Method for manufacturing magnetic disk, magnetic disk, and magnetic disk precursor

Abstract

A magnetic disk for a hard disk drive device comprises a substrate, a magnetic recording layer, and a heat insulating layer disposed between the substrate and the magnetic recording layer. The heat insulating layer allows even a substrate with low heat resistance to be used as a substrate for a magnetic disk that can withstand heat treatment (high temperature annealing).

Description

Technical Field

[0001] The present invention relates to a magnetic disk for a hard disk drive device, a precursor thereof, and a method for manufacturing the magnetic disk. Background Art

[0002] With the recent rise of cloud computing, a large number of hard disk drive devices are being used in cloud-oriented data centers to increase storage capacity.

[0003] In order to improve the recording density as a means of increasing storage capacity, heat-assisted magnetic recording (hereinafter referred to as HAMR) and microwave-assisted magnetic recording (hereinafter referred to as MAMR) have been proposed as recording methods for magnetic disks.

[0004] HAMR and MAMR are methods that temporarily weaken the coercive force of a magnetic recording layer by applying energy such as heat or microwaves. The magnetic recording head then reverses the magnetization of the recording layer, allowing information to be written into the recording layer. Therefore, these methods are collectively referred to as energy-assisted magnetic recording (EAMR).

[0005] As such an EAMR-oriented magnetic disk, a magnetic recording medium for thermally assisted recording having a structure in which a magnetic recording layer is stacked on a non-magnetic substrate and a heat insulating layer is stacked on the non-magnetic substrate is known (Patent Document 1). The magnetic recording medium has a structure in which a laminated body is provided on a non-magnetic substrate, and the laminated body includes at least a magnetic recording layer, a heat insulating layer, a carbon-based protective layer, and a lubricating layer in this order. According to this magnetic recording medium, since a heat insulating layer is provided between the magnetic recording layer and the carbon-based protective layer, heating of the lubricating layer and the protective layer located on the upper layer thereof due to energy such as heat and microwaves imparted to the magnetic recording layer during magnetic recording is suppressed, and degradation of the performance of the lubricating layer and the protective layer is suppressed, thereby providing a magnetic recording medium with better durability and reliability.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-153012 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, when manufacturing a magnetic disk for EAMR, a magnetic film that becomes a magnetic recording layer is formed on a substrate, and the magnetic film is heat-treated, so that the magnetic film can be made into the best magnetic recording layer for EAMR. The magnetic recording layer uses a magnetic material that exhibits high coercive force even in a small size. For example, FePt-based alloys or CoPt-based alloys are used as the magnetic material of the magnetic film that becomes the magnetic recording layer, and these magnetic films formed by sputtering or the like are heat-treated (high-temperature annealing), thereby obtaining a magnetic recording layer of Fe-Pt or Co-Pt containing a prescribed magnetic layer structure, such as an L10-type ordered structure (also called "L10-type crystal structure"). Such a magnetic recording layer is expected to have a high magnetic anisotropy constant Ku, for example, 10 7 [erg / cm 3 ]above.

[0011] However, in the heat treatment (high-temperature annealing) used to obtain the magnetic layer structure, the magnetic film is heated to a high temperature, for example, above 600°C, so the substrate is also heated to a high temperature at the same time as the magnetic film. Typically, aluminum alloy substrates (for example, Al-Mg alloy substrates) and glass substrates are often used as substrates for magnetic disks. However, most of the substrates used in the past have low heat resistance. Such substrates with low heat resistance are easily thermally deformed by the above-mentioned heat treatment (high-temperature annealing), making them unsuitable for use as substrates for EAMR magnetic disks. Therefore, there is a problem that substrates for EAMR magnetic disks are limited to substrates with high heat resistance.

[0012] Therefore, the object of the present invention is to provide a disk precursor that can be used as a substrate for a disk, a disk as a product thereof, and a method for manufacturing a disk, even if the substrate has low heat resistance and cannot withstand the temperature conditions of high-temperature annealing during disk manufacturing.

