JP4102221B2 - Method for manufacturing magnetic recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a perpendicular magnetic recording type magnetic recording medium and a manufacturing method thereof.
[0002]
[Prior art]
As the amount of information processing in a computer system increases, storage capacity such as a hard disk is required to increase. In recent years, perpendicular magnetic recording type magnetic recording media have attracted attention in order to satisfy such requirements. The perpendicular magnetic recording type magnetic recording medium is disclosed in, for example, the following Patent Documents 1 to 4.
[0003]
[Patent Document 1]
JP-A-52-134706
[Patent Document 2]
JP-A-7-129953
[Patent Document 3]
JP 2001-283419 A
[Patent Document 4]
JP 2002-358615 A
[0004]
FIG. 9 shows a magnetic disk X2 which is an example of a conventional magnetic recording medium of a perpendicular magnetic recording system. In FIG. 9, a partial perspective view of the magnetic disk X2 is shown together with the magnetic head H for recording. The magnetic disk X2 includes a substrate S, a recording magnetic layer 31, a soft magnetic layer 32, an intermediate layer 33, and a protective film 34. Each layer and film is formed by laminating the soft magnetic layer 32, the intermediate layer 33, the recording magnetic layer 31, and the protective film 34 in this order from the substrate S side.
[0005]
The recording magnetic layer 31 is a perpendicular magnetization film that is magnetized with an easy magnetization axis in a direction perpendicular to the film surface of the magnetic film constituting the layer. The soft magnetic layer 32 is an in-plane magnetization film that is made of a magnetic film having a high magnetic permeability and is magnetized with an easy magnetization axis in a direction parallel to the film surface of the magnetic film (in-plane direction). The intermediate layer 33 is made of a nonmagnetic material, and is for magnetically separating the recording magnetic layer 31 and the soft magnetic layer 32. The protective film 34 is for physically and chemically protecting the recording magnetic layer 31 from the outside.
[0006]
When recording on the magnetic disk X2, as shown in FIG. 9, a magnetic head H, which is an electromagnet, is placed close to and opposed to the recording magnetic layer 31 side of the magnetic disk X2, and the recording magnetic layer 31 is formed by the magnetic head H. Is applied with a recording magnetic field. A part of the recording magnetic field passes through the recording magnetic layer 31 by being magnetized perpendicularly, changes its direction at the soft magnetic layer 32, passes again through the recording magnetic layer 31 again, and returns to the magnetic head H. By changing the direction of the magnetic field from the magnetic head H while relatively moving the magnetic head H in the direction indicated by the arrow A with respect to the magnetic disk X2, the recording magnetic layer 31 is magnetized in the vertical direction and alternately reversed. A plurality of magnetic domains 31a are formed continuously in the track direction of the magnetic disk X2. In this way, the magnetic domain 31a corresponding to a predetermined signal is recorded in the recording magnetic layer 31. On the other hand, when the magnetic disk X2 is reproduced, a change in the direction of the magnetic field from the magnetic domain 31a formed in the recording magnetic layer 31 is changed as a change in the magnetization direction of the recording magnetic layer 31 via the magnetic head for reading. Detected.
[0007]
[Problems to be solved by the invention]
In manufacturing the conventional magnetic disk X2, the recording magnetic layer 31 is formed by uniformly depositing and growing a predetermined magnetic material by sputtering or vacuum evaporation. The recording magnetic layer 31 formed in this way is generally a polycrystalline film, and is known to be composed of columnar magnetic particles extending in the thickness direction of the layer. FIG. 10 is a partially enlarged cross-sectional view of the recording magnetic layer 31 having a polycrystalline structure along the surface spreading direction, and schematically shows a cross section of a plurality of magnetic particles 31 b constituting the recording magnetic layer 31.
