JPH04132015A - Perpendicular magnetic recording tape consisting of cocr and production thereof - Google Patents

Abstract

PURPOSE:To extremely improve the crystal orientability of a soft magnetic lining layer consisting of 'Permalloy(R)' and further a magnetic recording layer consisting of CoCr and to improve magnetic characteristics as a perpendicular magnetic recording medium by forming an orientation degree control layer consisting of a low-saturation magnetized thin film of the CoCr as an underlying layer. CONSTITUTION:This recording tape has the orientation degree control layer which consists of the low-saturation magnetized CoCr contg. >=20at.% Cr and has DELTAtheta50<=10 deg. half-amplitude level of dispersion angle of the c-axis and 50 to 200Angstrom thickness and the soft magnetic lining layer which is epitaxially grown on this thin film, consists of the 'Permalloy(R)' contg. 75 to 85at.% Ni and has >=100Angstrom thickness and the critical film thickness or below on a substrate of a flexible tape. The tape has further the magnetic recording layer of 400 to 3,000Angstrom thickness consisting of the high-saturation magnetized layer of the CoCr which is epitaxially grown further in superposition on this soft magnetic lining layer and contains >=80at.% Co. The 'Permalloy(R)' layer having the good crystal orientability and eventually the magnetic recording layer of the CoCr having likewise the good crystal orientability are obtd. in this way and the excellent magnetic characteristics are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a CoCr perpendicular magnetic recording tape and a method for manufacturing the same, particularly by effectively improving the crystal orientation of a soft magnetic underlayer and a magnetic recording layer. This is an attempt to advantageously improve magnetic properties as a magnetic recording medium.

(Prior Art) Since the perpendicular magnetic recording method was proposed as a next-generation high-density magnetic recording method, much research has been conducted on perpendicular magnetic recording media. As a result, it has been found that a CoCr film is the most promising as a perpendicular magnetic recording medium, and various research and developments are currently being carried out on methods for forming the film. Note that there are various media formats such as hard disks, floppy disks, and tapes, and manufacturing methods vary accordingly. Among these, in the case of tape media, there are many technical problems because it is necessary to continuously form a CoCr film with good crystallinity without causing thermal damage to the substrate tape.

(Issues to be Solved by the Invention) The details of the above technical problem are as follows.

(1) As the substrate tape, it is preferable to use thermoplastic tape such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET), but since this type of tape usually has poor heat resistance, thermal Damage must be avoided as much as possible.

(2) Since the recording and reproducing output is proportional to the saturation magnetization of the magnetic recording layer, it is preferable to use CoCr exhibiting as high a saturation magnetization as possible; however, it is generally difficult to form a CoCr film with high saturation magnetization with good crystallinity.

(3) In order to obtain perpendicular magnetic anisotropy, the hc of CoCr is
Since it is necessary to orient the C axis of the p-crystal structure perpendicularly to the tape surface, when forming a film on a moving tape, the film must be formed so as not to cause canting in which the C axis is tilted.

(4) Improve the interfacial bonding between the permalloy layer, which is a soft magnetic underlayer, and the highly saturated magnetized CoCr layer, which is a magnetic recording layer,
Dispersion angle half width Δ of C axis of highly saturated magnetized CoCr magnetic recording layer
Create a film with good orientation with θ50 of 10° or less.

(5) The above process is performed continuously without reducing the film formation rate.

Film forming methods include vacuum evaporation, three-pole sputtering, DC two-pole sputtering, RF2F2 type sputtering, and magnetron sputtering, but a manufacturing method that overcomes all of the above problems has not yet been developed. .

The purpose of this invention is to effectively solve the above problems and provide a CoCr perpendicular magnetic recording tape with excellent magnetization characteristics.
The present invention is proposed together with its advantageous manufacturing method.

