JP2017182861A - Method for manufacturing vertical magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnetic recording medium which excels in magnetic head floatability and includes a protective layer having excellent corrosion resistance.SOLUTION: The present invention relates to a method for manufacturing a magnetic recording medium which includes a substrate, a magnetic recording layer including regular alloy and nonmagnetic grain boundary material and a protective layer. This method includes: (a) a step for preparing the substrate; (b) a step for sputtering an element constituting the regular alloy and the nonmagnetic grain boundary material and forming a magnetic recording layer that includes a first magnetic layer and a thin layer comprising the nonmagnetic grain boundary material on the first magnetic layer; and (c) a step for forming the protective layer, characterized in that in the step (c), a gas pressure at sputtering time is set to 1.5 Pa or higher and a thin layer comprising the nonmagnetic grain boundary material is formed on the first magnetic layer. The step (b) of this method may further include a step for forming a second magnetic layer comprising a regular alloy-C layer before the magnetic recording layer is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a magnetic recording medium. Specifically, the present invention relates to a method for manufacturing a magnetic recording medium used in a hard disk magnetic recording device (HDD).

  In recent years, with the increase in the amount of information handled by information processing devices such as computers and the miniaturization of information processing devices, the storage capacity of information recording devices has been increased, and there is a need for magnetic recording media used in information recording devices. Memory capacity is steadily increasing.

  As a technique for realizing high density magnetic recording, a perpendicular magnetic recording system is adopted. The perpendicular magnetic recording medium includes at least a substrate and a magnetic recording layer formed of a hard magnetic material. The perpendicular magnetic recording medium is optionally formed of a soft magnetic material, and a soft magnetic backing layer that plays a role of concentrating the magnetic flux generated by the magnetic head on the magnetic recording layer, and a hard magnetic material of the magnetic recording layer. It may further include an underlayer for orientation in the direction, a protective layer for protecting the surface of the magnetic recording layer, and the like.

  For the purpose of obtaining good magnetic properties, it has been proposed to form a magnetic recording layer of a perpendicular magnetic recording medium using a granular magnetic material. The granular magnetic material includes a magnetic crystal grain made of an ordered alloy and a grain boundary part made of a non-magnetic grain boundary material segregated so as to surround the periphery of the magnetic crystal grain. The individual magnetic crystal grains in the granular magnetic material are magnetically separated by the grain boundary portion of the nonmagnetic grain boundary material.

  To increase the recording density of the magnetic recording medium, the thickness of the protective layer of the magnetic head, the distance between the outermost surface of the magnetic head and the outermost surface of the magnetic recording medium (head flying height), the thickness of the lubricating layer of the magnetic recording medium, etc. Further thinning is required.

  In order to improve the reliability of the magnetic recording medium, it is particularly desirable to ensure sufficient reliability in the protective layer. That is, the protective layer is required to have corrosion resistance, sliding durability, and magnetic head flying property, and is required to have the same reliability as before even if it is thinned. However, the protective layer formed by the conventional method may not obtain sufficient reliability with respect to various performances.

  Therefore, in order to improve such a problem, for example, an invention described in JP-A-9-138943 (Patent Document 1) has been proposed. That is, in Patent Document 1, an underlying layer made of Si, Ge, Sn, or the like is interposed between the magnetic layer and the protective layer, and this is used as a buffer film to reduce the residual strain of the protective layer that is a carbon layer. It is reduced. This improves sliding durability and attempts to reduce the total thickness of the buffer film and the protective layer, but is still insufficient.

  In JP 2008-176915 A (Patent Document 2), JP 2008-192288 A (Patent Document 3) and JP 2008-234828 A (Patent Document 4), the double excellent in wear resistance and corrosion resistance. A protective layer has been proposed. As the underlayer in the double protective layer, transition metal oxynitrides composed of aluminum oxynitride, silicon oxynitride, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or W have been proposed. . The underlayer compensates for the stress of the carbon layer as the protective layer, and the carbon layer is effectively attached to the magnetic layer to form a strong and stable bond.

  However, if the thickness of the protective layer is reduced, the microscopic density of the protective layer is increased. Therefore, when a lubricating layer is provided, the thickness of the lubricating layer is biased and the flying performance of the magnetic head becomes unstable. That is a problem.

  Japanese Patent Laid-Open No. 2014-49156 (Patent Document 5) is good even if the thickness of the protective layer is reduced by forming an amorphous metal layer on the magnetic layer and forming a carbon layer thereon. It has been shown that high magnetic head flying characteristics and corrosion resistance can be obtained. The recording medium described in this document also requires a process for forming an amorphous metal layer.

Further, JP 2011-154746 A (Patent Document 6) discloses a heat-assisted magnetic recording medium having a high recording density. This heat-assisted magnetic recording medium has a magnetic layer including at least a first magnetic layer and a second magnetic layer on a substrate, and the first magnetic layer is made of an FePt ordered alloy and a SiO ₂ nonmagnetic grain boundary material. The content of the nonmagnetic grain boundary material is reduced from the substrate toward the magnetic layer surface side. This document does not pay attention to the magnetic head flying property and corrosion resistance related to the protective layer of the heat-assisted magnetic recording medium. Therefore, this document does not mention a method for manufacturing a magnetic recording medium for improving the magnetic head flying characteristics and corrosion resistance characteristics in relation to the protective layer.

