JPH0542052B2 - - Google Patents

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 more specifically, the present invention relates to a magnetic recording medium suitable for a perpendicular magnetic recording method capable of high-density recording. The present invention relates to an improvement in a magnetic recording medium in which a magnetic recording layer consisting of a perpendicular magnetic layer having an easy axis is sequentially formed, and a method for manufacturing the improved magnetic recording medium. [Prior Art] The above-mentioned two-layer magnetic recording medium consisting of a low coercive force layer and a perpendicular magnetization layer was developed as a perpendicular magnetic recording medium that can be efficiently recorded by a unipolar head in the perpendicular magnetic recording system. −91 Publication, Special Publication 1987
It is publicly known from Publication No.-10769 and the like. This known magnetic recording medium with a two-layer film structure (hereinafter referred to as a "double-layer film medium")
) is specifically created using the RF two-pole sputtering method, with a low coercive force layer made of permalloy mainly composed of Ni (nickel) and Fe (iron), and a perpendicular magnetic layer Co (cobalt) - Cr (chromium). It is composed of an alloy film,
Although this is an excellent device that can obtain high recording sensitivity and large reproduction output, the output in the high frequency region decreases, and further improvement is desired. [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, Another object of the present invention is to realize a magnetic recording medium having improved high recording sensitivity and high reproduction output, and to provide a manufacturing method that enables stable production thereof. [Structure, Effects of the Invention] The present invention provides the above-mentioned two-layer film medium, that is, a low coercive force layer made of a permalloy thin film mainly composed of Fe and Ni on a nonmagnetic substrate, and a film magnetized in a direction perpendicular to the film surface. In a magnetic recording medium having a magnetic recording layer having an easy axis, the permalloy thin film of the low coercive force layer is
Characterized by a Mn (manganese) content of 100ppm (weight%) or more and 6000ppm (weight%) or less,
The first invention provides a magnetic recording medium in which the low coercive force layer has very good soft magnetic properties. A second invention provides a manufacturing method for forming the low coercive force layer of the magnetic recording medium of the first invention by a sputtering method that can stably form the low coercive force layer. The above-mentioned present invention was made as follows. Figure 1 shows a measurement example showing the relationship between the coercive force of the low coercive force layer of a two-layer film medium and the reproduction output.From the figure, it can be seen that the smaller the coercive force of the low coercive force layer of a two-layer film medium, the more recording is possible. It can be seen that this is advantageous in terms of sensitivity, reproduction output, etc. Note that the vertical axis of the figure also shows the relative value of the reproduced output, which is standardized with the output of the sample indicated by the black circle in the figure as a reference. The horizontal axis is the coercive force of the low coercive force layer, and the unit is Oersted (Oe). Incidentally, the low coercive force layer is usually formed by sputtering using a permalloid target.
The in-plane coercive force of the sputtered low coercive force layer is not necessarily constant and varies depending on the sputtering conditions. Among these, the target composition, sputtering pressure, sputtering temperature, etc. greatly affect the in-plane coercive force, and strict condition control is required to obtain a permalloy film with a constant low coercive force. Further, even if these conditions are optimized, the in-plane coercive force may not necessarily be a sufficiently small value. Generally, in order to maximize the magnetic permeability of the permalloy layer forming the low coercive force layer, a permalloy alloy having a composition with a high magnetic permeability is used. for example
One example is a permalloy alloy with a composition of 18wt%Fe-78wt%Ni-4wt%Mo. Furthermore, in order to reduce the in-plane magnetic anisotropy or the coercive force, the above-mentioned composition may be slightly changed to change, for example, the magnetostriction constant. However, even if the permalloy composition of the target, especially the wt% of Ni, is changed by about ±10% from the above-mentioned value, the coercive force does not necessarily become sufficiently small. As a result of intensive research based on this situation, the present inventor found that 100ppm (weight%) of conventional permalloy alloy
The inventors discovered that the coercive force of a permalloy thin film, which becomes a low coercive force layer, can be easily maintained at a sufficiently small value by adding Mn as described above, and the present invention was conceived. In addition,
The upper limit of the amount of Mn added is sufficient as long as the coercive force of the permalloy thin film can be kept at a sufficiently small value, and as is clear from the examples described later, it is 6000 ppm (wt%).
The following is sufficient. That is, the present invention has Fe and Ni as main components, and a third additive element.
