JPS6111919A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To make use of merits of a Co-Cr vertical magnetic medium having excellent recording-reproduction characteristics in the shortwave region and to form a magnetic recording medium capable of obtaining a high reproduction output over a wide band leading further to the long-wave region by providing a laminated structure specifying the orientation of the C axis of a Co crystal to a magnetic layer. CONSTITUTION:The magnetic layer having a laminated structure consists of the first layer having 15-30 deg. DELTAtheta50 index which shows the orientation of the C axis of a Co crystal on a substrate and the second layer having <=15 deg. DELTAtheta50 on the first layer, and is formed by gaseous-phase thin film deposition. The magnetic layer having larger DELTAtheta50 is placed at the lower side so that the recording layer for long-wave recording which is less affected by the spacing may be placed at the lower side and the shortwave recording layer may be placed at the upper side to reduce a decrease in the output with the shortwave. When the DELTAtheta50 of the first layer exceeds 30 deg., the orientation of the Co-Cr film of the second layer is disturbed, and the DELTAtheta50 of the second layer does not become less than 15 deg.. The Cr/Co ratio in the Co-Cr film is preferably regulated in the range 0.1-0.35 throughout the first and the second layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a Co
-This invention relates to a Cr-based metal thin film type recording medium.

In recent years, various devices have become smaller and lighter, and in the field of magnetic recording, for example, the diameter of floppy disks has decreased to 8 inches, 5.25 inches, and 3 degrees. In addition, recording devices are rapidly becoming smaller. In magnetic recording media, in response to such miniaturization, even higher recording density is required. In order to increase the density, measures such as making the recording layer thinner, increasing the coercive force, and increasing the residual magnetic flux density are being adopted in the conventional in-plane magnetization method. An example of this is Co-N produced using an oblique evaporation method.
It is a metal thin film type recording medium such as i. As a means of increasing density, on the other hand, perpendicular magnetization methods that do not suffer from self-demagnetization in the short wavelength region, which is a problem with in-plane magnetization methods, are being actively developed. Developments are currently being carried out centering on Ba ferrite coatings.

However, in this perpendicular magnetization method.

Contrary to the in-plane magnetization method, there is a problem in that self-demagnetization occurs at long wavelengths. As a result, compared to the in-plane magnetized medium, the perpendicularly magnetized medium has the respective reproduction outputs of curve 11 (metal coated medium) and curve '12 (co
-Cr perpendicular magnetization media), although it is excellent in recording and reproducing at short wavelengths, it has the drawback of low effective value output at long wavelengths. This is the biggest obstacle to using perpendicularly magnetized media for analog recording using a wide band.

The present invention eliminates the drawbacks of the perpendicularly magnetized medium described above, takes advantage of the advantages of the Co-Cr perpendicularly magnetized medium, which has excellent recording and reproducing characteristics in the short wavelength region, and furthermore covers a wide band up to long wavelengths. The purpose of the present invention is to provide a recording medium that can provide high reproduction output.

lMitate 11 The magnetic recording medium of the present invention has been developed to achieve the above-mentioned object, and more specifically, the magnetic recording medium of the present invention is developed by forming a magnetic layer mainly composed of Co and Cr on a non-magnetic substrate. In the magnetic recording medium, the magnetic layer is a first layer in which the index Δθ, which represents the crystal C-axis orientation of Co, is from 15 to 30°, and the Δθ is 15° or less! It is characterized by having a laminated structure in which the s2 layer is deposited as a vapor phase thin film on the substrate in this order.

The circumstances leading to the present invention will be briefly explained.

A necessary condition for a perpendicularly magnetized film is that the magnetic anisotropy Ku in the direction perpendicular to the film surface is larger than the demagnetizing field energy 2πM s 2 . Here Ms is the saturation magnetization of the film. In a Co--Cr film that is a perpendicularly magnetized film, the C-axis direction of Co is the direction of easy magnetization, and by selecting film-forming conditions, the C-axis can be oriented in the film thickness direction. In addition, since the addition of Cr does not significantly impair the C-axis orientation and crystal anisotropy and lowers Ms, the crystal C-axis orientation is an important factor for the Co-Cr layer to become a perpendicularly magnetized film. be.

The half-width Δθ leap of the rocking curve of the C-axis (002,) in X-ray diffraction has conventionally been used as an index representing this orientation. It was discovered that there is a close relationship between the reproduction frequency characteristics of the C,o-Cr medium, and the reproduction frequency characteristics from short wavelengths to long wavelengths have been comprehensively improved. This was a successful development of a recording medium.