[0008]
Each magnetic domain 31a formed in the recording magnetic layer 31 by the recording process as described above includes a plurality of magnetic particles 31b magnetized in the same direction. In the technical field of magnetic recording media, as long as the magnetic domain 31a can exist stably, it is known that the smaller the magnetic particle 31b, the smaller the magnetic domain can be formed and the higher the recording resolution. On the other hand, it is known that as the recording magnetic layer 31 is formed thinner, the particle size of the magnetic particles 31b becomes smaller. However, as the recording magnetic layer 31 is formed thinner, the volume of each magnetic particle 31b becomes smaller, and the perpendicular magnetic anisotropy of the recording magnetic layer 31 tends to decrease. A decrease in perpendicular magnetic anisotropy leads to a decrease in stability of the magnetic domain 31a and hinders improvement in recording resolution. In the ordered alloys such as FePt and CoPt, which are attracting attention as recording magnetic layer materials for achieving high recording density because of their large magnetic anisotropy energy and high thermal stability, such perpendicular magnetic anisotropy The tendency to decline is remarkable.
[0009]
As described above, the conventional technique related to the magnetic recording medium has difficulty in reducing the particle size of the magnetic particles constituting the recording magnetic layer. Therefore, according to the conventional technology, there are cases where a desired recording resolution cannot be achieved in a perpendicular magnetic recording type magnetic recording medium.
[0010]
On the other hand, the degree of unevenness at the magnetic domain interface (indicated by a thick line in FIG. 10) in the recording magnetic layer 31 depends on the particle size of the magnetic particles 31b. Specifically, the smaller the particle size of the magnetic particles 31b, the finer the irregularities at the magnetic domain interface. As the unevenness becomes finer, the magnetization transition in the recording magnetic layer 31 becomes steeper and the medium noise is reduced. However, the conventional technique related to the magnetic recording medium has difficulty in reducing the diameter of the magnetic particles 31b constituting the recording magnetic layer 31, as described above. Therefore, according to the conventional technique, there is a case where medium noise cannot be sufficiently reduced in a perpendicular magnetic recording type magnetic recording medium.
[0011]
The present invention has been conceived under such circumstances, and an object of the present invention is to improve recording resolution and reduce medium noise in a perpendicular magnetic recording type magnetic recording medium.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, a magnetic recording medium is provided. The magnetic recording medium includes a plurality of magnetic columns made of a magnetic material and having parallel perpendicular magnetic anisotropy, and a nonmagnetic region made of a nonmagnetic material and interposed between the plurality of magnetic columns. A recording magnetic layer is provided.
[0013]
According to such a configuration, the recording resolution of the magnetic recording medium can be improved. The recording magnetic layer according to the first aspect of the present invention includes a plurality of magnetic columns made of a magnetic material, each of which functions as an independent magnetic recording unit, that is, a columnar magnetic region, and a nonmagnetic region made of a nonmagnetic material. Comprising. Such a recording magnetic layer is formed, for example, by first depositing a magnetic material on a predetermined base material and then etching the magnetic material film through a predetermined mask to stand up on the base material. It can be formed by forming magnetic columns and then filling nonmagnetic material between the magnetic columns. The magnetic material film can be formed to have a thickness greater than that of the magnetic material film, and thus the magnetic column to be formed therefrom, to obtain good magnetism. For example, when a magnetic material film is formed of FePt or CoPt that can be ordered to acquire magnetism, the magnetic material film is more than the thickness for forming crystal grains having an orientation suitable for ordering. Can be formed. Further, by making the masking area of the mask used for etching the magnetic material film sufficiently small, the diameter of the cross section of the magnetic column formed by the etching, that is, the grain size can be reduced to a desired level. . As described above, the magnetic recording medium according to the first aspect of the present invention can achieve a small particle size while imparting good magnetism to the magnetic column that functions as a single magnetic particle in the recording magnetic layer. Therefore, high recording resolution can be achieved in the recording magnetic layer.
[0014]
In addition, in the magnetic recording medium according to the first aspect of the present invention, each magnetic column that functions as an independent magnetic recording unit or a single magnetic particle can be formed small in the recording magnetic layer. Unevenness at the interface of the magnetic domains formed in the recording magnetic layer can be miniaturized. When the unevenness of the magnetic domain interface in the recording magnetic layer becomes fine, the magnetization transition in the recording magnetic layer becomes steep and the medium noise is reduced.
[0015]
As described above, in the magnetic recording medium according to the first aspect of the present invention, recording resolution can be improved and medium noise can be reduced. Such a magnetic recording medium is suitable for practical use as a high recording density perpendicular magnetic recording medium.