[0013] Means for solving problems

[0014] One embodiment of the present invention is a method for manufacturing a magnetic disk, comprising the following steps:

[0015] manufacturing a magnetic disk precursor, the magnetic disk precursor comprising a substrate, a magnetic film, and a heat insulating layer disposed between the substrate and the magnetic film; and

[0016] The magnetic anisotropy constant Ku of the magnetic film is increased by performing heat treatment so that the temperature of the magnetic disk precursor on the surface side of the heat insulating layer is higher than the temperature of the heat insulating layer on the substrate side.

[0017] The heat treatment is preferably performed by irradiating the magnetic film with the laser beam focused on the magnetic film.

[0018] The heat treatment is preferably performed by irradiating the magnetic film with the laser beam focused on the magnetic film.

[0019] The heat-insulating layer preferably contains a metal oxide having a thermal conductivity of 40 [W / (m·K)] or less as a main component.

[0020] Furthermore, another aspect of the present invention is a magnetic disk including a substrate, a magnetic recording layer, and a heat insulating layer provided between the substrate and the magnetic recording layer.

[0021] The thermal conductivity of the main component of the heat-insulating layer is preferably 40 [W / (m·K)] or less.

[0022] The main component of the heat-insulating layer is preferably a metal oxide.

[0023] The magnetic recording layer preferably has an L10 type crystal structure.

[0024] In addition, the thickness of the magnetic disk is preferably 0.5 mm or less.

[0025] The heat-insulating layer contains 80% by weight or more of SiO2 and has a film thickness of 5 nm or more.

[0026] Another aspect of the present invention is a magnetic disk precursor including: a substrate; a magnetic film before heat treatment, which becomes a magnetic recording layer of a magnetic disk by the heat treatment; and a heat insulating layer provided between the substrate and the magnetic film.

[0027] The thermal conductivity of the main component of the heat-insulating layer is preferably 40 [W / (m·K)] or less.

[0028] The main component of the heat-insulating layer is preferably a metal oxide.

[0029] The magnetic recording layer preferably includes a FePt-based alloy or a CoPt-based alloy.

[0030] Effects of the Invention

[0031] According to the magnetic disk, magnetic disk precursor, and magnetic disk manufacturing method described above, even a substrate having low heat resistance can be used as a substrate for a magnetic disk that can withstand heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a perspective view of the appearance of an example of a substrate of the EAMR magnetic disk according to the present embodiment.

[0033] Figure 2 This is a diagram showing an example of a laminated structure formed on the main surface of the EAMR magnetic disk according to the present embodiment. DETAILED DESCRIPTION

[0034] The magnetic disk, magnetic disk precursor, and magnetic disk manufacturing method of the present invention are described in detail below. In the following embodiments, an EAMR magnetic disk is used as an example. However, the magnetic disk of the present invention is not limited to EAMR magnetic disks and may also be a magnetic disk using a conventional recording method in which information is written by reversing the magnetization of the magnetic recording layer without supplying energy such as heat or microwaves to the magnetic recording layer.

[0035] Figure 1 This is a perspective view of an example of a substrate of a magnetic disk for EAMR (hereinafter referred to as a magnetic disk) according to one embodiment. Figure 2 1 is a diagram showing an example of a laminated structure formed on a substrate of a magnetic disk according to one embodiment. Figure 1 As shown, the magnetic disk 10 is in the shape of a ring having a pair of main surfaces. Specifically, the magnetic disk 10 has a circular outer peripheral shape and a circular inner peripheral shape provided with a circular inner hole concentric with the circle.

[0036] A multilayered portion 18 including a magnetic recording layer 18a is formed on the main surfaces 11p and 12p on both sides of the substrate 14 of the magnetic disk 10 (see Figure 2 ), the magnetic recording layer 18a is used to function as a magnetic disk. Figure 2 As shown, a heat insulating layer 16 is provided between the multi-layered stack 18 provided on the substrate 14 and the substrate 14. That is, the magnetic disk 10 includes the substrate 14, the magnetic recording layer 18a, and the heat insulating layer 16 provided between the substrate 14 and the magnetic recording layer 18a.

