JPH0785442A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To realize a vertical magnetic recording medium being superior in productivity and having excellent recording-reproducing characteristics. CONSTITUTION:The vertical magnetic recording medium is constructed from a nonmagnetic base 11 and a soft magnetic backing layer 12 and a vertical magnetization recording layer 13 provided thereon. In this vertical magnetic recording medium, a CoB film 21 is used for the soft magnetic backing layer 12 and the film is divided into at least two layers or more by a nonmagnetic film 22.

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 which has excellent recording and reproducing characteristics and is excellent in productivity when used in a magnetic disk device of a perpendicular magnetic recording system.

In a conventional magnetic disk device, information is recorded by a horizontal recording method in which a recording medium is magnetized in a horizontal direction. In this method, a minute magnet magnetized in the horizontal direction with respect to the recording layer repels the adjacent magnet,
They weaken each other's magnetization. This effect becomes conspicuous when information is recorded at a high density, and there is a limit to the high density recording of information.

Perpendicular magnetic recording has been proposed to overcome this limitation, and the most common recording medium that realizes this is a two-layer film medium in which a CoCr film and a NiFe film are laminated. The CoCr film is a recording layer, and recording is performed with magnetization left perpendicular to the film. The NiFe film is a backing layer,
The recording magnetic field from the magnetic head plays the role of returning the magnetic field to the head after magnetizing the CoCr recording layer, and is considered to be a part of the magnetic head, and it is necessary to have excellent soft magnetic characteristics.

[0004]

2. Description of the Related Art As shown in FIG. 5, a conventional perpendicular double-layered recording medium has a high magnetic permeability backing layer 12 and a perpendicular magnetization recording layer 13 formed on a non-magnetic disk substrate 11. As the backing layer 12, for example, a NiFe film formed to have a thickness of 4 μm on the non-magnetic substrate 11 made of aluminum subjected to NiP surface treatment by electrolytic plating is used. The thickness of the backing layer 12 is the variation (modulation) of the recording / reproducing characteristics within one round of the disc.
Considering the above, 3 to 4 μm or more is necessary.

The perpendicular magnetization recording layer 13 is made of CoCr having a thickness of 0.15 μm, for example, by sputtering. Further, if necessary, the perpendicular magnetization recording layer 1
A lubrication protective film is provided on the surface of No. 3.

In recent years, the magnetic disk apparatus using such a recording medium has been rapidly miniaturized, and the disk size to be used is changed from 5.25 inches to 3.5 inches, and further 2.
It has been reduced to 5 inches.

When the disk size is reduced as described above, the number of man-hours required for setting the film forming apparatus is increased, which is a heavy burden particularly when forming a NiFe film as a backing layer to be formed by electrolytic plating. Further, the saturation magnetic flux density of the NiFe film is at most 10000 Gauss, and as described above, as the backing layer which plays a role as a part of the head,
It is desirable to set it to 13000 to 15000 Gauss like the head magnetic pole. As such a backing layer having a high saturation magnetic flux density, a CoB film having a high saturation magnetic flux density that can be formed by electroless plating may be used.

[0008]

The above CoB film has excellent characteristics, but since it is formed by the electroless plating method, the deposition rate of CoB decreases as the film thickness increases, and the CoB deposition rate decreases to 1 μm.
There is a problem that it becomes difficult to stably form a film having a thickness of m or more. Further, in order to eliminate the variation (modulation) of the recording / reproducing characteristics within one round of the disk, it is necessary to align the magnetic anisotropy in the disk surface of the backing layer in the same direction.

The present invention intends to realize a perpendicular magnetic recording medium having excellent productivity and good recording / reproducing characteristics.

[0010]

In the perpendicular magnetic recording medium of the present invention, a perpendicular magnetic recording comprising a non-magnetic substrate 11, a soft magnetic backing layer provided thereon, and a perpendicular magnetization recording layer 13. In the medium, the soft magnetic backing layer 12 is
The CoB film 21 is used, and the film is divided into at least two layers by the nonmagnetic film 22. In addition to that, the thickness of the non-magnetic film 22 is set to 10 nm or more,
Each film thickness is set so that the film thickness ratio with the CoB film 21 is at least ½ or less.