[0016]
The first aspect of the present invention preferably has a laminated structure comprising a recording magnetic layer, a soft magnetic layer, and a nonmagnetic layer between them. The magnetic recording medium according to the first aspect is preferably implemented as a magnetic recording medium having such a so-called backing soft magnetic layer.
[0017]
Preferably, the average cross-sectional diameter of the plurality of magnetic columns and the average separation distance of the plurality of magnetic columns are smaller than the thickness of the recording magnetic layer. The average cross-sectional diameter of the plurality of magnetic columns is the average diameter of the cross-section in the in-plane direction of the recording magnetic layer in the plurality of magnetic columns. Preferably, the ratio of the average separation distance of the plurality of magnetic columns to the average cross-sectional diameter of the plurality of magnetic columns is 1 or less. The average separation distance of a plurality of magnetic columns is the average of the shortest distances between adjacent magnetic columns. These configurations are suitable for obtaining good recording characteristics in the recording magnetic layer while achieving miniaturization of the magnetic column cross section.
[0018]
Preferably, the magnetic column is made of an ordered alloy or a rare earth-transition metal amorphous alloy. As the ordered alloy, it is preferable to employ FePt or CoPt. Further, as the rare earth-transition metal amorphous alloy, it is preferable to employ TbFeCo. These magnetic materials are suitable as magnetic column materials for forming a recording magnetic layer of a perpendicular magnetic recording medium.
[0019]
Preferably, the nonmagnetic layer is made of a nonmagnetic oxide for controlling the crystal orientation of the ordered alloy. Such a configuration is suitable for developing magnetism in the ordered alloy.
[0020]
According to a second aspect of the present invention, a magnetic comprising a recording magnetic layer including a plurality of parallel magnetic columns having perpendicular magnetic anisotropy and a nonmagnetic region interposed between the plurality of magnetic columns. A method for manufacturing a recording medium is provided. This manufacturing method includes a step for forming a magnetic material film by depositing a magnetic material on a substrate, and an etching mask for masking a magnetic column forming region on the magnetic material film. A mask forming step, a step for forming a plurality of magnetic columns arranged in parallel and spaced apart by etching a magnetic material film through an etching mask, and a nonmagnetic material is filled between the plurality of magnetic columns. And a nonmagnetic region forming step for forming a nonmagnetic region interposed between the plurality of magnetic columns. In the present invention, the base material is a base material having an exposed surface on which a magnetic material film is laminated, and includes a substrate alone and a substrate on which a soft magnetic layer, a nonmagnetic layer, and the like are already laminated.
[0021]
According to such a method, the magnetic recording medium according to the first aspect of the present invention can be manufactured. Therefore, according to the second aspect of the present invention, the same effect as described above with respect to the first aspect can be achieved in the magnetic recording medium to be manufactured.
[0022]
In the second aspect of the present invention, in the mask formation step, preferably, a first material film having a surface energy smaller than that of the recording magnetic layer is formed on the magnetic material film to form a first material film. A plurality of second material grains are formed by depositing a second material in a granular form on the first material film, and a third material is deposited on each of the second material grains as an etching mask. The mask particles are formed. In this case, it is preferable that a base point on which the second material is deposited and grown is formed on the first material film after forming the first material film and before forming the second material grains. Alternatively, in the mask formation step, a mask particle solution is applied onto the magnetic material film, and then the mask components as an etching mask are deposited from the applied solution, for example, by evaporating the liquid component of the solution. Also good. These methods are suitable for forming a fine etching mask.
[0023]
In the nonmagnetic region forming step, preferably, the nonmagnetic material is filled between the plurality of magnetic columns by supplying the nonmagnetic material from above the plurality of magnetic columns while heating the magnetic column. Alternatively, in the non-magnetic region forming step, a non-magnetic material is filled between the plurality of magnetic columns by supplying a non-magnetic material having a surface energy smaller than that of the recording magnetic layer from above the plurality of magnetic columns. Also good. These nonmagnetic region forming methods are suitable for appropriately achieving magnetic separation and physical separation between magnetic columns.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows a partial cross section of a magnetic recording medium X1 according to the first embodiment of the present invention. The magnetic recording medium X1 is configured as a perpendicular magnetic recording type magnetic disk including a substrate S, a recording magnetic layer 11, a soft magnetic layer 12, a nonmagnetic layer 13, and a protective film 14.