Japanese Patent Laid-Open No. 9-138943 JP 2008-176915 A JP 2008-192288 A JP 2008-234828 A JP 2014-49156 A JP 2011-154746 A

  As described above, a method for manufacturing a magnetic recording medium for the purpose of obtaining a protective layer excellent in flying characteristics and corrosion resistance of a magnetic head includes a step of separately providing a base layer other than the protective layer. There was a problem in productivity.

  Therefore, an efficient method for manufacturing a magnetic recording medium is desired which can form a protective layer with good floating properties of the magnetic head and excellent corrosion resistance.

A method of manufacturing a magnetic recording medium according to one embodiment is a method of manufacturing a magnetic recording medium including a substrate, a magnetic recording layer including an ordered alloy and a nonmagnetic grain boundary material, and a protective layer.
(A) preparing the substrate;
(B) A magnet including a first magnetic layer and a book layer made of the nonmagnetic grain boundary material on the first magnetic layer by sputtering the elements constituting the ordered alloy and the nonmagnetic grain boundary material. Forming a recording layer;
(C) forming the protective layer,
In the formation of the magnetic recording layer in the step (b), a gas pressure during sputtering is set to 1.5 Pa or more, and a book layer made of the nonmagnetic grain boundary material is formed on the first magnetic layer. It is characterized by.

  The step (b) may further include a step of forming a second magnetic layer by sputtering an element constituting the ordered alloy and carbon (C) before forming the magnetic recording layer.

  Further, the ordered alloy of the first magnetic layer and the second magnetic layer is at least one element selected from the group consisting of Fe and Co and at least one element selected from the group consisting of Pt, Pd, Au and Ir Are preferably included.

The nonmagnetic grain boundary material is at least one material selected from the group consisting of C, B, Ag, Ge, W, SiO ₂ , Al ₂ O ₃ , TiO ₂ , GeO ₂ and B ₂ O _3. It is preferable to include.

In a preferred embodiment, the ordered alloy is FePt and the nonmagnetic grain boundary material is SiO ₂ .

  According to the method for manufacturing a magnetic recording medium of the above invention, it is possible to form a magnetic recording medium with good magnetic head flying and excellent corrosion resistance.

It is a schematic sectional drawing which shows the magnetic recording medium of one embodiment. It is the schematic which shows the process of manufacturing the magnetic-recording medium of one embodiment. It is a figure for demonstrating the state at the time of forming a magnetic-recording layer in the case of manufacturing a magnetic-recording medium. It is the schematic which shows the process of manufacturing the magnetic recording medium of another embodiment. It is a transmission electron microscope (TEM) cross-sectional image which shows the magnetic-recording layer and protective layer of the magnetic-recording medium produced in the Example.

  Hereinafter, a magnetic recording medium manufacturing method and a magnetic recording medium manufactured by the manufacturing method will be described with reference to the drawings, but the following description is merely an example and is intended to limit the present invention. is not.

A method of manufacturing a magnetic recording medium according to one embodiment is a method of manufacturing a magnetic recording medium including a substrate, a magnetic recording layer including an ordered alloy and a nonmagnetic grain boundary material, and a protective layer.
(A) preparing the substrate;
(B) Sputtering the elements constituting the ordered alloy and the nonmagnetic grain boundary material to include a first magnetic layer and a book layer made of the nonmagnetic grain boundary material on the first magnetic layer. Forming a magnetic recording layer;
(C) forming the protective layer,
In the formation of the magnetic recording layer in the step (b), a gas pressure during sputtering is set to 1.5 Pa or more, and a book layer made of the nonmagnetic grain boundary material is formed on the first magnetic layer. It is characterized by. In this specification, the manufacturing method of this embodiment is also referred to as the manufacturing method of the first embodiment, the manufacturing method of the magnetic recording medium of the first embodiment, or the like.

  Here, the magnetic recording medium manufactured by the manufacturing method of the first embodiment includes a substrate and a magnetic recording layer, and an adhesion layer, a soft magnetic backing layer, a heat sink layer, an underlayer, and / or a layer between these layers. Or it may further comprise a layer known in the art such as a seed layer. In addition, the magnetic recording medium includes a protective layer on the magnetic recording layer. Further optionally, it may further comprise a layer known in the art such as a liquid lubricant layer. FIG. 1 shows one configuration example of a magnetic recording medium 100 including a substrate 20, a seed layer 40, a magnetic recording layer 60, and a protective layer 80. The magnetic recording layer 60 of the magnetic recording medium 100 includes a first magnetic layer 62 including an ordered alloy and a nonmagnetic grain boundary material surrounding the ordered alloy. The magnetic recording layer 60 also includes a book layer 64 formed by depositing a nonmagnetic grain boundary material on the surface side of the first magnetic layer. In the present specification, the book layer 64 is also referred to as a nonmagnetic grain boundary material layer.

  Each process of the manufacturing method of the magnetic recording medium of 1st Embodiment is demonstrated with reference to FIG.

Step (a) is a step of preparing a magnetic recording medium substrate 20 (FIG. 2A). The substrate is not particularly limited as long as the substrate has a smooth surface. For example, the substrate can be formed using a material generally used for magnetic recording media. Materials that can be used include Ni alloy plated Al alloy, MgO single crystal, MgAl ₂ O ₄ , SrTiO ₃ , tempered glass, crystallized glass, Si / SiO _{2 and the} like.