(Means for Solving the Problems) In order to achieve the above object, the inventors have conducted intensive research and have obtained the knowledge described below.

i) For magnetic recording tapes, it is desirable to have a permalloy soft magnetic backing layer as an underlayer for recording and reproduction purposes, but permalloy inherently has poor crystallinity, and therefore the CoCr magnetic recording layer formed on it has poor crystallinity. It also impairs crystallinity. In this regard, according to the inventors' research, the hcp (002) plane of CoCr and the fcc (111) plane of permalloy
A plane has a heteroepitaxial effect. Therefore, if a thin CoCr film with good crystallinity is formed before forming a permalloy layer, a permalloy layer with good crystal orientation can be formed, and a permalloy layer with good crystal orientation can also be formed. A CoCr magnetic recording layer can be obtained.

ii) Facing target sputtering allows coatings to be applied without plasma damage to the film being deposited or to the substrate tape.

This invention is based on the above knowledge.

That is, the gist of the present invention is as follows.

1. Cr content: 2 on the flexible tape substrate
An orientation control layer made of CoCr with low saturation magnetization of 0 at% or more, with a half-value width of the C-axis dispersion angle Δθ50≦10°, and a thickness of 250 to 200 mm, and the Ni content epitaxially grown on this thin film:
Thickness 8100 made of permalloy of 75~85a t%
A soft magnetic backing layer with a thickness of Å or more and a critical film thickness or less, and a high saturation magnetization C with a Co content of 80 at% or more, which is further epitaxially grown on this soft magnetic backing layer.
CoCr perpendicular magnetic recording tape comprising an oCr layer with a thickness of 400 to 3000 magnetic recording layers (first invention)
.

2. The flexible tape as a substrate is continuously supplied to a film formation zone divided into three parts, and while passing through the film formation zone, an orientation control layer and a soft magnetic backing are sequentially applied to one side of the substrate by sputtering. In forming the layers and the magnetic recording layer, a facing target sputtering method is used as a means of forming each layer. First, in the first film formation zone, using a narrow slit to suppress oblique incidence to the substrate, Sputtering Ar gas pressure:
At low pressure of 1mTorr or less, Cr content: 20at%
The above low saturation magnetization CoCr layer was deposited to a thickness of 50 to 200, and then sputtered at Ar gas pressure of 5 mTo in the second film formation zone using a wide slit that allowed oblique incidence.
rr or less, a permalloy layer with a Ni content of 75 to 85 at% is formed to a thickness of 100 Å or more and below the critical film thickness, and then in the third film formation zone, a wide slit that also allows oblique incidence is used. Below, sputtering Ar gas pressure:
A method for manufacturing a CoCr perpendicular magnetic recording tape comprising depositing a highly saturated magnetized CoCr layer with a Co content of 80 at% or more at a thickness of 400 to 3000 at a pressure of 5 mTorr or less (
2nd invention).

This invention will be specifically explained below.

FIG. 1 schematically shows the procedure for manufacturing a perpendicular magnetic recording tape according to the present invention, and FIGS. 2a to 2d schematically show the state of film formation on the tape after each film forming process.

Number l in the figure is flexible tape, 2-1. 2-2 and 2-3 are both can rolls, and 3-13-
2 and 3-3 are opposed target sputtering apparatuses for producing the orientation control layer, the soft magnetic backing layer, and the magnetic recording layer, respectively.As shown in FIG. -1.2-2 and 2
During conveyance in synchronization with the rotation of the flexible tape 1 (FIG. 2a), the orientation control layer 4 (the A perpendicular magnetic recording tape is manufactured by sequentially depositing a soft magnetic underlayer 5 (FIG. 2C) and a magnetic recording layer 6 (FIG. 2D).

Further, FIG. 3 shows the facing target type sputtering apparatus 3 in a perspective view, in which numbers 7-1, 7-2 are targets arranged facing each other, and numbers 8-1, 8-2 are arranged on the back side of each target. 9 is a mask; 9 is a mask;
And 10 is a slit provided in the mask 9.

