JP2007066477A - Perpendicular magnetic recording medium and perpendicular magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably obtain, with high productivity, a perpendicular magnetic recording medium wherein a soft magnetic layer to be provided between the substrate and the perpendicular magnetic recording layer of the recording medium can be formed in a thick coated film in a short period of time and spike noise and noise of the soft magnetic layer are reduced by forming the soft magnetic layer using an alloy plating method by which the complex state of a complex is not changed and stable continuous plating is made possible. <P>SOLUTION: The perpendicular magnetic recording medium is formed by forming a soft magnetic backing layer made of a Co-Ni-P alloy plating layer, a soft magnetic buffer layer composed of two layers of a Ni-Fe alloy and a Co-Fe, an anti-ferromagnetic layer, an underlayer and a perpendicular magnetic recording layer sequentially from a lower side on a substrate or a glass substrate wherein an amorphous Ni-P alloy plating layer is provided to an aluminum plate or an aluminum alloy plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a perpendicular magnetic recording medium that can suppress noise caused by a soft magnetic backing layer, particularly spike noise, and can be suitably applied to a hard disk, a magnetic tape, and the like, and a perpendicular magnetic recording apparatus using the perpendicular magnetic recording medium.

  Conventionally, as a magnetic recording medium mounted on a magnetic recording device such as a hard disk drive (HDD), data is recorded with a magnetization direction fixed in a direction parallel to the surface of the recording medium, that is, in an in-plane direction of the magnetic recording layer. The in-plane recording method is used. In this in-plane recording method, it is required to further increase the recording density per unit area, and it has been dealt with by increasing the coercive force. However, if the coercive force becomes too high, there are problems such as data writing using a ring head becoming impossible.

  On the other hand, in the perpendicular magnetic recording method in which data is recorded in a direction perpendicular to the surface of the recording medium using a single magnetic pole head, it is possible to record even a recording medium having a high coercive force. A recording density higher than that of the method can be obtained. For this reason, research and development of recording media using the perpendicular magnetic recording method has been conventionally performed. As the perpendicular magnetic recording medium, a perpendicular magnetic recording medium having a structure in which a soft magnetic layer and a perpendicular magnetic recording layer are provided on a recording medium substrate is used. In this perpendicular magnetic recording medium having a two-layer structure, a soft magnetic layer made of an amorphous material such as a permalloy-based crystalline material or CoZrNb having a thickness 10 times or more that of the perpendicular magnetic recording layer is provided by a sputtering method. However, there is a drawback that spike noise frequently occurs due to leakage of magnetic flux from the domain wall formed in the soft magnetic layer.

  In order to suppress the occurrence of spike noise, the following techniques have been proposed. For example, an antiferromagnetic thin film made of a Mn alloy containing Co or a Mn alloy containing Ir is formed between a base and a soft magnetic layer made of an amorphous Co alloy, and the soft magnetic layer is made of exchange coupling. A method of suppressing the occurrence of spike noise by fixing the magnetization to prevent the domain wall formation in the soft magnetic layer is disclosed (for example, see Patent Document 1). In this method, an antiferromagnetic thin film layer, a soft magnetic layer, a magnetic recording layer, and the like are formed on a substrate using a sputtering method. The thickness of the soft magnetic layer may be an antiferromagnetic thin film layer or a magnetic recording layer. For example, it is necessary to form a thick film up to nearly 10 times as thick as the above, and a long-time sputtering process is required, resulting in poor productivity.

  Further, an antiferromagnetic layer is provided between the perpendicular magnetization film and the backing soft magnetic layer at a distance of 100 nm or less from the perpendicular magnetization film, and a nonmagnetic intermediate layer is disposed between the perpendicular magnetization film and the antiferromagnetic layer, Disclosed is a method for reducing spike noise generated from a backing soft magnetic layer by providing a layer composed of a nonmagnetic intermediate layer and a ferromagnetic layer (soft magnetic film) between a perpendicular magnetization film and an antiferromagnetic layer. (For example, refer to Patent Document 2). Also in this method, each of these layers is formed by sputtering, but the soft magnetic layer needs to be formed with a thickness of 10 times or more the thickness of each layer. Is forced to be less productive.

