JPH06215346A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having improved coercive force and decreased low-frequency modulation by forming the lower layers of plural layers of two-layered surfaces and forming a first thin film of chromium and a second thin film of a chrome-vanadium alloy. CONSTITUTION: This magnetic recording medium has a substrate 10 having the substrate surface thin film 14 of an NiP alloy deposited by a non-electrolytic treatment and a disk base body 12 of an AlMg alloy, a plurality of layers of the lower layers 20 (consisting of the thin films 22, 24) formed on this substrate 10 and a protective coating 40 formed on a magnetic layer 30 of a Co alloy. A layer 50 of a liquid lubricant is added thereto. The first thin film 22 of a plurality of layers of the lower layers 20 is Cr and the second thin film 24 is Cr80 V20 . These thin films are formed by deposition by sputtering. As a result, the magnetic recording disk of the thin film Co alloy having the greatly improved coercive force and the decreased low-frequency modulation is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film cobalt alloy magnetic recording disk for horizontal recording, and more particularly, it has a lower layer deposited in a plurality of layers, and has the magnetic properties of the deposited magnetic layer. An improved magnetic recording disk.

[0002]

2. Description of the Related Art Generally, a thin film cobalt alloy magnetic recording disk for horizontal magnetic recording is formed on a glass substrate or an aluminum-magnesium alloy (AlMg) substrate having a surface coating of phosphorus nickel alloy (NiP) and a substrate. An underlayer, such as deposited chromium (Cr) or a chromium-vanadium alloy (CrV), a cobalt-based alloy sputter layer deposited as a magnetic layer on the underlayer, and a sputter deposit formed on the magnetic layer. A thin film of deposited amorphous carbon or a protective coating such as a thin film of hydrogenated carbon.

Coercive force of cobalt alloy magnetic disk (coer
civity), coercivity squareness, and remanence squareness (ratio of remanent magnetization to saturation magnetization) are influenced by the structure and composition of the lower layer. US Pat. No. 4,610,911
And No. 4,631,202 disclose thin film magnetic disks having a conventional single underlayer of chromium and a magnetic layer of cobalt-platinum alloy (CoPt), which describes the effect of the underlayer of chromium on the coercivity of the disk. is doing. U.S. Pat. No. 4,652,499 discloses a thin film magnetic of cobalt-platinum-chromium alloy (CoPtCr) having a single chromium-vanadium alloy underlayer that provides a higher coercivity and coercivity squareness than a chromium underlayer of the same thickness. Discs are disclosed.

In addition to the magnetic properties that a good disk preferably contains high values of coercivity, coercivity squareness and remanence magnetism squareness, a relatively constant magnetic property over the entire disk surface. Must indicate In the case of a disk that does not have such magnetic properties, the amplitude of the read signal may change around the disk,
As a result, the unwanted low frequency modulation (L
FM) is a problem. US Patent No. 4
No. 8333020 discloses a cobalt alloy disc having two underlayers to reduce signal modulation, the first layer on the substrate side being zirconium (Zr),
Titanium (Ti), Silicon (Si), Germanium (G
e), silicon dioxide (SiO ₂ ) is desirable, and
It is described that chromium (Cr) is preferably used for the second layer on which the magnetic layer is applied. In another embodiment described in this US patent, these two underlayers are Cr / Cr.
It is described that the structure is acceptable, and each Cr in this case is
The layers are sputtered under different conditions.

Other publications describe cobalt alloy disks with two underlayers, but no benefit in reducing LFM. For example, US Pat. No. 4,828,905.
Discloses a cobalt alloy disk having two lower layers, in which the first layer formed on the substrate is a relatively thin chromium oxide layer or an oxide such as a titanium oxide layer. The second layer is a much thinner chrome layer. IBM Technical Disclosure Bulletin Vol. 35, No. 1A, June 1992
Cobalt with increased coercivity with two layers underlayer of chromium and tin (Sn) at pages 65 and 266.
A platinum-chromium alloy (CoPtCr) disk is described, the first layer of which is Cr and the second layer
Layer is Sn and a thin film of CoPtCr alloy is deposited on the second layer.

Low-frequency modulation (LF) by improving magnetic properties
It is clear that there is a need for a cobalt alloy thin film magnetic recording disk with an underlayer that reduces M).

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cobalt alloy magnetic recording disk having an underlayer which improves magnetic properties and reduces LFM.

