JPS63815A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a perpendicularly magnetically anisotropic film having high S/N even if a substrate having low heat resistance is used by forming a magnetic layer consisting of Co, Cr, Ni, Al, and Cu having the compsn. in a specific range and trace impurities on the substrate. CONSTITUTION:Even if the substrate 1 such as PE terephthalate film having the low heat resistance is used, the perpendicularly magnetically anisotropic film having the high S/N is obtd. by forming the magnetic layer consisting of 7-26wt% Cr, 5-30wt% Ni, 0.1-4wt% Al, <=4wt% Cu and the balance Co and trace impurities on such substrate 1. The productivity of the tape-shaped perpendicular magnetic recording medium is improved if the magnetic layer is formed by using a vacuum evaporation device. The substrate 1 travels is an arrow A direction along a cylindrical can 2. A mask 5 is disposed between an evaporating source 6 and the can a the evaporating atoms stick through a slit S onto the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thin film magnetic recording medium for perpendicular recording having 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 approximately perpendicular to the film surface of the medium. Therefore, as the wavelength of the signal becomes shorter, the demagnetizing field within the medium decreases, and a immersed reproduction output can be obtained. The most excellent perpendicular magnetic anisotropic films have been those that are deposited directly on a nonmagnetic substrate such as a polymeric material or nonmagnetic metal, 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-Orr perpendicular magnetic anisotropic film) is formed by sputtering or vacuum evaporation.

Problems to be Solved by the Invention When producing a Co-Or perpendicular magnetic anisotropic film with satisfactory recording and reproducing characteristics using the spunter method or vacuum evaporation method, it is necessary to keep the substrate temperature at about 200°C. be.

A perpendicular magnetic anisotropic film can be obtained even at temperatures below 200'C, but the coercive force Hc in the direction perpendicular to the film surface is small. In particular, in the vacuum evaporation method, which is considered optimal for mass production, the Hc concentration is 20,000 or less at a substrate temperature of 200° C. or less. In addition, the magnetization mechanism is not only due to magnetic rotation as perpendicular magnetic recording media, but 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, at a substrate temperature of about 200°C, G
When an o -Or perpendicular magnetic anisotropy film is formed, the Hc becomes about 500 to 100,000, 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 described above, in order to fabricate a perpendicular magnetic anisotropic film having a high S/N ratio, it is necessary to set the substrate temperature to about 200°C. This means that it is difficult to use substrates with poor heat resistance, such as inexpensive polyethylene terephthalate films, which are currently used in large quantities and stably in magnetic tapes and flonobie disks. Unless a substrate with poor heat resistance such as a polyethylene terephthalate film can be used, it is extremely difficult to actually mass-produce perpendicular magnetic anisotropic films. When using polyethylene terephthalate film as a substrate, it is necessary to keep the substrate temperature below 100'C, and it is important to find the conditions for this.
This is the biggest challenge at the moment.

Means to solve problems In order to achieve this purpose, the present invention deposits Co on a substrate.

Cr+ Ni, AJ or Go, Cr, Ni, person 1
．． A magnetic layer made of Cu and trace impurities is formed.

Function: In contrast to the conventional Go-Cr perpendicular magnetic anisotropic film, the film having the composition of the present invention can be used at a substrate temperature of 100°C or less, where polyethylene terephthalate film can be used as a substrate.
Can be used on high Hc. That is, a perpendicular magnetic anisotropic film having a high S/N ratio can be obtained even at a substrate temperature of 100'C or less.

Examples Examples of the present invention will be described below. Co23 heavy ffi%Cr was deposited on a 10 μm thick polyethylene terephthalate film by vacuum evaporation.

