JPS63291213A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain high S/N and stable reproduction output by consisting a low coercive force layer of a specific thin 'Permalloy(R)' film. CONSTITUTION:The low coercive force layer consists of the specific thin 'Permalloy(R)' film. Namely, the compsn. contains 78-83wt.% Ni and consists of the balance Fe and <=1.5wt.% impurity elements. The apparent coercive forces measured by an oscillating sample type magnetometer within the film plane is specified to >=4oersted (Oe) and <=15Oe in all the directions within the film plane. The apparent demagnetization curve measured by a VSM within the film plane indicates the demagnetization curve of the shape in which the saturation of magnetization is exhibited at >=60Oe and the magnetization begins to decrease at <=60Oe when the impressed magnetic field is decreased from the saturation state, then the magnetization inverts sharply near the coercive force. In addition, the film thickness is specified to >=0.3mum and <=0.7mum. The characteristics of the two-layered medium are thereby improved.

Description

Detailed Description of the Invention [Field of Application] The present invention relates to a magnetic recording medium suitable for a perpendicular magnetic recording system capable of high-density recording, and a method for manufacturing the same, and more specifically relates to a low-retention magnetic recording medium made of a magnetic thin film on a non-magnetic substrate. The present invention relates to a magnetic recording medium suitable for a flexible disk in which a magnetic layer and a magnetic recording layer having perpendicular magnetic anisotropy are sequentially formed, and a method for manufacturing the same.

[Prior Art] The above-mentioned two-layer magnetic recording medium consisting of a low coercive force layer and a perpendicular magnetic anisotropic layer was developed as a perpendicular magnetic recording medium that can be efficiently recorded by a unipolar head in the perpendicular magnetic recording system. This method is known from Japanese Patent Publication No. 58-91, Japanese Patent Publication No. 58-10769, and the like. This known magnetic recording medium with a two-layer film structure (hereinafter referred to as "two-layer film medium") is specifically produced by RF bipolar sputtering, and the low coercive force layer is made of Ni), Fe (iron). Permalloy whose main component is C. The perpendicular magnetization layer is C.

(Cobalt) - Cr (Chromium) alloy film, and is excellent in that it can obtain high recording sensitivity and large playback output, but it has problems with signal-to-noise ratio (S/N) and stability of playback output. Further improvement is desired in terms of (modulation).

[Object of the Invention] The present invention aims to improve the characteristics of the above-mentioned two-layer film medium, and by focusing on the permalloy thin film that constitutes the low coercive force layer and improving its characteristics, The object of the present invention is to realize a magnetic recording medium having an improved high S/N ratio and stable reproduction output, and to provide a manufacturing method that enables stable production thereof.

Structure 2 of the Invention: Effects] The present invention provides the above-mentioned two-layer film medium, that is, a low coercive force layer made of a permalloy thin film containing Fe and Ni as main components on a nonmagnetic substrate, and having perpendicular magnetic anisotropy. In a magnetic recording medium having a magnetic recording layer, the low coercive force layer can be stably obtained by a sputtering method using a permalloy alloy having a grain size number of 5 or more as a target.
A two-component permalloy thin film that does not contain 5 wt% or more of No, Cu, or Cr and is essentially composed of Ni and e, and the permalloy thin film has a specific film thickness and magnetic properties. The above objective has been achieved.

That is, the present invention provides Ni and Fe on a nonmagnetic substrate.
In a magnetic recording medium formed by sequentially forming a low coercive force layer made of a permalloy thin film containing as a main component and a magnetic recording layer having perpendicular magnetic anisotropy, the low coercive force layer has a composition of 78 to 83% by weight. of Ni, the balance is Fe
and 1.51 fi% or less of impurity elements (however, Ar (argon) in the film is removed before opening), ■ Apparent holding force measured in the film plane using a VSM (vibrating sample magnetometer). is 4 Oe or more and 15 Oe or less in all directions within the film plane; ■ The apparent saturation curve measured by VSM within the film plane shows magnetization saturation at 6 Oee or above; And when the applied magnetic field is reduced from the saturated state, the magnetization starts to decrease below 6 Oee, the magnetization changes almost linearly until near the coercive force, and the demagnetization curve has a shape where the magnetization sharply reverses near the coercive force. The first invention is a magnetic recording medium characterized by being made of a permalloy thin film that satisfies all of the following requirements: (1) The film thickness is 0.3 μm or more and 0.7 μm or less; In the method for manufacturing the medium, the low coercive force layer is made of Ar with a permalloy alloy having a grain size number of 5 or more as a target.
iI! of a magnetic recording medium characterized in that it is formed on a continuously running long non-magnetic substrate by sputtering in a gas atmosphere. The manufacturing method is the second invention.