  In the step (b), the element constituting the ordered alloy and the nonmagnetic grain boundary material are sputtered on the substrate 20 to form the first magnetic layer 62 and the nonmagnetic grain boundary material on the first magnetic layer. Then, the magnetic recording layer 60 including the book layer 64 made of is formed (FIG. 2B).

The element constituting the ordered alloy is preferably at least one element selected from the group consisting of Fe and Co and at least one element selected from the group consisting of Pt, Pd, Au, and Ir. Preferred ordered alloy is FePt, CoPt, FePd, and L1 ₀ type ordered alloy selected from the group consisting of CoPd. For property modulation, the ordered alloy may further include at least one element selected from the group consisting of Ni, Mn, Cu, Ru, Ag, Au, and Cr. Desirable property modulation includes a decrease in temperature required for ordering of the ordered alloy. A preferred ordered alloy is FePt. Particularly preferred ordered alloy is L1 ₀ type FePt.

The nonmagnetic grain boundary material is selected from elements such as C and B, metals, carbides, oxides, nitrides and the like. Preferably, at least one material selected from C, B, Ag, Ge, W, SiO ₂ , Al ₂ O ₃ , TiO ₂ , GeO ₂ , and B ₂ O ₃ can be included. Particularly preferred non-magnetic grain boundary material is SiO _2.

  The first magnetic layer 62 of the magnetic recording layer 60 and the nonmagnetic grain boundary material layer 64 made of a nonmagnetic grain boundary material are formed by depositing a constituent element of an ordered alloy and a nonmagnetic grain boundary material on a substrate by sputtering. Can be formed.

  In this specification, “sputtering” means only a step of ejecting atoms, clusters, or ions from a target by collision of high-energy ions, and all of the elements contained in the ejected atoms, clusters, or ions are on the substrate. Does not mean to be fixed to. That is, the thin film obtained in the “sputtering” step in this specification does not necessarily contain the element that has reached the substrate in the ratio of the amount reached.

Sputtering can be performed by a co-sputtering method using an ordered alloy target and a nonmagnetic grain boundary material target. For example, when the first magnetic layer 62 is formed of an ordered alloy FePt and an SiO ₂ nonmagnetic grain boundary material, an ordered alloy target containing Fe and Pt in a predetermined ratio and an SiO ₂ target can be used. Further, an Fe target and a Pt target may be used as the target of the ordered alloy. Alternatively, a target containing Fe, Pt, and SiO ₂ at a specific ratio may be used. The ratio of the ordered alloy and the ratio of the nonmagnetic grain boundary material in the magnetic recording layer can be controlled by adjusting the power applied to each target.

  In the step (b), as shown in FIG. 2B, the magnetic recording layer 60 is formed on the substrate 20 as a first magnetic layer 62 made of an ordered alloy and a nonmagnetic grain boundary material, and a nonmagnetic grain boundary material. A nonmagnetic grain boundary material layer 64 is formed. The nonmagnetic grain boundary material layer 64 is formed during the step (b).

Step (b) will be described in more detail with reference to FIG. In the following description, a case where a seed layer is provided on a substrate and an FePt—SiO ₂ layer is formed on the seed layer by a sputtering method is taken as an example.

FIGS. 3A and 3B are views showing a growth process when FePt—SiO ₂ is deposited on the seed layer 310 by a sputtering method. As shown in FIG. 3A, when FePt—SiO ₂ is deposited by the sputtering method, the FePt rule is formed on the seed layer 310 toward the surface of the magnetic recording medium shown as the direction 330 in FIG. A grain boundary portion 320 made of a non-magnetic grain boundary material of SiO ₂ surrounding the magnetic crystal grains 300 of the alloy grows. When deposition of FePt—SiO ₂ is further advanced from this state, SiO ₂ wraps around the surface of the magnetic recording medium of the magnetic crystal grains of the FePt ordered alloy, and d in FIG. A SiO ₂ thin film as shown by the thickness is formed. Thus, in the step (b), the first magnetic layer 62 and the nonmagnetic grain boundary material layer 64 are formed during the sputtering step for forming the magnetic recording layer 60.

In addition, the gas pressure during sputtering of the magnetic recording layer in the step (b) is preferably 1.5 Pa or more. By forming the magnetic recording layer 60 with such a gas pressure, the nonmagnetic grain boundary material layer 64 is formed on the surface of the first magnetic layer 62 while maintaining a good granular structure of the first magnetic layer 62. be able to. Moreover, Ar, N, etc. are preferable and the gas to be used has more preferable Ar.

  By using the above conditions, a nonmagnetic grain boundary material made of a nonmagnetic grain boundary material is formed on the first magnetic layer 62 of the ordered alloy-nonmagnetic grain boundary material without adding a step of separately providing the nonmagnetic grain boundary material layer 64. The magnetic grain boundary material layer 64 can be formed. Thus, the nonmagnetic grain boundary material layer 64 is formed during the sputtering process for forming the magnetic recording layer. This nonmagnetic grain boundary material layer 64 improves the performance of the protective layer 80. For this reason, the nonmagnetic grain boundary material layer 64 functions as an underlayer for the protective layer. From the viewpoint of recording, the thickness of the nonmagnetic grain boundary material layer 64 (d in FIG. 3B) is preferably as thin as possible as long as the function of the underlayer of the protective layer can be exhibited.