As a method for obtaining a thick soft magnetic layer, there is a method in which a permalloy of a Ni—Fe based alloy is formed using an electroless plating method using a B compound or a P compound as a reducing agent. Fe ²⁺ ions in a plating bath There to easily oxidized to Fe ³⁺ ions becomes bath composition in the atmosphere will change with time, it is difficult to continuously plating stably.

  As a method of forming a soft magnetic layer using an electroless plating method, a method of forming a film containing two or more metals selected from Ni, Fe, and Co and P (for example, is disclosed) When a plating bath containing ammonium ions in the plating bath is used, the ammonium ions constituting the ammine complex are volatilized and dissipated as ammonia gas by the plating for a long time, but the lost ammonium Even if ions are replenished, the complexing state of the ammine complex changes and the plating deposition rate decreases, making it difficult to perform stable and continuous plating.

As described above, the prior art information relating to the present application includes the following.
JP 2001-291224 A JP 2002-298326 A Japanese Patent Application Laid-Open No. 09-171925

  In the present invention, the soft magnetic layer provided between the substrate of the recording medium and the perpendicular magnetic recording layer can be formed into a thick film in a short time, and the alloy can be continuously plated stably without changing the bath composition. It is an object to stably obtain a perpendicular magnetic recording medium with reduced spike noise and soft magnetic layer noise by using a plating method with high productivity.

In order to achieve the above object, a perpendicular magnetic recording medium of the present invention is a perpendicular magnetic recording medium having a perpendicular magnetic recording layer via a soft magnetic underlayer, and is formed by electroless plating with a substrate. The soft magnetic backing layer made of -P alloy plating, an antiferromagnetic layer formed on the soft magnetic backing layer, and an underlayer formed on the antiferromagnetic layer using a sputtering method And a perpendicular magnetic recording medium (claim 1) comprising a perpendicular magnetic recording layer formed on the underlayer by sputtering.
In the perpendicular magnetic recording medium of the above (Claim 1), the Co content in the soft magnetic underlayer made of the Co—Ni—P alloy plating is 60 to 73 wt% when the sum of Co + Ni + P is 100 wt%. %, Ni content is 20 to 30% by weight, and P content is 7 to 13% by weight (Claim 2), and the perpendicular magnetic recording medium according to (Claim 1 or 2) is characterized in that The Co—Ni—P alloy plating is formed by electroless plating using a plating bath containing amino acid ions (Claim 3), and the perpendicular magnetic recording medium according to (Claim 3) The amino acid ion is characterized in that the compound is glycine (Claim 4), and in the perpendicular magnetic recording medium of any of the above (Claims 1 to 4), the soft magnetic underlayer is The thickness after polishing is 100 to 1000 nm, the surface roughness Ra (JIS B 0601) is 0.5 nm or less (Claim 5), and any of the above (Claims 1 to 5) In the perpendicular magnetic recording medium, the soft magnetic underlayer has a saturation magnetic flux density of 1.0 T or more and a coercive force of 5 Oe or less (Claim 6), and any of the above (Claims 1 to 6) Such a perpendicular magnetic recording medium is characterized by comprising a substrate in which an amorphous Ni—P alloy plating layer is formed on an aluminum substrate or a glass substrate (Claim 7), and any of the above (Claims 1 to 7). In the perpendicular magnetic recording medium, a soft magnetic buffer layer is provided between the soft magnetic underlayer and the antiferromagnetic layer (Claim 8), and the perpendicular of the above (Claim 8). In magnetic recording media, Serial soft buffer layer, the two layers the lower layer of Ni-Fe alloy layer and the upper layer of Co-Fe alloy layer and wherein (claim 9).
The perpendicular magnetic recording apparatus of the present invention is a perpendicular magnetic recording apparatus (claim 10) using any one of the perpendicular magnetic recording media described above (claims 1 to 9).

