JPS62298918A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain high reproduction output even at >=180KFRPI recording density by forming a magnetic layer essentially consisting of Co and Cr and consisting of additives which are Ni and at least one element among Cu, P and Al and trace impurities in such a manner that the concn. of Cu, P and Al or the concn. of Ni and Cu, P, Al near the substrate is lower than the average concn. over the entire part of the film. CONSTITUTION:The magnetic layer essentially consisting of Co and Cr and consisting of the additives which are Ni and at least one element along Cu, Al, and P and trace impurities is formed on the substrate in such a manner that the concn. of Cu, Al and P or the concn. of Ni and Cu, Al and P is lower than the average concn. over the entire part of the film. The film having such constitution has the high reproduction output even at the substrate temp. below 100 deg.C at which a PE terephthalate is usable as the substrate and at >=180KFRPI recording density.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a thin-film magnetic recording medium for perpendicular recording with excellent high-density recording characteristics.

2. Description of the Related Art Conventionally, a perpendicular recording method has been known as a magnetic recording method with excellent short wavelength recording characteristics. This method requires a perpendicular magnetic recording medium having perpendicular magnetic anisotropy. When a signal is recorded on such a medium, the residual magnetization is oriented in a direction substantially perpendicular to the film surface of the medium. Therefore, the shorter the wavelength of the signal, the smaller the demagnetizing field within the medium, and a immersed reproduction output can be obtained. What has traditionally been considered the best perpendicular magnetic recording medium is a perpendicular magnetic recording medium that is formed on a non-magnetic substrate made of a polymeric material or a non-magnetic metal, either directly or through a soft magnetic layer such as a permalloy film. A magnetic layer containing CO and Cr as main components and having perpendicular magnetic anisotropy (hereinafter this magnetic layer will be referred to as a CO--Cr perpendicular magnetic anisotropic film) is formed by sputtering or vacuum evaporation.

G has satisfactory magnetic properties when used with sputtering or vacuum evaporation.
When producing an o-Cr perpendicular magnetic anisotropy film, the total substrate temperature must be about 200°C.

Perpendicular magnetic anisotropy films can be obtained even below 200°C, but the coercive force Hc in the direction perpendicular to the film surface is small. In terms of temperature, NO is less than 20,000.

Furthermore, the magnetization mechanism is not limited to magnetization rotation, which is suitable for a perpendicular magnetic recording medium, but is also largely due to domain wall movement. As a result, the playback output is low, the noise is high, and the S/N is high.
is not obtained. On the other hand, Go-C at a substrate temperature of about 200℃
When a perpendicular magnetic anisotropic film is formed, H, F is 600 to 1
0000e, and the magnetization mechanism is mainly magnetization rotation. In this case, the reproduction output is high, the noise is low, and a high S/N ratio is obtained. As mentioned above, in order to fabricate a Go-Cr perpendicular magnetic anisotropic film with a high S/N ratio, it is necessary to keep the substrate temperature at about 200°C. It has been difficult to mass-produce perpendicular magnetic anisotropic films using substrates with poor heat resistance such as inexpensive polyethylene terephthalate films, but we have developed a method using at least N1, Cu, P, and Al. Co-Or-Ni-M perpendicular magnetic anisotropic film (M=Cu.

It has already been found that a perpendicular magnetic anisotropy film having a high H6□ can be obtained even at a substrate temperature of 100° C. or lower by using P1. Also, the recording density is 120
The playback output or S/N of KFRPI is based on the C on the high temperature board.
It is no different from the o-0r perpendicular magnetization film.

Problems to be Solved by the Invention However, although the Co-Or-Ni-M perpendicular magnetic anisotropic film has a high H6, when the recording density reaches about 180 KFRPI, the same Ho□ It has become clear that the reproduction output is lower than that of a Co-0r perpendicularly magnetized film having . That is, at a recording density of 180 KFRP or higher, the reproduction output of the Co--Cr-N1-M perpendicular magnetic anisotropic film was inferior to that of the Go-Cr perpendicular magnetic anisotropic film.

Means for solving the problem A substrate containing Co, Cr as main components, Ni and Cu
.

AI! , P, and a trace amount of impurity, the concentration of Cu, kl, and P in the vicinity of the substrate, or the concentration of N1 and Cu, A7. The film is formed so that the concentration of P is lower than the average concentration of the entire film.

Function Conventional Go-Cr-Ni-M perpendicular magnetic anisotropic film (M=C
u, mu1. P), the film having the structure of the present invention has a recording density of 180KFRP at a substrate temperature of 100°C or less, where polyethylene terephthalate can be used as a substrate.
It has high reproduction output even at I or higher.