  The temperature of the substrate at the time of forming the magnetic recording layer 60 is desirably set to a temperature at which the degree of ordering of the ordered alloy is sufficiently high and does not cause an increase in grain size. More preferably, the temperature of the substrate is 400 ° C. or higher, preferably 400 ° C. to 700 ° C. Further, the power applied to the sputtering target at the time of forming the magnetic recording layer 60 is not particularly limited as long as it has a desired composition of the magnetic recording layer.

  In the method for manufacturing a magnetic recording medium, the thickness of the magnetic recording layer 60 is 4.2 to 19 nm, preferably 6.2 to 13 nm. Further, the thickness of the first magnetic layer 62 of the magnetic recording layer 60 is preferably thicker from the viewpoint of recording retention. For example, the film thickness of the first magnetic layer 62 is 4 to 16 nm, preferably 6 to 12 nm. The film thickness of the nonmagnetic grain boundary material layer 64 needs to be thick enough to protect, but is preferably thinner from the viewpoint of recording. The film thickness of the nonmagnetic grain boundary material layer 64 is 0.2 to 3 nm, preferably 0.2 to 1 nm.

  The ratio of the ordered alloy to the nonmagnetic grain boundary material is preferably vol%, and the ordered alloy: nonmagnetic grain boundary material = 90: 10 to 50:50. Further, at least one element (A) selected from the group consisting of Fe and Co, which is an ordered alloy material, and at least one element (B) selected from the group consisting of Pt, Pd, Au and Ir The ratio is at% and is preferably (A) :( B) = 42: 58 to 58:42. For example, in the case of an FePt ordered alloy, it is preferable that Fe (at%): Pt (at%) = 48:52 to 52:48.

  The magnetic recording layer 60 may have a structure in which more magnetic recording layers are stacked. For example, the magnetic recording layer 60 may have a structure in which a magnetic layer made of a material having a composition or a constituent element different from that of the first magnetic layer is further stacked on the first magnetic layer 62 as an additional layer. Good. In the present invention, the magnetic recording layer 60 may be provided with an additional layer such as a CAP layer.

  Step (c) is a step of forming the protective layer 80.

  The protective layer 80 can be formed using a material conventionally used in the field of magnetic recording media. Specifically, the protective layer 80 can be formed using a nonmagnetic metal such as Pt, a carbon-based material such as diamond-like carbon, or a silicon-based material such as silicon nitride. The protective layer 80 may be a single layer or may have a laminated structure. The laminated protective layer 80 may be, for example, a laminated structure of two types of carbon materials having different characteristics, a laminated structure of a metal and a carbon material, or a laminated structure of a metal oxide layer and a carbon material. Good. The protective layer 80 can be formed using any method known in the art such as a CVD method, a sputtering method including a DC magnetron sputtering method, and a vacuum deposition method.

  As described above, the method of manufacturing the magnetic recording medium includes at least the substrate 20, the first magnetic layer 62, the magnetic recording layer 60 on which the nonmagnetic grain boundary material layer 64 is formed, and the protective layer 80. A method of manufacturing a magnetic recording medium including the same. As described above, the nonmagnetic grain boundary material layer 64 has a function of an underlayer for improving the characteristics of the protective layer 80. This manufacturing method does not require a separate process for forming the nonmagnetic grain boundary material layer 64, and maintains a good granular structure of the first magnetic layer 62 while maintaining the nonmagnetic grain boundary on the first magnetic layer 62. A material layer 64 can be formed. By forming the protective layer 80 on the nonmagnetic grain boundary material layer 64, good magnetic head flying characteristics and corrosion resistance can be realized.

  Next, another embodiment of the magnetic recording medium will be described. The magnetic recording medium manufacturing method of this embodiment is also referred to as a magnetic recording medium manufacturing method of the second embodiment, a manufacturing method of the second embodiment, and the like.

  In this method of manufacturing a magnetic recording medium, step (b) of the manufacturing method of the first embodiment described above is performed by sputtering the elements constituting the ordered alloy and carbon (C) before forming the magnetic recording layer. The method further includes the step of forming a second magnetic layer.

More specifically, the method of manufacturing a magnetic recording medium is a method of a magnetic recording medium including at least a substrate, a magnetic recording layer including an ordered alloy and a nonmagnetic grain boundary material, and a protective layer.
(A) preparing the substrate;
(B) forming the magnetic recording layer,
(B-1) a step of forming a second magnetic layer by sputtering an element constituting the ordered alloy and carbon (C); and (b-2) an element constituting the ordered alloy and the non-magnetic. Sputtering a grain boundary material to form a first magnetic recording layer including a first magnetic layer and a book layer made of the nonmagnetic grain boundary material on the first magnetic layer;
A process including:
(C) forming the protective layer,
In the formation of the magnetic recording layer in the step (b), the gas pressure at the time of sputtering in the step (b-2) is set to 1.5 Pa or more, and the book made of the nonmagnetic grain boundary material in the step (b-2). A layer is formed on the first magnetic layer.

  With reference to FIG. 4, a method of manufacturing the magnetic recording medium will be described. In this manufacturing method, step (a) and step (c) are the same as the manufacturing method of the first embodiment described above.

  First, in the step (a), the substrate 20 is prepared similarly to the manufacturing method of the first embodiment (FIG. 4A).