  In the perpendicular magnetic recording medium of the present invention, the soft magnetic backing layer provided between the substrate of the recording medium and the perpendicular magnetic recording layer is formed by forming a thick film in a short time by an electroless plating method. Thus, a perpendicular magnetic recording medium can be obtained with higher productivity than when a thick soft magnetic backing layer is provided. Also, as the electroless plating bath, a Co-Ni-P alloy plating bath containing amino acid ions and no ammonium ions as a complexing agent is used, so that high productivity can be maintained stably without reducing the plating deposition rate. Thus, a soft magnetic film can be formed. In particular, when using a substrate on which an Ni-P alloy plating layer for ensuring surface hardness is formed by electroless alloy plating, which is a wet film formation method, on an aluminum plate or an aluminum alloy plate, the film formation method is subsequently changed. Without forming the soft magnetic backing layer by electroless alloy plating, which is a wet film forming method, it is possible to form a film with extremely high efficiency and high productivity. In addition, by providing a soft magnetic buffer layer using a sputtering method on a soft magnetic backing layer formed using an electroless plating method, and further providing an antiferromagnetic layer thereon, the occurrence of spike noise is suppressed. be able to.

  Hereinafter, an embodiment of a perpendicular magnetic recording medium of the present invention and a magnetic recording apparatus including the same will be described with reference to the drawings. These embodiments are specifically described for better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified.

FIG. 1 is a schematic sectional view showing an example of an embodiment of the perpendicular magnetic recording medium of the present invention. The perpendicular magnetic recording medium 10 includes a soft magnetic buffer layer 4 composed of two layers of a soft magnetic backing layer 3, a Ni—Fe alloy layer 4 a and a Co—Fe alloy layer 4 b in order from the bottom on the substrate 1 on the substrate 1. The magnetic layer 5, the underlayer 6, the perpendicular magnetic recording layer 7, the protective film 8, and the lubricating film 9 are formed. FIG. 2 is a schematic cross-sectional view showing another example of the embodiment of the perpendicular magnetic recording medium of the present invention, in which a substrate 1a made of an aluminum substrate and an amorphous Ni—P alloy plating layer 1b formed thereon is used. FIG.

  Examples of the substrate 1 include a disk made of a nonmagnetic metal or resin for a magnetic disk or another nonmagnetic film formed thereon. As a disk made of a nonmagnetic metal or resin, a disk made of aluminum, titanium, an alloy mainly containing them, glass, silicon, carbon, ceramics, resin, or a composite made of two or more of these. Can be used. As the glass substrate, it is more preferable to use a glass substrate made of tempered glass having a compressive stress applied to the surface using crystallized glass or an ion exchange method. Films formed on these disks do not become magnetized even when heated to high temperatures, have electrical conductivity, have excellent thermal conductivity, can be easily machined such as polishing, and must be handled easily. A non-magnetic film having an appropriate hardness that is difficult to stick to is used, and there is a film made of an alloy such as Ni-P, Ni-Ta, Ni-Ti, Ni-Al, a sputtering method, a vapor deposition method, and a plating method. The film can be formed using, for example. The amorphous Ni—P alloy plating layer 1b formed on the substrate 1a is also a nonmagnetic film.

  The present invention is characterized in that the soft magnetic backing layer 3 is formed by an electroless plating method which is a wet film forming method. Therefore, an amorphous Ni-P alloy is similarly formed on an aluminum substrate 1a (including an aluminum alloy plate, hereinafter the same) as shown in FIG. 2, which is also widely manufactured as a magnetic disk substrate using the wet film formation method. Use of the substrate 1 on which the plating layer 1b is formed is preferable from the viewpoint of productivity because a plating apparatus or plating waste liquid treatment equipment having a common structure can be used.