[0008]

In the magnetic disk of the first embodiment of the present invention, the lower layer of a plurality of layers has a two-layer structure, the first thin film is chromium (Cr), and the second thin film. Is a chromium-vanadium alloy (CrV). The magnetic disk in the second embodiment of the present invention comprises a first thin film of CrV containing a relatively small amount of oxygen atoms (a thin film adjacent to the substrate) and a second thin film of CrV containing a relatively large amount of oxygen atoms. It has a lower layer of 2 layers made with a thin film of.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a cross-sectional view of a thin film cobalt alloy magnetic disk according to the present invention. This disk is made of phosphorus nickel alloy (N
a substrate 10 having an aluminum-magnesium alloy (AlMg) disk substrate 12 having a substrate surface thin film 14 of iP), and a plurality of lower layers 20 formed on the substrate 10.
(Two thin films 22 and 24 in the illustrated embodiment)
And a protective coating 40 formed on the magnetic layer 30. A layer of liquid lubricant 50 is typically provided on the protective coating 40.
Has been added.

In the first embodiment of the present invention, in the lower layer 20 of a plurality of layers, the first thin film 22 is Cr and the second thin film 24 is Cr ₈₀ V ₂₀ (an alloy of 80% chromium and 20% vanadium). ) Are two lower layers. This two-layer structure is the first sputter-deposited Cr layer from the Cr target,
The second layer is formed by a sputter-deposited Cr ₈₀ V ₂₀ layer from a target having the same alloy composition.

A 600 Å Cr / 600 Å Cr ₈₀ V ₂₀ bilayer underlayer;
The coercivity for a disk with 0 angstrom thick Co ₆₇ Pt ₁₆ Cr ₁₇ magnetic layer is 120
It was shown to be dramatically increased compared to a similar disk 1200 Elsted with a 0 Å Cr underlayer. As shown in FIG. 2, for such an underlayer of two layers, where the sum of the thicknesses of the two thin films is constant, the coercivity has little effect on the ratio of the Cr and Cr ₈₀ V ₂₀ thin film thicknesses. Do not receive Further, in FIG. 2, Cr of the present invention is used.
The coercive force of a disk having a two-layer underlayer of Cr / CrV layer is the same as that of a disk having only Cr ₈₀ V ₂₀ having the same thickness as the total thickness of two thin films in the above-mentioned two-layer underlayer. It is shown to be larger than the coercive force of. Cr
The above discovery is important because the V spatula target is considerably more expensive than the Cr sputter target.
As a result, using a large amount of the lower layer formed of the first thin film of Cr using the lower layer of the two-layer structure has a higher coercive force due to less cost than the disk having the lower layer of the CrV of the single layer structure. You can get a disk. The squareness S ^* of the coercive force is 0.85 to 0.95 for various disks made under the two-layer structure of Cr / CrV.
, Which is clearly acceptable for magnetic recording.

In the second embodiment of the present invention, the lower layer of the two-layer structure is the first thin film (thin film on the disk substrate), and the second thin film is made of Cr ₈₀ V ₂₀ having relatively few oxygen atoms. Is made of Cr ₈₀ V ₂₀ which contains many oxygen atoms. Thin films depleted of oxygen atoms have a mediocre “vacuum cast” with an oxygen atom concentration of less than about 0.05 atomic percent.
-VC) "target for sputtering is first subjected to sputtering on the substrate. A thin film containing a large amount of oxygen atoms can be formed by applying “powder-pressed-PP” to 0.0
Desirably, it is made by sputtering from a CrV target having an oxygen atom concentration in the range of 5 to 5 atomic percent on a thin film of oxygen atoms. As an alternative, a thin film rich in oxygen atoms can be used in the presence of oxygen such that the CrV thin film is "doped" with oxygen atoms when chromium and vanadium atoms are deposited on the substrate of the disk.
It can be prepared by subjecting rV to reaction sputtering.

To compare the magnetic properties of cobalt alloy disks with five types of underlayers as follows:
An experimental disk was made using an in-line pallet type sputter device. The lower layers of the five types are (1)
CrV lower layer with a single layer structure by PP treatment, and (2) V
CrV lower layer of single layer structure by C treatment, and (3) 1st
As a thin film, a CrV layer by PP processing and as a second thin film, a lower layer of a two-layer structure (P
P / VC), (4) as a first thin film, as a CrV layer and a second thin film by a VC treatment, as a lower layer (VC / PP) having a two-layer structure of a CrV layer by a PP treatment, and (5) as a first thin film. , Cr and the second thin film, CrV by PP treatment
It is the lower layer of the two-layer structure of layers. Tables 1 and 2 below show the measurement results of the magnetic characteristics, coercive force H _c , coercive force squareness S ^* , remanent magnetism squareness S, and LFM of the above-mentioned five types of lower layer discs. Is. For the sake of convenience, Table 1 and Table 2 are separated separately, but it should be noted that Table 1 is followed by Table 2 as a unitary table.