Go-20% by weight Cr-20% by weight Ni, Co-19% by weight 0r-30% by weight Ni, Go-23% by weight Cr-〇, 4% by weight Ml, Co-19% by weight Cr-6% by weight A1
．． C0-20% by weight Cr-19% by weight Ni-4% by weight
Films having the following compositions were formed: Co-18% by weight, Cr-18% by weight, N=-3% by weight, and the magnetostatic properties, crystal orientation, and recording/reproducing properties of these films were investigated. FIG. 1 shows an outline of the internal structure of the vacuum evaporation apparatus used to prepare the film. The substrate 1 runs along the cylindrical can 2 in the direction of the arrow. A mask 6 is provided between the evaporation source 6 and the cylindrical can 2.
are arranged, and the evaporated atoms pass through the slit S and adhere to the substrate 1. 3 and 4 are a supply roll and a take-up roll for the substrate 1, respectively. When a magnetic layer is formed using a vacuum evaporation apparatus as shown in FIG. 1, a tape-shaped perpendicular magnetic recording medium can be obtained with very high productivity. During vapor deposition,
The deposition rate of the magnetic thin film was 6000 A/sec, and the film thickness and saturation magnetization Ms were 2500 and 320 to 360 em, respectively.
u/.

And so. Note that the Cr concentration and AJ concentration in the film were adjusted by supplying particulate Or and Al into the evaporation source during vapor deposition. Also, make sure that the temperature of the cylindrical can surface during vapor deposition is 80'C.

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

Crystal orientation was evaluated by measuring Δθ5o using an X-ray analyzer. Δθ5o is also summarized in Table 1. Note that Δθ5o
is the half-width of the rocking curve for 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 surface. - In general, the smaller the Δθ5o, the better the C-axis is oriented perpendicular to the film surface, the higher the perpendicular magnetic anisotropy energy, and the better the film is as a perpendicular magnetic recording medium. 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. 120K FRP signal reproduction output, noise and S
/N is shown in Table 1. Note that 120KFRPI is a recording density of a digital signal in which magnetization is reversed 120,000 times per inch. Also, playback output, noise and S/N
Both are based on Co-23wt%Or film, that is, Od
B is shown as a relative value.

From Table 1, the conventional composition Coo-23M amount%Cr
Membrane HCJ- is very low at 1200e, and H
It can be seen that cID is larger than Hc, and domain wall movement accounts for a considerable proportion of the magnetization mechanism.

Further, the absolute value of the reproduction output of the Go-23 weight % Cr film at 120 KFRPI is 150 μVpp/rtrx.

T, m7 seconds. 150μVP, /pat, T, m
7 seconds means that the trunk width of the head is IMM, the number of turns of the head coil is 1 turn, and the relative speed between the head and the medium is 1.
This means that the output when converted to m/sec is 150 μvp-p. Looking at the characteristics of the Go-20wt%Cr-20wt%NN simulated film and the Co-19wt%0r-30wt%Ni film, it is found that when N is added to Co-0r, the Hc becomes somewhat larger, but Δθ5o It can be seen that the crystal orientation becomes larger and the crystal orientation deteriorates.

When Δθ5o is 10' or less, there is almost no deterioration in the recording and reproducing characteristics, but when it exceeds 1c3, the reproduction output, especially in the short wavelength region, decreases. Only adding N1 to Go-Cr does not significantly improve reproduction output, noise, and S/N.

Next, a film in which λβ is added to Go-Or will be described.

Go-23 wt% 0r-0,4 wt% Al film is Hc
The upper one is slightly higher than Go-23 weight % Cr, but Δθ5o is also somewhat larger. The S/N improvement is on the order of 2'dB. In addition, the Go-1e;zwt%Cr-〇wt%AJ film with increased Al addition
The upper one is high at 30006, but Δθ5o is 26
The size of the film is extremely large, making it difficult to record in the direction perpendicular to the film surface. As a result, the playback output of 120KFRPI is -6d for Go-23wt% Cr film.
It is low as B. As mentioned above, only by adding human e to Go-Or, there is not much improvement in S/H. If the amount of Al added is greater than 4% by weight, the orientation of the C-axis in the direction perpendicular to the film surface will be greatly disturbed, and the film will no longer be a perpendicular magnetic anisotropic film.