[0025]
The substrate S is a nonmagnetic substrate made of, for example, an aluminum alloy, glass, or ceramics. The surface of the substrate S is smoothed by a chemical method, a physical method, or a mechanical method.
[0026]
The recording magnetic layer 11 has a sufficiently large coercive force and includes a plurality of magnetic columns 11a and nonmagnetic regions 11b for exhibiting magnetism. The plurality of magnetic columns 11a are parallel to and spaced apart from each other, and each of them has perpendicular magnetic anisotropy and is magnetized upward or downward in the drawing. FIG. 2 is a partially enlarged cross-sectional view of the recording magnetic layer 11 and shows a cross section of the magnetic column 11a.
[0027]
The magnetic column 11a is made of, for example, an ordered alloy or a rare earth-transition metal amorphous alloy. For example, FePt or CoPt can be used as the ordered alloy. As the rare earth-transition metal amorphous alloy, for example, TbFe, TbCo, TbFeCo, or the like can be employed. For example, FePt, CoPt, and rare earth-transition metal amorphous alloys having magnetism that can acquire magnetism by ordering have large perpendicular magnetic anisotropy energy and high thermal stability. 11 is suitable as a magnetic material for constituting 11. On the other hand, the nonmagnetic region 11b is made of, for example, SiO. ₂ , Al ₂ O _Three , MgO, or SiN. Or you may comprise the nonmagnetic area | region 11b by Cr, Ti, Al, Ag, or these alloys.
[0028]
The average diameter of the cross section of the plurality of magnetic columns 11a is, for example, 3 to 7 nm. The average separation distance between adjacent magnetic columns in the plurality of magnetic columns 11a is, for example, 1 to 3 nm. In these ranges, the ratio of the average separation distance to the average cross-sectional diameter is preferably 1 or less. The thickness of the recording magnetic layer 11 is, for example, 10 to 30 nm. According to such a configuration, a fine column structure in which each magnetic column is isolated can be appropriately formed in the recording magnetic layer 11.
[0029]
The soft magnetic layer 12 exhibits in-plane magnetic anisotropy having an easy axis of magnetization in a direction parallel to the film surface of the magnetic film constituting the layer. The easy magnetization axis of the soft magnetic layer 12 is preferably oriented in the radial direction of the disk. The soft magnetic layer 12 has a sufficiently small coercive force. Such a soft magnetic layer 12 can be made of, for example, permalloy, sendust, Co-based amorphous material, or Fe-based amorphous material. The thickness of the soft magnetic layer 12 is, for example, 100 to 300 nm.
[0030]
The nonmagnetic layer 13 is made of a nonmagnetic material, and is for magnetically separating the recording magnetic layer 11 and the soft magnetic layer 12 appropriately. The thickness of the nonmagnetic layer 13 is, for example, 1 to 15 nm.
[0031]
When the magnetic column 11a is made of an ordered alloy, the nonmagnetic layer 13 is made of a nonmagnetic oxide for controlling the crystal orientation of the adopted ordered alloy. As such a nonmagnetic oxide, for example, MgO, ZnO, or RuO can be employed.
[0032]
In addition, when the magnetic column 11a is made of a rare earth-transition metal amorphous alloy, the surface irregularities on the recording magnetic layer side in the nonmagnetic layer 13 do not need to be fine. In the conventional technique, when the recording magnetic layer is made of a rare earth-transition metal amorphous alloy, it is necessary to make the surface irregularities of the underlayer (nonmagnetic layer) on which the recording magnetic layer is formed fine. This is for the purpose of miniaturizing the magnetic domain structure by suppressing the fluctuation or movement of the domain wall existing in the magnetic domain structure inside the recording magnetic layer by the pinning action of the fine surface irregularities. On the other hand, in the present invention, even when a rare earth-transition metal amorphous alloy is employed as a material for developing magnetism in the recording magnetic layer 11, the magnetic developing material is isolated from each other by the nonmagnetic region 11b. Since the magnetic domain structure of the recording magnetic layer 11 can be miniaturized by such a magnetic column structure, the recording magnetic property in the nonmagnetic layer 13 that is the underlayer of the recording magnetic layer 11 is provided. It is not necessary to make the surface irregularities on the layer side fine.