Now, such a facing target type sputtering apparatus 3 has, as a sputtering source, two target plates (7-1, 7-2) of, for example, 10 x 10 cmz, arranged facing each other with a distance of about 10 cm, and a magnetic pole 8 installed behind each target. -1°8
7-1. By applying a negative DC to 7-2, sputtered particles are supplied to the tape substrate 1 while confining the plasma between the two targets. A slit 10 is disposed between the sputtering source and the substrate 1 to control the amount of sputtered particles flying from the target. At this time, the substrate surface is placed 3 to 10 cm away from the edges of the two targets, perpendicular to the target surfaces, and centered between the targets. Here, a film is continuously formed on the tape surface while the tape surface is wound on a can roll at the position of the substrate surface and passes along with the rotation of the roll. According to this facing target sputtering method, films can be formed in a plasma-free state where the object to be processed is not exposed to plasma, so it does not damage objects that are relatively susceptible to thermal damage, such as thin plastic films. It can be coated.

(Function) Now, in the first zone, when sputtering is performed with the slit width widened (for example, 10 cm), out of the sputtered particles flying from the target source,
Those passing through the center of the slit reach the roll curved surface by vertical incidence, while those passing through the ends of the slit reach the roll curved surface by oblique incidence, forming a film. At this time, in the film formed by oblique incidence, C-axis canting occurs, and its magnetic properties deteriorate.

To prevent such canting, it is possible to prevent oblique incidence by widening the slit width as much as possible (for example, about 2CT11), but this method causes a significant decrease in the film formation rate, so It is difficult to coat a film with several thousand holes. However, a very thin film made by about 10 to 200 people, for example, can be made in a short time even with a narrow slit, making high-speed film formation possible.

Therefore, in the present invention, in the first zone, the film thickness is increased to 20 mm by using a narrow slit to suppress oblique incidence to the substrate.
Create an orientation control layer that serves as a base with a thickness of 0 Å or less. What is important here is that the sputtering Ar gas pressure P Ar is l mTor
Sputtering is performed at a very low gas pressure of less than r, preferably less than 0.5 w+Torr.

This is because when PAr exceeds 1 mTorr, the crystallinity deteriorates. In this respect, the facing target sputtering method has a very superior feature compared to other sputtering methods in that it can stably discharge even at a low gas pressure of 1 mTorr or less. For this reason, the mean free path of the sputtered particles becomes large, and they reach the substrate tape with large kinetic energy, causing sufficient migration on the tape.Moreover, since it is a plasma fleece particle,
C with good crystallinity from a very thin film thickness of 0 to 100
An oCr film can be formed, and this has been confirmed by electron beam diffraction and X-ray diffraction.

In this invention, the crystal orientation is evaluated by the dispersion angle half width Δθ50 of the C axis of the CoCr layer, and if this value is 10° or less, the crystal orientation can be said to be good.

Here, the orientation control layer has a Cr content of 20 at.
% or more (preferably 40at% or less) of low saturation magnetization C
oCr, particularly Co5qCrz+, is preferred. Further, the thickness of the CoCr underlayer needs to be 50 to 200 layers. This is because if the film thickness is less than 50%, the canting becomes thick (and the half-width Δθ50 of the C-axis dispersion angle, which is an index of crystal orientation, exceeds 10°, making it difficult to function as an orientation control layer. On the other hand, if the number exceeds 200, not only will canting increase, but if a permalloy soft magnetic backing layer is formed thereon, soft magnetic properties will deteriorate.

In other sputtering methods, such as magnetron sputtering, stable discharge is difficult at low pressures of 1 mTorr or less, and the substrate is exposed to plasma, so
In a thin film of ~200 people, a microcrystalline initial layer with poor crystallinity is formed.