The present invention described above was accomplished as follows.

Although the details will be described later, the present inventors conducted research in which a two-layer film medium was formed on a polyester film using a winding facing target type continuous sputtering device shown in Fig. 5, and the film was punched out into a flexible disk. During the process, it was discovered that the low coercive force layer constituting the two-layer film medium had two serious problems.

One of them is related to the control of the coercive force of the low coercive force layer, and the other is related to the control of the in-plane magnetic anisotropy of the low coercive force layer. Conventionally, it has been believed that the smaller the coercive force, the greater the reproduction output. In fact, N contains about 5% by weight of Ho.

When a permalloy thin film is used, a saturation magnetization curve as shown in FIG. 2 can be obtained, and in such a case, the smaller the coercive force, the larger the reproduction output. Figure 2 shows H of 0.51tm.
o Permalloy thin film (No 5wt%, Ni79W [%,
The solid line is measured in the longitudinal direction of the long film (running direction during continuous sputtering, hereinafter referred to as MD (1°)), and the dotted line is the direction perpendicular to MD (rt) direction; hereinafter referred to as TD. ), and the coercive force is 1 to 2 Oe. (as judged from Figure 2)
The No permalloy thin film has small in-plane magnetic anisotropy. In a flexible disk which is a double-layered film medium having such a low coercive force layer, the modulation of the reproduction output specified in JIS-C-6290 is good at a few percent or less. However, research by the present inventors has revealed that such a low coercive force layer is not necessarily superior from the viewpoint of stable production. In particular, polyethylene terephthalate (PET) and polyethylene naphthalate (PET)
When forming a No. Permalloy thin film while continuously running the film for the purpose of a flexible disk using a 30 μm to 120 μm film (EN) or a polyester film, which is a preferred representative example, as a support,
It is difficult to obtain a thin film with in-plane isotropic magnetic properties as shown in FIG. 2, and a thin film with large in-plane magnetic anisotropy as shown in FIG. 3 is often obtained.

In such a two-layer film medium having a low coercive force layer with large in-plane magnetic anisotropy, the reproduction output is small when the magnetic head passes in the direction of the easy axis of magnetization of the low coercive force layer, and the reproduction output is small when the magnetic head passes in the direction of the axis of easy magnetization of the low coercive force layer. As the playback output increases when the disk passes, the fluctuation (modulation) of the playback output becomes large during one rotation of the head on a flexible disk, and the system limit is regulated by the minimum value of the playback output, which is extremely inconvenient. This is well known.

The inventors have determined that the cause of this in-plane magnetic anisotropy is No.
It has been found that this is due to the effect of anisotropy induced in the magnetic field due to the permalloy thin film being formed in the opposing target space, and the inverse magnetostriction effect due to the internal stress of the thin film and the external response received from the support. It has been found that the magnitude of anisotropy caused by the inverse magnetostrictive effect is difficult to control by continuous sputtering of flexible films such as polyester films. On the other hand, if the coercive force of the Ho permalloy thin film has the shape illustrated in FIGS. 1 and 4 and is large, about 5 to 1 Oee, the modulation of the reproduction output will be good. However, it has been difficult to stably increase the coercive force in the No permalloy thin film. Although the reason for this is not clear, it may be understood from the fact that the permalloy alloy (bulk) was originally developed for the purpose of having low coercive force and high magnetic permeability, as is called supermalloy. In addition, although it is known that a good soft magnetic film can be easily obtained using the facing target sputtering method (see Japanese Patent Application Laid-Open No. 158380/1983), this is a disadvantage in increasing the coercive force. There is a possibility that it is. Furthermore, when the shape is as shown in FIG. 4, the reproduction output is significantly reduced.