Further, a hard magnetic film or a semi-hard magnetic film (31) is formed on the non-magnetic substrate 11, and a residual magnetization in a uniaxial direction, for example, a radial direction of the non-magnetic substrate 11 or a circumferential direction is applied to the film. The soft magnetic backing layer 12 is formed after the application.

By adopting this structure, a perpendicular magnetic recording medium having excellent productivity and good recording / reproducing characteristics can be obtained.

[0013]

In the present invention, the soft magnetic backing layer 12 is made of CoB.
By using the film 21 and dividing the CoB film 12 into at least two layers by the nonmagnetic film 22, a CoB film having a thickness that can be stably deposited can be formed on the nonmagnetic film, and the CoB film can be formed to a desired thickness. By repeatedly forming the film, a backing layer having a film thickness on the order of μm can be obtained.

Further, the non-magnetic substrate 11 and the soft magnetic backing layer 1
2 is provided with a hard magnetic or semi-hard magnetic film 31, and the film 3
By imparting residual magnetization to No. 1 in the radial direction or the circumferential direction, the magnetic anisotropy of the CoB film 21, which is the soft magnetic backing layer, is aligned in the radial direction or the circumferential direction, and the soft anisotropy in one circumference of the disk is increased. Since the magnetic characteristics are uniform, good modulation characteristics can be obtained.

[0015]

1 is a sectional view showing a first embodiment of the present invention. In this embodiment, the CoB film 21 is formed on the non-magnetic substrate 11 made of aluminum which is surface-treated with NiP.
5 μm in thickness, 0.1 μm in thickness of non-magnetic film 22 made of NiP, 6 layers of CoB film and 5 layers of NiP film are alternately formed, and the total thickness of CoB is 3.0 μm.
(0.5 × 6 μm), the total film thickness of NiP is 0.5 μ
m (0.1 × 5 μm), and the total thickness of the soft magnetic backing layer 12 was 3.5 μm. Further, a perpendicular magnetization recording layer 13 of CoCrTa is further formed thereon by a sputtering method.
Was deposited to a thickness of 0.1 μm.

Here, the CoB film is formed by electroless plating by heating a plating solution containing cobalt sulfate and dimethylamine borane as main components to 60 ° C. and immersing the solution for a predetermined time.
The NiP film is formed by electroless plating by heating a plating solution containing nickel chloride and sodium hypophosphite as main components to 80 to 90 ° C. and immersing it for a predetermined time. Also, C
The conditions for forming the oCrTa film by sputtering are a power density of 5.5 w / cm ² , a gas pressure of 5 mTorr, and a substrate temperature of 250 ° C.

As a backing layer, 3 is formed by the above multi-layer film formation.
It is possible to obtain a film having a thickness of μm or more, and the reproduction output and D ₅₀ and other recording and reproducing characteristics are almost the same as those of the conventional NiFe film. In addition, since the CoB film and the NiP film can be formed by electroless plating in the film forming process, it is not necessary to replace the substrate mounting jig, and the CoB film bath and the NiP film bath are alternately dipped to form a multi-layered film. Since it can be formed, the number of steps can be significantly reduced as compared with electroplating.

In the above embodiment, the thickness of the CoB film and the thickness of the NiP film are 0.5 μm and 0.1 μm, respectively. The allowable range (the thickness of the non-magnetic film is preferably as thin as possible), the total thickness, and the number of layers may be taken into consideration. However, the thickness of the NiP film is set to 10 nm, which is the minimum required to divide the CoB film, and the thickness of the CoB film is at least twice that.

FIG. 2 is a sectional view showing a second embodiment of the present invention. This embodiment is basically the same as the previous embodiment,
The difference is that the non-magnetic substrate 11 and the soft magnetic backing layer 12 are
That is, a hard magnetic or semi-hard magnetic film 31 is provided between and. As the hard magnetic or semi-hard magnetic film 31, for example, a CoCr film having a thickness of 0.1 μm can be used. This C
The oCr film has a power density of 5.5 w / cm by the sputtering method.
^{2. A} film can be formed at a gas pressure of 5 mTorr and a substrate temperature of 150 ° C.
Then, the residual magnetization is left in a uniform direction during or after the film formation.