  Step (b) is a step of forming the magnetic recording layer 60 (FIG. 4B). In this step, the magnetic recording layer 60 is formed by first forming the second magnetic layer 61 (step (b-1)), and then from the first magnetic layer 62 and the nonmagnetic grain boundary material of the first magnetic layer. The first magnetic recording layer 65 including the nonmagnetic grain boundary material layer 64 is formed (step (b-2)).

  In the step (b-1), the element constituting the ordered alloy and the carbon (C) which is a nonmagnetic grain boundary material are sputtered on the substrate 20 to form the second magnetic layer 61 (FIG. 4 ( b)).

The ordered alloy of the second magnetic layer is preferably an alloy containing at least one element selected from Fe, Co, Ni and the like and at least one element selected from Pt, Pd, Au, Cu, Ir and the like. More preferably, the ordered alloy is an L1 ₀ type alloy composed of a material selected from the group consisting of FePt, CoPt, FePd, and CoPd, and most preferably an L1 ₀ type FePt alloy.

Thus, in a particularly preferred embodiment, the second magnetic layer 61 is ordered alloy is L1 ₀ type FePt alloy, nonmagnetic grain boundary material surrounding the ordered alloy is carbon (C). In the present embodiment, since the first magnetic recording layer 65 are the same as those in the first embodiment is particularly preferred that an ordered alloy of the first magnetic recording layer 65 is L1 ₀ type FePt alloy, nonmagnetic The grain boundary material is preferably SiO ₂ . The ordered alloy of the second magnetic layer 61 is preferably the same as that of the first magnetic layer 62, but is not limited to this, and an element different from that of the first magnetic layer 62 may be used.

  The second magnetic layer 61 has a granular structure composed of an ordered alloy and a nonmagnetic grain boundary material made of carbon (C). The second magnetic layer 61 functions as a template layer, and the first magnetic layer 62 having a granular structure similar to the granular structure of the second magnetic layer 61 can be efficiently formed. In the present embodiment, the first magnetic recording layer 65 in which the nonmagnetic grain boundary material layer 64 is formed on the first magnetic layer 62 can be formed with high efficiency.

  Sputtering of an ordered alloy and carbon (C) can be carried out by a co-sputtering method using an ordered alloy target and a target of carbon (C) that is a nonmagnetic grain boundary material. For example, when the second magnetic layer 61 is formed of ordered alloy FePt and carbon (C), an ordered alloy target containing Fe and Pt in a predetermined ratio and a carbon (C) target can be used. Further, an Fe target and a Pt target may be used as the target of the ordered alloy. Alternatively, a target containing Fe, Pt, and C at a specific ratio may be used. The ratio of the ordered alloy in the second magnetic layer 61 and the ratio of carbon (C) which is a nonmagnetic grain boundary material can be controlled by adjusting the power applied to each target.

  Further, the gas pressure during sputtering when forming the second magnetic layer 61 is not particularly limited as long as it can realize a good granular structure of ordered alloy-carbon (C), but is preferably 1.0 Pa or more, More preferably, the pressure is 1.5 Pa or more. Moreover, Ar, N, etc. are preferable and the gas to be used has more preferable Ar.

  The temperature of the substrate during sputtering when forming the second magnetic layer 61 is desirably set to a temperature at which the degree of ordering of the ordered alloy is sufficiently high and does not increase the grain size. For example, the temperature of the substrate is 400 ° C. or higher, preferably 400 ° C. to 700 ° C. The power applied to the sputtering target when forming the second magnetic layer 61 is not particularly limited as long as the second magnetic layer 61 having a desired composition is formed.

  The proportion of carbon which is an ordered alloy and a non-magnetic grain boundary material is preferably vol%, and is ordered alloy: carbon = 90: 10 to 50:50. The ratio of at least one element (A) selected from the group consisting of Fe and Co, which is an ordered alloy, and at least one element (B) selected from the group consisting of Pt, Pd, Au, and Ir is: , At%, (A) :( B) = 42: 58 to 58:42 is preferable. For example, in the case of an FePt ordered alloy, Fe: Pt = 42: 58 to 58:42 is preferable, and Fe (at%): Pt (at%) = 48:52 to 52:48 is more preferable.

  Step (b-2) is a step of forming the first magnetic recording layer 65. This step (b-2) is the same as the step (b) which is the step of forming the magnetic recording layer 60 described in the manufacturing method of the first embodiment.

  In this manufacturing method, the magnetic recording layer 60 includes a first magnetic recording layer 65 including a first magnetic layer 62 and a nonmagnetic grain boundary material layer 64 made of a nonmagnetic grain boundary material of the first magnetic layer, and a first magnetic recording layer 65. 2 magnetic layer 61 is included at least. The first magnetic recording layer 65 is the same as that described as the magnetic recording layer 60 of the first embodiment. Therefore, the ordered alloy and the nonmagnetic grain boundary material surrounding the ordered alloy are as described in the first embodiment. In the magnetic recording medium of the present invention, when the first magnetic recording layer 65 is formed on the second magnetic layer 61, the magnetic particles of the second magnetic layer 61 and the magnetic particles of the first magnetic recording layer 65 are one to one. The magnetic recording layer 60 may be a so-called 1by1 grown and integrated magnetic recording layer 60.