As mentioned above, as is well known, double-layer media having a low coercive force layer with a low coercive force of 1 to 2 oe or less may provide good reproduction output, but have difficulty controlling magnetic anisotropy. It was found that it is difficult to control the coercive force of a material with a coercive force of about 5 to 1 Oe0. Here, a contradictory problem was raised, and based on this situation, the present inventors conducted intensive research in order to reduce noise and modulation without reducing the reproduction output, and as a result, the present invention was achieved.

The present invention will be described in detail below.

The low coercive force layer of the present invention is an alloy thin film containing 78 to 83 wt % Ni and the total amount of Ni and Fe being 98.5 wt % or more. With such a composition, even in facing target sputtering, the production method described below can stably produce 4 to 1
It was found that it is easy to obtain a coercive force of about 5 Oe. A material containing impurity elements (especially) io, Cu, Cr, etc. in an amount of 1.5 wt% or more is disadvantageous because the coercive force cannot be stably increased. If the Ni content is out of the range of 78 to 83%, the magnetostriction increases and the stress when the magnetic head comes into contact changes the magnetic properties, making the reproduction output unstable, and continuous sputtering film formation. The in-plane magnetic anisotropy becomes large due to the inverse magnetostrictive effect caused by the film stress that sometimes occurs, making it difficult to stably control the coercive force, and the magnetization curve no longer exhibits a desirable shape as described below. , this inconvenience occurs.

Here, the coercive force of the low coercive force layer is approximately 0.05 μm
-Has a film thickness of 0.5 μm and has a saturation magnetization of approximately 150~
In VSM (vibrating sample magnetic force training), a magnetic recording layer of 1 Oe0 emu/cc is formed as a two-layer film, and the measurement magnetic field (
For example, it refers to the apparent coercive force measured within the film plane (±2 OeOe or less). The reason why the apparent coercive force is used in this way is that the low coercive force layer is used for recording and reproduction as a two-layer film medium with a magnetic recording layer formed thereon, so the apparent coercive force can be measured as it is as a two-layer film. This is because the magnetization curve seems to have a deeper correlation with recording/reproducing characteristics. Note that the apparent coercive horn and apparent magnetization curve, and the coercive force and magnetization curve of only the low coercive force layer obtained by removing the recording layer from a two-layer film medium, are those with a coercive force of about 4 to 15 Oe. In this case, there is only a difference of several Oe or less in coercive force, and the shape of the magnetization curve hardly changes.

It is known that the apparent coercive force changes depending on the saturation magnetization of the magnetic recording layer and the remanent magnetization state of the layer, so when determining the apparent coercive force, the two-layer film medium must be vertically moved sufficiently large. It is preferable to apply a magnetic field (for example, about 15 koe) to bring the magnetic recording layer into a state of residual magnetization in a substantially perpendicular direction.

Above) The small apparent coercive force should be 4 oersteds (Oe) or more and 15 Oe or less. When it is less than 4 Oe, it is inconvenient because it does not exhibit the preferred shape of the magnetization curve, and when it is greater than 15 Oe, it is inconvenient that the reproducing no.

In addition, the film thickness of the low coercive force layer is 0.3 μm or more, 0.7 μm
Must be below. If it is less than 0.3 μm, the reproduction output will be small and in-plane magnetic anisotropy will easily occur, and if it is more than 0.7 μm, the double-layer film medium will become hard, and when used as a flexible disk, the contact condition with the head will deteriorate and the reproduction output will decrease. is not stable.

Furthermore, the low coercive force layer of the present invention is characterized in that it exhibits an apparent magnetization curve shaped as shown in FIG. That is, in Fig. 1, llc is the coercive force, and H3 is the applied magnetic field that results in saturation magnetization. However, if the applied magnetic field is avoided by decreasing (or increasing by 7 Jl) from the saturated state, the magnetization will approximately reach the coercive force of 11c. It decreases (or increases) linearly with a constant slope to 40-80% of the saturation magnetization, and the coercive force tl
Tls
The value of must be 6 Oee or less. Coercive force (Hc)
Even if the values are the same, when IIs is greater than 6 Oee, the reproduction output decreases significantly.