Next, in the second zone, the slits are opened all at once, and permalloy as a soft magnetic underlayer is formed on the orientation control layer while feeding the substrate tape. Of course, this includes not only normal incidence but also oblique incidence,
On the orientation control layer, which is a special underlayer as described above, the (111) plane of the permalloy fcc structure grows epitaxially on the (002) plane of the hcρ structure of the underlayer.
Δθ50 is about 8°, and a permalloy layer with good crystallinity without canting of the (111) axis can be obtained at a high deposition rate. On the other hand, when the film is formed without the orientation control layer, the Δθ50 of the permalloy layer becomes 20° or more, and (111) axis cantig occurs. Note that permalloy has a Ni content of 75 to 85 at%, especially Ni□FeB.
is preferred. At this time, PAr needs to be 5 mTorr or less. This is because, if it exceeds 5 mTorr, scattering between sputtered particles and Ar gas will increase, causing a decrease in crystallinity. Further, the film thickness needs to be 100 Å or more and less than the critical film thickness. This means that the film thickness is 100
This is because if the film thickness is less than the critical thickness, the function as a soft magnetic underlayer cannot be fully exhibited, while if it exceeds the critical film thickness, the soft magnetic properties will deteriorate. The term "critical film thickness" here refers to a phenomenon in which when a strong magnetic field is applied, the direction of the axis of easy magnetization of the permalloy layer instantaneously rotates in the direction of the applied magnetic field.
This is the film thickness at which nisotropy begins to occur, and although it varies somewhat depending on the film manufacturing conditions, it is usually about 3,000.

It has been confirmed that when the thickness of the CoCr orientation control layer is 200 Å or less, it does not adversely affect the soft magnetic properties of permalloy.

Next, in the third zone, open the slits all at once, and
A Cr magnetic recording layer is deposited on the above permalloy layer while feeding the tape. Since the recording and reproducing output is proportional to the saturation magnetization of the magnetic recording layer, it is preferable to use CoCr with high saturation magnetization as the CoCr magnetic recording layer. However, in general, it is difficult to form a CoCr film with high saturation magnetization with good crystallinity. difficult. However, even though vertically and obliquely incident particles are included here, on the above-mentioned special permalloy layer with good crystal orientation, CoC is formed on the (111) plane of permalloy.
The (002) plane of r grows epitaxially, and Δθ5
A CoCr magnetic recording layer having an excellent crystal orientation with no C-axis canting can be formed at a high deposition rate with an angle of about 8@.

Here, the CoCr magnetic recording layer has a Co content of 80
CoCr having a high saturation magnetization of at % or more (preferably 90 at % or less), particularly Co113Cr17, is preferred. Furthermore, if 7r is too high, the crystallinity will decrease due to scattering of sputtered particles and Ar gas, so it is necessary to set it to 5 mTorr or less. Furthermore, if the film thickness is less than 400, it will become an in-plane magnetized film, while if it exceeds 3,000, the flexibility will decrease, so the film thickness should be between 400 and 300.
Limited to 0 people.

The film obtained as described above has a dense structure and excellent flexibility.

In this way, (CoCrvt recording layer/permalloy soft magnetic backing layer/CoCr orientation control layer) can be formed on the tape substrate. At this time, the substrate tape may be polyethylene naphthalate tape (PEN), polyethylene terephthalate tape (PF, T) and polyimide tape are preferred, and the thickness thereof is preferably about 5 to 50 μm.

It should be noted that such magnetic recording media are required to have corrosion resistance from the viewpoint of long-term storage of records, and wear resistance from the viewpoint of high-speed contact between the medium surface and the sensor during use. Therefore, for magnetic recording tapes in which a magnetic recording medium is formed on a plastic substrate, a top coat is applied to the surface to protect the surface of the magnetic recording medium, and also to prevent static electricity and lower the coefficient of friction on the tape surface to improve the slippage between the tapes. From this point of view, it is preferable to apply a back coat to the back surface, and any conventionally known protective film is suitable as such a protective film.

(Example) FIG. 4 schematically shows a magnetic recording tape manufacturing apparatus suitable for carrying out the present invention. The gist of the configuration is the same as that shown in Figure 1, so it will be denoted by the same number. Numbers 2-4 and 3-4 in the figure are the can roll and facing target type sputter for producing the protective film, respectively. In addition, 11 is a vacuum chamber, and 12 and 13 are an unwinding roll and a winding roll of the substrate tape, respectively.