Examples Examples of the present invention will be described below. Inside the vacuum chamber 1
After evacuation to X1 o -5 torr or less, Go-23 weight t % Or + Go - 20 weight % 0 r -19 weight t4 N = -o, s weight % Cu, Go
-20% by weight Ct -19% by weight Ni - 0.4% by weight
Ag, Go -20% by weight, Co-20 heavy feeding Chi Cr -
Films having a composition of 19% by weight y1-o and s% by weight P were formed, and the magnetostatic properties, crystal orientation, and recording and reproducing properties of these films were investigated. FIG. 1 shows a schematic diagram of the vacuum evaporation apparatus used to form the film.

The substrate 1 runs along the cylindrical first can 2 and second can 3 in the direction of the arrow. A first mask 5 is arranged between the first evaporation source 4 and the first can 2, and a second mask 7 is arranged between the second evaporation source 6 and the second can 3.
, the evaporated atoms pass through the slits S1 and S2 and adhere to the substrate 1. Reference numerals 8 and 9 are a supply roll and a take-up roll for the substrate 1, respectively. 10 is a guide roller. During the vapor deposition, the magnetic thin film was deposited at a deposition rate of 1500 people/second and a film thickness of 2500 people/second. The Cr concentration and the Cu, Ag, and P concentration in the evaporated atoms are determined by the concentration of granular Or and Cu during evaporation.
Person 1. C: Prepared by feeding o-P alloy into an evaporation source. At that time, the composition of the formed film was varied in the film thickness direction by varying the amounts of Cu, Kl, and Go-P alloy supplied to the first evaporation source and the second evaporation source.

The ratio of the film thickness d1 formed by the first evaporation source to the film thickness d2 formed by the second evaporation source can be determined by changing the ratio of the widths of the slits S1 and slits S2 by operating from outside the vacuum chamber.
It was varied within the range of d2=2.23 to 1:0. The saturation magnetization MS averaged in the film thickness direction of the film thus obtained was in the range of M s "300 to 3806 mu/CC. Also, the surface temperature of the first and second cans during vapor deposition was The temperature was set at 40°C.

The magnetostatic properties of the deposited film were measured using a vibrating sample magnetometer, and the coercive force H0 in the direction perpendicular to the film surface and the coercive force H67 in the film surface were determined. The results are summarized in Table 1.

The crystal orientation was evaluated by measuring Δθ5o using an X-ray diffractometer, and the Δθ5o is also summarized in Table 1. Note that Δθ,. is the half width of the rocking curve with respect to the (002) plane of a magnetic thin film having a dense hexagonal structure, and indicates the degree of orientation of the C axis in the direction perpendicular to the film plane.

In general, film types with a small Δθ5o, in which the C axis is well oriented perpendicular to the film surface, have a large perpendicular magnetic anisotropy energy, and are excellent as perpendicular magnetic recording media.

The recording and reproducing characteristics were measured using a ring-shaped head made of Mn-Zn ferrite and having a gap length of 0.14 μm. 1
The reproduction output of the 80KFRPI signal is also shown in Table 1. In addition, 180KFRP I means 1 inch per inch.
This is the recording density of a digital signal with o00 magnetization reversals. In addition, the playback output is based on Go-23 weight% Cr film.
That is, it is expressed as a relative value in OdB.

From Table 1, it can be seen that the Go-23 wt% Cr film has a H6 coating of 100%
0e, which is very low, and H67 is larger than H,E, indicating that domain wall movement accounts for a considerable proportion of the magnetization mechanism. Also, 180K of co-23 wt% Cr film
The absolute value of the playback output in FRPI is 60 μV, -
, 7mm -Tm 7 seconds.

60μV, -,10-T-m 7 seconds means that the output is 60μvp-p when the head nodrak width is 1 ff, the number of turns of the head coil is 1 turn, and the relative speed between the head and the medium is 1 m/s. That's true.

(Left below) Table 1 shows the film thickness d formed by the first evaporation source, the film thickness d2 formed by the second evaporation source, and the film composition of the portion formed by each evaporation source. The film composition of each part is determined by atomic absorption spectrometry by setting S2 or S to O and d2 or dl to Q. The composition of the entire film was also determined using atomic absorption spectroscopy. Assuming that the filling factor was 1, the film thickness was calculated by dividing the film mass obtained from the results of atomic absorption spectrometry by the compositional average density of the constituent elements.

From the results of d in Table 1: 2500 people, d2=0, Ni
and Cu, person 6. By adding a type of Go-Cr, the H0 performance is improved and the playback output at 180KFRPI is
It can be seen that there is an improvement of edB to 7 dB compared to the perpendicular magnetic anisotropic film. However, Ni and Cu.

Due to the addition of Al and P, the crystal orientation is disturbed,
Δθ5o is large. When recording and reproducing at a 120 KFRP process level, if Δθ5o is about 100 or less, the reproduction output has almost no relation to Δθ5o, but as the recording density becomes higher, the conditions for Δθ5o may become even more severe. So d1=1000 people, d2=150
Cu, kl that is 0 people and included in the first layer
, the concentration of P in the film was set to about A of the average composition of the entire film.