  The film thicknesses of the first and second magnetic layers are preferably thicker from the viewpoint of record retention. The film thickness of the second magnetic layer is 4 nm or less, preferably 2 to 4 nm. If the thickness exceeds 4 nm, growth inhibition and secondary growth of the ordered alloy by carbon (C) occur. Next, the thickness of the first magnetic layer 62 is preferably 3 to 7 nm from the viewpoint of maintaining high magnetic anisotropy. The film thickness of the nonmagnetic grain boundary material layer 64 is 0.2 to 3.0 nm, preferably 0.2 to 1.0 nm.

  In the method for manufacturing a magnetic recording medium, the total film thickness of the magnetic recording layer 60 including the second magnetic layer 61 and the first magnetic recording layer 65 is not particularly limited. However, from the viewpoint of achieving both high productivity and high recording density, the total film thickness of the magnetic recording layer 60 is desirably at least 5 nm, preferably 8 nm. A more preferable film thickness of the magnetic recording layer 60 is 6 to 16 nm, and more preferably 8 to 11 nm.

  Next, step (c) is a step of forming the protective layer 80. The protective layer 80 can be formed in the same manner as the manufacturing method of the first embodiment.

  By forming the magnetic recording layer 60 by this manufacturing method, the first magnetic layer 62 of the ordered alloy-nonmagnetic grain boundary material on the ordered magnetic alloy-carbon (C) second magnetic layer 61, and the nonmagnetic grains. At least a nonmagnetic grain boundary material layer 64 made of a field material can be formed.

  According to the method for manufacturing a magnetic recording medium, the magnetic recording layer 60 including a plurality of magnetic layers on the substrate 20 has the first magnetic recording layer 65 having the nonmagnetic grain boundary material layer 64 formed as the uppermost layer. Thus, a magnetic recording medium in which the protective layer 80 is provided on the first magnetic recording layer can be manufactured. This manufacturing method does not require a separate step of forming the nonmagnetic grain boundary material layer 64, and forms the nonmagnetic grain boundary material layer 64 thereon while maintaining a good granular structure of each magnetic layer. be able to. Then, by forming a protective layer on this nonmagnetic grain boundary material layer, it is possible to achieve good magnetic head flying characteristics and corrosion resistance. The nonmagnetic grain boundary material layer 64 has a function of an underlayer for improving the performance of the protective layer 80. The thickness of the nonmagnetic grain boundary material layer 64 is preferably as thin as possible from the viewpoint of recording as long as the function of the underlayer of the protective layer can be exhibited.

Also, in the method of manufacturing a magnetic recording medium, the second magnetic layer 61 is formed in advance as a magnetic layer made of ordered alloy-carbon (C), and the ordered alloy-SiO ₂ or the like is formed on the second magnetic layer 61. By forming the first magnetic layer 62 of the ordered alloy-nonmagnetic grain boundary material, it is possible to increase the thickness of the entire magnetic recording layer 60 while maintaining high magnetic anisotropy.

  The magnetic recording layer 60 of this embodiment may have a structure in which more magnetic recording layers are stacked. For example, the magnetic recording layer 60 has a structure in which a plurality of the first magnetic layer and the second magnetic layer described above are stacked, and a nonmagnetic grain boundary material layer 64 is provided as the uppermost layer. Good. Alternatively, it has a structure in which a magnetic recording layer made of a material having a different composition or constituent element from those of the first magnetic layer and the second magnetic layer is further laminated, and the top layer is a non-magnetic grain. A field material layer 64 may be included. The magnetic recording layer 60 may have a structure in which, for example, a first magnetic layer, a second magnetic layer, and a first magnetic recording layer are stacked in this order. Furthermore, in the present invention, the magnetic recording layer 60 may be provided with an additional layer such as a CAP layer.

  As described above, the magnetic recording medium may optionally include various layers other than the magnetic recording layer. These layers are described below.

  An adhesion layer (not shown) that may be optionally provided is used to enhance adhesion between a layer formed on the adhesion layer and a layer formed below the adhesion layer. The layer formed below the adhesion layer includes the substrate 20. The material for forming the adhesion layer includes metals such as Ni, W, Ta, Cr, and Ru, and alloys containing the aforementioned metals. The adhesion layer may be a single layer or may have a laminated structure of a plurality of layers. The adhesion layer can be formed using any method known in the art such as sputtering and vacuum deposition.

  An optional soft magnetic backing layer (not shown) controls the magnetic flux from the magnetic head to improve the recording / reproducing characteristics of the magnetic recording medium. Materials for forming the soft magnetic underlayer include crystalline materials such as NiFe alloy, Sendust (FeSiAl) alloy, CoFe alloy, microcrystalline materials such as FeTaC, CoFeNi, CoNiP, and Co alloys such as CoZrNb and CoTaZr. Includes amorphous material. The optimum value of the thickness of the soft magnetic underlayer depends on the structure and characteristics of the magnetic head used for magnetic recording. When the soft magnetic backing layer is formed continuously with the other layers, it is preferable that the soft magnetic backing layer has a film thickness in the range of 10 nm to 500 nm (including both ends) in consideration of productivity. The soft magnetic backing layer can be formed using any method known in the art such as sputtering or vacuum deposition.