A permanent magnet as shown in FIG. 3 or FIG. 4 is used as the method of giving the residual magnetization. The method shown in FIG.
An annular magnet 42 magnetically coupled by 3
And a columnar magnet 41 are combined. As shown in the figure, the disk substrate during or after film formation is opposed to the magnet and magnetized in the radial direction to give residual magnetization. The method shown in FIG. 4 uses two rectangular parallelepiped magnets 51 and 52 that are magnetically coupled by a yoke 53, and positions the disk substrates so that parts of them face each other. Remanent magnetization is applied in the circumferential direction.

On the hard magnetic or semi-hard magnetic film 31 thus imparted with the residual magnetization, a multilayer film of the CoB film 21 and the non-magnetic film 22 such as NiP is formed as in the first embodiment. The modulation waveform of this embodiment formed in this way is uniform and good over the entire circumference. In this embodiment, as an example of a hard magnetic or semi-hard magnetic film, hard magnetic CoCr is used.
Although the film is used, other materials such as Co alloy, γ-iron oxide, and chromium oxide may be used. Alternatively, a FeCo-based alloy or the like may be used as the semi-hard magnetic film.

Although a sputtered CoCr alloy film is used as the perpendicular magnetization recording layer in both the first and second embodiments,
It goes without saying that other materials such as CoNiRe alloy for plating may be used. If necessary, a protective film such as a carbon film and a lubricating film may be provided on the perpendicular magnetization recording layer.

[0023]

According to the present invention, a CoB film is used as the soft magnetic backing layer, and the backing layer is divided into at least two layers with a non-magnetic film such as NiP, so that a backing film having a thickness on the order of μm can be obtained. The layer can be easily obtained by electroless plating with excellent mass productivity.

Further, after forming a hard magnetic or semi-hard magnetic film on a non-magnetic substrate and giving residual magnetization to this film in the radial direction or the circumferential direction of the non-magnetic substrate, the CoB film is made of non-magnetic material such as NiP. By forming a backing layer divided by a magnetic film, Co
The magnetic anisotropy of the B film can be aligned in the circumferential direction or the radial direction of the non-magnetic substrate, and the magnetic characteristics within one circumference of the disk can be made uniform to obtain good modulation characteristics. Therefore, it is possible to obtain a perpendicular magnetic recording medium which is excellent in mass productivity and has good recording and reproducing characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a diagram showing an example of a magnet that applies remanent magnetization to a perpendicular magnetic recording medium in a uniform direction.

FIG. 4 is a diagram showing another example of a magnet that applies remanent magnetization to a perpendicular magnetic recording medium in a uniform direction.

FIG. 5 is a cross-sectional view showing an example of a conventional perpendicular magnetic recording medium.

[Explanation of reference numerals] 11 ... Non-magnetic substrate 12 ... Soft magnetic backing layer 13 ... Perpendicular recording layer 21 ... CoB film 22 ... Non-magnetic film (NiP film) 31 ... Hard magnetic or semi-hard magnetic film

Claims (3)

[Claims] 1. A non-magnetic substrate (11), a soft magnetic backing layer (12) and a perpendicular magnetization recording layer (1) provided thereon.
In the perpendicular magnetic recording medium of 3), the soft magnetic backing layer (12) comprises a CoB film (21), which is divided into at least two layers by a non-magnetic film (22). Characteristic perpendicular magnetic recording medium. 2. The nonmagnetic film (22) has a film thickness of 10 nm or more, and a film thickness ratio to the CoB film (21) is at least 1.
2. The perpendicular magnetic recording medium according to claim 1, wherein each film thickness is set to be ½ or less. 3. A hard magnetic film or a semi-hard magnetic film (31) is formed on the non-magnetic substrate (11), and uniaxial residual magnetization is applied to the film, and then a soft magnetic backing layer (12) is formed. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is formed.