In the present invention, in particular, a Co—Ni—P alloy is formed as the soft magnetic backing layer 3 by an electroless plating method. The soft magnetic layer is composed of a ferromagnetic metal such as Fe, Ni, or Co. However, when the ferromagnetic metal is deposited by using an electroless plating method, Fe is easily oxidized in the atmosphere, and a typical soft magnetic film is formed. When a Ni-Fe alloy film such as permalloy is formed by a wet plating method, since Fe ²⁺ ions as the Fe supply source in the plating bath easily change to Fe ³⁺ ions during plating, it is continuously stable. It is difficult to obtain a soft magnetic film having the composition described above. Therefore, in the present invention, a Co—Ni alloy in which metal ions in a plating bath are not oxidized in the atmosphere is formed as a soft magnetic film made of a Co—Ni—P alloy by an electroless plating method using a P compound as a reducing agent. Let

  As a plating bath for forming a Co—Ni—P alloy by an electroless plating method, Co ions and Ni ions such as cobalt sulfate and nickel sulfate are used as metal ions, and sodium hypophosphite and sodium phosphite are used as reducing agents. Hypophosphite ions and / or phosphite ions such as alkali metal salts of organic acids such as sodium citrate and sodium tartrate as complexing agents, amino groups and carboxyl groups such as α alanine, β alanine, glycine, glutamic acid It is preferable to use a plating bath containing one or more of amino acid ions having both of these, and it is more preferable to use a plating bath containing glycine that supplies amino acid ions as a complexing agent. Further, sodium hydroxide is preferably added to adjust the pH of the bath. When ammonia water is used to adjust the pH of the plating bath, or a substance containing ammonium ions such as ammonium sulfate is added to the plating bath as a plating bath stabilizer, ammonium ions are volatilized and dissipated as ammonia gas from the heated plating bath. Thus, the complexing state of the ammine complex is changed, the deposition rate of the plating film is lowered, and it becomes difficult to obtain a soft magnetic film having a stable film composition at high speed.

  Fig. 3 shows continuous plating in the case of continuous plating using a plating bath containing glycine and not containing ammonia (glycine bath), and in the case of continuous plating using a plating bath containing no glycine and containing ammonia (ammonia bath). The influence of the plating deposition rate due to the change with time is shown. When the glycine bath is used, the plating deposition rate is almost constant 2 μm / H even if 17 hours or more elapses after the plating bath is built and heated to 80 ° C., whereas the ammonia bath is used. In this case, the plating rate starts to decrease after 4 hours from the start of plating, and the plating does not precipitate at all after 15 hours. Thus, without using ammonium ions in the plating bath, by including glycine that supplies amino acid ions as an alternative complexing agent for ammonium ions, a stable film composition can be obtained without reducing the deposition rate of the plating film. A soft magnetic film is obtained.

  In general, in the case of a perpendicular magnetic recording medium, it is preferable that the gap between the magnetic head and the perpendicular magnetic recording medium is small in order for the magnetic head to satisfactorily read a signal written on the perpendicular magnetic recording medium. In particular, when the magnetic head performs recording / reproduction while flying above the perpendicular magnetic recording medium, the flying height is preferably as small as possible. Further, it is more preferable that recording / reproduction can be performed by bringing the magnetic head into contact with the surface of the perpendicular magnetic recording medium without flying. Accordingly, the substrate for the perpendicular magnetic recording medium is preferably one having excellent surface smoothness, and further, one in which the parallelism of the front and back surfaces of the substrate and the circumferential waviness of the substrate are appropriately controlled. preferable.

  Since the soft magnetic backing layer 3 provided on the substrate 1 functions as a part of the head magnetic circuit, it is deposited to a thickness of 50 to 500 nm, and then the surface is polished for use. Therefore, from the viewpoint of productivity, it is more advantageous to use a wet film forming method such as electroless plating than to use a film forming method such as sputtering or vapor deposition. In particular, when an aluminum plate on which a Ni-P alloy plating layer is formed is used as the substrate 1, it is more advantageous because a plating apparatus having a common structure, a common plating waste liquid treatment facility, and the like can be used as described above.