As shown in the figure, this manufacturing apparatus has four film forming zones in a vacuum chamber 11, and each zone is equipped with a facing target type sputtering source and a tape conveying can roll. The facing target type sputter source is approximately 1010X1
0” two targets 10cm apart, facing each other.
A permanent magnet is installed on the back side of each target, and a magnetic field of 250 (Gauss) is applied perpendicularly to each target surface between the two targets, and a negative DC (approximately 2 kW) is applied to both targets. ) is applied to supply sputtered particles to the substrate tape. A slit is placed between the sputtering source and the substrate tape to control the amount of sputtered particles flying from the target. At this time, the substrate surface was placed 10 cm from the edges of the two targets, perpendicular to the target surfaces, and centered between the targets. Here, a 12 μm thick polyethylene naphthalate tape surface wrapped around a 15 cm diameter can roll surface is placed at the position of the substrate surface.
The mechanism is such that a film is continuously formed on the tape surface while the tape moves in synchronization with the rotation of the roll.

The target composition is COt*C1+ in the first zone and COt*C1+ in the second zone.
Zone is Nis+Fe+w, 3rd zone is C0Il, C
rI? , and the fourth zone is carbon for a protective film.

Also, the sputtering gas pressure PAr is 0.2 in the first zone.
5mTorr, 2nd, 3rd and 4th zones are both l
mTorr. Further, the slit width was 2 cm in the first zone and 10 cm in the 2nd, 3rd, and 4th zones.

Under the above conditions, first, the film thickness in the first zone: 0°100
, a CoCr underlayer of 200.300 m thick in the second zone, a permalloy soft magnetic backing layer of 1550.2000 m thick in the third zone, a CoC thickness of 1300 mn in the third zone.
r magnetic recording layer, and in the fourth zone, a protective film with a thickness of 200 layers was respectively formed.

FIG. 5 shows the results of an investigation on the relationship between the thickness of the base film of the two-layer film (permalloy layer/underlayer for orientation control) and the in-plane coercive force of the permalloy layer.

As is clear from the figure, when the thickness of the underlayer is less than 200 Å, there is almost no increase in the coercive force, and no adverse effect of the underlayer on the soft magnetism of the permalloy layer is observed.

Next, in Fig. 6, (Co, 3Cr, 7 layers/permalloy layer/
The results of an investigation into the relationship between the thickness of the base film and canting in a three-layer film (base layer for controlling orientation degree) are shown.

As is clear from the figure, the canting was extremely large when there was no base layer, but when the base layer was
Canting is significantly improved by coating the Co7wCrz+Fi film with a thickness of about 0 to 200.

Next, FIG. 7 shows the relationship between the base film thickness and the X-ray diffraction intensity IF and Δθ50 of the same three-layer film (C05zCr+ layer/parts 0 layer/base layer for controlling degree of orientation).

First, regarding I, when there is no underlayer, no peak appears from the permalloy layer, and only a very weak peak appears from the C05zCr+ layer. The reason for this is considered to be that the crystallinity of the permalloy layer is very poor when there is no underlayer, and therefore the crystallinity of the CO53Crt7 layer thereon is also poor.

In contrast, there are only 50 to 200 special Coyote
*Ni1lf'e1 by just covering Crz+base layer
Strong peaks appeared for both the 4-layer and the COs+Cr r q layer, indicating that the crystallinity of both layers was significantly improved.

This is clear from the change in Δθ50, and Δθ50 is C
This is significantly reduced due to the crystallinity orientation effect of the OtwCrz+underlayer, supporting the improvement in the crystal orientation of both layers.