A magnetic layer made of a permalloy alloy containing Mn of 100 ppm (wt%) or more and 6000 ppm (wt%) or less is added to a conventional permalloy alloy containing Mo, Cr, Cu, etc. without substantially changing its composition ratio. This is a magnetic recording medium with a magnetic layer. As mentioned above, the permalloy that becomes the low coercive force layer of the present invention can be a conventionally known permalloy whose main components are Ni and F, and it goes without saying that it may also contain a third element such as Mo, Cr, Cu, etc. Nor. Further, the film thickness must be within the conventionally known range of several micrometers or less and must be appropriately designed depending on the purpose. Further, the perpendicular magnetization layer can be a magnetic film having an axis of easy magnetization in a direction perpendicular to the film surface and having magnetic properties known from Japanese Patent Publication No. 1982-91 and the like. Therefore, the Co-Cr alloy film known from Japanese Patent Publication No. 58-10764, etc.
Various magnetic films such as a barium ferrite coating film oriented perpendicularly to the film surface can be applied, and a Co--Cr alloy film to which a third component such as W (tungsten) or Ta (tantalum) is added may also be used. Further, the low coercive force layer and the perpendicular magnetization layer do not need to be in direct contact with each other, and an adhesive layer or the like may be interposed therebetween, or may be provided on both sides of the substrate. On the other hand, in the method for manufacturing a magnetic recording medium according to the second aspect of the invention, if the low coercive force layer is formed by the facing target sputtering method, it is possible to perform production under a wide range of conditions. Here, the facing target sputtering method is a method known from Japanese Patent Application Laid-Open No. 158380/1980, etc., in which a magnetic field for trapping plasma (electrons) is formed between a pair of facing targets. This is a sputtering method in which a film is formed on a substrate placed on the side of the substrate. By the way, if the above-mentioned perpendicular magnetization layer is also formed by the same facing target sputtering method, it is possible to form a film at a low temperature, a polyester film or the like with low heat resistance can be used as a substrate, and both layers can be continuous in one vacuum chamber. It can be made by using the same method, and the manufacturing cost can be greatly reduced. Hereinafter, details of the above-mentioned present invention will be explained based on examples. FIG. 2 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 was developed in the above-mentioned JP
It has basically the same structure as the facing target sputtering device known in Japanese Patent No. 158380. That is, in the figure, 10 is a vacuum chamber, 20 is an exhaust system consisting of a vacuum pump etc. for evacuating the vacuum chamber 10, and 30 is an exhaust system that introduces a predetermined gas into the vacuum chamber 10 to reduce the pressure inside the vacuum chamber 10 to 10 ^-1. This is a gas introduction system that is set to a predetermined gas pressure of ~10 ^-4 Torr. In the vacuum chamber 10, targets T ₁ and T ₂ are held by target holders 15 and 16 fixed to the side plates 11 and 12 of the vacuum chamber 10 via insulating members 13 and 14 as shown in the figure. The surfaces T _1s and T _2s to be sputtered are arranged so as to face each other in parallel across a space. And target T ₁ ,
T ₂ and its corresponding target holder 15,
16, targets T ₁ , T ₂ , permanent magnets 152 ,
162 is cooled. The magnets 152 and 162 are disposed so that their north and south poles are opposed to each other via the targets T ₁ and T ₂ , so that the magnetic field is directed to the targets T _{1 and T 2} .
Formed only in the direction perpendicular to T ₂ and between targets. Note that 17 and 18 are insulating members 13 and 1
4 and target holders 15 and 16 from plasma particles during sputtering, and to prevent abnormal discharge in areas other than the target surface. Further, a substrate holding means 41 for holding a substrate 40 on which a magnetic thin film is formed is provided in the vacuum chamber 10 on the side of the targets T ₁ and T ₂ . Substrate holding means 4
Reference numeral 1 denotes a feed roll 41a, a support roll 41b, and a take-up roll 41, which are supported rotatably and parallel to each other by support brackets (not shown).
