JPH06215348A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To suppress a change with the lapse of time and to reduce medium noise at the time of recording and reproduction as well as to increase coercive force and the product of the thicknesses of residual magnetization films in a magnetic recording medium. CONSTITUTION:An underlayer 2 contg. Cr and Mo is formed on a glass substrate (nonmagnetic substrate) 1 and a magnetic layer 3 contg. Co and Pt or further contg. Mo is formed on the underlayer 2. Other additive elements may further be added to the underlayer 2 and the magnetic layer 3 if necessary and a protective layer 4 and a lubricative layer 5 are successively formed on the magnetic layer 3 if necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic thin film medium for magnetic recording such as a magnetic disk, a flexible disk, a still camera or a video.

[0002]

2. Description of the Related Art Generally, Co having a high coercive force (Hc) and a remanent magnetization film thickness product (Mr.delta.) Is used as an alloy for magnetic recording media.
A Pt-based alloy is used. When a magnetic recording medium is formed using this CoPt-based alloy, an underlayer is generally formed between the substrate and the magnetic layer in order to improve its magnetic characteristics. For example, Japanese Patent Publication No. 4-1684
No. 8 (hereinafter referred to as "reference 1") discloses that Cr is used as an underlayer.
A magnetic recording medium containing V or CrFe and CoPt in the magnetic layer is shown, and it is described that the coercive force and the squareness ratio of the magnetization curve can be improved in this magnetic recording medium.

Further, in the magnetic recording medium, a third component is added to the CoPt magnetic film in order to increase the coercive force and the remanent magnetization film thickness product. As such a magnetic recording medium, for example, , The Television Society Journal 4
Volume 0, No. 6, 475 to 480 (1986)
The magnetic recording medium described in (hereinafter referred to as "Document 2") is known. In this magnetic recording medium, CoPt
The magnetic layer containing Mo as a component is directly formed on the glass substrate. It is described that this magnetic recording medium has a coercive force of 500 Oersted (Oe) or more, and moreover, not only the coercive force can be controlled in a wide range but also high density recording can be performed.

Further, a magnetic recording medium of this type is disclosed in Journal of Applied Physics (J. Appl.
Phys. 67 (12), 15 June 1990
pp7507-7509) (hereinafter referred to as “Reference 3”), in this magnetic recording medium, a metal containing a small amount of Mo added to Cr is used as an underlayer, and a magnetic layer made of CoNiCr is formed on the underlayer. Forming layers.

[0005]

By the way, although the magnetic recording medium described in Document 1 can obtain a high coercive force to some extent, the coercive force is about 1600 Oe at the maximum, and therefore high-density recording is required. Is not a satisfactory value.

Further, in the magnetic recording medium described in Document 2, as described above, the magnetic layer is directly formed on the glass substrate without interposing the underlayer, and the coercive force of the magnetic layer made of CoPt is 1000 Oe. Despite the above, C
In a magnetic layer made of oPtMo, its coercive force tends to decrease as the Mo concentration increases. For example, when the Mo concentration is about 14 at%, the coercive force is about 350.
It becomes Oe.

In addition, in the magnetic recording medium described in Document 2, the saturation magnetic flux density (Bs) also decreases with an increase in the Mo concentration, and the reduction of the saturation magnetic flux density (Bs) reduces the residual magnetization film thickness product (Mr).・ Δ) will also decrease.

As described above, in Reference 2, CoPt
It can be seen that the coercive force and the remanent magnetization film thickness product decrease when the magnetic layer added with Mo is used.

On the other hand, the coercive force of the magnetic recording medium shown in Document 3 is 1120 Oe, and the coercive force (128) of the magnetic recording medium using the underlayer formed of Cr alone.
The coercive force is smaller than that of 0 Oe).

As can be understood from the descriptions of Documents 2 and 3, Mo is added to the underlayer in which Mo is added to Cr and CoPt.
In a magnetic recording medium having a magnetic layer to which is added, the coercive force and the remanent magnetization film thickness product decrease.