  As the soft magnetic backing layer 3, Ni—Fe, Ni—Fe—Co, Co—Zr—Nb, Fe—Al—Si, Co—Ta—Zr, Fe—Ta—C, Fe— An alloy such as N can be used, but in the present invention, the Co—Ni—P alloy plating layer using the P compound as a reducing agent is softened by using the electroless plating method which is a wet film forming method as described above. The magnetic backing layer 3 is applied. When an aluminum plate having an amorphous Ni—P alloy plating layer formed on the substrate 1 is used, a Co—Ni—P alloy plating layer is formed on the amorphous Ni—P alloy plating layer using an electroless plating method. To do.

  When the Co—Ni—P alloy plating layer is applied as the soft magnetic backing layer 3, the Co content is 60 to 73 wt% when the total of Co + Ni + P in the Co—Ni—P alloy plating layer is 100 wt%. By setting the Ni content to 20 to 30% by weight and the P content to 7 to 13% by weight, the saturation magnetic flux density can be made 1.0 T or more and the coercive force can be made 5 Oe or less. Become crystalline. In Co-Ni-P alloy plating, in order to keep the contents of Co, Ni, and P within the above ranges, the plating bath temperature can be changed in alloy plating to adjust the deposition rate of the plating layer, The pH is appropriately adjusted by changing the pH.

  The thickness of these soft magnetic backing layers 2 is preferably 100 to 1000 nm, more preferably 300 to 500 nm, as the thickness after polishing. If it is less than 100 nm, it will be difficult to ensure sufficient polishing accuracy during polishing, and if it exceeds 1000 nm, the advantage of improving the recording density will not be improved and it will not be economically advantageous.

  Further, the surface roughness Ra (JIS B 0601) of these soft magnetic backing layers 3 needs to be 0.5 nm or less. When the surface roughness Ra (JIS B 0601) exceeds 0.5 nm, not only the noise power observed in the noise power spectrum increases, but also head crashes easily occur. For this purpose, when an aluminum plate having an amorphous Ni—P alloy plating layer is used as the substrate 1, the surface roughness Ra (JIS B 0601) is 0.2 nm or less after the amorphous Ni—P alloy plating. After forming the Co—Ni—P alloy plating layer with the above thickness on the amorphous Ni—P alloy plating layer whose surface has been polished, the surface roughness Ra (JIS B) is obtained by repolishing the surface. 0601) can be 0.5 nm or less. Further, the surface polishing performed after forming the amorphous Ni—P alloy plating layer on the aluminum plate was omitted to form the Co—Ni—P alloy plating layer, and then the surface polishing was performed to obtain the surface roughness Ra ( JIS B 0601) may be 0.5 nm or less.

  In general, in a perpendicular magnetic recording medium, a soft magnetic layer is provided on a substrate and then an antiferromagnetic layer is provided thereon. The antiferromagnetic layer is a layer provided to suppress spike noise without forming a Bloch domain wall in the soft magnetic layer by an exchange coupling action with the soft magnetic layer. In particular, fixing the magnetization of the soft magnetic underlayer in the radial direction of the substrate (disk) and making it a single domain in the residual magnetization state can completely eliminate the leakage magnetic flux from the Bloch domain wall, thereby suppressing the occurrence of spike noise. Therefore, it is preferable. In order to induce large unidirectional magnetic anisotropy by exchange coupling with the soft magnetic layer, the soft magnetic buffer is interposed between the soft magnetic layer and the antiferromagnetic layer for the purpose of controlling crystal growth and crystal orientation of the antiferromagnetic layer. A layer may be provided. In the present invention, as described above, the Co—Ni—P alloy plating layer is formed on the substrate 1 as the soft magnetic backing layer 3, and the soft magnetic buffer layer 4 is formed thereon. The soft magnetic buffer layer 4 is not particularly limited, but a soft magnetic material that can control the structure of the antiferromagnetic layer without depending on the structure of the plated soft magnetic layer, A soft magnetic material capable of inducing a large unidirectional magnetic anisotropy by a combination with the antiferromagnetic layer 5 formed above, or a laminated structure thereof may be used. Specifically, it is preferable to use a single layer made of a Co—Fe alloy or two layers made of a Ni—Fe alloy 4a and a Co—Fe alloy 4b from the substrate side as shown in FIG. The thickness of the soft magnetic buffer layer 4 is preferably 1 to 20 nm from the viewpoint of productivity. Either the wet film formation method or the dry film formation method can be applied to the formation of the soft magnetic buffer layer 4, but dry film formation such as sputtering is preferred from the viewpoint of strict control of the film thickness.