  When the magnetic recording medium of the present invention is used in a heat-assisted magnetic recording system, a heat sink layer (not shown) may be provided. The heat sink layer is a layer for effectively absorbing excess heat of the magnetic recording layer 60 generated during heat-assisted magnetic recording. The heat sink layer can be formed using a material having high thermal conductivity and specific heat capacity. Such a material includes Cu simple substance, Ag simple substance, Au simple substance, or an alloy material mainly composed of them. Here, “mainly” means that the content of the material is 50 wt% or more. Further, from the viewpoint of strength and the like, the heat sink layer can be formed using an Al—Si alloy, a Cu—B alloy, or the like. Furthermore, the heat sink layer can be formed using Sendust (FeSiAl) alloy, soft magnetic CoFe alloy, or the like. By using a soft magnetic material, the function of concentrating the perpendicular magnetic field generated by the head on the magnetic recording layer 60 can be imparted to the heat sink layer, and the function of the soft magnetic backing layer can be supplemented. The optimum value of the film thickness of the heat sink layer varies depending on the heat quantity and heat distribution during heat-assisted magnetic recording, the layer configuration of the magnetic recording medium, and the thickness of each component layer. In the case of continuously forming with other constituent layers, the thickness of the heat sink layer is preferably 10 nm or more and 100 nm or less in consideration of productivity. The heat sink layer can be formed using any method known in the art, such as a sputtering method or a vacuum evaporation method. Usually, the heat sink layer is formed using a sputtering method. The heat sink layer can be provided between the substrate 20 and the adhesion layer, between the adhesion layer and the underlayer, etc. in consideration of characteristics required for the magnetic recording medium.

  The underlayer (not shown) is a layer for controlling the crystallinity and / or crystal orientation of the seed layer 40 formed thereabove. The underlayer may be a single layer or a multilayer. The underlayer is preferably nonmagnetic. The nonmagnetic material used for forming the underlayer is at least one selected from the group consisting of Pt metal, Cr metal, or Cr, which is a main component, Mo, W, Ti, V, Mn, Ta, and Zr. Includes alloys with added metals. The underlayer can be formed using any method known in the art such as sputtering.

The function of the seed layer 40 is to control the grain size and crystal orientation of the ordered alloy magnetic crystal grains in the upper magnetic recording layer 60. The seed layer 40 may have a function of ensuring adhesion between the layer under the seed layer 40 and the magnetic recording layer 60. Further, another layer such as an intermediate layer may be disposed between the seed layer 40 and the magnetic recording layer 60. When an intermediate layer or the like is disposed, the grain size and crystal orientation of the ordered magnetic alloy grains of the magnetic recording layer 60 are controlled by controlling the grain size and crystal orientation of the ordered alloy magnetic crystal grains of the intermediate layer. It will take on the function. The seed layer 40 is preferably nonmagnetic. The material of the seed layer 40 is appropriately selected according to the material of the magnetic recording layer 60. More specifically, the material of the seed layer 40 is selected according to the ordered alloy material of the magnetic recording layer. For example, if the magnetic recording layer 60 is formed by L1 ₀ type ordered alloy, it is preferable to form the seed layer 40 by using a NaCl-type compounds. Particularly preferably, the seed layer 40 is formed using an oxide such as MgO or SrTiO ₃ or a nitride such as TiN. The seed layer 40 can also be formed by stacking a plurality of layers made of the above materials. From the viewpoint of improving the crystallinity of the magnetic crystal grains of the ordered alloy of the magnetic recording layer 60 and improving the productivity, the seed layer 40 preferably has a thickness of 1 nm to 60 nm, preferably 1 nm to 20 nm. The seed layer 40 can be formed using any method known in the art such as sputtering.

  Layers known in the art, such as adhesion layers, soft magnetic backing layers, heat sink layers, underlayers and / or seed layers, which are formed on the substrate prior to the formation of the above magnetic recording layers, In the method for manufacturing a magnetic recording medium, it may be formed before the step of forming the magnetic recording layer.

  In addition, optionally, the magnetic recording medium of the present invention may further include a liquid lubricant layer (not shown) provided on the protective layer 80. The liquid lubricant layer can be formed using a material conventionally used in the field of magnetic recording media. The material of the liquid lubricant layer includes, for example, a perfluoropolyether lubricant. The liquid lubricant layer can be formed using, for example, a coating method such as a dip coating method or a spin coating method.

  A layer known in the art such as a liquid lubricant layer placed on the protective layer 80 may be formed after the step (c) of forming the protective layer 80 in the method for manufacturing the magnetic recording medium. Good.

(Example)
Example 1
A chemically strengthened glass substrate (N-10 glass substrate manufactured by HOYA) having a smooth surface was washed to prepare a substrate 20. The cleaned substrate 20 was introduced into the sputtering apparatus.

  Next, each layer of the magnetic recording medium was formed with an in-line film forming apparatus without being released to the atmosphere. First, a Ta adhesion layer was formed on the substrate 20 with a film thickness of 5 nm by a DC magnetron sputtering method in an Ar atmosphere using a pure Ta target. The pressure of Ar gas during film formation was 0.5 Pa. Further, the temperature of the substrate during film formation was room temperature, and the DC power was 100 W.

  Next, a Cr underlayer was formed to a thickness of 20 nm by a DC magnetron sputtering method in an Ar atmosphere using a pure Cr target. The pressure of Ar gas during film formation was 0.25 Pa. Further, the temperature of the substrate during film formation was room temperature, and the DC power was 300 W.