[0037] The substrate 14 is, for example, an Al-Mg alloy substrate. A coating film, such as a Ni-based alloy, is typically formed on the surface of the Al-Mg alloy substrate. Examples of the Ni-based alloy include Ni-P alloy and Ni-PW alloy. The thickness of the Ni-based alloy coating film on one main surface is, for example, 1 μm to 20 μm. In this specification, unless otherwise specified, the term "Al-Mg alloy substrate" refers to an Al-Mg alloy substrate having a Ni-based coating film on its surface. A glass substrate made of crystallized glass or amorphous glass may be used in place of the Al-Mg alloy substrate. Providing a heat-insulating layer 16 between the substrate 14 and the magnetic recording layer 18a allows the use of Al-Mg alloy substrates that have low heat resistance and cannot withstand the temperature conditions of conventional heat treatment (high-temperature annealing), or glass substrates with a relatively low glass transition temperature of 600°C or less, as the substrate 14. Furthermore, a glass plate with high heat resistance, such as one with a glass transition temperature exceeding 600°C, may also be used as the substrate 14. In this way, there is no restriction on the temperature conditions of the heat treatment, and even a substrate with low heat resistance that could not be used conventionally can be used as the substrate 14 .

[0038] An example of the multi-layered laminated portion 18 will be described below, but the invention is not limited to the following example.

[0039] The multi-layer laminated portion 18 has the following structure: a close contact layer, a soft magnetic layer, a heat dissipation layer, a seed layer, a base layer, a magnetic recording layer 18a, a protective layer and a lubricant layer are stacked from the substrate 14 (or the heat insulating layer 16) side. Therefore, the heat insulating layer 16 is in contact with the close contact layer. Figure 2 In FIG, only the magnetic recording layer 18a is shown for simplicity.

[0040] The adhesion layer is used to improve adhesion between the heat dissipation layer and the underlying thermal insulation layer 16 and is provided as needed. Amorphous alloy materials such as CrTi or NiTa are preferably used for the adhesion layer. Alternatively, another adhesion layer may be provided between the thermal insulation layer 16 and the substrate 14.

[0041] The soft magnetic layer is used to temporarily form a magnetic path during recording, allowing a strong magnetic flux to pass through the recording layer in a perpendicular direction in the perpendicular magnetic recording method. The soft magnetic layer can be composed of cobalt alloys such as CoTaZr, Co-Fe alloys such as CoCrFeB and CoFeTaZr, etc.

[0042] The heat sink layer rapidly dissipates heat from the magnetic recording layer 18a, which is heated by the energy supplied during magnetic recording. Metal materials with high thermal conductivity, such as Cr, Ag, Al, Cu, W, and Mo, are used for this layer. A heat sink layer is provided as needed. However, even with a heat sink layer, during the high-temperature annealing process used to form the magnetic recording layer 18a by structuring the atomic arrangement within the magnetic film during disk manufacturing, heat supplied to the magnetic film is not sufficiently dissipated within the heat sink layer and flows to the substrate 14, causing the substrate 14 to easily reach a high temperature. Therefore, a thermal insulation layer 16 is provided. When a heat sink layer is provided, it is preferably positioned between the heat sink layer and the substrate 14. This prevents deformation of the substrate during the high-temperature annealing of the magnetic film and rapidly dissipates heat from the magnetic recording layer 18a, which is heated by the energy supplied during magnetic recording. The thermal conductivity of the material used for the heat sink layer is, for example, 100 [W / (m·K)] or higher. Using such a material as the main component of the heat sink layer allows the aforementioned effects to be fully achieved during energy-assisted magnetic signal recording and high-temperature annealing of the magnetic film.

[0043] The seed layer offsets the crystal orientation of the lower layer and makes the crystal orientation of the upper foundation layer into a predetermined direction. For example, an alloy material such as CrTi, NiTa, or AlTi is used for the seed layer.

[0044] The base layer controls the grain size, crystal orientation, flatness, etc. of the magnetic recording layer 18a, thereby improving the characteristics of the magnetic recording layer 18a. The base layer can be composed of a single layer (e.g., MgO, Ru) or a multilayer. In the case of a multilayer structure, for example, it can include a nitride base layer (e.g., TaN, NbN, HfN, AlN) and an oxide base layer (e.g., MgO). In addition, although MgO is an oxide, its thermal conductivity exceeds 40 [W / (m·K)], so it is not preferred as a heat insulating layer in the present invention.