  The antiferromagnetic layer 5 includes alloys such as Mn—Ir, Co—Mn, Ni—Mn, and Pt—Mn, and other metals as long as they do not adversely affect the properties of the antiferromagnetic layer. What added the above can be used. Since the thickness is a spacing loss from the viewpoint of the head system magnetic circuit, the thickness is preferably thin enough not to impair the function of inducing unidirectional magnetic anisotropy. Specifically, it is preferable to provide a layer having a thickness of 1 to 10 nm. Both the wet film formation method and the dry film formation method can be applied to the formation of the antiferromagnetic layer 5, but a dry film formation method such as a sputtering method is more preferable from the viewpoint of strict control of the film thickness.

  Next, the underlayer 6 may be provided on the antiferromagnetic layer 5 by sputtering. The underlayer 6 may be made of any material as long as it is a material for forming the perpendicular recording layer 7 formed thereon into a perpendicular magnetization film. For example, Ru, Hf, nonmagnetic CoCr, Pt, and Pd can be used. In addition to the single layer structure, the underlayer 6 may have a multilayer structure of two layers or more.

  The perpendicular magnetic recording layer 7 formed by sputtering may be a ferromagnetic material whose easy axis is oriented with magnetic anisotropy in one direction substantially perpendicular to the film surface, and its composition is particularly limited. However, for example, a hexagonal closest packed structure in which Co and Cr are main components and the easy magnetization axis is oriented with magnetic anisotropy in one direction substantially perpendicular to the film surface. Co-Cr-based ferromagnetic material having a) is preferably used. This Co—Cr based ferromagnetic material may be added with other elements as required.

Specific examples of the CoCr-based ferromagnetic material include Co—Cr (Cr <25 atomic%), Co—Cr—Ni, Co—Cr—Ta, Co—Cr—Pt, Co—Cr—Pt—Ta, and Co—. Examples include Co—Cr alloys such as Cr—Pt—B. Also, the grain size control and grain segregation control of the perpendicular magnetic recording layer 7, crystal grain magnetic anisotropy constant (Ku), grain size control, corrosion resistance control, correspondence to low temperature process For these purposes, O, SiO _x , MgO _x , TaO _x , ZrO _x , Fe, Mo, V, Si, B, Ir, W, Hf, Nb, Ru, rare earth elements, etc. are appropriately added to these alloys. Also good.

In addition, ferromagnetic materials other than the above Co-Cr alloys, for example, materials excellent in thermal disturbance resistance such as Co-Pt, Co-Pd, and Fe-Pt, and B, N, A material to which O, SiO _x , MgO _x , TaO _x , ZrO _x , Zr, or the like is added may be used. Furthermore, a perpendicular recording layer having a multilayer structure in which a large number of Co layers and Pt layers are laminated is also applicable. Examples of such a perpendicular recording layer having a multilayer structure include a Co layer and a Pd layer, or a multilayer perpendicular recording layer in which an Fe layer and a Pd layer, etc. are combined, or B, N, O, Zr, and SiO _{x in} each of these layers. Those to which etc. are added are also applicable. Regardless of which recording layer material is selected, the thickness of the perpendicular magnetic recording layer 7 is preferably 5 to 100 nm.

  In this way, the perpendicular magnetic recording medium of the present invention can be obtained. However, when actually used in a drive, it is necessary to provide the protective film 8 on the perpendicular magnetic recording layer 7 and the lubricating film 9 on the protective film 8. There is. The protective layer 8 is for protecting the surface of the perpendicular magnetic recording layer 7 and may be any layer provided with mechanical strength, heat resistance, oxidation resistance, corrosion resistance, etc. necessary as a protective film. Although the material composition is not limited, for example, carbon is preferably used. The lubricating film is for stably floating the magnetic head when the substrate is rotating. For example, perfluoropolyether is preferably used.

