recording medium 1 having such a structure magnetizes the perpendicular recording layer 4 vertically, and then the soft magnetic backing layer immediately below the perpendicular recording layer 4. Recording is performed by a magnetic circuit that passes through the layer 3 in the horizontal direction, passes through the perpendicular recording layer 4 again, and returns to the perpendicular magnetic head 5. In addition, the main magnetic pole 6 of the perpendicular magnetic head 5 is magnetized by the recording magnetic field leaked from the already recorded perpendicular recording layer 4, and the coil 7 interlinks with it.
Reproduction is performed by outputting the voltage generated at the reproduction signal.

[0006]

By the way, the soft magnetic backing layer 3 having a high relative permeability in the perpendicular magnetic recording medium 1 is used.
Plays a part of the function of the perpendicular magnetic head 5 at the time of recording / reproducing, such as increasing the strength of the recording magnetic field from the main magnetic pole 6 of the perpendicular magnetic head 5 as described above, and improves the recording / reproducing efficiency. Play a role.

However, due to the existence of the soft magnetic backing layer 3, on the contrary, even a stray magnetic field leaking from the outside unrelated to the recording magnetic field to the tip of the main magnetic pole 6 of the perpendicular magnetic head 5 facing the recording medium 1 is inevitable. The magnetic field is concentrated and becomes a strong magnetic field to magnetize the opposing perpendicular recording layer 4, or magnetically saturate the tip of the main magnetic pole 6 of the perpendicular magnetic head 5 or the soft magnetic underlayer 3 corresponding to the tip of the main magnetic pole 6. As a result, the phenomenon that the regeneration efficiency is lowered occurs.

The source of the stray magnetic field is mainly a disk rotating motor in the magnetic disk device, a voice coil motor (VCM) for controlling the head position, and the like, both of which are located close to the perpendicular magnetic recording medium 1. The stray magnetic field leaking from these portions is weak, which is several thousandths of the recording magnetic field. At such a stray magnetic field, the recording magnetization of the perpendicular recording layer 4 is demagnetized. Or it does not degauss.

However, such a weak stray magnetic field is also absorbed in a wide area of the soft magnetic backing layer 3 and concentrated on the tip of the main magnetic pole 6 of the perpendicular magnetic head 5 which opposes it, whereby the recording magnetization of the perpendicular recording layer 4 is increased. Is abnormally increased to such an extent that it is demagnetized or demagnetized.

This phenomenon becomes stronger as the recording / reproducing efficiency becomes higher, and the existence of the soft magnetic backing layer 3 increases the risk of losing the recording magnetization due to the stray magnetic field. Therefore, there is a big defect that the recording magnetization of the perpendicular recording layer 4 is demagnetized by the stray magnetic field whose magnetic field strength is increased by the concentration, or erased (demagnetized) when the magnetic field strength is remarkably increased.

Therefore, as a method of solving such a problem, the soft magnetic backing layer is made to have a relative magnetic permeability of 50 to 800 to reduce the concentration of a stray magnetic field leaking from the outside at the tip of the main magnetic pole of the head. When the relative permeability of the magnetic backing layer is lowered, the magnetic resistance of the magnetic circuit composed of the perpendicular magnetic head and the soft magnetic backing layer at the time of reproduction increases and the reproduction efficiency deteriorates. JP-A-3-224122 has already proposed to increase the thickness to reduce the magnetic resistance.

However, if the relative magnetic permeability of the soft magnetic backing layer is lowered, when the stray magnetic field leaking from the outside is stronger, the head main magnetic pole tip or the soft magnetic backing layer corresponding to the main magnetic pole tip is also formed. Magnetically saturated to reduce the reproduction efficiency. Further, the soft magnetic backing layer having a low relative magnetic permeability has a large coercive force as compared with a conventional soft magnetic backing layer having a high relative magnetic permeability, and when the film thickness of the soft magnetic backing layer having a low relative magnetic permeability is increased,
There has been a problem that the leakage of magnetic flux from the domain wall formed in the soft magnetic underlayer increases, and the magnetic flux becomes noise and increases during reproduction, degrading the reproduction characteristics.

In view of the conventional problems described above, the present invention suppresses the stray magnetic field absorbed in the soft magnetic backing layer as much as possible, and the recording magnetization of the perpendicular recording layer due to the magnetic field concentration at the tip of the corresponding main magnetic pole of the perpendicular magnetic head. It is an object of the present invention to provide a novel perpendicular magnetic recording medium in which the demagnetization, demagnetization, etc. are prevented and the noise caused by the domain wall of the thick soft magnetic backing layer having a low relative permeability is reduced.