An object of the present invention is to provide a magnetic recording medium which can obtain a sufficient coercive force and a product of remanent magnetization film thickness and has little change with time.

[0012]

According to the present invention, there is provided a magnetic recording medium having a nonmagnetic substrate, an underlayer formed on the nonmagnetic substrate, and a magnetic layer formed on the underlayer. Therefore, the underlayer contains chromium (Cr) and molybdenum (Mo), and the magnetic layer contains cobalt (C).
A magnetic recording medium characterized by containing o) and platinum (Pt) is obtained.

Further, in the present invention, the magnetic layer may further contain molybdenum (Mo). Further, Ta, B, Cr, O, N, Nb, Mn, and
At least one of Zn, W, Pb, Re, V, and Zr may be contained.

In addition, in the present invention, W,
B, V, Nb, Ta, Fe, Ni, Re, Cu, Zr,
At least one of Zn, P, Si, Ga, Ge, Hf, Al, and Ti may be contained.

When forming the underlayer, the Mo concentration may be increased in the direction from the non-magnetic substrate to the magnetic layer.

When forming the protective layer on the magnetic layer, it is desirable that the protective layer contains Cr and Mo.

[0017]

In the present invention, Mo forms a solid solution with Cr in the underlayer containing Cr and Mo. And Mo
The lattice expands in accordance with the amount of addition of Cr and the lattice spacing in the (110) plane of chromium approaches the lattice (002) plane of the magnetic layer containing Co and Pt. As a result, the orientation of the magnetic layer changes, and the coercive force of the magnetic layer can be improved.

By further adding Mo to the magnetic layer, not only the coercive force increases due to the pinning effect of the domain wall, but also the magnetic isolation of the magnetic grains is promoted and the coercive force increases. Further, the coercive force increases due to the miniaturization of the magnetic particles. The increase in this coercive force reduces the peak width in the reproduced wave and reduces the medium noise. Further, addition of Mo to the magnetic layer increases the pinning number and reduces the width of the zigzag wall, which also reduces the medium noise.

In addition, by including the same component in the underlayer and the magnetic layer (that is, by including Mo), diffusion of Mo is facilitated at the interface between the underlayer and the magnetic layer, and as a result, The magnetic isolation of the magnetic particles is further promoted and the adhesion strength between the underlayer and the magnetic layer can be increased.

When the above-mentioned Zr, Zn, Cu and the like are added to the underlayer containing Cr and Mo, these additional elements are difficult to form a solid solution with Cr or Mo in the underlayer, and as a result,
The additive element is segregated at the grain boundaries of the crystal grains in the underlayer to promote the refinement of the crystal grains and the separation between the grains. This promotes the miniaturization of crystal grains in the magnetic layer and the separation between the grains (magnetic isolation) by reflecting the film structure of the underlayer, thereby increasing the coercive force and reducing the medium noise. it can.

[0021]

EXAMPLES The present invention will be described below with reference to examples.

(Embodiment 1) Referring to FIG. 1, a diameter of 65 m
A glass substrate 1 having a thickness of 0.9 mm is prepared, and the glass substrate 1 is provided with an RF magnetron sputtering device (not shown).
Install in the chamber. And 5 in the chamber
Depressurize to a pressure of × 10 ^-7 Torr or less. Then, using argon gas as the sputtering gas, the gas pressure is 10 mTorr.
To a sputtering apparatus, the substrate temperature is room temperature, the input power density is 2.5 W / cm ² , and Cr ₈₀ Mo ₂₀ (at%) is a target to form a base layer 2 having a film thickness of 1000 Å on the glass substrate 1. (General formula Cr _100-x M
o _x (x = 0 to 100) and x = 20). Then, similarly, using argon gas as a sputtering gas and Co ₈₂ Pt ₁₈ (at%) as a target,
A magnetic layer 3 having a composition of ₈₂ Pt ₁₈ and a film thickness of 400 angstrom was formed on the underlayer 2. Then, a Cr ₈₀ Mo ₂₀ layer 4a having a film thickness of 50 Å and a carbon layer 4b having a film thickness of 400 Å are formed on the magnetic layer 3 by using argon gas as a sputtering gas.
_{The 80} Mo ₂₀ layer 4a and the carbon layer 4b were used as the protective layer 5.
A lubricating layer 5 made of perfluoropolyether was applied on the protective layer 4 to a thickness of 20 angstroms to obtain a magnetic disk (magnetic recording medium) 6. This magnetic disk 6 was designated as disk A.