The low coercive force layer has the shape shown in FIG.
A low coercive force layer smaller than e0, and most preferably smaller than 7 Oe, having the above-mentioned composition range of constituent elements and the above-mentioned film thickness range can be stably obtained by the manufacturing method described below, and the second
The modulation of the playback output when used as a flexible disk, which has the same playback output as the double-layered film medium with the No permalloy thin film illustrated in the figure, is the same as that of any recording/playback head (for example, an auxiliary pole excitation type single-pole head). mosquito,
Even for any head (whether it is a main pole excitation type head), it was always 5% or less, which was good.

Although the reason for the above-mentioned effect is not clear, it may be considered as follows. The magnetization curve shown in Figure 1 has long been known as rotational magnetic anisotropy, and it is interpreted that the magnetization is not completely in-plane, but rises obliquely. The magnetization rises in an oblique direction and the coercive force is 15 Oe.
, preferably less than 1 Oe0, is advantageous for magnetization reversal at high frequencies and contributes to improving the reproduction output, and it is thought that the small Hs, preferably less than 6 Oee, contributes to improving recording sensitivity. It will be done. Roughly speaking, a NiFe thin film with such a magnetization curve always shows the same shape of magnetization polarity regardless of the in-plane measurement direction, that is, a film with in-plane isotropic magnetic properties can be easily obtained under a wide range of film-forming conditions. This is thought to contribute to the reduction in modulation and stable control.

The low coercive force layer made of the old "e" alloy core film mentioned above can now be obtained stably and with good controllability by the following manufacturing method.

As mentioned above, the NiFe thin film has a larger coercive force when formed by sputtering than the )lo permalloy and Cu)to permalloy thin films, but the value is lower than that of organic polymers with relatively poor heat resistance such as polyester films. In continuous sputtering of molecular films, 2Oe0 or more was common. On the other hand, to lower the coercive force, apply a bias voltage of about -150 volts to the substrate, form a film under moderate Ar ion bombardment, and/or lower the substrate temperature by 2 Oe to 3 Oe.
℃ or higher, but in continuous sputtering, it is difficult to apply a bias voltage due to the equipment, and even if it were possible, the bombardment of Ar ions would cause an increase in the temperature of the plug, so polyester Difficult to apply to film. Also, for the same reason, the substrate temperature should be adjusted to 2Oe~3Oe°.
It is extremely inconvenient to cover it with C.

Under such circumstances, the present inventors determined that the grain size number was 5.
When using a NiFe alloy target having fine crystal grains as described above, it is expected that the coercive force of the NiFe alloy thin film will decrease.

The grain size number mentioned here is JIS GO551-19.
It shall be measured in accordance with the steel grain size test method specified in 77. In other words, Targera 1-(
Prepare a NiFe alloy (NiFe alloy) or a test piece thereof, and dip its surface on absorbent cotton with a solution of a 2:1 (weight ratio) mixed solution of concentrated hydrochloric acid and concentrated nitric acid, and a mixture of 10% by weight of cupric chloride. Continue rubbing until the crystal grains can be detected. The crystal grain pattern that appears in this way is indicated by the grain size number in Table 1 according to the judgment method specified in the JIS above. The thinner the target crystal grains are, the It is currently unclear why the coercive force of the NiFe alloy thin film obtained by sputtering this target becomes smaller.When elements with different sputtering rates are combined, such as No permalloy, the crystal grains become thinner. Although it is quite conceivable that the soft magnetic properties are improved by uniformly mixing the constituent elements in the film, Ni
It is surprising that such an effect was found in Fe alloys.

If a NiFe alloy target with a grain size number of 5 or more is used, the target can be sputtered to produce NiF
Although it was mentioned above that the coercive force of the e-alloy 'a film becomes small,
In order to control the coercive force within a narrower range, it is preferable to adjust the argon gas pressure introduced during sputtering. Generally A
The lower the gas pressure, the lower the coercive force of the permalloy thin film. In the present invention, about 3. An Ar gas pressure range of OPa or less and 0.2 Pa or more is used depending on the desired coercive force. In particular, the NiFe alloy thin film constituting the low coercive force layer contains manganese()In) in the range of 0.3 to 1.2% by weight.
11.1, which contains 11.1 as its constituent element, is preferable because the allowable range of Ar gas pressure that can be selected is a high gas pressure, and sputter molding can be maintained stably at a low voltage.