In other words, the long-wavelength reproduction waveform (input is a sine wave) when recording and reproducing with a ring head is as shown in FIG. 2 for an in-plane magnetized medium (corresponding to curve 11 in FIG. (corresponding to curve 12 in Fig. 1), Fig. 3,
In the Co-Cr medium, which shows the waveform as shown in
Beyond the time when Δθ (equity) is approximately 15'', media with large Δθ exhibit the same reproduction waveform as shown in Figure #12 as in-plane magnetized media, and media with small 60 questions exhibit the third waveform peculiar to perpendicular magnetization. Co-Cr which shows the reproduced waveform in the figure, that is, has a large Δθ (equity)
It was found that the in-plane magnetization component of the medium contributes in the long wavelength region. As a result, Co-Cr with large Δθ garden
The frequency characteristics of the medium are similar to those of the in-plane medium shown in FIG. 1, and the output is large at long wavelengths. On the other hand, a Co--Cr medium with a small Δθso, that is, a good C-axis orientation, is superior in terms of output at short wavelengths.

The above results show that Δθsono has the excellent high-density recording and reproducing characteristics inherent to the Go-Cr medium, which is a perpendicularly magnetized film, by stacking two layers of a Co-Cr film and a Go-Crltl film with a small Δθ jump. , and a recording medium having high reproduction output over a wide band including the long wavelength region can be realized.

More specifically, the magnetic recording medium of the present invention comprises a first Co-Cr film having a Δθ haze of 15 to 30” on a non-magnetic substrate made of polyester, polyimide, polycarbonate, etc.
layer, and a second Co layer with Δ0(equity) smaller than 15°.
The -Cr layer is obtained by vapor phase thin film deposition. In this way, the reason why the Δθ garden places a large magnetic layer at the bottom is that the recording layer that records long wavelengths, which is less affected by spacing, is placed at the bottom, and the short wavelength recording layer is placed at the top, which reduces the output at short wavelengths. This is to make it smaller.

Note that Δ0 of the first layer! When la exceeds 30”, the second layer C
The orientation of the o-Cr film is disordered, and Δθ of the second layer.

is not less than 15°.

The ratio of the thickness of each layer is 1. 5:1 to 1 between the first layer and the second layer
:2 is suitable, and the total thickness is suitably in the range of 0°2 to 2 pm. The second layer increases the spacing between the head and the first layer when viewed from the first layer, which is the layer below it.
In order to effectively use the magnetic flux from the layer, the second layer cannot be made too thick. From FIG. 1, it is seen that the output of the in-plane magnetized medium exceeds the output of the perpendicularly magnetized medium in a region where the wavelength is approximately 5 lumen or more. That is, the thickness of the second layer is preferably 0.5 JLm or less.

Also, through the first layer and the second layer, C in the Co-1cr film is
The r/Co ratio is preferably in the range of 0.1 to 0.35(7). If it is less than 0.1, the second layer will not become a perpendicularly magnetized film, and if it exceeds 0.35, it will become non-magnetic.

In this way, the first and second CoQs with different ΔθIIo
In order to sequentially form t@, a method of changing the partial pressure of an inert gas such as argon during vapor phase deposition such as sputtering (lowering the partial pressure when forming the second layer compared to when forming the first layer); Change the distance between the target and the substrate (distance is smaller when forming the second layer than when forming the first layer)
Alternatively, a method of changing the angle of incidence on the substrate using a mask or the like can be adopted.

Komu 1 Hereinafter, the present invention will be explained in more detail with reference to Examples.

1 Presentation 1'' Magnetic recording in which an S1 layer with a thickness of 0.31 m and a Go-Cr film as a second layer with a thickness of 0.27 m are formed on a polyester film with a thickness of 12 μm by high-frequency magnetron sputtering. Got the medium. Target is Go82%, Cr
1B% metal target, and the sputtering conditions were the first
During layer formation, the argon gas atmosphere during sputtering was adjusted to 8×10
−3 Torr, and 2×10=Torr when forming the second layer.

Δ0 of the first layer of the obtained magnetic recording medium (sample No. 1)
．． . is 17°, and the combined Δθ5o of the first and second layers is 11
''. From this result, the Δθ50 of the second layer was approximately 96
It is estimated that

As a comparative sample, "2, Part 2" was applied on a polyester film.
A magnetic recording medium in which a single-layer Co--Cr film with a thickness of 0.5 JLm was formed under the layer formation conditions was obtained (sample No. 2).
:c7) The Δθ50 of the Co-Cr film was 5°・Sample No. 11 according to the example of the present invention and comparative example No. 0
The coercive force Hc of 92 is 5400e and 4100, respectively.
It was e. We made these samples into tapes and measured the wavelength dependence of the playback output when self-recording and playback was performed using a ring-shaped head with a gear width of 0.3 μm. As shown in Figure 4, the output in the short wavelength region There is not much difference between the two,
However, in the long wavelength region, sample No. 1 (curve 41) of the present invention has a wavelength of 2 to 4 compared to sample No. 2 (curve 42).
It gave a dB larger playback output.