  Next, the substrate was heated to 430 ° C., and a seed layer 40 having a thickness of 5 nm was formed by RF sputtering using an MgO target. The MgO layer as a seed layer was formed with an RF power of 200 W under the condition of Ar gas pressure of 0.1 Pa.

  Next, the second magnetic layer 61 was formed. The second magnetic layer is a FePt—C layer. First, the second magnetic layer 61 was formed by a co-sputtering method using an FePt alloy target and a C target while heating the substrate on which the above layers were formed to 430 ° C. A DC magnetron sputtering method was used for co-sputtering to form a second magnetic layer having a thickness of 2 nm. The FePt—C layer was formed by adjusting the power applied to the target to 40 W for the FePt alloy target and 210 W for the C target. With this power, an FePt-C layer of FePt (60 vol%)-C (40 vol%) was obtained. The FePt alloy target is prepared such that the FePt of the FePt-C layer has a composition of Fe (at%): Pt (at%) = 50:50.

Next, the first magnetic recording layer 65 was formed. The first magnetic recording layer 65 of this embodiment includes a first magnetic layer 62 of FePt—SiO ₂ layer and a nonmagnetic grain boundary material layer 64 made of SiO ₂ . The first magnetic recording layer 65 was formed by co-sputtering using an FePt alloy target and a SiO ₂ target. Here, a DC magnetron sputtering method using a power of 40 W was used for FePt, and a RF sputtering method using a power of 200 W was used for SiO ₂ . With this electric power, an FePt—SiO ₂ layer of FePt (70 vol%) — SiO ₂ (30 vol%) was obtained. The FePt alloy target is prepared so that the FePt of the FePt—SiO ₂ layer has a composition of Fe (at%): Pt (at%) = 50:50. The thickness of the obtained first magnetic recording layer 65 was 6 nm.

  The pressure of Ar gas when forming the first magnetic recording layer and the second magnetic layer was adjusted to three types of 1.0 Pa, 1.5 Pa, and 3.0 Pa.

  Next, a 2 nm thick Pt protective layer was formed by DC magnetron sputtering using a Pt target under an Ar gas pressure of 0.5 Pa. The temperature of the substrate during film formation was room temperature, and the power during sputtering was 50 W. A magnetic recording medium was obtained by the above procedure.

  The conditions for film formation of the magnetic recording medium are summarized in the following table.

(result)
About each magnetic recording medium obtained on the said conditions, the cross-sectional TEM image was measured with the transmission electron microscope (TEM), and the particle structure of the magnetic recording medium was confirmed. The results are shown in FIG. As shown in FIG. 5, a nonmagnetic grain boundary material layer made of SiO ₂ is formed on the FePt—SiO ₂ layer when the Ar gas pressure during film formation of FePt—SiO ₂ is 1.5 Pa or more. I understood. In FIG. 5, consisting of SiO ₂ nonmagnetic grain boundary material layer, indicated as "SiO ₂ thin film". In the case of this example, the magnetic recording layer was integrated by so-called 1-by 1 growth in which the magnetic particles of the second magnetic layer and the magnetic particles of the first magnetic recording layer were grown one-to-one.

  In the method for manufacturing a magnetic recording medium, a nonmagnetic grain boundary material layer is formed on the uppermost part of the magnetic recording layer when the Ar gas pressure during the formation of the magnetic recording layer is 1.5 Pa or more. Then, by providing a protective layer on the nonmagnetic grain boundary material layer, a magnetic recording medium including a protective layer having good magnetic head floating properties and excellent corrosion resistance can be formed.

20 substrate 40 seed layer 60 magnetic recording layer 61 second magnetic layer 62 first magnetic layer 64 nonmagnetic grain boundary material layer 65 first magnetic recording layer 80 protective layer

Claims (5)

A method for producing a magnetic recording medium comprising a substrate, a magnetic recording layer containing an ordered alloy and a nonmagnetic grain boundary material, and a protective layer,
(A) preparing the substrate;
(B) Sputtering the elements constituting the ordered alloy and the nonmagnetic grain boundary material to include a first magnetic layer and a book layer made of the nonmagnetic grain boundary material on the first magnetic layer. Forming a magnetic recording layer;
(C) forming the protective layer,
In the formation of the magnetic recording layer in the step (b), the gas pressure during sputtering is set to 1.5 Pa or more, and the book layer made of the nonmagnetic grain boundary material is formed on the first magnetic layer. A method of manufacturing a magnetic recording medium.   The step (b) further includes a step of forming a second magnetic layer by sputtering an element constituting the ordered alloy and carbon (C) before forming the magnetic recording layer. Item 2. A method for manufacturing a magnetic recording medium according to Item 1.   2. The ordered alloy includes at least one element selected from the group consisting of Fe and Co and at least one element selected from the group consisting of Pt, Pd, Au, and Ir. Or the manufacturing method of the magnetic-recording medium of Claim 2. The nonmagnetic grain boundary material includes at least one material selected from the group consisting of C, B, Ag, Ge, W, SiO ₂ , Al ₂ O ₃ , TiO ₂ , GeO _2, and B ₂ O _3. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic recording medium. 5. The method of manufacturing a magnetic recording medium according to claim 1, wherein the ordered alloy is FePt, and the nonmagnetic grain boundary material is SiO ₂ .