Further, the general formula Cr _100-x Mo _x (x = 0
X in 0 to 100) are 0, 10, 30, 4 respectively.
As 0, 50, 60, 70, 80, 90, that is, C
r, Cr ₉₀ Mo ₁₀ , Cr ₇₀ Mo ₃₀ , Cr ₆₀ Mo ₄₀ , Cr
₅₀ Mo ₅₀ , Cr ₄₀ Mo ₆₀ , Cr ₃₀ Mo ₇₀ , Cr ₂₀ M
A magnetic disk having ₈₀ and Cr ₁₀ Mo ₉₀ (at%) as underlayers was prepared. At this time, the glass substrate,
The magnetic layer, the protective layer, and the lubricating layer were the same as those of the disk A, and the other conditions such as the film thickness were the same as those of the disk A.

A sample having a diameter of 8 mm was cut out from each of these disks, and a coercive force (Hc) and a residual magnetization film thickness product (Mr.
δ) was measured. At this time, the maximum external applied magnetic field was set to 12 kOe and the magnetic field was applied in the film surface direction. The result is shown in FIG. In FIG. 2, ⊚ indicates the coercive force of each sample.

As is apparent from FIG. 2, it is understood that a magnetic recording medium having a high coercive force can be obtained by using the magnetic layer made of CoPt and the underlayer made of CrMo. In particular, the general formula Cr _100-x Mo _x
It can be seen that in (x = 0 to 100), the coercive force becomes higher by using the underlayer of x = 10 to 80.

Next, it has a magnetic layer of Co ₇₄ Pt ₁₈ Mo ₈ and has the general formula Cr _100-x Mo _x (x = 0 to 100).
The magnetic disk having the underlayer having the composition shown in was prepared by changing x in the range of 0 to 90 as described above. At this time, the glass substrate, the protective layer, and the lubricating layer were the same as those of the disk A, and other conditions such as the film thickness were also the same as those of the disk A. 8 diameters from each of these discs
mm sample is cut out and using a vibrating sample magnetometer,
The coercive force (Hc) and the residual magnetization film thickness product (Mr · δ) of each sample were measured. The result is shown in FIG. In FIG. 2, ◯ indicates the coercive force of each sample.

As can be seen from FIG. 2, a magnetic recording medium having a high coercive force can be obtained by using the magnetic layer made of CoPtMo and the underlayer made of CrMo. In particular, the general formula Cr _100-x M
In o _{x (x} = 0~100), it can be seen that the coercive force becomes higher by using the underlayer of x = 10 to 80.

Further, by using the same method as that for producing the disk A, the general formula Cr _100-xy Mo _y Zr _x (at
%) And a Co ₇₄ Pt ₁₈ Mo ₈ (a
A magnetic disk having a composition of t%) was sequentially formed on a glass substrate to obtain a magnetic disk. At this time, the Mo concentration in the underlayer is set to 9 at% (that is, y = 9), and the Zr concentration is changed in the range of 0 to 50 at% (that is, x =
Multiple magnetic disks were obtained (as 0 to 50). Similarly, the Mo concentration in the underlayer is set to 18 at% (that is, y = 18), the Zr concentration is changed in the range of 0 to 50 at% (that is, x = 0 to 50), and a plurality of magnetic fields are obtained. I got a disc. Then, the coercive force of these magnetic disks was measured in the same manner as the disk A. The results of this measurement are shown in FIG. 3 (in FIG. 3, ⋄ indicates that the Mo concentration is 9a.
represents the case of t%, and ◆ represents the case of Mo concentration of 18 at%).