[0033]
The protective film 14 is for physically and chemically protecting the recording magnetic layer 11 from the outside, and is made of, for example, amorphous carbon, diamond-like carbon, SiN, or SiC. The film thickness of the protective film 14 is, for example, 1 to 5 nm.
[0034]
The magnetic recording medium X1 may further have an adhesion layer between the substrate S and the soft magnetic layer 12. The adhesion layer is for appropriately fixing the soft magnetic layer 12 formed on the substrate S, and is made of, for example, Cr, Ti, NiP, or NiAl. The thickness of the adhesion layer is, for example, 1 to 5 nm.
[0035]
3 to 5 show a method for manufacturing the magnetic recording medium X1. In the manufacture of the magnetic recording medium X1, first, the substrate S is subjected to a smoothing surface treatment, and then the soft magnetic layer 12 and the nonmagnetic layer 13 are sequentially laminated on the substrate S, thereby forming the structure shown in FIG. ) Is formed. The soft magnetic layer 12 and the nonmagnetic layer 13 can be formed by a sputtering method using a single target or a plurality of targets made of a predetermined material corresponding to each.
[0036]
Next, as shown in FIG. 3B, a magnetic material film 11a ′ is formed by forming a magnetic material on the nonmagnetic layer 13 by sputtering. Next, as shown in FIG. 3C, mask fine particles 15 are formed on the magnetic material film 11a ′. The mask fine particles 15 are for masking a portion formed as the magnetic column 11a in the magnetic material film 11a ′, that is, a magnetic column forming region in a later etching process.
[0037]
FIG. 4 shows a method for forming the mask fine particles 15. Each step in FIG. 4 is shown in an enlarged manner as compared with FIG. In forming the mask fine particles 15, first, as shown in FIG. 4A, a base material 16 is formed by depositing a dielectric material on the surface of the magnetic material film 11 a ′. As the dielectric material, a material having a surface energy smaller than that of the magnetic material film 11a ′ is used. As such a dielectric material, for example, SiN, SiO, AlN, AlO can be employed.
[0038]
Next, as shown in FIG. 4B, material grains 15 a are formed on the base layer 16. Specifically, the material grains 15a are formed by depositing and growing a predetermined material in an island shape on the magnetic material film 11a ′ by a sputtering method using a predetermined target. As a material for forming material grains, for example, Ag, Cr, W, Mo, Ta, or an alloy thereof can be employed. Further, as the material grain forming material, it is preferable to select a material having a surface energy larger than that of the underlayer 16. As the surface energy of the material for constituting the material grain 15a is larger than that of the underlayer 16 and the difference between both surface energies is larger, the diameter of the material grain 15a formed in this step becomes smaller. Fine particles. In the present invention, before the formation of the material grains 15a, a base point for accelerating the growth of the material grains 15a may be formed in advance on the underlayer by, for example, a sputtering method. As the material for forming the base point, for example, a noble metal oxide such as ruthenium oxide or palladium oxide can be employed.
[0039]
In forming the mask fine particles 15, next, as shown in FIG. 4C, an enhancement material 15b is deposited on the material grains 15a. As the enhancement material 15b, for example, carbon or boron can be employed. As the enhancement material 15b, a material having a relatively small atomic radius is preferable. In this way, a large number of minute mask fine particles 15 can be formed with high accuracy on the surface of the magnetic material film 11a ′. The mask fine particles 15 are dispersedly formed according to the cross-sectional size and the formation density of the magnetic column 11a to be formed.
[0040]
In forming the mask fine particles 15, instead of the method described above with reference to FIG. 4, a solution in which components that can be precipitated as so-called nanoparticles are dissolved is applied to the surface of the magnetic material film 11 a ′ by spin coating. Thereafter, the liquid component of the solution may be evaporated to deposit nanoparticles. For example, granular Pt, Au, Pd, FePt, or CoPt can be used as the nanoparticle. When such a method is adopted, the content rate of the nanoparticles in the solution is determined according to the cross-sectional size and the formation density of the magnetic column 11a to be formed. Also by such a method, a large number of minute mask fine particles 15 can be formed on the magnetic material film 11a ′ with high accuracy.