It consists of three rolls (c) and is arranged so as to hold the substrate 40 in a direction substantially perpendicular to the sputtering surfaces T _1s and T _2s so as to face the space between the targets T ₁ and T ₂ . Therefore, the substrate 40 can be moved by the take-up roll 41c in a direction perpendicular to the sputtering surfaces T _1s and T _2s . Note that the support roll 41b
Its surface temperature can be adjusted. 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 the targets T ₁ and T ₂ , respectively. Therefore, the sputter power from the power supply means 50 is supplied between the anode and the cathode, with the ground as the anode and the targets T ₁ and T ₂ as the cathodes. In order to protect the substrate 40 during press sputtering, a shutter (not shown) is provided between the substrate 40 and the targets T ₁ and T ₂ to move in and out. As mentioned above, the structure is basically the same as that of the above-mentioned Japanese Patent Application Laid-open No. 57-158380, and as is known, high-speed low-temperature sputtering is possible. That is, in the space between the targets T ₁ and T ₂ , sputter gas ions, γ electrons emitted by the sputter, etc. are bound by the action of the magnetic field, and a high-density plasma is formed. Therefore, the sputtering of the targets T ₁ and T ₂ is promoted, the amount of deposition increases from the space, the deposition rate on the substrate 40 increases, high-speed sputtering is possible, and the substrate 40
0 is on the side of the targets T ₁ and T ₂ , low-temperature sputtering is also possible. Note that the opposed target sputtering method of the present invention is not limited to the above-mentioned apparatus;
As mentioned above, this is a sputtering method in which a substrate is placed on the sides of a pair of targets facing each other, and a perpendicular magnetic field is applied between the targets to perform sputtering to form a film on the substrate. Therefore, the magnetic field generating means may also be an electromagnet instead of a permanent magnet. Further, the magnetic field may be one that closes and confines γ electrons, etc. in the space between the targets, and therefore it also includes the case where it is generated not over the entire surface of the target but only around the target. Next, an embodiment of a perpendicular magnetic recording medium according to the present invention, which is implemented using the above-mentioned facing target type sputtering apparatus, will be described. The magnetic properties of the medium were determined using a vibrating sample magnetometer. The recording and playback characteristics of the double-layer film media were described in the above-mentioned Special Publication No.
The evaluation was carried out using an auxiliary magnetic pole excitation type vertical magnetic head similar to the one known in Japanese Patent Application No.-91. The film thickness and composition were determined from a curve calibrated in advance using a fluorescent X-ray device. Examples 1 to 4 A low coercive force layer made of permalloy was created on a substrate by changing the Ar gas pressure during formation of the low coercive force layer to four levels (Examples 1 to 4) under the following conditions.
A two-layer film medium was prepared by sequentially forming perpendicular magnetization layers made of -Cr using the sputtering apparatus shown in FIG. A Apparatus conditions A-1 Low coercive force layer a Target T ₁ and T ₂ materials: Mo-4wt%, Ni-78wt%, Fe- both containing 0.5wt% Mn.
18 wt% permalloy b Substrate 40: 50 μm thick polyethylene terephthalate (PET) film c Target T ₁ , T ₂ spacing: 120 mm d Target surface magnetic field: 100 to 200 Gauss e Target T ₁ , T ₂ shape: 100 mm L x 150 mm W
x12mmt rectangle f Distance between substrate 40 and target _T1 , _T2 ends: 20
mm A-2 Co-Cr perpendicular magnetization layer a Target _T1 , _T2 material: Both Co-80wt%, Cr
-20wt% alloy c Target T ₁ , T ₂ spacing: 160 mm d Target surface magnetic field: 100 to 200 Gauss e Target T ₁ , T ₂ shape: 100 mm L x 150 mm W
x12mmt rectangle f Distance between substrate 40 and target _T1 , _T2 ends: 20
mm B Operating procedure The following procedures were carried out under conditions A-1 and A-2. a After installing the substrate, evacuate the inside of the vacuum chamber 10 until the ultimate vacuum level is 1×10 ^-6 Torr or less. b Introduce Ar (argon) gas to a predetermined pressure, perform press sputtering for 3 to 5 minutes, open the shutter, and perform film formation while transferring the substrate 40 in the opposite direction of the targets T ₁ and T ₂ as shown in the figure. Summer. In addition, in the case of A-1, Ar during sputtering
The gas pressure was 0.25 to 1 Pa. In addition, in the case of A-2, it was set to 0.5Pa. c The power input during sputtering is for both A-1 and A-2.
It was done with 3KW. d The substrate temperature is 90°C for A-1 and A-2, respectively.