As is apparent from FIG. 3, it is understood that the coercive force of the magnetic disk can be increased by adding Zr to the underlayer made of CrMo. And, the added amount of Zr in the underlayer is 0.1 to 30 at%
In the range of, the coercive force becomes high, and in particular, 0.1-4
It can be seen that the coercive force is higher than that of the magnetic disk using the underlayer made of only CoMo in the range of at%.

Next, a magnetic disk having an underlayer of Cr ₈₀ Mo ₂₀ (at%) and a magnetic layer of Co ₇₄ Pt ₁₈ Mo ₈ (at%) (hereinafter, this magnetic disk is referred to as "disk B", Other components and film thickness of the disk B are the same as those of the disk A) and Cr ₈₀ Mo ₁₈ Zr ₂ (at%).
Magnetic disk having a base layer of Co ₇₄ Pt ₁₈ Mo ₈ (at%) and a magnetic layer of Co ₇₄ Pt ₁₈ Mo ₈ (at%) (hereinafter, the magnetic disk is referred to as “disk C”. The same was used) to measure the recording / reproducing output. Here, the flying height of the magnetic head is 0.055 μm.
The thin film head of No. 1 was used, the relative speed between the thin film head and the disk B was set to 6 m / s, and the linear recording density was 80 kfci (1
The recording / reproducing output at a linear recording density of 80,000 bits per inch) was measured. The results are shown in Table 1 (Table 1 also shows the coercive force and the residual magnetization film thickness product in addition to the recording / reproducing output, and also shows the measurement results of a magnetic disk using only Cr as the underlayer as a comparative example. In Table 1, disks B and C are referred to as Examples 2 and 3, respectively. The thin film head used in the above measurement has 50 coil turns, a track width of 6 μm, and a magnetic head gap length of 0.25 μm.

[0031]

[Table 1]

As is clear from Table 1, since the disk B uses CrMo as the underlayer, the magnetic recording / reproducing characteristics are significantly improved as compared with the comparative example using the underlayer containing only Cr. Similarly, in the disk C as well, since CrMoZr is used as the underlayer, the magnetic recording / reproducing characteristics are significantly improved as compared with the comparative example using the underlayer containing only Cr.

Further, the disks A and B are heated to a temperature of 80 ° C.
A corrosion resistance test was conducted by leaving the sample in a constant temperature and humidity chamber having a humidity of 80% for 1000 hours. Then, the saturation magnetization (Ms) of the disks A and B was measured from immediately before the corrosion resistance test to after 1000 hours. The measurement result is shown in FIG.

In FIG. 4, the horizontal axis represents time and the vertical axis represents the value obtained by normalizing the saturation magnetization at each time with the saturation magnetization (Ms ₀ ) immediately before the start of the corrosion resistance test. As is clear from FIG. 4, the magnetic layers of CoPt (disk A) and CoPtMo (disk B) have excellent corrosion resistance.
It can be seen that the corrosion resistance is remarkably improved by adding Mo to Pt.

Next, the noise spectrum at the time of signal recording / reproduction of the disks A, B, and C was measured by the spectrum analyzer with the carrier frequency of 9.4 MHz and the measurement band of 15 MHz (medium noise Nm).
Represents). As a result, the medium noise is 7.
The disk B had a medium noise of 5.08 μVrms, while the disk B had a magnetic noise of 58 μVrms.
By using PtMo, the medium noise could be further reduced. Also, in the disk C, the medium noise is 4.85 μV.
rms, CoPtMo is used for the magnetic layer, and CrMoZr is used for the underlayer, whereby the medium noise can be further reduced.

(Examples 4 to 10) In the same manner as in Example 1, Cr ₈₀ Mo ₂₀ (at%) was used as a target, and a film thickness of 150 was formed on a glass substrate having a diameter of 65 mm and a thickness of 0.9 mm.
A 0 Å underlayer (Cr ₈₀ Mo ₂₀ layer) was formed. Subsequently, a film thickness 4 having a composition of Co ₇₀ Pt ₁₈ Mo ₁₂ is set with Co ₇₀ Pt ₁₈ Mo ₁₂ (at%) as a target.
A magnetic layer of 00 Å was formed on the underlayer.
SiO ₂ was formed as a protective layer on the magnetic layer to a thickness of 50 Å to obtain a magnetic disk (Example 4). Then, the coercive force and the residual magnetization film thickness product of this magnetic disk were measured in the same manner as in Example 1. The results are shown in Table 2.