Hereinafter, the present invention will be described in detail with reference to examples.
(Creation of substrate)
An amorphous Ni—P alloy plating is applied to a 2.5-inch diameter disc (diameter: 65 mm) made of an aluminum alloy for a magnetic disk and having a hole in the center, and then an alumina-based polishing liquid is used. After rough polishing using this, finish polishing was performed using a colloidal silica polishing liquid, and the surface roughness Ra (JIS B 0601) was polished to 0.2 nm to obtain a substrate.

(Formation of soft magnetic backing layer)
A composition of Co (68.8 wt%)-Ni (24.2 wt%)-P (7.0 wt%) was formed on this substrate using a Co—Ni—P alloy plating bath having the following bath composition. The Co—Ni—P alloy layer having Next, the surface was polished with a colloidal silica polishing liquid to obtain a soft magnetic backing layer having a surface roughness (Ra): 0.29 nm and a thickness: 300 nm, and a sample of sample number 1 was obtained. When the soft magnetic properties of the soft magnetic backing layer of the sample No. 1 obtained in this way were measured using a vibrating sample magnetometer (VSM: BHV-35 manufactured by Riken Denshi Co., Ltd.), the coercive force was 0. 5 Oe, saturation magnetic flux density: 1.1 T.

[Co-Ni-P alloy plating bath]
Cobalt sulfate 10g / L
Nickel sulfate 3g / L
Trisodium citrate 30g / L
Sodium tartrate 30g / L
Glycine 7.5g / L
Sodium hypophosphite 25g / L
pH (adjusted with aqueous sodium hydroxide) 9.0
Bath temperature 80 ° C

(Formation of soft magnetic buffer layer)
The sample of Sample No. 1 in which the Co—Ni—P alloy plating layer was formed on the substrate and the surface was polished as described above was applied to the Ni (81 wt%)-Fe (19 A thickness of 6 nm Fe-Ni alloy layer and a thickness of Co (70 wt%)-Fe (30 wt%): a Co-Fe alloy layer of 4 nm in thickness. : A 10 nm soft magnetic buffer layer was formed.

(Formation of antiferromagnetic layer)
An antiferromagnetic layer made of MnIr with a thickness of 6 nm was formed on the soft magnetic buffer layer by sputtering, and the easy axis of magnetization was induced in the radial direction. For comparison, a sample (sample number 2) in which an antiferromagnetic layer was not provided on the sample of sample number 1 was also produced.

(Determination of spike noise)
By evaluating the magnetic domain structure of the disk-shaped soft magnetic layer using the optical surface analyzer for the sample No. 1 after forming the antiferromagnetic layer and the sample No. 2 without the antiferromagnetic layer, The presence or absence of spike noise was determined. The results are shown in FIG. 4 and FIG. FIG. 4 shows the magnetic domain structure of Sample No. 2. A striped pattern indicating the generation of a domain wall is recognized, and therefore spike noise is generated. On the other hand, FIG. 5 shows the magnetic domain structure of Sample No. 1, the striped pattern 16 indicating the generation of the domain wall is not recognized, and spike noise does not occur.

(Formation of underlayer and perpendicular magnetic recording layer)
Next, a Ru layer having a thickness of 20 nm was formed as an underlayer on the antiferromagnetic layer of the sample of sample No. 1 by using sputtering, and then Co (65 wt%) was formed on the underlayer Ru layer. A perpendicular magnetic recording layer made of a Co—Cr—Pt alloy having a thickness of 22 nm and a composition of —Cr (20 wt%) — Pt (15 wt%) was formed.

(Formation of protective film and lubricating film)
Next, a protective film made of carbon having a thickness of 7 nm is formed on the perpendicular magnetic recording layer by sputtering, and then a lubricating film made of perfluoropolyether having a thickness of 2 nm is formed by using an immersion method. did. The perpendicular magnetic recording medium of the present invention was produced as described above.