(Effects of the Invention) Thus, according to the first invention, in a CoCr perpendicular magnetic recording medium provided with a permalloy backing layer, an orientation control layer made of a low saturation magnetization CoCr'fiI film is formed as an underlayer. As a result, the crystal orientation of the permalloy soft magnetic underlayer and further of the CoCr magnetic recording layer can be significantly improved, and as a result, the magnetic properties of a perpendicular magnetic recording medium can be significantly improved.

Further, according to the second invention, since the film can be formed in a plasma-free situation where the object to be processed is not exposed to plasma, damage can be caused even on tape substrates that are relatively susceptible to thermal damage, such as plastic tape. Each layer can be coated without any trouble. Moreover, since the orientation control layer formed with a narrow slit for eliminating C-axis canting can be extremely thin, it can be formed in a short time, and continuous high-speed film formation is possible in the entire process.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the procedure for manufacturing a perpendicular magnetic recording tape according to the present invention, FIG. 2 a and d are schematic diagrams showing the state of film formation on the tape after each film forming process, and FIG. , a perspective view of a facing target type sputtering device, FIG. 4 is a schematic diagram of a perpendicular magnetic recording tape manufacturing device suitable for carrying out the present invention, and FIG. 5 is a (permalloy layer/base layer for controlling degree of orientation). Figure 6 is a graph showing the relationship between the base film thickness of the two-layer film and the in-plane coercive force of the permalloy layer. Figure 7 is a graph showing the relationship between the base film thickness and canting. This is a graph showing the relationship between 1... Flexible tape 2-L 2-2. 2-3. 2-4... Can roll 3-1. 3-2. 3-3. 3-4... Opposed target sputtering device 4... Orientation degree control layer 5... Soft magnetic backing layer 6
...Magnetic recording layer 7-1. 7-2...Target 8-1. 8-2...Magnetic pole 9...Mask 10...Slit 11...Vacuum chamber 12
... t = exit roll 13 ... winding roll 1 Fig. 10-11 - pickpocket 1F Fig. 4 13--11 R1 space 8-f, 8-2-- - , in, scratched Figure 5 Bottom film thickness (A) Figure 6 T crucible II (A) Figure 7 Bottom tall (A>

Claims (1)

[Claims] 1. On the substrate of the flexible tape, made of low saturation magnetization CoCr with a Cr content of 20 at% or more, a degree of orientation of c-axis dispersion angle half width Δθ_5_0≦10°, thickness: 50 to 200 Å a control layer, a soft magnetic backing layer epitaxially grown on this thin film and made of permalloy with a Ni content of 75 to 85 at% and having a thickness of 100 Å or more and not more than a critical film thickness; Epitaxially grown high saturation magnetization C with Co content: 80 at% or more
A CoCr perpendicular magnetic recording tape characterized by comprising a magnetic recording layer consisting of an oCr layer having a thickness of 400 to 3000 Å. 2. A flexible tape serving as a substrate is continuously supplied to a film formation zone divided into three parts, and while passing through the film formation zone, an orientation control layer and a soft magnetic backing are sequentially applied to one side of the substrate by sputtering. In forming the layers and the magnetic recording layer, a facing target sputtering method is used as a means for forming each layer. First, in the first film forming zone, using a narrow slit to suppress oblique incidence to the substrate, Sputtering Ar gas pressure:
At low pressure of 1mTorr or less, Cr content: 20at%
The above low saturation magnetization CoCr layer was deposited to a thickness of 50 to 200 Å, and then sputtered at Ar gas pressure of 5 mTorr in the second film formation zone using a wide slit that allowed oblique incidence.
A permalloy layer with a Ni content of 75 to 85 at% is formed to a thickness of 100 Å or more and less than the critical film thickness, and then in the third film formation zone, a wide slit that also allows oblique incidence is used. Below, sputtering Ar gas pressure: 5
A method for manufacturing a CoCr perpendicular magnetic recording tape, characterized in that a highly saturated magnetized CoCr layer having a Co content of 80 at % or more and a thickness of 400 to 3000 Å is formed at a pressure of mTorr or less.