[0041]
In the manufacture of the magnetic recording medium X1, next, as shown in FIG. 5A, the mask material 15 is used as an etching mask to etch the magnetic material film 11a ′ until the nonmagnetic layer 13 is reached. Apply. Thereby, the magnetic column 11a is formed. In this etching process, a dry etching method performed in a high vacuum may be employed, or a wet etching method performed using a predetermined etching solution may be employed. In this step, a part of the mask fine particles 15 is removed by etching together with a part of the magnetic material film 11a ′. Therefore, in the process described above with reference to FIG. 3C, it is preferable to determine the constituent material and height of the mask fine particles 15 in consideration of the removal amount.
[0042]
Next, as shown in FIG. 5B, a nonmagnetic region 11b is formed between the magnetic columns. Specifically, a nonmagnetic material having a relatively low melting point is supplied from above the magnetic column 11a by sputtering while maintaining the magnetic column 11a at a predetermined high temperature by heating from the substrate S side. According to such a method, due to the difference in surface diffusion temperature between the magnetic column 11a and the nonmagnetic material, the nonmagnetic material fills the space between the magnetic columns due to the meniscus effect. As a result, nonmagnetic regions 11b that are appropriately filled between the magnetic columns are formed. When such a method is employed, as the nonmagnetic material, for example, Ag, Al, or an alloy thereof can be employed.
[0043]
In forming the nonmagnetic region 11b, instead of the above-described method, a nonmagnetic material having a surface energy smaller than the magnetic column 11a by a predetermined degree may be supplied from above the magnetic column 11a by sputtering. According to such a method, due to the difference in surface energy between the magnetic column 11a and the nonmagnetic material, the nonmagnetic material fills the space between the magnetic columns. As a result, nonmagnetic regions 11b that are appropriately filled between the magnetic columns are formed. When such a method is employed, for example, SiN, SiO, AlN, or AlO can be employed as the nonmagnetic material.
[0044]
In the manufacture of the magnetic recording medium X1, next, as shown in FIG. 5C, a protective film 14 is formed on the recording magnetic layer 11 by sputtering or CVD. As described above, the magnetic recording medium X1 can be manufactured.
[0045]
When recording on the magnetic recording medium X1, a magnetic head for recording is made to face the recording magnetic layer 11 of the magnetic recording medium X1 through the protective film 14 in close proximity to the recording magnetic layer 11 by the magnetic head. On the other hand, a recording magnetic field is applied. A part of the recording magnetic field passes perpendicularly through the recording magnetic layer 11, passes through the nonmagnetic layer 13, changes direction in the soft magnetic layer 12, and then perpendicularizes the soft magnetic layer 12 and the recording magnetic layer 11 again. Pass through and return to the magnetic head. By changing the direction of the magnetic field from the magnetic head while moving the magnetic head relative to the magnetic recording medium X1, a plurality of magnetic domains that are magnetized in the perpendicular direction and are alternately inverted in the recording magnetic layer 11 are magnetic recording medium. It is formed continuously in the track direction of X1. In this way, the magnetic domain corresponding to the predetermined signal is recorded in the recording magnetic layer 11. On the other hand, when reproducing the magnetic recording medium X1, the change in the direction of the magnetic field from the magnetic domain formed in the recording magnetic layer 11 is changed as the change in the magnetization direction of the recording magnetic layer 11 through the magnetic head for reading. Detected.
[0046]
In the magnetic recording medium X1, a soft magnetic layer 12 having a high magnetic permeability is provided close to the recording magnetic layer 11 as a backing soft magnetic layer. Therefore, in the magnetic recording medium X1, a large recording magnetic field can be obtained in the above-described recording process, and as a result, excellent recording sensitivity can be achieved.
[0047]
Further, the magnetic recording medium X1 is excellent in the recording resolution of the recording magnetic layer 11. In the technical field of magnetic recording media, it is known that the smaller the particle size of magnetic particles that exhibit the magnetic function in the recording magnetic layer, the smaller the medium noise and the higher the recording resolution in the recording magnetic layer. In the magnetic recording medium X1 manufactured by the above-described method, a small particle size (cross-sectional diameter in the in-plane direction) can be achieved for the magnetic column 11a that exhibits the magnetic function of the recording magnetic layer 11, and thus high recording is achieved. It is possible to obtain resolution.