Finally, a film obtained by adding Ni and AJ to Go-1r will be described. For both the C0-20wt%0r-19wt%N1-0.4wt%Al film and the Go-18wt%Cr-18wt%Ni-3wtAl film, the Hc value exceeds 60006, and Δθ50 is 16 or less. The recording and reproducing properties of these films are almost the same, and Go-23% by weight
Compared to the Cr film, the reproduction output of the 120K FRP material is edB higher and the noise is 7 dB lower. As a result, the S/N is 13 dB higher. The absolute value of the playback output at 120KFRPr K is 30071 Vp-p/Ml −
T 6m 7 seconds, which is a very high value. Furthermore, Hc is larger than Ha/, and magnetization rotation is the main factor in the magnetization mechanism.

Add 4% by weight of Cu to Go-Cr-Ni-41
If added below, the Hc value will increase to 600 to 7000e. With such a film, the reproduction output at 12oK FRPI is approximately the same as that of a film without Cu added, but the noise is reduced by 1 to 3 dB and the S/N is improved. Quadruple Rs
If Cu is added in an amount exceeding 10, Δθ5o becomes 10 or more, and the reproduction output in the short wavelength region decreases by a large amount.

For comparison, the temperature of the cylindrical can surface was set at 200°C, and a film thickness of 1
Film thickness: 250 mm formed on 2 μm polyimide film
Table 2 shows the same properties as in Table 1 for the 0 Co to 23 weight coefficient Or films.

Table 2 As can be seen by comparing Tables 1 and 2, Qo -cr
The film doped with KNi, A, and l was prepared at a can surface temperature of 60°C, which is the temperature at which polyethylene terephthalate film can be used. It has almost the same magnetostatic properties and recording/reproducing properties as the Go-Cr film produced in . Note that Δθ5o is Co-CrK
Ni and Hkl all added, fcjN is more Go-Cr
Although the angle is sharper than that of the film, if the angle is 10° or less, it will hardly affect the recording and reproducing characteristics.

Go -Cr -Ni-Al film or Co -0r-
If the amount of Cr added to the Ni-) or 1-Cu film is less than 7% by weight, the perpendicular magnetic anisotropy is insufficient and perpendicular recording cannot be performed. As a result, the output in the short wavelength region is very low. Even when the amount of Cr added is as high as 26%, Ms
It becomes too small and the output is very low. Therefore, the amount of Cr added needs to be within the range of 7 to 26% by weight. Regarding the amount of Ni added, if the amount of Ni added is less than 5% by weight, no effect of Nl is observed. If it exceeds 30% by weight, perpendicular magnetic anisotropy becomes insufficient and perpendicular recording becomes impossible.

When the amount of mulch added is less than 0.1 weight, no effect of human e is observed. If the amount added exceeds 4 weight St, the perpendicular magnetic anisotropy will become insufficient and the reproduction output in the short wavelength region will drop significantly.

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, polymer films and C0-0r, Co-Cr-
Ni, Go-Cr-J.

Go-Or-Ni-mul, Go-Or-Ni
- A soft magnetic film such as a permalloy film between the Al-Cu film,
Ti.

Ge, Si, l! Even when a non-magnetic film such as 20s was provided, the same effect as above was obtained.

Effects of the Invention According to the present invention, a thin film magnetic recording medium for perpendicular recording having a high S/N in a 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 drawings]

The figure is a schematic diagram of the internal structure of the vacuum evaporation apparatus. 1... Substrate, 2... Cylindrical xeno, 3
...... Supply port - le, 4... Take-up and reroll, 5... Mask, 6... Evaporation source. Name of agent Patent attorney Toshio Nakao and 1 other person To 1 Totsu 2-11 μm Nobuhiro f2 3. ---One-street Seno to Ha--One run to the right meat

Claims (2)

[Claims] (1) Co, Cr, Ni, Al or Co on the substrate,
A magnetic recording medium in which a magnetic layer made of Cr, Ni, Al, Cu, and trace impurities is formed. (2) 7 to 26% by weight of Cr, 5 to 30% by weight of Ni,
2. The magnetic recording medium according to claim 1, wherein Al is 0.1 to 4% by weight, Cu is 4% by weight or less, and the remainder is Co and trace impurities.