[0037]

[Table 2]

Further, magnetic disks were prepared with the compositions of the underlayer, the magnetic layer and the protective layer shown in Table 2 (Examples 5 to 10). Then, the coercive force and the remanent magnetization film thickness product of these magnetic disks were measured in the same manner as in Example 4.

As is clear from Table 2, C is used as the underlayer.
It can be seen that the coercive force and the remanent magnetization film thickness product can be increased by using rMo and using a magnetic layer in which CoPt is added with Mo up to 30 at% as the magnetic layer.

(Examples 11 to 15) A glass substrate having a diameter of 65 mm and a thickness of 0.9 mm is prepared, and this glass substrate is mounted in the chamber of a DC magnetron sputtering apparatus (not shown). Then, the inside of the chamber is 8 × 10 ^-7 T
Depressurize to a pressure below orr. After that, argon gas was supplied as a sputtering gas at a gas pressure of 15 mTorr to the sputtering apparatus, the input power density was 18 W / cm ² , and the substrate temperature was 100 ° C. (Example 11), 200 ° C. (Example 12), 250 ° C. Example 13), 300 ° C. (Example 14), and 400 ° C. (Example 15) as Cr ₇₀ Mo
Target a film thickness of ₃₀ (at%) and a film thickness of 2 on a glass substrate
An underlayer (Cr ₇₀ Mo ₃₀ layer) of 000 Å was formed. Then, using Ar gas as a sputtering gas and Co ₆₈ Pt ₁₇ Mo ₁₅ (at%) as a target, C
A magnetic layer having a composition of o ₆₈ Pt ₁₇ Mo ₁₅ and a film thickness of 350 angstrom was formed on the underlayer. Then, a protective film having a film thickness of 80 angstrom is formed on the magnetic layer by using Cr ₇₀ Mo ₃₀ (at%) as a target with argon gas as a sputtering gas, and a film having a film thickness of 15 Å is formed on the protective film.
A magnetic disk was manufactured by forming a protective layer made of SiO _{2 of} 0 angstrom.

The coercive force and the residual magnetization film thickness product of the magnetic disks of Examples 11 to 15 were measured in the same manner as in Example 1. The measurement results are shown in Table 3.

[0042]

[Table 3]

As is clear from Table 3, the substrate temperature is set to 40
It can be seen that even if the temperature is raised to 0 ° C. to produce a magnetic disk, good magnetic characteristics can be obtained without deterioration of the magnetic characteristics.

(Examples 16 to 35) Using the same method as in Example 1, magnetic disks (Examples 16 to 35) having an underlayer, a magnetic layer and a protective layer having the compositions shown in Table 4 were prepared. Then, for the magnetic disks of Examples 16 to 35, the coercive force and the residual magnetization film thickness product were measured in the same manner as in Example 1.

[0045]

[Table 4]

As is apparent from Table 4, the coercive force and the remanent magnetization film thickness product can be increased even if the underlayer in which the additional component other than Zr is added to CrMo is added.

(Examples 36 to 61) Using the same method as in Example 4, an underlayer (film thickness 2000 Å), a magnetic layer (film thickness 450 Å), and a protective layer (film) having the compositions shown in Table 5 were used. A magnetic disk (Examples 36 to 61) having a thickness of 150 Å was prepared, and
For the magnetic disks of Examples 36 to 61, the coercive force and the residual magnetization film thickness product were measured in the same manner as in Example 4.

[0048]

[Table 5]

As is clear from Table 5, the coercive force and the remanent magnetization film thickness product can be increased even if the magnetic layer in which other additional components are added to CoPtMo is used.