[0048]
In addition, in the magnetic recording medium X1, the magnetic columns 11a each functioning as a single magnetic particle in the recording magnetic layer 11 can be formed with a small cross-sectional size, so that the magnetic domains formed in the recording magnetic layer 11 can be formed. The unevenness of the interface can be miniaturized. When the unevenness at the magnetic domain interface in the recording magnetic layer 11 becomes fine, the medium noise is reduced.
[0049]
【Example】
Next, examples of the present invention will be described together with comparative examples.
[0050]
[Example 1]
<Preparation of magnetic recording medium>
A magnetic recording medium of this example was manufactured as a magnetic disk having the stacked configuration shown in FIG. Specifically, first, a CoZrNb alloy is formed by DC sputtering on a glass disk substrate (φ2.5 inches) that has been subjected to surface smoothing by polishing until the surface roughness Ra becomes 0.2 nm or less. Thus, an in-plane magnetization soft magnetic layer having a thickness of 150 nm was formed. For the sputtering, an in-line rotary cathode type DC / RF magnetron sputtering apparatus that can have a plurality of targets was used. This apparatus was also used in the subsequent sputtering. In this sputtering, Co ₈₅ Zr _Ten Nb _Five An alloy target was used, the gas pressure was 0.3 Pa, and the deposition rate was 29 nm / min. The formed in-plane magnetization soft magnetic layer is made of Co. ₈₅ Zr _Ten Nb _Five The saturation magnetic flux density was 1.1 T (Tesla).
[0051]
Next, a 15-nm-thick nonmagnetic layer was formed by depositing MgO on the soft magnetic layer by RF sputtering. In this sputtering, an MgO target was used, the gas pressure was 0.5 Pa, and the deposition rate was 8 nm / min.
[0052]
Next, a magnetic material film having a thickness of 10 nm was formed by depositing FePt on the nonmagnetic layer by DC sputtering. Specifically, the magnetic material film was formed by co-sputtering of simultaneously sputtering an Fe (purity 99.9%) target and a Pt (purity 99.99%) target. In this sputtering, the gas pressure was 2.0 Pa and the film formation rate was 13.5 nm / min. The formed magnetic material film is Fe ₅₀ Pt ₅₀ The composition was After sputtering, heat treatment was performed at 400 ° C. for 40 minutes in order to magnetize the FePt constituting the magnetic material film by regular arrangement. When the magnetic properties of the magnetic material film subjected to the heat treatment were examined using a vibrating sample magnetometer (VSM), the coercive force Hc was 7.3 kOe, the saturation magnetization Ms was 745 emu / cc, and the film surface It was magnetized in the perpendicular direction.
[0053]
Next, an underlayer (thickness 1 nm) for forming mask fine particles was formed by depositing SiN on the magnetic material film by DC sputtering. SiN has a smaller surface energy than FePt constituting the recording magnetic layer. Specifically, an Si gas (purity 99.99%) target is used, and Ar gas and N as sputtering gases. ₂ A SiN film was formed by reactive sputtering using a gas. In this sputtering, Ar gas and N ₂ The gas flow ratio was 2: 1, the gas pressure was 0.32 Pa, and the deposition rate was 13.6 nm / min.
[0054]
Next, ruthenium oxide (RuOx) was formed on the base layer by DC sputtering to form a base layer (thickness 0.6 nm) for forming mask fine particles. Specifically, a Ru (purity 99.99%) target is used, and Ar gas and O as sputtering gas. ₂ A RuOx film was formed by reactive sputtering using a gas. In this sputtering, Ar gas and O ₂ The gas flow ratio was 5: 1, the gas pressure was 1.2 Pa, and the deposition rate was 2 nm / min.
