JPS6083218A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin film medium for vertical magnetic recording having a high output-noise ratio even when recording is carried out at about 150kBPI high density, by alternately laminating thin films having vertical magnetic anisotropy and nonmagnetic layers. CONSTITUTION:Thin films 12, 12' of a magnetic alloy having high magnetic permeability such as Co-Zr-Mo or Ni-Fe, nonmagnetic layers 13, 13' of Cr, Ti, Al2O3 or the like, thin films 14, 14' of Co, Co-Cr or the like having vertical magnetic anisotropy, nonmagnetic layers 15, 15' of Cr, Ti, Al2O3, CrO or the like, and thin films 16, 16' of Co, Co-Cr-Rh, Co-Cr-Mo or the like having vertical magnetic anisotropy are successively formed on a substrate 11 of glass or the like. Since the thin films 14, 14', 16, 16' having vertical magnetic anisotropy and the nonmagnetic intermediate layers 13, 13', 15, 15' are alternately laminated, high density and a considerably high output-noise ratio are provided.

Description

Detailed Description of the Invention [Field of Application of the Invention] □ The present invention relates to a multilayer magnetic recording medium suitable for use in perpendicular magnetic recording, especially high-density recording.

[Background of the invention]

Conventional perpendicular magnetic recording media have been manufactured by forming Co--Cr to a thickness of about 0.2 to 5 .mu.m on a substrate by sputtering, vacuum evaporation, or the like. Generally, when a thin film is formed using these methods, as the film thickness increases, the crystal grain size also becomes larger. Therefore, especially when trying to achieve a high recording density of about 150 kBPI, the Co--Cr film thickness should be 0.5 kBPI.
Even when the medium is as thin as about 2 μm, there is a drawback that when recording is performed on this medium, a large amount of noise is generated during reproduction, resulting in a deterioration of the output noise ratio.

[Purpose of the invention]

An object of the present invention is to provide an N-film medium for perpendicular magnetic recording that has a high output noise ratio even when recording at a high density of about 150 kBPI.

[Summary of the invention]

The inventors of the present invention have conducted intensive studies on a film formation method that keeps the crystal grain size in a fine state without impairing the perpendicular orientation of the medium. As a result, the present inventors have found that a thin film with perpendicular magnetic anisotropy can be formed using non-magnetic Nf:
It has become clear that the above objective can be achieved by laminating the two layers with each other. When this medium is recorded at a high density of about 150 kDPI, the noise is much lower than that of a medium made using a conventional method.Furthermore, by backing this thin film with a high permeability magnetic layer, the output noise ratio can be improved. A immersed f'c film with further characteristics was obtained, and this effect was particularly remarkable when the thin film having perpendicular magnetic anisotropy was made of a magnetic metal mainly composed of co or cofc.

The Ministry of the Invention and others have developed the present invention based on the above facts, and it is preferable that thin films having perpendicular magnetic anisotropy are laminated via a non-magnetic layer, and even more preferably, the laminated film is layered with a high magnetic permeability magnetic layer. Even more preferably, the thin film having perpendicular magnetic anisotropy is made of CO or a magnetic alloy mainly composed of CO, and has a high output noise ratio at high density. This is what we provide.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 11
is glass, A4. Substrate made of polyester, polyimide, and PET, 12.12” is Co Z rM O+
High permeability magnetic base metal thin film made of NIFe etc., 1
3.13' is Cr, Ti.

Non-magnetic layer made of A720a etc., 14.14' is c
thin film with perpendicular magnetic anisotropy consisting of o, co-cr, etc., 15.15' is Cr, 'l' i, ktzo
3+Nonmagnetic layer made of CrO etc., 16.16' is Co
, Co-Cr-R)l, Co-Cr-)yJo, etc., and has perpendicular magnetic anisotropy. The composition and material of each layer of the perpendicular magnetic thin film may or may not be the same.

Second. FIG. 3 shows another embodiment. 21゜31ba At
, a substrate made of polyimide, PET, etc., 22 is Co
High permeability magnetic alloy thin film consisting of -Zr-W, Fe-8i, etc., 23, 25, 27° 29.32.32'
, 34.34' is co-Cr.

24. Perpendicular magnetic anisotropy film such as co-cr-w.
26, 28, 33, and 33' are nonmagnetic layers made of CoO, AlzOs, or the like.

In each case, the number of stacked layers of perpendicular magnetic anisotropic films is 2 to 4, but even more layers may be used.