[0014]

[Table 1]

[0015]

[Table 2]

The data in Tables 1 and 2 above are Crv
Cr / C compared to the lower disk only for (PP processing)
It is shown that the disk having the lower layer of rV and the lower layer of the combination of CrV (VC processing) / CrV (PP processing) has higher coercive force and coercive force squareness S ^* . In addition, the LFM has reduced both discs of a two-layer structure compared to a single layer disc of CrV (PP treated). LFM is reduced by Cr or CrV
This is a result of the crystal orientation of the Cr alloy being changed by the nucleation of the seed layer of (VC treatment). A CrV (PP treated) layer is epitaxially grown on the first layer in order to maintain a low modulation direction.

In order to better understand the effect of oxygen in the lower layer of the CrV / CrV bilayer structure, a thin film structure formed on a silicon (Si) substrate and having the following structure is used: Auger depth concentration profile prof
The amount and distribution of oxygen present in the two Cr ₈₀ V ₂₀ thin films was determined.

The above-mentioned structure is based on 500 Å VC processed Cr.
A structure containing the _{80 V 20 / 500Å Cr 80 V} 20 / 200Å of PP processing carbon.

As a result of measurement of this structure, oxygen was not detected in the VC-treated thin film, while 1.7 atomic percent oxygen was measured in the PP-treated thin film. In addition, Auger measurements were made after eight separate spatula times, and when the Auger sampling zone moved from the center of the PP-treated film and was no longer detected at the center of the VC-treated film. It was shown that the oxygen peak value decreased.

The samples and experimental disks described above are made of Si.
And on the AlMg / NiP substrate,
It should be noted that the disk improved by the present invention does not depend on a specific substrate, and the same improvement result can be obtained by using another substrate such as glass.

Although the above description relates only to the structure of the lower layers and the magnetic layer and does not refer to other known disk structures or methods of manufacturing the disk, the thin film cobalt alloy magnetic disk. It is known to provide a protective coating 40 (FIG. 1) such as a substantially amorphous hydrogenated carbon thin film sputter deposited on the magnetic layer.

[0022]

According to the present invention, a magnetic recording disk of a thin film cobalt alloy having a significantly improved coercive force and reduced low frequency modulation is provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a magnetic recording disk to which the present invention is applied.

FIG. 2 is a graph showing coercive force as a function of thickness for two thin films composed of the lower layer of a two-layer structure.

[Explanation of symbols]

 10 Disk Substrate 12 Disk Substrate 14 Substrate Surface Thin Film 20 Lower Layer 22 First Thin Film 24 Second Thin Film 30 Magnetic Layer 40 Protective Coating 50 Lubricant Layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kwang Kong Kim Westfield Avenue, San Jose, California, USA 2749 (72) Inventor Thomas Earl Shirt Morgan Hill, Kore, USA Enrique 15400 (72) Inventor Andrew Chiu Wang Ting United States California, San Jose, Glen Ely Avenue 1218 (72) Inventor Chikwang Sea Wang United States California, San Jose, Wash Drive 1186 (72) Invention Pau Wang 1227 Valley Quail Circle, San Jose, CA, USA

Claims (8)

[Claims] 1. A magnetic recording medium for horizontal magnetic recording, comprising: a substrate; and a first non-magnetic thin film formed on the substrate and selected from the group consisting of chromium and a chromium-based alloy.
A lower layer formed on the first non-magnetic thin film and including a second non-magnetic thin film containing a chromium-based alloy; and a cobalt-based alloy formed on the lower second thin film. A magnetic recording medium comprising a magnetic layer. 2. A magnetic recording disk for horizontal recording, comprising a hard substrate, a first thin film formed on the substrate and made of chromium or a chromium-based alloy, and a first thin film on the first thin film. A magnetic recording disk comprising a lower layer formed and including a second thin film of a chromium-based alloy thin film, and a magnetic layer formed on the second thin film. 3. The magnetic recording medium according to claim 1, or the magnetic recording disk according to claim 2, wherein the substrate is silicon. 4. The magnetic recording medium according to claim 1, or the magnetic recording disk according to claim 2, wherein the substrate is glass. 5. The magnetic recording medium according to claim 1, or the magnetic recording disk according to claim 2, wherein the substrate contains an aluminum alloy having a thin film of nickel-amorphous surface formed on the substrate. 6. The magnetic recording medium according to claim 1, or the magnetic recording disk according to claim 2, wherein the first thin film is chromium and the second film is a chromium-vanadium alloy. 7. The magnetic recording medium according to claim 1, wherein the first thin film contains a chromium-vanadium alloy containing almost no oxygen atoms, and the second thin film contains a chromium-vanadium alloy containing oxygen atoms. 2. The magnetic recording disk according to 2. 8. The magnetic recording medium according to claim 1, further comprising a protective coating formed on the magnetic layer, or the magnetic recording disk according to claim 2.