As a result, the crystal orientation was improved and the Δθ5o value became 5° or less. However, in such a configuration, the H6 process is not very large, and therefore the reproduction output increases by only about +1 to +3 dB compared to the G o -Or perpendicular magnetic anisotropic film. Next, the results when d1=500 people and d2=2000 people will be described. Cu contained in the first layer as before.

The concentrations of Al and P in the film were defined as the average composition of the entire film. Then, Δθ5o is 5° or less and H0 work is d1=2
500 people, almost the same size as in the case of d2=o. The reproduction output was also increased by +9 to +11 dB compared to the co-Cr perpendicular magnetic anisotropic film. This playback output is d
1 = 2500 people, +3 to +4 than when d2 - ○
This seems to represent the effect of suppressing Δθ5o to 5° or less, which increases by dB. d, = 200 people,
Even when d2 = 2300 people, dl: 600 people, d2 =
Similar results were obtained for 2,600 people. In addition, d1
= 500 people, d2 = 2000 people, if the first and second layers are both VCGo-23Cr F), there is no improvement in H6, and the playback output is 61 = 2500 people, d
There was no difference from the 2=O Go-23Or film.

For comparison, G of 2S00 people with a film thickness of 2S00 was formed on a polyimide film with a film thickness of 12 μm with the surface temperature of the cylindrical can being 200°C, d1==2500 people, and d2=○.
The same characteristics as in Table 1 of the o-23 wt% Cr film are shown in Table 2.
Shown in the table.

° (Hereafter the margin) As you can see by comparing Tables 1 and 2, Go.

In a film doped with CrKNi and one of Cu, P, and P, if the concentration of Cu, P, and P in the 200 to 500 region near the substrate is lower than the average concentration of the entire film,
4.Polyethylene terephthalate film can be used.
Even though it was made at a can surface temperature of 0℃,
It has almost the same magnetostatic properties and recording/reproducing properties as a Co-Or film produced on a heat-resistant polyimide film at a can surface temperature of 200°C, even at a high recording density of 180KFRPI.

If the thickness of the first layer exceeds 500, the composition of the second layer will be high.
Even if the composition is above c, the influence of the first layer becomes dominant, and the entire film becomes a low Hc soil. On the other hand, if the thickness of the first layer was less than 200, it was insufficient to stabilize the crystal orientation, and the Δθ5o of the entire film was almost determined by the composition of the second layer. Therefore Cu, person 1. The thickness of the region with less P is 200 to 500
Approximately one person is considered desirable. In addition, generally the first layer C
u, Al.

The lower the P concentration, the lower Δθ5o is 9, and the reproduction output increases, but this effect becomes clearer when CuA4 in the first layer,
This was a case in which the P concentration was lower than about IA, which is the average value of the entire film.

Table 3 shows the same characteristics as in Table 1 when not only the Cu, β, and P concentrations in the first layer but also the Ni concentration were set to about A, which is the average value of the entire film. By creating a Ni concentration gradient in the film thickness direction! 1lGo-Cr-Ni-personl, G
Also in the case of o-Cr-Ni-P, +2 to + compared to Table 1.
The 3 dB playback output was further improved (see the margin below). It is said that the orientation is improved and the playback output is increased, and that corrosion resistance is improved by making the Cr concentration near the film surface higher than the average Cr concentration of the film. You can see the effect.

Although the above example uses a polyethylene terephthalate film or a polyimide film as a substrate, the results will not change even if a polymer film other than these or a nonmagnetic metal substrate is used. In addition, in the above explanation, we have described the case where the film was fabricated by changing the film composition discontinuously using two cans and two evaporation sources.
u.

AI! , P, Ni, and Cr concentrations, or by unevenly distributing the supply position of Cu, Mul, and Co-P grains with respect to the center of the evaporation source.
, similar results were obtained by continuously changing the P concentration.

Effects of the Invention According to the present invention, a thin film magnetic recording medium for perpendicular recording having high reproduction output in the short wavelength region can be obtained even if a substrate with poor heat resistance such as a polyethylene terephthalate film is used.

[Brief explanation of the drawing]

The figure is a schematic diagram of the internal structure of the vacuum evaporation apparatus. 1... Board, 2... First can, 3.
...Second can, 4...First evaporation source, 5
...First mask, 6...Second evaporation source,
7...Second mask, 8...Supply roll, 9...Take-up reroll, Sl, S2...
·slit.

Claims (2)

[Claims] (1) Co and Cr are the main components on the substrate, and Ni and Cu
, P, Al, and a small amount of impurity, and the magnetic layer is made of carbon near the substrate.
u or P or Al or Ni and Cu or P or A
A magnetic recording medium characterized in that the concentration of l is lower than the average concentration of the entire film. (2) Cu or P or Al or Ni and Cu or P or A within 500 Å from the interface between the substrate and the magnetic layer.
2. The magnetic recording medium according to claim 1, wherein the average concentration of l is 1/2 or less of the average concentration of the entire film.