(Example 62) Subsequently, a glass substrate having a diameter of 65 mm and a thickness of 0.9 mm was mounted in the chamber of an RF magnetron sputtering apparatus (not shown), and the chamber was kept at 5 x 10 ^-7 Torr or less. Reduce to pressure. Then, using argon gas as the sputtering gas, the gas pressure is 10 mT.
Orr was supplied to the sputtering apparatus, the substrate temperature was set to room temperature, and the Cr target and the Mo target were simultaneously discharged. At this time, the input power density for Cr target and 2.5 W / cm ^2, the input power density for a Mo target was changed from 0.1 W / cm ² to 1.2 W / cm ^2, thickness 1500 Å on a glass substrate Underlayer was formed. As a result, in the underlayer, the Mo concentration gradually increased from the bottom to the top.

Similarly, using Ar gas as a sputtering gas, Cr ₇₄ Pt ₁₈ Mo ₈ (at%) as a target, and a film thickness of 40 having a composition of Cr ₇₄ Pt ₁₈ Mo ₈ was used.
A 0 angstrom magnetic layer was formed on the underlayer. Then, by using argon gas as a sputtering gas, a Cr layer having a film thickness of 50 Å and a film thickness of 300 are formed on the magnetic layer.
Angstrom SiO ₂ was formed, and these Cr layer and SiO ₂ layer were used as protective layers. Then, a lubricating layer made of perfluoropolyether was applied on the protective layer to a thickness of 20 Å to obtain a magnetic disk (magnetic recording medium).

The coercive force (Hc) of this magnetic disk was measured using a vibrating sample magnetometer. On this occasion,
The magnetic field was applied in the film surface direction with the maximum externally applied magnetic field of 12 kOe. As a result, the coercive force was 2500 Oe.

Further, the recording / reproducing output of the above magnetic disk was measured. Here, a thin film head having a magnetic head flying height of 0.055 μm is used, the relative speed between the thin film head and the disk B is 6 m / s, and the linear recording density is 8
The recording / reproducing output at 0 kfci was measured. As a result, the recording / reproducing output was 225 μV.

Further, the noise spectrum at the time of signal recording / reproduction was measured for the above magnetic disk with a carrier frequency of 9.4 MHz and a measurement band of 15 MHz (represented by medium noise Nm). As a result, the medium noise was 5.15 μVrms.

The thin film head used in the above measurement has 50 coil turns, a track width of 6 μm, and a magnetic head gap length of 0.25 μm.

In this way, by changing the Mo concentration in the underlayer so as to increase upward (direction from the substrate to the magnetic layer), good magnetic characteristics can be obtained.

(Example 63) Input power density was 2.5 W /
cm ² and the other conditions were the same as in Example 62, using an RF magnetron apparatus, Cr target, Cr ₉₅ Mo ₅
A target, a Cr ₉₀ Mo ₁₀ target, a Cr ₈₅ Mo ₁₅ target, and a Cr ₈₀ Mo ₂₀ target are simultaneously discharged to produce Cr, Cr ₉₅ Mo ₅ , Cr ₉₀ Mo ₁₀ , C on the substrate.
The substrate is sequentially transported in the RF magnetron device so that a film is formed in the order of r ₈₅ Mo ₁₅ and Cr ₈₀ Mo ₂₀ . As a result, an underlayer having a film thickness of 1500 angstrom was formed on the substrate. In this way, by sequentially transporting the substrates to the targets having different Mo concentrations,
In the underlayer, the Mo concentration gradually increases upward. Then, similarly to Example 62, a magnetic layer, a protective layer, and a lubricating layer were sequentially formed on the underlayer to obtain a magnetic disk. Then, in the same manner as in Example 62, the coercive force, the recording / reproducing output, and the medium noise were measured. As a result, the coercive force,
Recording / reproducing output and medium noise are 2550O each
e, 225 μV, and 5.10 μVrms.

As described above, good magnetic characteristics can be obtained even if the underlayer is formed by using a plurality of films whose Mo concentration increases successively.