[0045] In addition, a BCC base layer may be further provided as part of the base layer. The BCC base layer is a layer that controls the orientation of the magnetic recording layer 18a. The BCC base layer, for example, contains Cr, Mo, Nb, Ta, V, and W, or contains at least one of Mn, Mo, Ru, Ti, V, and W with Cr as the main component, and has a (100) orientation in the BCC structure. In addition, in this specification and claims, the main component refers to a substance (element, compound, etc.) with a content of 50% by weight or more, preferably 60% by weight or more, or a content of 50 mol% or more, preferably 60 mol% or more. Here, in the absence of a substance with a content of 50% by weight or more or 50 mol% or more, the main component refers to the substance with the highest content.

[0046] The magnetic recording layer 18a is, for example, a layer whose main component is an alloy having an L10 type ordered structure. The magnetic recording layer 18a is preferably formed by magnetic particles of several nm separated by grain boundary segregation materials, but if the volume of the magnetic particles becomes too small, the written magnetic signal is easily affected by heat and becomes unstable. Therefore, the magnetic recording layer 18a uses a magnetic recording layer with an L10 type ordered structure with a high magnetic anisotropy constant Ku. For example, the main component is an FePt alloy or a CoPt alloy. Furthermore, the magnetic recording layer 18a may also contain at least one oxide or element selected from SiO2, TiO2, Cr2O3, Al2O3, Ta2O5, ZrO2, Y2O3, CeO2, MnO, TiO, ZnO, and C as an additive. When these are added, the magnetic recording layer 18a easily becomes a granular structure, which can make the magnetic particles miniaturized and improve the S / N ratio (signal / noise ratio) characteristics of the EAMR disk. The film thickness of the magnetic recording layer 18a can be set to, for example, 5 to 20 nm.

[0047] The protective layer is made of a material with excellent mechanical durability and heat resistance, and protects the portion of the multilayered stack 18 that is located below the protective layer. For example, the protective layer is a single or multilayer carbon layer. DLC (diamond-like carbon) to which hydrogen, nitrogen, or a metal is added is preferably used as the carbon layer. The carbon layer is formed, for example, by CVD or ion beam deposition.

[0048] The lubricant layer is provided to improve lubricity and wear resistance when the magnetic head and the surface of the magnetic disk slide against each other, and is made of, for example, perfluoropolyether.

[0049] The thermal insulation layer 16 is provided between the magnetic recording layer 18a and the substrate 14. The thermal insulation layer 16 is more preferably provided between the multi-layer laminate 18 and the substrate 14. The thermal insulation layer 16 preferably uses a material having a thermal conductivity of 40 [W / (m·K)] or less. The thermal conductivity of the material used for the thermal insulation layer 16 is more preferably 30 [W / (m·K)] or less, more preferably 20 [W / (m·K)] or less, and further preferably 10 [W / (m·K)] or less. By using these materials with low thermal conductivity as the main component of the thermal insulation layer 16, it is possible to appropriately suppress the heat used for heat treatment of the magnetic film from being conducted to the substrate, and as a result, deformation of the substrate due to heat can be suppressed. Such a thermal insulation layer 16 preferably contains a metal oxide such as Al2O3 or SiO2 as a main component. According to various documents, regarding thermal conductivity (unit: W / (m·K)), for example, Al2O3 is 21, SiO2 is 1.38 (300K), polycrystalline TiO2 is 8.4 (300K), and ZrO2 (zirconium oxide) is 4.0. From the viewpoint of improving the thermal insulation effect, the material forming the thermal insulation layer 16 preferably contains an amorphous structure. The thickness of the thermal insulation layer 16 is preferably greater than 2nm. In the case where the thickness of the thermal insulation layer 16 is less than 2nm, the thermal insulation layer 16 is formed in an island shape and gaps are generated, and the thermal insulation effect may be insufficient. In addition, after being formed into a "layer" once, the thicker it is, the greater the thermal insulation effect. Therefore, the thickness of the thermal insulation layer 16 is more preferably greater than 15nm, more preferably greater than 20nm, and further preferably greater than 50nm. In addition, it is preferably greater than 20% of the thickness of the magnetic recording layer 18a. The upper limit of the film thickness of the thermal insulation layer 16 does not need to be specifically set, but from the viewpoint of productivity, it can be set to, for example, less than 500nm.