[0014]

To achieve the above object, the present invention provides a magnetic recording medium comprising a non-magnetic substrate and a soft magnetic backing layer and a perpendicular recording layer laminated on the non-magnetic substrate. Has a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more.

The thickness of the soft magnetic backing layer δu (μ
m) and the relative magnetic permeability μu have a relationship of μu × δu (μm)> 200. Further, the soft magnetic backing layer has a structure in which at least two soft magnetic films having a thickness of 2 μm or less are laminated.

Further, a non-magnetic dividing layer having a thickness of 0.1 μm or less is provided between the soft magnetic films laminated in the plurality of layers. Furthermore, in a magnetic recording medium in which a soft magnetic backing layer and a perpendicular recording layer are laminated on a non-magnetic substrate, a relative magnetic permeability of 20 to 1000 and 10 KG are provided between the soft magnetic backing layer and the perpendicular recording layer. An intermediate magnetic layer having the above saturation magnetic flux density is provided.

Further, the film thickness δi (μm) of the intermediate magnetic layer and the relative magnetic permeability μi have a relation of μi × δi (μm) <200.

[0018]

In the perpendicular magnetic recording medium of the present invention, a soft magnetic backing layer having a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more is formed on a non-magnetic substrate by a relative magnetic permeability μu × film thickness δu (μm). >
By providing a film thickness of the relationship of 200, by forming a perpendicular magnetic recording layer laminated on the soft magnetic backing layer,
Since the relative permeability μu of the soft magnetic underlayer is low and the saturation magnetic flux density is large, magnetic saturation of the head main pole tip or the soft magnetic underlayer corresponding to the tip of the main pole due to the stray magnetic field leaking from the outside occurs. It becomes difficult and the film thickness is controlled in consideration of the low relative permeability, so that the magnetic resistance becomes small, the reduction of the reproducing efficiency is eliminated, and the stray magnetic field is concentrated on the tip of the main magnetic pole of the head. It is possible to prevent demagnetization and demagnetization of recording magnetization.

Further, an intermediate magnetic layer having a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more is provided between the high magnetic permeability soft magnetic backing layer provided on the non-magnetic substrate and the perpendicular recording layer. When the medium structure is such that the relative magnetic permeability μi x the film thickness δi (μm) <200, the intermediate magnetic layer has a low relative magnetic permeability μi and a large saturation magnetic flux density. Magnetic saturation of the intermediate magnetic layer corresponding to the head main magnetic pole tip due to the stray magnetic field leaking from the magnetic field hardly occurs, and the area where the stray magnetic field is concentrated is at most 1 mm from the head main magnetic pole tip.
Since the distance is up to .mu.m, by setting the thickness of the intermediate magnetic layer to at least 1 .mu.m, magnetic saturation of the high-permeability soft magnetic backing layer immediately thereunder does not occur, and the high permeability The presence of such a soft magnetic backing layer reduces its magnetic resistance, eliminating the decrease in reproduction efficiency.
Moreover, it is possible to prevent demagnetization, demagnetization, etc. of the recording magnetization of the perpendicular recording layer due to the concentration of the stray magnetic field at the tip of the head main magnetic pole.

Further, as a soft magnetic backing layer, a plurality of soft magnetic films having a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more and a thickness of 2 μm or less are repeatedly laminated on a non-magnetic substrate, By adopting a medium structure in which a perpendicular recording layer is provided on the soft magnetic backing layer, magnetic saturation of the soft magnetic backing layer of the above-mentioned laminated structure corresponding to the head main magnetic pole tip due to a stray magnetic field leaked from the outside is less likely to occur. Also, since the magnetic flux leaking from the domain wall formed in each laminated soft magnetic film is reduced, the noise due to the leakage of the magnetic flux is also reduced, and the reproducing characteristic can be improved.

Furthermore, as a soft magnetic backing layer on a non-magnetic substrate, a soft magnetic film having a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more and a thickness of 2 μm or less and a non-magnetic component layer are repeatedly formed. By stacking multiple layers and providing a perpendicular magnetic recording layer on the soft magnetic backing layer, each soft magnetic film is reliably magnetically separated by a non-magnetic dividing layer, and the stray magnetic field leaks from the outside. Magnetic saturation of the soft magnetic backing layer having the above-described laminated structure corresponding to the tip of the head main magnetic pole is less likely to occur. Further, the magnetic flux leaking from the domain wall formed in each laminated soft magnetic film is significantly reduced, the noise due to the leak of the magnetic flux is further reduced, and the reproducing characteristic can be improved.