Example 64 A Cr target, a Mo target and a Zr target were used and these targets were simultaneously discharged. At this time, the input power density to the Cr target was set to 2.5 W / cm ^2, and the input power density to the Zr target was fixed to 0.1 W / cm ² .
Input power density to Mo target is 0.1 W / cm
An underlayer having a film thickness of 1500 Å was formed on the substrate under the same conditions as in Example 62 except that the temperature was continuously changed from ² to 1.2 W / cm ² . As a result, in the underlayer, the Mo concentration gradually increased from the bottom to the top. Then, similarly to Example 62, a magnetic layer, a protective layer, and a lubricating layer were sequentially formed on the underlayer to obtain a magnetic disk. Then, in the same manner as in Example 62, the coercive force, the recording / reproducing output, and the medium noise were measured. As a result, the coercive force,
Recording / playback output and medium noise are 2600O each
e, 230 μV, and 4.90 μVrms.

In this way, even if the Mo concentration in the underlayer is sequentially increased upward, good magnetic characteristics can be obtained.

(Example 65) The input power density was 2.5 W /
cm ² and the other conditions were the same as in Example 62, using an RF magnetron apparatus, Cr target, Cr ₉₅ Mo ₃
Zr ₂ target, Cr ₉₀ Mo ₈ Zr ₂ target, C
r ₈₅ Mo ₁₃ Zr ₂ target and Cr ₈₀ Mo ₁₈ Zr ₂ target
The target is discharged at the same time and Cr, Cr _{95 is} deposited on the substrate.
Mo ₃ Zr ₂ , Cr ₉₀ Mo ₈ Zr ₂ , Cr ₈₅ Mo ₁₃ Zr
₂ and Cr ₈₀ Mo ₁₈ Zr ₂ so that the film is formed in this order on the substrate in the RF magnetron device. As a result, an underlayer having a film thickness of 1500 angstrom was formed on the substrate. In this way, by sequentially transporting the substrate to the targets having different Mo concentrations, the Mo concentration in the base layer increases sequentially upward. Then, similarly to Example 62, a magnetic layer, a protective layer, and a lubricating layer were sequentially formed on the underlayer to obtain a magnetic disk. Then, in the same manner as in Example 62, the coercive force, the recording / reproducing output, and the medium noise were measured. As a result, the coercive force,
Recording / reproducing output and medium noise are 2630O each
e, 225 μV, and 4.88 μVrms.

As described above, good magnetic characteristics can be obtained even if the underlayer is formed by using a plurality of films whose Mo concentration increases successively.

Although the Mo concentration in the underlayer is increased in the direction from the substrate to the magnetic layer in the above-described embodiment, the Mo concentration is not limited to Mo and the Cr or Zr concentration may be changed.

As is clear from the above examples, the underlayer must contain at least Cr and Mo. For example, when the underlayer is made of Cr and Mo, a sufficient coercive force is obtained. In order for that ratio to be Cr
It is desirable that _100-x Mo _x (1 ≦ x ≦ 90),
Particularly, it is preferable that 10 ≦ x ≦ 80.

The magnetic layer needs to contain at least Co and Pt. For example, the underlayer contains C.
In the case of using O and Pt, in order to obtain a sufficient coercive force, the ratio is preferably Cr _100-y Mo _y (5 ≦ y ≦ 30).

Further, in addition to Co and Pt, Mo is contained in the magnetic layer.
Although the remanent magnetization (Mr) tends to decrease by adding, the medium noise is reduced and the S / N ratio is increased. In order to minimize the reduction in output due to the reduction in residual magnetization, the proportions of Co, Pt, and Mo should be Co.
_{100-yz Pt y Mo z (} at%) (5 ≦ y ≦ 30,0 <
z ≦ 30) is preferable, and particularly 5 ≦ y ≦ 3.
It is preferable that 0,5 ≦ z ≦ 20.

In addition, as is clear from the above-mentioned examples, other components may be added to the underlayer. For example, W, B, V, Nb, Ta, Fe, Ni, Re, C
u, Zr, Zn, P, Si, Ga, Ge, Hf, Al,
Further, at least one of Ti and Ti may be further contained. Then, in order to obtain a sufficient coercive force, the added amount of these additional components is preferably 30 at% or less. Medium noise can be reduced by adding Cu, Zr, B, Zn, Ta, and Nb (that is, S
/ N ratio can be increased). In particular, the addition of Zr has a great effect on reducing the medium noise.