Co-co
A Cr film was formed on a polyimide film with a thickness of 1.21 m.

That is, in this continuous electron beam evaporation apparatus, a rotating can 53 is arranged in a vacuum chamber 52 connected to an exhaust system, and the base film 50 unwound from a roller 54 is moved along the rotating can via a free roller 55. Roller 5
6, the base film 5 on the rotating can 53
0, the electron beam 59 is irradiated onto the Co evaporation source 58 and the Cr evaporation source 58a while adjusting the incident angle using a shielding plate 57 to perform sputtering.

The ultimate vacuum level before evaporation is 7X10-・Torr, Can 5
The temperature in No. 3 was set at 250° C., and the tape (substrate film) feeding speed was 4.5 m/min. c.

By controlling the respective evaporation rates from the evaporation source 58 and the Cr evaporation source 58a, Cr in the Go-Cr film
The composition was 18 to 20%.

The crystal orientation of the Go-Cr film, that is, the crystal orientation in FIG. 40 was controlled by changing the incident direction of the deposited particles. C.

The incident angle θ of the particles is 700~45′″ and 90°~4
The Δθ (value) of the two types of Co--Cr films formed with an angle of 5° was 24° for the former and 8° for the latter. θ of the first layer is 70° to 45°, θ of the second layer is 90°
Sample No. obtained by forming a film with a thickness of 0.2 ILm each with the angle limited to ~45°.

Δθ of 3. was 13'', and Hc was 890' Oe. Figure 6 shows the thus obtained magnetic recording medium sample No. 3.
and magnetic recording medium sample No. in which a single-layer Co--Cr film was formed with θ limited to 90 to 45 degrees.

4 ()ic=580 Qe), which is the frequency characteristic of the reproduced output measured by the same method as in Example 1. Sample 3 (curve 61) having the two-layer structure of the present invention is better than sample 4 (curve 62). ), a larger reproduction output is obtained over almost the entire frequency range.

Note that in the above-described embodiment, the first layer and the second layer were formed using the same method, but the same effect can be obtained even if a different film forming method is used for each layer.

As explained above, according to the invention, a Co-Cr magnetic film, which is a perpendicular magnetization medium, is
By creating a two-layer structure in which the magnetic field is large near the substrate and small on the surface side, it has the excellent short wavelength recording and reproducing characteristics of perpendicular magnetization, and has great effectiveness even in the long wavelength region. An excellent recording medium for high-density analog recording that provides a value reproduction output is provided.

[Brief explanation of drawings]

Figure 1 is a comparison of reproduction output versus wavelength, or frequency characteristics, of in-plane magnetization media and perpendicular magnetization media. The s2 diagram shows long wavelength (λ
=IOpm), the output waveform of the in-plane magnetized medium, Figure 3 is λ
= Output waveform of the perpendicularly magnetized medium at 10 pm, Figure 4 shows reproduction output frequency characteristics of inventive samples No. 1 of Example 1 and comparison sample No. 12, and Figure 5 shows electron beam evaporation characteristics used in Example 2. A schematic diagram of the apparatus, FIG. 6 shows the present invention sample N of Example 2.
Reproduction of o, 3 and comparative sample No. 46. This is the power frequency characteristic. 11-@- Reproduction output of in-plane magnetization medium, 12... Reproduction output of perpendicular magnetization medium. 41・φ・Reproduction output of the present invention sample No. 001, 42・・Reproduction output of comparison sample No. 2, 501・Base film, 51・Exhaust system, 52φ・vacuum chamber, 53・Rotating can, 54...Unwinding roller, 551.Free roller, 56.φ.Take-up roller, 57.φ.shielding plate, 58.--Co evaporation source, 58a...Cr evaporation source, 59.--electron beam , 61-... Reproduction output of present invention sample No. 3, 62...
Reproduction output of comparison sample No. 4. Illusion LLl: Figure 4 Figure 1 Figure 17 Reunion Chief (J, lm-1) 12ffl Figure 3! 14 Figure 1/Icho (JJm”1 Figure 5 6 Figure 1/Icho [μm-zl Procedural Amendment August 1981: JI date)

Claims (1)

[Claims] 1. A magnetic recording medium in which a magnetic layer mainly composed of Co and Cr is formed on a non-magnetic substrate, wherein the magnetic layer is made of Co and Cr.
It has a laminated structure in which a first layer having an index Δθ_5_0 representing the crystal C-axis orientation of 15 to 30°, and a second layer having a Δθ_5_0 of less than 15° are deposited as vapor phase thin films on a substrate in this order. A magnetic recording medium characterized by: 2. Cr/Co weight ratio in the magnetic layer is 0.1 to 0.35
A magnetic recording medium according to claim 1. 3. The magnetic recording medium according to claim 1, wherein the thickness of the second layer is 0.5 μm or less.