[0050] Based on the above perspectives, several preferred examples of the structure of the thermal insulation layer 16 are listed below. When Al2O3 is used as the main component of the thermal insulation layer 16, the thermal insulation layer 16 preferably contains 80% by weight or more of Al2O3 and has a thickness of preferably 10 nm or more, more preferably 20 nm or more. Furthermore, when SiO2 is used as the main component of the thermal insulation layer 16, the thermal insulation layer 16 preferably contains 80% by weight or more of SiO2 and has a thickness of preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more.

[0051] The heat-insulating layer 16 can be formed by various film-forming techniques such as sputtering, CVD, and electron beam deposition, and film-quality modification techniques such as ion implantation.

[0052] On the other hand, the total film thickness below the magnetic film (on the substrate side) in the laminated portion 18 is preferably at least 30 nm, more preferably at least 40 nm. If the total film thickness is less than 30 nm, and if the thermal insulation layer contains an oxide as a main component, the crystal orientation of the magnetic film cannot be fully improved, and the Ku of the magnetic recording layer may decrease after heat treatment.

[0053] The magnetic recording layer 18a is a layer having a portion with an ordered atomic arrangement structure, for example, by heat treatment (high temperature annealing) of a magnetic film formed by sputtering or the like. The magnetic anisotropy constant Ku of the magnetic recording layer 18a is high, for example, 10 7 [erg / cm 3 ] or more, preferably 2×10 7 [erg / cm 3 ] or more layers. When the magnetic film is composed of a FePt alloy or a CoPt alloy, an L10-type ordered structure magnetic recording layer 18a can be formed. In addition, the ordered structure of the alloy is not limited to the L10 type, and other ordered structures may also be used.

[0054] Conventionally, during the heat treatment (high-temperature annealing) for forming an ordered structure, the substrate 14 also reached a high temperature, often reaching a temperature of, for example, 600°C or higher. In this case, the heat-resistant temperature of an Al-Mg alloy substrate is relatively low, at approximately 300°C, making it unsuitable for use as a substrate for a magnetic disk 10 having a magnetic recording layer 18a having a high Ku. In contrast, by providing the heat-insulating layer 16 between the magnetic film before it becomes the magnetic recording layer 18a and the substrate 14, even when heat-treated under the temperature conditions of the aforementioned heat treatment (high-temperature annealing), the substrate 14 is less likely to reach a high temperature, for example, 600°C or higher, thereby suppressing deformation of the substrate 14 and deterioration in its flatness. Consequently, substrates with low heat resistance, such as Al-Mg alloy substrates, which were previously difficult to use, can be used as the substrate 14.

[0055] In addition, in the above-mentioned embodiment, the position where the heat insulating layer 16 is provided is between the close-contact layer in the multi-layer stacking portion 18 and the substrate 14, but it is not necessarily limited to this position. As long as the flatness of the substrate 14 does not deteriorate due to high-temperature annealing, the position where the heat insulating layer 16 is provided can be at least between the magnetic recording layer 18a and the substrate 14. In addition, here, the flatness does not deteriorate, specifically, for example, means that the increase in the flatness of the substrate 14 caused by the heat treatment is less than 30 μm. In other words, the difference between the flatness of the substrate 14 after the heat treatment and the flatness of the substrate 14 before the heat treatment is less than 30 μm. The smaller the increase (or difference) in the flatness of the above-mentioned substrate, the better, more preferably less than 10 μm. Here, flatness refers to the PV (Peak to Valley) value at a specified plane.

[0056] Therefore, before manufacturing such an EAMR disk, that is, before heat treatment, the EAMR disk precursor includes a substrate 14; a magnetic film before heat treatment, which becomes an energy-assisted magnetic recording layer 18a by heat treatment; and a heat insulating layer provided between the substrate 14 and the magnetic film.