Figure 6 shows the obtained values of 0 and 5 for the gas pressure during sputtering.
This shows the coercive force of a NiFe alloy thin film with a thickness of μm, and a in the figure shows Ni 80wt% and Fe 19.9wt%.
It was made from an old Fe alloy target with a high purity grain size number 6 containing Ni 79.
5°Fe 19.8. Crystal grain size number 6 with a composition of Mn O, 5 (each wt'%, the remainder being ordinary impurity elements such as Si)
This was obtained from the NlFeHn alloy target.

) In-added NiFe alloy thin film (b in Figure 6) has a higher
It is understood that it is advantageous to obtain a lower coercive force with a higher Ar gas pressure. Addition of Hn (6) is 0.3wt
% or less, there is no effect in reducing the coercive force, and if it is 1.2 wt% or more, the reproducibility of the obtained coercive force deteriorates. Hn is 1
．． When the amount is 2 wt% or more, In is likely to precipitate at the polycrystalline grain boundaries of the N t Fe thin film, and the unstable amount of In is thought to deteriorate the reproducibility of coercive force. The reason is unclear.

The grain size of permalloy alloys for such targets depends on the conditions during target manufacture, heat treatment temperature and time.

Forging ratio, or additives such as sulfur.

It can be controlled by manganese, etc.

-8 The magnetic recording layer having perpendicular magnetic anisotropy in the present invention is not particularly limited, has an axis of easy magnetization in a direction substantially perpendicular to the film surface, and has magnetic properties known from Japanese Patent Publication No. 58-91, etc. A magnetic film having the following can be applied. Therefore,
Various magnetic films can be applied, such as the Co-Cr alloy film known in Publication No. 764, and the barium ferrite coating film oriented perpendicular to the film surface.
A third component such as tantalum) may also be added.

Further, the substrate, the low coercive force layer, and the magnetic recording layer do not need to be in direct contact with each other, and an adhesive layer or the like may be interposed therebetween.

The substrate of the present invention may be any non-magnetic material such as organic polymer, glass, A1 alloy, etc., but especially when a flexible disk is intended, an organic polymer film having flexibility that allows continuous production is preferable. used. Furthermore, the present invention is most preferably applied to films made of polyethylene terephthalate or polyethylene naphthalate, which have good mechanical properties and good surface properties and are inexpensive.

The magnetic recording medium of the present invention is intended for use as a flexible disk, and usually has a low coercive force layer and a magnetic recording layer of the same composition formed on both sides of a 30-120 μm film. Note that the magnetic properties of the low coercive force layer in this case are measured separately for each side.

Furthermore, even if the medium has a two-layer film formed only on one side of the substrate, it does not matter as long as it can be used as a flexible disk.

In the method for manufacturing the magnetic recording medium of the present invention, stable production can be achieved under a wide range of conditions, particularly if the low coercive force layer is formed by facing target sputtering.

Here, the facing target sputtering method is
- A sputtering method known from the 158380 publication, etc., in which a magnetic field for capturing plasma (electrons) is formed between two facing targets, and a film is formed on a substrate placed on the side of the target. To tell.

By the way, if the above-mentioned perpendicular magnetic anisotropy layer is also created by the facing target sputtering method, it is possible to form a low-humidity film, a polyester film with low heat resistance can be used as a substrate, and both layers can be formed in one vacuum chamber. It can be produced continuously, greatly reducing manufacturing costs.

Hereinafter, the details of the above-mentioned present invention will be explained based on examples.

FIG. 5 is a block diagram of a facing target type sputtering apparatus used in carrying out the present invention.

As is clear from the figure, this device is based on the aforementioned Japanese Unexamined Patent Publication No. 57-15
It has basically the same configuration as the facing target type sputtering apparatus known in Japanese Patent No. 8380.

In the figure, 10 is the vacuum chamber, and 20 is the vacuum chamber 1.
30 is an exhaust system consisting of a vacuum pump or the like that evacuates 0, and 30 introduces a predetermined gas into the vacuum chamber 10 and sets the pressure inside the vacuum chamber 10 to a predetermined gas pressure of about 10-1 to 10-4 Torr. Gas introduction system.