In the magnetic layer, for example, Ta, B, C
r, O, N, Nb, Mn, Zn, W, Pb, Re, V,
At least one of Zr and Zr may be added. Then, in order to obtain a sufficient coercive force, the added amount of these additional components is preferably 30 at% or less.

Although the glass substrate is used as the non-magnetic substrate in the above-mentioned embodiments, it is not particularly limited as long as it is non-magnetic, and for example, a crystallized glass substrate and an aluminum substrate can be used.

When the protective layer is formed, the type of the protective layer is not particularly limited, and a protective layer composed of a single layer or multiple layers may be provided. Examples of the protective layer include silicon oxide (S
iO ₂ ), carbon (C), zirconium oxide (ZrO
₂ ), silicon nitride (Si ₃ N ₄ ), boron nitride (B
N), chromium (Cr), and chromium molybdenum alloy (C
rMo) is used, but it is particularly preferable to use a protective layer having the same composition as the underlayer, for example, a metal containing Cr and Mo, in order to generate a diffusion effect from above and below the magnetic layer.

When forming the lubricating layer, the kind of the lubricating layer is not particularly limited, and for example, perfluoropolyether, fatty acid, fatty acid amide, fatty acid ester, and fluorocarbon may be used individually or as a mixture.

[0072]

As described above, in the magnetic recording medium according to the present invention, not only the coercive force and the remanent magnetization film thickness product can be increased, but also the corrosion resistance can be increased. In particular, Co, Pt, and M are used in the magnetic layer.
By including o, not only high recording / reproducing output can be obtained at high linear recording density but also medium noise can be reduced. As a result, there is an effect that the S / N ratio at the time of recording / reproducing can be improved at a high linear recording density.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetic recording medium according to the present invention.

FIG. 2 shows Co ₈₂ Pt ₁₈ (⊚) and Co ₇₄ Pt ₁₈ Mo ₈ (∘) as magnetic layers in the magnetic recording medium according to the present invention.
It is a figure which shows the change of the coercive force when changing Mo content in a base layer (CrMo) using (at%).

FIG. 3 shows a magnetic recording medium according to the present invention in which Co ₇₄ Pt ₁₈ Mo ₈ (at%) is used as a magnetic layer and an underlayer (Cr
Mo at 9 at% (◇) and 18 at%
It is a figure which shows the change of coercive force when changing the Mo content in an underlayer as (◆).

FIG. 4 is a diagram showing a relationship between a test time and a saturation magnetization in a corrosion resistance test.

[Explanation of symbols]

 1 Glass Substrate 2 Underlayer 3 Magnetic Layer 4 Protective Layer 5 Lubricating Layer 6 Magnetic Recording Medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Nozawa 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Hoya Co., Ltd.

Claims (6)

[Claims] 1. A magnetic recording medium having a non-magnetic substrate, an underlayer formed on the non-magnetic substrate, and a magnetic layer formed on the underlayer, wherein Cr and Mo are contained in the underlayer.
And a magnetic recording medium containing Co and Pt in the magnetic layer. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer further contains Mo. 3. The magnetic recording medium according to claim 2, wherein the magnetic layer further comprises Ta, B, Cr, O, N,
A magnetic recording medium containing at least one of Nb, Mn, Zn, W, Pb, Re, V, and Zr. 4. The magnetic recording medium according to claim 1, further comprising W, B, and
V, Nb, Ta, Fe, Ni, Re, Cu, Zr, Z
A magnetic recording medium containing at least one of n, P, Si, Ga, Ge, Hf, Al, and Ti. 5. The magnetic recording medium according to claim 1, wherein the Mo concentration in the underlayer increases in a direction from the non-magnetic substrate toward the magnetic layer. Magnetic recording medium. 6. The magnetic recording medium according to claim 1, further comprising a protective layer formed on the magnetic layer, wherein the protective layer contains Cr and Mo. A magnetic recording medium characterized by the above.