[0057] Figure 1 The dimensions of the magnetic disk 10 shown are not particularly limited, and are, for example, equivalent to the dimensions of a magnetic disk with a nominal diameter of 2.5 inches or 3.5 inches. In the case of a magnetic disk with a nominal diameter of 2.5 inches, the outer diameter (diameter) is 55-70 mm, for example, the outer diameter (diameter) is 65 mm or 67 mm, the inner hole diameter (diameter) is 20 mm, and the plate thickness is 0.3-1.3 mm. In the case of a magnetic disk with a nominal diameter of 3.5 inches, the outer diameter is 85-100 mm, for example, the outer diameter is 95 mm or 97 mm, the inner hole diameter is 25 mm, and the plate thickness is 0.3-1.8 mm. In addition, if the plate thickness is less than 0.5 mm, the flatness of the substrate is likely to deteriorate during heat treatment, but by providing the heat insulating layer 16 of the present invention, the deterioration of the above-mentioned flatness can be suppressed. Therefore, the present invention is preferably applicable to substrates with a plate thickness of 0.5 mm or less. In addition, the values of the diameter and plate thickness related to the dimensions of the magnetic disks are all nominal values. That is, during mass production, dimensional deviations of several tens of micrometers may be included in the positive and negative directions around the nominal value.

[0058] In such a method for manufacturing a magnetic disk 10, the aforementioned precursor is prepared, and the magnetic film of the precursor on the surface side closer to the main surfaces 11p, 12p than the thermal insulation layer 16 is heat-treated, thereby increasing the magnetic anisotropy constant Ku of the magnetic film. This allows the magnetic film to become a magnetic recording layer with a high Ku that is optimal for the energy-assisted magnetic recording layer 18a. Furthermore, the heat treatment can be performed at any time, as long as it is after the thermal insulation layer is formed. For example, the magnetic film can be heat-treated after the thermal insulation layer is formed and before the protective layer is formed. Alternatively, the heat treatment can be performed while the magnetic film is being formed.

[0059] The method for heat treating (high-temperature annealing) the magnetic film is not particularly limited, but is preferably performed by irradiating the magnetic film (inside) with a laser from the surface side of the substrate. In particular, when the magnetic film has a protective layer on top, laser irradiation from the surface side allows the laser to be focused on the portion (depth) of the magnetic film inside (in other words, aligning the laser focus with the position of the magnetic film). This allows efficient heating and annealing of the magnetic film. By rotating the substrate 14 while scanning the laser along the circumference of the substrate 14, the entire main surface of the substrate can be easily irradiated with the laser. Furthermore, spiral scanning of the laser is preferred because it allows for more efficient and uniform heat treatment of the entire main surface. Alternatively, a laser beam with a spot diameter adjusted to approximately 0.5 to 5.0 mm on the main surface of the substrate can be used for spiral scanning. Alternatively, the substrate can be fixed and the laser spot moved as a method for spiral laser irradiation. Furthermore, heat treatment can be performed without rotating the substrate by using a laser beam with an irradiation spot diameter that is larger than the substrate diameter.

[0060] In this way, by performing heat treatment on the surface side of the magnetic disk precursor closer to the thermal insulation layer (i.e., performing heat treatment with the surface side closer to the thermal insulation layer as the target), the magnetic anisotropy constant Ku of the magnetic film can be increased, and the temperature rise on the substrate side (inner side) closer to the thermal insulation layer can be suppressed, thereby reducing the deformation of the substrate caused by heat.

[0061] In other words, by performing heat treatment in such a manner that the temperature of the disk precursor on the surface side relative to the thermal insulation layer is higher than the temperature on the substrate side relative to the thermal insulation layer, the magnetic anisotropy constant Ku of the magnetic film can be increased, and the temperature rise on the substrate side (inner side) relative to the thermal insulation layer can be suppressed, thereby reducing the deformation of the substrate caused by heat.

[0062] The laser used for heating may be appropriately selected from, for example, CO 2 laser, YAG laser, fiber laser, semiconductor laser, etc., taking into consideration the material of the substrate surface and the like.

[0063] In addition to the above-mentioned method, the substrate may be heated by heat radiation using a lamp heater, etc. The heat insulating layer 16 can block or alleviate the flow of heat from the heated magnetic film to the substrate 14 .