In the vacuum chamber 10, a pair of targets TI and T2 are sputtered by a target holder 15.16 fixed to the side plate 11.12 of the vacuum chamber 10 via an insulating member 13.14 as shown in the figure. The surfaces T1s and '2s are arranged so as to face each other in parallel across a space. Inside the target holder 15 and 16 is a cooling pipe 1.
Cooling water circulates through 51.161 and targets T1
．． T2. Permanent magnets 152, 162 are cooled.

Magnets 152, 162 are connected to target T1. N via T2
very.

The south poles are arranged to face each other, so that a magnetic field is formed in a direction perpendicular to the targets T+ and Tz and between the targets. Incidentally, 17 and 18 are shields for protecting the insulating members 13 and 14 and the target holders 15 and 16 from plasma particles during sputtering and for preventing abnormal discharge on parts other than the target surface.

Further, the substrate holding means 41 that holds the substrate 40 on which the magnetic thin film is formed is a target T+ in the vacuum chamber 10 .

It is provided on the side of T2. The substrate holding means 41 includes three rolls, a feed roll 41a, a support roll 41b, and a take-up roll 41C, which are supported rotatably and parallel to each other by support brackets (not shown).
The substrate 40 is set as a target T1. Sputtered surface T13. facing the space between Tz. It is arranged so as to be supported in a direction substantially perpendicular to T2S. Therefore, the substrate 40 must be continuously movable in the direction perpendicular to the sputtering surfaces '1s and '2s by the substrate holding means. Note that the support roll 41b
Its surface temperature can be adjusted. Note that 42 is a mask for making uniform the film thickness distribution in the 1'' direction (TD>) of the substrate.

On the other hand, a power supply means 50 consisting of a DC power source for supplying sputtering power has its positive side connected to the ground and its negative side connected to targets r+ and T2, respectively. Therefore, the power supply means 5
Sputtering power from 0 is supplied between the anode and the cathode with the ground as the anode and the targets TI and T2 as the cathodes.

Note that in order to protect the substrate 40 during pre-sputtering,
A shutter (not shown) is provided between the targets T+ and T2.

As described above, the structure is basically the same as that of the above-mentioned Japanese Patent Application Laid-Open No. 57-158380, and high-speed low-temperature sputtering is possible as is known. That is, targets T+, T
In the space between z, sputter gas ions,
γ electrons etc. emitted by sputtering are bound to form high-density plasma. Therefore, Targera l"T1.T2
sputtering is promoted and the amount of precipitation increases from the space,
The deposition rate on the substrate 40 is increased and high-speed sputtering is possible, and since the substrate 40 is on the side of the target layer 1''TI, T2, low-temperature sputtering is also possible.

Note that the facing target sputtering method in the present invention is as follows:
The device is not limited to the one described above, and as described above, a substrate is placed on the side of a pair of facing targets, and a perpendicular magnetic field is applied between the targets to perform sputtering to form a film on the substrate. This refers to the sputtering method that forms . Therefore, the magnetic field generating means may also be an electromagnet instead of a permanent magnet. Also,
The magnetic field may be one that confines γ electrons and the like in the space between the targets, and therefore includes the case where it is generated not over the entire surface of the target but only around the target.

Next, an example of a perpendicular magnetic recording medium according to the present invention, which was implemented using the facing target type sputtering apparatus shown in (a) above, will be described.

The magnetic properties of the medium were determined by measurement using a vibrating sample magnetometer (VSM).

The recording/reproducing characteristics of the double-layer film media were described in the above-mentioned Japanese Patent Publication No. 58-91.
Assistance similar to that publicly known in the No. 1 publication, etc.! Evaluation was performed using an a-pole excitation type vertical magnetic head.

The film thickness and composition were determined from a curve calibrated in advance using a fluorescent X-ray device.

Example A permalloy target with particle size number 6 was used under the following conditions, and the Ar gas pressure during formation of the low coercive force layer was set to 0.5 Pa (Pascal).1. After creating a low coercive force layer made of permalloy on a substrate, a perpendicular magnetic anisotropy layer made of Co-Cr was sequentially formed using the sputtering apparatus shown in Fig. 5 to create a 50 m long two-layer film medium. did.