[0022]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view of essential parts showing a first embodiment of a perpendicular magnetic recording medium according to the present invention.

In the figure, 11 is a non-magnetic substrate made of aluminum whose surface is NiP plated, for example.
On the non-magnetic substrate 11, for example, with low relative permeability (μu = 200),
A soft magnetic backing layer 12 made of a FeCo film having a thickness of δu of 10 μm having a saturation magnetic flux density of 20KG, and an easy axis of magnetization perpendicular to the film thickness direction of the soft magnetic backing layer 12 on the soft magnetic backing layer 12 The perpendicular recording layer 13 made of a CoCr film having a film thickness of 0.1 μm is arranged in a laminated form.

The soft magnetic backing layer 12 and the perpendicular recording layer 13 have a power power density for sputtering of 5.5 W / cm ² ,
Sputtering gas pressure of Ar etc. is 5 mTorr, substrate temperature is 2
A film is formed by the sputtering method under the sputtering condition of 00 ° C.

In the perpendicular magnetic recording medium of the first embodiment described above, the dependence of the reproduction output by computer simulation on the relative permeability μu × thickness δu of the soft magnetic backing layer 12 is shown in FIG.
Therefore, the relative magnetic permeability of the soft magnetic backing layer 12 μu × film thickness δu
If is over 200, the playback output is almost saturated. Therefore,
Since it is appropriate that the film thickness δu of the soft magnetic backing layer 12 is 10 μm or less in view of the internal stress in the medium structure, the relative magnetic permeability μu must be 20 or more.

FIG. 3 shows the dependence of the reproduction output on the relative magnetic permeability of the soft magnetic backing layer in the maximum stray magnetic field of 8 Oe predicted in the magnetic disk drive. When the relative magnetic permeability μu of 1000 is 1000 or more, the reproduction output decreases due to magnetic saturation, so it is necessary to set it to 1000 or less.

Further, FIG. 4 also shows the dependence of the reproduction output on the relative magnetic permeability and the saturation magnetic flux density of the soft magnetic underlayer in the stray magnetic field of 8 Oe. From this figure, the relative magnetic permeability μu is 500, In each perpendicular magnetic recording medium having three kinds of soft magnetic backing layers, the relative magnetic permeability μu x the film thickness δu was made constant by changing the film thickness to 1000, 2000 and the film thickness was also changed. The saturation magnetic flux density of the soft magnetic backing layer is required to be 5 kg or more, and the saturation magnetic flux density of the soft magnetic backing layer having a relative magnetic permeability of 1000 is required to be 10 kg or more.

Further, FIG. 5 shows the reproduction output measured in a state where an external stray magnetic field is applied perpendicularly to both recording medium surfaces of the perpendicular magnetic recording medium of the first embodiment and the conventional perpendicular magnetic recording medium while varying its strength. It was found that the perpendicular magnetic recording medium of the first embodiment did not lower the reproduction output even with an external stray magnetic field of about 7 Oe, which is stronger than the conventional perpendicular magnetic recording medium. It should be noted that when an external stray magnetic field whose reproducing output is reduced by about 80% is applied to the perpendicular magnetic recording medium of the first embodiment and then the external stray magnetic field is removed, the reproducing output returns to the original state. The recording magnetization of the perpendicular recording layer is not demagnetized by the strength of the external stray magnetic field, but the magnetic saturation of the head main magnetic pole tip or the soft magnetic backing layer corresponding to the main magnetic pole tip causes the reproduction output to decrease. Was recognized.

Further, FIG. 6 shows B—H magnetization curves of the soft magnetic backing layer of the first embodiment and the soft magnetic backing layer of the conventional example, and this figure shows that the soft magnetic backing layer of the conventional example does not. It is clear that the soft magnetic backing layer of the first embodiment having a low relative magnetic permeability and a high saturation magnetic flux density does not magnetically saturate up to a large external stray magnetic field strength.

Therefore, in such a perpendicular magnetic recording medium of the first embodiment, magnetic saturation of the head main magnetic pole tip or the soft magnetic underlayer corresponding to the main magnetic pole tip occurs due to the stray magnetic field leaking from the outside. It becomes difficult, and the film thickness is controlled in consideration of the low relative magnetic permeability to reduce the magnetic resistance, so that the reduction of the reproducing efficiency is eliminated, and the stray magnetic field is concentrated on the tip of the main magnetic pole of the head, so that It is possible to prevent demagnetization and demagnetization of the recording magnetization.