[0064] (Example)

[0065] Two types of EAMR disk precursors were prepared using an Al-Mg alloy substrate with a NiP alloy coating on its surface and a glass substrate with a glass transition temperature (Tg) of 500°C as substrate 14. Specifically, a 20nm thick thermal insulation layer 16 composed of Al2O3 was formed on the surface of substrate 14 by sputtering, and then the aforementioned laminated portion 18 was sequentially formed using a prescribed film formation process. The magnetic film was formed by sputtering an FePt-based alloy to a thickness of approximately 10nm. The dimensions of the precursors corresponded to the nominal 3.5-inch dimensions of an EAMR disk (outer diameter: 95mm, inner hole diameter: 25mm, plate thickness: 0.635mm).

[0066] The precursors are irradiated with laser light focused on the magnetic films on their main surfaces. The substrate 14 is rotated while irradiating the laser light, so that the laser irradiation position is spirally scanned around the substrate 14, thereby heat-treating (high-temperature annealing) the magnetic films on the main surfaces.

[0067] The magnetic film subjected to this heat treatment becomes a layer having an Fe-Pt L10-type ordered structure, namely, the magnetic recording layer 18a. The change in flatness of the substrate 14 before and after the heat treatment was less than 10 μm. In contrast, the change in flatness before and after the heat treatment when the thermal insulation layer 16 was not provided was greater than 30 μm. The flatness was measured using an optical flatbed (optical interferometry surface profilometer).

[0068] Next, similar to the above-described embodiment, two types of EAMR magnetic disk precursors were prepared, using an Al-Mg alloy substrate and a glass substrate as substrate 14, except that the thermal insulation layer 16 was made of 15 nm thick SiO2 and the substrate 14 was set to 0.500 mm thick. The magnetic films were then heat-treated. As a result, the heat-treated magnetic film became a magnetic recording layer 18a having an Fe-Pt L10-type ordered structure. The change in flatness of the substrate 14 before and after the heat treatment was less than 30 μm.

[0069] Through these experiments, it was confirmed that the heat-insulating layer 16 is effective in improving the heat resistance of the substrate 14 during heat treatment.

[0070] The magnetic disk, magnetic disk precursor, and magnetic disk manufacturing method of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications are possible without departing from the spirit of the present invention.

[0071] Description of Reference Numerals

[0072] 10EAMR disk

[0073] 11p, 12p main surface

[0074] 14 substrates

[0075] 16 insulation layers

[0076] 18-layer stacking unit

[0077] 18a magnetic recording layer

Claims

1. A method for manufacturing a perpendicular magnetic disk, wherein: The following steps are involved: preparing a perpendicular magnetic disk precursor having a doughnut-shaped substrate, a soft magnetic layer provided on the substrate, and a magnetic film as a magnetic recording layer; and heat-treating the magnetic film of the perpendicular magnetic disk precursor, The heat treatment increases the magnetic anisotropy constant Ku of the magnetic film. The heat treatment is performed by rotating the substrate while scanning the laser light along the circumference of the substrate, or fixing the substrate while moving the laser spot, and irradiating the main surface of the perpendicular magnetic disk precursor with the laser light in a spiral or helical shape in the circumference of the substrate. The change in flatness of the substrate before and after the heat treatment is 30 μm or less.

2. The method for manufacturing a perpendicular magnetic disk according to claim 1, wherein: The heat treatment is performed by irradiating the magnetic film with the laser beam focused on the magnetic film.

3. The method for manufacturing a perpendicular magnetic disk according to claim 1, wherein: The spot diameter of the laser on the main surface of the substrate is 0.5 mm to 5.0 mm.

4. The method for manufacturing a perpendicular magnetic disk according to claim 2, wherein: The spot diameter of the laser on the main surface of the substrate is 0.5 mm to 5.0 mm.

5. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The substrate is an aluminum alloy substrate or a glass substrate having a Ni-based alloy plating film on the surface.

6. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The magnetic disk precursor includes a heat insulating layer between the substrate and the magnetic film.

7. The method for manufacturing a perpendicular magnetic disk according to claim 6, wherein: The thermal conductivity of the main component of the heat-insulating layer is 40 [W / (m·K)] or less.

8. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The magnetic film includes a FePt-based alloy or a CoPt-based alloy.

9. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The magnetic film after the heat treatment has an L10 type crystal structure.

10. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The substrate has a thickness of 0.5 mm or less.

11. The method for manufacturing a perpendicular magnetic disk according to any one of claims 1 to 4, wherein: The magnetic disk is a magnetic disk for energy-assisted magnetic recording.

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