A, device conditions A-1, low coercive force layer a, target TI, T2 material: particle size number 61 composition N
i-80wt%, Fe-19.9wt% Permalloy B, Substrate 40: 50μm thick polyethylene terephthalate-1~(PET>Film C, target T+, T2 spacing: 120mmd, magnetic field on target surface: 1Oe~2Oe Gauss e, target TI, T2 shape: 1Oemm L x 150mmWX 12mmt rectangle f, distance between substrate 40 and target T1.T2 end: 0
mm A-2, Go-Cr perpendicular magnetic anisotropy layer a, target r+, Tz material: both Co-80wt%,
Cr-20wt% alloy C, Targutsu l"T+, Tz spacing: 160mmd, magnetic field on target surface: 1Oe~2Oe Gauss e, target TI, T2 shape: 1Oemm L x 150mmw x 12mmt rectangle [
, substrate 40 and target T1. Distance of T2 end = 0 mm B, operating procedure The following steps were carried out under the conditions of A-1 and A-2.

a,! After installing the three plates, the degree of vacuum achieved in the vacuum chamber 10 is 1X.
10' Evacuate to 101 guns or less.

b. Introduce Ar (argon) gas to a predetermined pressure, 3
After performing press sputtering for ~5 minutes, open the shutter, and press the substrate 40 as shown in the figure.

Film formation was performed while transferring in the opposite direction of T2. In addition, A
-1, the acid gas pressure during sputtering was 0.5 Pa.

Also in the case of A-2, the pressure was set to 0.5 Pa.

The power input during C1 sputtering was 31 Δ for both A-1 and A-2, and the film running speed was adjusted to form a laminate of a 0.5 μm thick permalloy thin film and 4 0.2 μm CoCr layers.

d. The substrate temperature is 90°C for A-1 and A-2, respectively.
The temperature was 130°C.

Results of C9 A flexible disk shape was struck from four locations in the length direction, that is, 10 m, 20 m, 30 m, and 40 m from the start of sputtering, from a 50 m long medium with a two-layer film formed on one side of the substrate film. There was a law. The disc was placed in a jacket, and while the curl was pressed down, the reproduction output and one-cycle modulation were measured using a '41h auxiliary pole excitation type vertical head. The measurement was carried out at a rotation speed of 30 Orpm at a radius of 30 mm after applying a lubricant, and at a frequency corresponding to a recording density of 30 kBPI. Table 1 shows the maximum and minimum values of the reproduced output after appropriate amplifier gain, and the modulation, along with the results of the comparative example described below.

The apparent coercive force of the No permalloy thin film was 7.0±0.5 Oe regardless of the measurement direction for all four samples, and all of the apparent magnetization curves were in the shape shown in FIG. C
The coercive force of the oCr alloy thin film was evaluated by VSM by taking out only the CoCr layer from the two-layer film, and found that it was 65 Oee in the vertical direction and 41 Oee in the in-plane direction. In addition, C.

No in-plane magnetic anisotropy was observed in the Cr layer.

In addition, various mechanical,
PET films with different thermal properties were used to form films in the same manner, but all media with almost the same properties could be stably produced.

Comparative Example Permalloy target composition in Example (8-1-a
) to 5wt%, Nr 79.6wt%, F
e A 50 m long two-layer film medium was prepared and evaluated in the same manner under all the same conditions except that a 15.3 Wt, % grain size MO pepperloy target was used.

The apparent coercivity of the Permalloy thin film was in the range of 1.0 to 2.4 Oe for all four samples, but the shape of the apparent magnetization curve was different between the four samples as shown in Table 1. In other words, changes were observed in the length direction.

The reason for this is that the temperature inside the vacuum (a) increases as sputtering progresses, and/or the film tension required for film feeding changes over time, and/or the level of impurity gases other than Ar gas during sputtering in the vacuum chamber increases. Fluctuations over time such as 1 mag. were considered, and such slight changes were uncontrollable.

Characteristics of CoCr alloy A9 membrane] The cows were the same as in the example.