FIG. 7 is a cross-sectional view of an essential part showing a second embodiment of the perpendicular magnetic recording medium according to the present invention, and the same parts as those in FIG. 1 are designated by the same reference numerals. The embodiment shown in this figure is different from the embodiment shown in FIG. 1 in that a saturated magnetic flux density of 20 KG is provided between the non-magnetic substrate 11 and the perpendicular recording layer 13 with high relative permeability (μ = 2000). The soft magnetic backing layer 21 made of a NiFe film having a film thickness of 10 μm and a low magnetic permeability (μi = 200) on the soft magnetic backing layer 21 having a saturation magnetic flux density of 10 KG
The intermediate magnetic layer 22 made of a FeCo film having a thickness of Δi is arranged.

In such a perpendicular magnetic recording medium of the second embodiment, the tip of the main magnetic pole 6 of the perpendicular magnetic head facing the conventional perpendicular magnetic recording medium in an external stray magnetic field of 3 Oe and its vicinity are calculated by a computer in FIG. As shown by the result of simulating the magnetic flux density of the magnetic recording medium, the area where the external stray magnetic field is concentrated is 1 μm at most from the tip of the main magnetic pole 6 of the perpendicular magnetic head to the soft magnetic backing layer 3 side of the perpendicular magnetic recording medium which faces the magnetic pole.
Since it is up to about m, the portion corresponding to the area has a low relative magnetic permeability (μi = 200) of 10 KG in this embodiment.
Since the intermediate magnetic layer 22 made of the FeCo film having a saturation magnetic flux density of 1 .mu.m and a film thickness .delta.i is provided, the intermediate magnetic layer 22
And magnetic saturation of the high-permeability soft magnetic backing layer 21 thereunder does not occur, and the presence of the high-permeability soft magnetic backing layer 21 reduces its magnetic resistance, resulting in a reduction in reproduction efficiency. Will be resolved. Further, it is possible to prevent demagnetization and demagnetization of the recording magnetization of the perpendicular recording layer 13 due to the concentration of the stray magnetic field at the tip of the head main magnetic pole.

FIG. 9 is a cross-sectional view of essential parts showing a third embodiment of the perpendicular magnetic recording medium according to the present invention. In this embodiment, the surface is a non-magnetic substrate made of aluminum whose surface is subjected to NiP plating, and the soft magnetic backing layer 31 on the non-magnetic substrate 11 has, for example, a low relative permeability (μu = 200) and a high strength of 20 KG. Soft magnetic film 32 made of FeCo film having a saturation magnetic flux density and a thickness of 1 μm
And a non-magnetic dividing layer 33 made of a Cr film having a thickness of 1 μm are alternately repeated to form about 10 layers, and the soft magnetic backing layer 31 is perpendicular to the thickness direction of the soft magnetic backing layer 31. A perpendicular recording layer 13 made of a CoCr film having a thickness of 0.1 μm and having an easy axis of magnetization is arranged.

In the perpendicular magnetic recording medium of the third embodiment as described above, each soft magnetic film 32 constituting the soft magnetic backing layer 31 is magnetically reliably separated by the non-magnetic dividing film, and the floating leaks from the outside. Magnetic saturation of the soft magnetic backing layer 31 of the above-described laminated structure corresponding to the tip of the main magnetic pole of the head due to a magnetic field is less likely to occur. Further, the magnetic flux leaking from the magnetic domain wall formed in each of the laminated thin soft magnetic films is reduced, the noise due to the leak of the magnetic flux is significantly reduced, and the reproducing characteristic can be improved.

FIGS. 10 (a) and 10 (b) show the results of examining whether or not a noise spectrum is generated during reproduction of the perpendicular magnetic recording media of the first and third embodiments. In the perpendicular magnetic recording medium of, since the thickness of the soft magnetic backing layer is large, the magnetic flux leaking from the domain wall increases in proportion to the film thickness of the soft magnetic backing layer, so that as shown in Fig. 10 (a). Noise caused by the domain wall of the soft magnetic underlayer occurs in the low frequency range. On the other hand, in the perpendicular magnetic recording medium of the third embodiment, as shown in FIG. 10 (b), the generation of noise due to the domain wall in the soft magnetic underlayer is hardly seen, and the reproduction characteristics are improved.