According to the present invention, since the crystal grain size can be maintained in a fine state without impairing the vertical orientation of the medium, noise can be significantly reduced. Film thickness is 0.01゜0.02,0.05
, 0.1, 0.25 with a film thickness of 0.
The half-width Δθ5o of the Xa1 fold peak, which indicates the vertical orientation of the medium, and the medium noise are expressed as 41 in FIG. Shown at ゜42. The same figure also shows Δθ5o and noise of a C'o-Cr single layer film with a film thickness of 0.5 μm, but from the same figure, when Co-cr is laminated via Tl, the C0-0r single layer It can be seen that the noise is reduced compared to the membrane case. Furthermore, if the film thickness for one layer of (:o-Cr is 0.015 μm or more, Δθ5G is as small as 40 or less, and the vertical alignment is equivalent to that of a multilayer film. It can be seen that the film is certainly suitable for recording images.

In fact, the film thickness Q is 1 μm of Co-Cr and the film thickness is 0.005 μm.
vertical coercive force 4500e, saturation magnetic flux density 350emu/
CoCo-2 with a thickness of 1 μm
When perpendicular magnetic recording and reproducing was carried out using a medium with the structure shown in Fig. 1 and lined with an r-amorphous magnetic alloy, high-density recording and reproducing characteristics were obtained as shown in Fig. 51. Obtained. The same figure also shows the characteristics when using a Co-cr single layer film.
2, but almost the same output is obtained in this case as well. However, when the output noise ratio at 150 kBPI was compared, the characteristics of the medium having the structure of the present invention were approximately three times higher, and the effect of the present invention was remarkable. Here, 13.1
In a medium with a structure as shown in Fig. 2 in which the Co-Cr layer is directly formed on the high permeability layer by omitting the 3' layer, the underlayer is made of high permeability magnetic alloy N1-pe, . When using PE-8i etc., the characteristics decreased by about 5%, but the underlying kco
When an amorphous high permeability magnetic alloy such as -Zr-=Mo or Co-Zr-Nb was used, the magnetism did not change.

However, in each case, an output noise ratio about three times that of a medium with a conventional structure was obtained.

Film thickness 0.15 μm, coercive force aoooo, saturation magnetization 450
emu/cc Co-Cr-Rh' (r, film thickness 0.0
When perpendicular magnetic recording and reproduction was performed on a medium having the structure shown in FIG. 3, in which two layers were formed by forming one layer of 0.05 μm Tl,
The characteristics shown in FIG. 661 are almost the same strongyle output as the characteristics 62 of a single membrane medium, but for example, 100k
The output noise ratio at BPI was improved by about 1.5 times. When the medium of this configuration was lined with a co-Zr-Nb amorphous high permeability layer with a film thickness of 1.5 μm, the output noise ratio was improved approximately twice.

The above effects are due to Ba-ferrite, CoXC0 oxide,
This has also been observed in Co-Pt, etc., and by using a medium with this structure, extremely good perpendicular magnetic recording and reproducing characteristics can be obtained.
.

〔Effect of the invention〕

The perpendicular magnetic recording medium of the present invention has a high density and a significantly improved output noise ratio by forming an a layer of a thin film having direct magnetic anisotropy via a nonmagnetic material.

[Brief explanation of drawings]

Figures 1 to 3 are cross-sectional views of the medium of the present invention, Figure 4 is a graph showing the film characteristics of the structure of the present invention, and Figures 5 and 6 are graphs showing the perpendicular magnetic recording and reproducing characteristics of the medium of the present invention. This is a graph showing. 11.21.31...Substrate, i2, 12', 22.
...High magnetic permeability layer, 1'4.14', 16.16',
23゜25.27, 29, 32.32', 34.34
'...layer having perpendicular magnetic properties, 13.13', 1
5゜15', 24, 26, 28, 33.33'...
Nonmagnetic intermediate layer, 41...Δθso of the film of the present invention, 42
...Noise, 51.61...Recording and reproducing characteristics of the medium of the present invention 1B Fig. 3 Fig. 15 tl乍禾2 Exhibition (ρ) Continued from page 1 0 Inventor Kosei Shinagawa Higashi Koigakubo, Kokubunji City Inside the Central Research Institute

Claims (1)

[Claims] 1. A perpendicular magnetic recording medium characterized by having a laminated film in which thin films having perpendicular magnetic anisotropy are laminated with a nonmagnetic layer interposed therebetween. 2. The perpendicular magnetic recording medium according to claim 1, wherein the laminated film is lined with a high permeability magnetic layer. 3. The thin film with perpendicular magnetic anisotropy is made of Co or C.
3. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is made of a magnetic metal mainly composed of o.