℃, conducted at 130℃. C. Results of implementation FIG. 3 shows the relationship between the Ar gas pressure during sputtering and the coercive force of the low coercive force layer in Examples 1 to 4. For the two-layer film media of Examples 1 to 4, rectangular samples were cut out and electromagnetic conversion characteristics were evaluated. The measurement results are shown in Table-1. Regarding the electromagnetic conversion characteristics, the tape ran at 4.75 cm/sec during recording and at 9.5 cm/sec during playback.

【table】

[Table] Examples 5 to 9 In Examples 1 to 4, sputtering was performed by changing the substrate temperature (B-d) at five levels (Examples 5 to 9) from 60°C to 130°C when forming the low coercive force layer. I went. However, at this time, the gas pressure during sputtering (B-
b) was set to 0.5Pa. The coercive force of the low coercive force layer and the reproduction output of the obtained samples of Examples 5 to 9 were measured in the same manner as described above. The results are shown in Table 1 and Figure 4. Comparative Examples 1 to 9 As a comparative example, the amount of Mn added in the target composition (A-1-a) in Examples 1 to 9 was substantially 0wt.
% (outside the detection limit), membranes were prepared in the same manner as in Examples 1 to 9 using a permalloiter target. The coercive force of the low coercive force layer and the reproduction output of the obtained samples (Comparative Examples 1 to 9) were measured. The results are shown in FIG. 3, FIG. 4, and Table 1. Comparison of Examples and Comparative Examples shows that the addition of Mn makes it possible to form a smaller low coercive force layer, and therefore exhibits a larger reproduction output. Further, in the examples, the coercive force is stable at a small value over a wide range of substrate temperature and sputtering pressure, which is very advantageous in terms of stable production. Examples 10 to 13 and Comparative Example 10 Using the same apparatus as in Examples 1 to 9, low coercive force layers were formed with different amounts of Mn added. The amount of Mn added was adjusted by using a permanent target having a composition of 18Fe-78Ni-4Mo as in the comparative example described above, placing Mn chips on target _T1 in FIG. 2, and changing the number of Mn chips. There are 5 levels of Mn addition (Examples 10 to 13) including 0 (Comparative Example 10).
A low coercive force layer was formed by sputtering at a sputtering pressure of 0.4 Pa and a substrate temperature of 90°C. Table 2 shows the measurement results of the coercive force of the obtained low coercive force layer. The coercive force of the low coercive force layers of Examples 10 to 13, which were prepared using targets containing 100 ppm or more of Mn, was significantly smaller than that of Comparative Example 10, which did not contain Mn.

[Table] As is clear from the above explanation, according to the magnetic recording medium of the present invention, the low coercive force layer contains 100 ppm or more.
If it contains less than 6000ppm (weight%) of Mn,
Compared to the component permalloy thin film, the recording and reproducing sensitivity has been greatly improved, making it possible to record at even higher density.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the coercive force of the low coercive force layer of a two-layer film medium related to the implementation of the present invention and the reproduction output, and FIG. 2 is an explanation of the facing target type sputtering apparatus used in the implementation of the present invention. FIG. 3 is a graph showing the relationship between Ar gas pressure and coercive force during sputtering in Examples and Comparative Examples, and FIG. 4 is a graph showing the relationship between substrate temperature and coercive force. T ₁ , T ₂ : Target, 10: Vacuum chamber, 20:
Exhaust system, 30: Gas introduction system, 40: Substrate, 50:
Spatuta power supply.

Claims (1)

[Claims] 1. A low coercive force layer made of a permalloy thin film containing Ni and Fe as main components and a magnetic recording layer having an axis of easy magnetization perpendicular to the film surface are sequentially formed on a nonmagnetic substrate. 1. A magnetic recording medium characterized in that the permalloy thin film has a Mn content of 100 ppm (wt%) or more and 6000 ppm (wt%) or less. 2. On a non-magnetic substrate, Ni and
In a method for manufacturing a magnetic recording medium in which a low coercive force layer consisting of a permalloy thin film mainly composed of Fe and a magnetic recording layer having an axis of easy magnetization in a direction perpendicular to the film surface are sequentially formed, the low coercive force layer is formed by sputtering. A method for manufacturing a magnetic recording medium, characterized by forming a magnetic recording medium. 3. The method of manufacturing a magnetic recording medium according to claim 2, wherein the low coercive force layer is formed by a facing target sputtering method. 4. The method of manufacturing a magnetic recording medium according to claim 3, wherein the magnetic recording layer is formed by a facing target sputtering method.