In the third embodiment, as the soft magnetic backing layer, a soft magnetic film made of FeCo film having a low relative permeability and a high saturation magnetic flux density and a film thickness of 1 μm and a Cr film having a film thickness of 0.1 μm are used.
An example of using a soft magnetic backing layer in which multiple layers of non-magnetic layers composed of films are alternately repeated has been described.For example, a low relative permeability of 20 to 1000 and high saturation of 10 KG or more Even when a soft magnetic backing layer having a structure in which a plurality of soft magnetic films having a magnetic flux density of 2 μm or less are repeatedly laminated is used, substantially the same effect as that of the third embodiment can be obtained.

Further, a soft magnetic backing layer, an intermediate magnetic layer, or a plurality of laminated layers made of a FeCo film having a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more in the first, second and third embodiments. When a soft magnetic film or the like having a thickness of 2 μm or less is formed, a magnetic field is applied in the radial direction or the circumferential direction of the non-magnetic substrate to align the easy axis of magnetization in the radial direction or the circumferential direction of the non-magnetic substrate. With the layered film structure, it is possible to further reduce the noise generated due to variations in the two-dimensional shape of the domain wall formed in each layered film, and to improve the reproduction characteristics.

11 (a) and 11 (b) show a soft magnetic backing layer made of a FeCo film formed by aligning the easy axis of magnetization in the radial direction or the circumferential direction of the non-magnetic substrate by applying a magnetic field, or an intermediate layer. Examine whether a noise spectrum is generated during reproduction of a perpendicular magnetic recording medium with a magnetic layer and a soft magnetic backing layer consisting of a FeCo film formed without applying a magnetic field, or a perpendicular magnetic recording medium with an intermediate magnetic layer. The perpendicular magnetic recording medium to which the soft magnetic backing layer made of FeCo film formed without applying a magnetic field or the intermediate magnetic layer is applied is shown in the figure.
As shown in 11 (a), while noise caused by the domain wall of the soft magnetic underlayer occurs in the low frequency range, a magnetic field is applied to the nonmagnetic substrate in the radial direction or the circumferential direction. In a perpendicular magnetic recording medium with a soft magnetic backing layer consisting of a FeCo film formed with the easy axis of magnetization aligned or with an intermediate magnetic layer, this is due to the domain wall in the soft magnetic backing layer as shown in Fig. 11 (b). The generation of noise is significantly reduced.

Further, in the above embodiments, the soft magnetic backing layer,
Alternatively, an example of using a FeCo film having a low relative magnetic permeability and a high saturation magnetic flux density as the intermediate magnetic layer has been described,
Instead of the FeCo film, a magnetic film in which a third element such as Ni is added to FeCo or a magnetic film having the same function as the FeCo film can be used, and the soft magnetic backing layer made of the FeCo film or the NiFe film can be used. The film forming method is not limited to the sputtering method, and the film may be formed by the plating method.

The perpendicular recording layer is not limited to the CoCr film, and a hard magnetic film such as a CoCrTa film may be used. Further, a protective film or a lubricating film may be provided on the perpendicular recording layer if necessary. Needless to say.

[0041]

As is apparent from the above description, according to the perpendicular magnetic recording medium of the present invention, the relative magnetic permeability of 20 to 1000 and the saturation magnetic flux of 10 KG or more are provided between the non-magnetic substrate and the perpendicular recording layer. The soft magnetic backing layer having a density is formed by comparing the relative magnetic permeability μu with the film thickness δ.
u (μm)> 200, or a medium structure provided with a film thickness that satisfies the relation, or a relative magnetic permeability of 20 to 1000 between the soft magnetic backing layer made of a NiFe film provided on a non-magnetic substrate and the perpendicular recording layer. When
The medium magnetic layer having a saturation magnetic flux density of 10 KG or more is formed to have a film thickness such that the relative magnetic permeability μi × the film thickness δi (μm) <200. Magnetic saturation of the main magnetic pole tip or the soft magnetic backing layer corresponding to the main magnetic pole tip is less likely to occur, and the magnetic resistance is also reduced by controlling the film thickness in combination with the low relative magnetic permeability, so that the reproduction efficiency is improved. Is eliminated, and demagnetization and demagnetization of the recording magnetization of the perpendicular recording layer due to the concentration of the stray magnetic field at the tip of the main magnetic pole of the head can be prevented.