In addition, when films were formed in the same manner as described above using PET films with different mechanical and thermal properties as in the example as the substrate, the in-plane magnetic anisotropy of the No permalloy thin film showed various changes, Fine adjustment of the film tension, etc. is required each time, and even then, with long media, the magnetic properties fluctuate in the length direction, making stable continuous production difficult.

Table 1 (*) The shape is intermediate between those in Figures 2 and 3, that is, it exhibits moderate in-plane magnetic anisotropy. As can be understood from Table 1, the two-layer film medium having a low coercive force layer of the present invention has excellent film formation stability and reproduction output value, and has extremely small modulation. Such a low coercive force layer can be preferably obtained using the substantially NiFe binary permalloy target having a grain size of 5 or more according to the present invention.

[Brief explanation of drawings]

FIG. 1 shows the shape of the preferred magnetization curve of the present invention, and FIGS. 2, 3, and 4 all show the shape of the magnetization curve of the HO permalloy thin film, and the solid line is M D
The dotted line is measured in the TD force direction. Fig. 5 is an explanatory diagram of a winding type continuous facing target type sputtering apparatus used in the implementation of the present invention, and Fig. 6 is an illustration of A during sputtering.
This is a graph showing the relationship between the r gas pressure and the coercive force of the obtained NiFeN film.
．． This relates to NiFe containing 5 wt%. TI, T2: target, 10: vacuum chamber, 20: exhaust system. 30: Gas introduction system, 40: Substrate, 50 Varnish butter power supply No. +1

Claims (1)

[Claims] 1) Magnetic recording in which a low coercive force layer made of a permalloy thin film containing Ni and Fe as main components and a magnetic recording layer having perpendicular magnetic anisotropy are sequentially formed on a nonmagnetic substrate. 1. A magnetic recording medium, wherein the low coercive force layer is made of a permalloy thin film having the following features. (1) The composition contains 78 to 83% by weight of Ni, and the balance is F.
and 1.5% by weight or less of impurity elements (however, calculations exclude Ar (argon) in the film). (2) The apparent coercive force measured by a VSM (vibrating sample magnetometer) within the membrane plane is 4 in all directions within the membrane plane.
Must be Oersted (Oe) or more and 15 Oe or less. (3) The apparent saturation magnetization curve measured by VSM in the film plane shows saturation of magnetization above 60 Oe, and when the applied magnetic field is reduced from the saturated state, the magnetization begins to decrease below 60 Oe. Showing a demagnetization curve in which the magnetization changes almost linearly up to the vicinity of the coercive force, and the magnetization reverses sharply near the coercive force. (4) The film thickness is 0.3 μm or more and 0.7 μm or less. 2) at least 0.3% by weight or more as the impurity element;
Claim 1 containing 1.2% by weight or less of Mn
) The magnetic recording medium described in item 2. 3) The magnetic recording medium according to claim 1) or 2), wherein the nonmagnetic substrate is a flexible organic polymer film. 4) On a non-magnetic substrate, (1) the composition contains 78 to 83% by weight of Ni, the balance being F;
and 1.5% by weight or less of impurity elements (however, calculations exclude Ar (argon) in the film). (2) The apparent coercive force measured by a VSM (vibrating sample magnetometer) within the membrane plane is 4 in all directions within the membrane plane.
Must be Oe or more and 12 Oe or less. (3) The apparent saturation magnetization curve measured by VSM in the film plane shows saturation of magnetization above 60 Oe, and when the applied magnetic field is reduced from the saturated state, the magnetization begins to decrease below 60 Oe. Showing a demagnetization curve in which the magnetization changes almost linearly up to the vicinity of the coercive force, and the magnetization reverses sharply near the coercive force. (4) The film thickness is 0.3 μm or more and 0.7 μm or less. In the method for manufacturing a magnetic recording medium, the low coercive force layer is formed by sequentially forming a low coercive force layer made of a permalloy thin film and a magnetic recording layer having perpendicular magnetic anisotropy, which satisfies all the requirements of A method for producing a magnetic recording medium, which comprises forming the medium on a continuously running elongated non-magnetic substrate by sputtering the above permalloy alloy as a target in an Ar gas atmosphere. 5) The method for manufacturing a magnetic recording medium according to claim 4, wherein the sputtering method is a facing target sputtering method.