  The perpendicular magnetic recording medium of the present invention is configured as described above, and since the soft magnetic underlayer is formed by an electroless plating method that is a wet film forming method, it is simpler than a sputtering method that is a dry film forming method. A thick soft magnetic backing layer can be formed in a short time. In addition, a soft magnetic backing layer is formed using a Co—Ni—P alloy plating bath that contains amino acid ions and no ammonium ions as a complexing agent, so that stable and high production can be achieved without reducing the plating deposition rate. The soft magnetic film can be formed while maintaining the properties. Furthermore, it is possible to obtain a perpendicular magnetic recording medium with high productivity and reduced spike noise as compared with a crystalline soft magnetic underlayer grown in a column shape by sputtering.

It is a schematic sectional drawing which shows an example of the Example of the perpendicular magnetic recording medium of this invention. It is a schematic sectional drawing which shows an example of the board | substrate used for the perpendicular magnetic recording medium of this invention. In the case of continuous plating using the plating bath containing glycine of the present invention and not containing ammonium-on (glycine bath), and in the case of continuous plating using the plating bath containing no ammonium ion for comparison (ammonia bath) The rough showing the influence of the plating deposition rate due to the change over time of continuous plating. It is a figure which shows the magnetic domain structure when not forming the antiferromagnetic layer for a comparison. It is a figure which shows the magnetic domain structure at the time of forming the antiferromagnetic layer of this invention.

Explanation of symbols

1 substrate 1a substrate (aluminum plate)
1b Amorphous Ni-P alloy plating layer 3 Soft magnetic backing layer 4 Soft magnetic buffer layer 4a Ni-Fe alloy 4b Co-Fe alloy 5 Antiferromagnetic layer 6 Underlayer 7 Perpendicular magnetic recording layer 8 Protective film 9 Lubricating film 10 Perpendicular magnetic recording medium 15 Sample without an antiferromagnetic layer 16 Striped pattern 20 showing the generation of a domain wall Sample after forming an antiferromagnetic layer

Claims (10)

A perpendicular magnetic recording medium having a perpendicular magnetic recording layer via a soft magnetic backing layer, the soft magnetic backing layer comprising a substrate and a Co—Ni—P alloy plating formed by an electroless plating method, and the soft magnetic An antiferromagnetic layer formed on the backing layer, an underlayer formed by sputtering on the antiferromagnetic layer, and formed by sputtering on the underlayer A perpendicular magnetic recording medium comprising: a perpendicular magnetic recording layer comprising: In the soft magnetic backing layer comprising the Co—Ni—P alloy plating, when the total of Co + Ni + P is 100% by weight, the Co content is 60 to 73% by weight, the Ni content is 20 to 30% by weight, The perpendicular magnetic recording medium according to claim 1, wherein the P content is 7 to 13 wt%. The perpendicular magnetic recording medium according to claim 1, wherein the Co—Ni—P alloy plating is formed by electroless plating using a plating bath containing amino acid ions. The perpendicular magnetic recording medium according to claim 3, wherein the amino acid ion is a compound of glycine. 5. The vertical according to claim 1, wherein the soft magnetic backing layer has a polished thickness of 100 to 1000 nm and a surface roughness Ra (JIS B 0601) of 0.5 nm or less. Magnetic recording medium. 6. The perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic backing layer has a saturation magnetic flux density of 1.0 T or more and a coercive force of 5 Oe or less. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is made of a substrate in which an amorphous Ni—P alloy plating layer is formed on an aluminum substrate or a glass substrate. The perpendicular magnetic recording medium according to claim 1, wherein a soft magnetic buffer layer is provided between the soft magnetic backing layer and the antiferromagnetic layer. The perpendicular magnetic recording medium according to claim 8, wherein the soft magnetic buffer layer is composed of two layers of a lower Ni—Fe alloy layer and an upper Co—Fe alloy layer. A perpendicular magnetic recording apparatus using the perpendicular magnetic recording medium according to claim 1.

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