Further, as a soft magnetic backing layer between the non-magnetic substrate and the perpendicular recording layer, a soft magnetic FeCo film having a relative permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more and a thickness of 2 μm or less is used. The film is repeatedly laminated into multiple layers, or a soft magnetic film made of the same FeCo film and a film thickness of 0.1 μm or less.
A structure in which a non-magnetic dividing layer made of a Cr film is alternately repeated to be laminated in a plurality of layers, and further, the directions of the easy axis of magnetization of the soft magnetic backing layer and the intermediate magnetic layer are aligned in the radial direction or the circumferential direction. As a result, magnetic saturation of the soft magnetic backing layer of the above-described laminated structure corresponding to the tip of the head main pole due to a stray magnetic field from the outside hardly occurs. Also a soft magnetic backing layer,
Noise due to leakage of magnetic flux due to magnetic domain walls in the intermediate magnetic layer is also significantly reduced, and there is an advantage that reproduction characteristics and reliability can be improved, and a practically excellent effect is exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of a perpendicular magnetic recording medium of the present invention.

FIG. 2 is a diagram showing changes in relative permeability × film thickness and reproduction output of the soft magnetic backing layer according to the first example of the present invention.

FIG. 3 is a diagram showing changes in relative permeability and reproduction output of the soft magnetic backing layer in a stray magnetic field according to the first example of the present invention.

FIG. 4 is a diagram showing changes in relative permeability and saturation magnetic flux density of the soft magnetic backing layer and reproduction output in a stray magnetic field according to the first example of the present invention.

FIG. 5 is a diagram showing changes in reproduction output according to the external stray magnetic field strength of the perpendicular magnetic recording media of the first embodiment of the present invention and the conventional example.

FIG. 6 is a diagram showing BH magnetization curves of the soft magnetic backing layer according to the first example of the present invention and the conventional soft magnetic backing layer.

FIG. 7 is a cross-sectional view of essential parts showing a second embodiment of the perpendicular magnetic recording medium of the present invention.

FIG. 8 is a diagram showing a magnetic flux density in the vicinity of a tip of a head main magnetic pole in an external stray magnetic field.

FIG. 9 is a cross-sectional view of essential parts showing a third embodiment of the perpendicular magnetic recording medium of the present invention.

FIG. 10 is a diagram showing how noise spectra are generated during reproduction of the perpendicular magnetic recording media of the first and third embodiments of the present invention.

FIG. 11 is a diagram showing a noise spectrum generation state during reproduction of a perpendicular magnetic recording medium to which a soft magnetic backing layer formed with or without application of a magnetic field of the present invention or an intermediate magnetic layer is applied.

FIG. 12 is a cross-sectional perspective view of an essential part for explaining a conventional perpendicular magnetic recording medium.

[Explanation of symbols]

 2,11 Non-magnetic substrate 3,12,21,31 Soft magnetic backing layer 4,13 Perpendicular recording layer 6 Main pole 22 Intermediate magnetic layer 32 Soft magnetic film 33 Non-magnetic separation layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Sato Kenji Sato 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Kenichi Aoshima 1015 Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (6)

[Claims] 1. A soft magnetic backing layer (1) on a non-magnetic substrate (11).
In the magnetic recording medium formed by laminating 2) and the perpendicular recording layer (13), the soft magnetic backing layer (12) has a relative magnetic permeability of 20 to 1000 and a saturation magnetic flux density of 10 KG or more. Characteristic perpendicular magnetic recording medium. 2. The film thickness δu (μ of the soft magnetic backing layer (12)
2. The perpendicular magnetic recording medium according to claim 1, wherein m) and relative permeability μu have a relationship of μu × δu (μm)> 200. 3. The perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic backing layer (12) is formed by laminating at least two soft magnetic films having a thickness of 2 μm or less. 4. The perpendicular magnetic recording medium according to claim 3, wherein a non-magnetic dividing layer (33) having a thickness of 0.1 μm or less is provided between the soft magnetic films (32) laminated in the plurality of layers. . 5. A soft magnetic backing layer (1) on a non-magnetic substrate (11).
In a magnetic recording medium in which 2) and a perpendicular recording layer (13) are laminated, between the soft magnetic backing layer (12) and the perpendicular recording layer (13), 20
A perpendicular magnetic recording medium comprising an intermediate magnetic layer (22) having a relative magnetic permeability of up to 1000 and a saturation magnetic flux density of 10 KG or more. 6. The perpendicular according to claim 5, wherein the film thickness δi (μm) of the intermediate magnetic layer (22) and the relative magnetic permeability μi have a relation of μi × δi (μm) <200. Magnetic recording medium.