[0055]
Next, mask fine particles were formed on the base layer using the aggregation effect. In forming the mask fine particles, first, an Ag alloy (Ag content: 98 at%), which is a low melting point material, was deposited in an island shape (thickness 0.8 nm) on the base layer by DC sputtering. In this sputtering, an Ag alloy (Ag content: 98 at%) target was used, the gas pressure was 2 Pa, and the deposition rate was 2.5 nm / min. Subsequently, in order to increase the height of the mask fine particles, an enhancement material C was further deposited (thickness 1 nm) on the Ag alloy deposited grains by DC sputtering. In this sputtering, a C target was used, the gas pressure was 2 Pa, and the deposition rate was 5.2 nm / min. Since carbon (C) has a small atomic radius, it is suitable as such an enhancement material. When the particle size of the mask fine particles formed in this manner was examined using a transmission electron microscope (TEM), the particle size was about 3 to 6 nm and the average particle size was 4 nm. Further, when the surface of the magnetic material film was examined using an atomic force microscope (AFM) after forming the mask fine particles, the average surface roughness Ra was 0.21 nm. Thus, it was confirmed that fine particles (mask fine particles) were formed on the magnetic material film.
[0056]
In the manufacture of the magnetic recording medium of this example, the magnetic material film was then etched up to the nonmagnetic layer by RF sputter etching using the mask fine particles as an etching mask. At this time, the etching rate of the mask fine particles was slower than that of the magnetic material film, but some of the mask fine particles were also removed by etching. In this sputtering, the RF input power was 450 W. After such an etching process, when the cross-sectional structure of the portion where the magnetic material film originally existed was examined using TEM, a plurality of magnetic columns were formed at intervals of about 1 to 5 nm. It was confirmed that
[0057]
Next, an Ag alloy (Ag content: 98 at%), which is a nonmagnetic material, is formed from above the magnetic column formed as described above by DC sputtering, thereby forming a nonmagnetic region between the magnetic columns. Formed. In this sputtering, the gas pressure was 2.5 Pa, the deposition rate was 2.1 nm / min, and the substrate temperature was 230 ° C. In this process performed under such conditions, it is considered that the low melting point Ag alloy material adhered to the magnetic column whose surface is activated by heating is separated by the meniscus effect to fill the space between the magnetic columns. After forming the recording magnetic layer composed of the magnetic column and the nonmagnetic region in this way, the cross-sectional structure of the recording magnetic layer was examined using TEM. The average cross-sectional diameter of the plurality of magnetic columns was 5 nm. The average separation distance between the magnetic columns was 2 nm.
[0058]
Next, a 3 nm thick protective film was formed by depositing amorphous carbon on the recording magnetic layer by DC sputtering. In this sputtering, a C (carbon) target was used, the gas pressure was 0.4 Pa, and the deposition rate was 27 nm / min.
[0059]
As described above, the magnetic recording medium of this example was manufactured. When the magnetic properties of the recording magnetic layer in the magnetic recording medium of this example were examined using VSM, the coercive force Hc was 7.0 kOe, the saturation magnetization Ms was 730 emu / cc, It was magnetized in the vertical direction.
[0060]
<Recording and playback characteristics>
The recording / reproducing characteristics of the magnetic recording medium produced as described above were examined. Specifically, first, using a single magnetic pole head (magnetic flux density Bs of single magnetic part: 2T, write core width: 0.2 μm), a linear recording density of 20 kFCI with respect to the magnetic recording medium of this example. The signal was recorded. Next, the recording signal was reproduced using a GMR head (reproduction core width: 0.16 μm, shield gap length: 0.08 μm), and the output of the reproduction signal was detected using a spectrum analyzer.
[0061]
As a result, the reproduction signal amplitude at a linear recording density of 20 kFCI was 0.71 mV, and the medium noise at this time was about 3 μVrms. Using the same single magnetic pole head and GMR head, the recording / reproduction characteristics of the magnetic recording medium of this example were examined for a recording signal with a linear recording density of 300 kFCI. The reproduction signal amplitude was 0.42 mV, and the medium noise Was 5.3 μVrms. Using the same single magnetic pole head and GMR head, the recording / reproducing characteristics of the magnetic recording medium of this example were examined with respect to a recording signal having a linear recording density of 800 kFCI. Was 7.2 μVrms.
[0062]
[Example 2]
<Preparation of magnetic recording medium>
The magnetic recording medium of this example was manufactured as another magnetic disk having the stacked configuration shown in FIG. Specifically, first, in the same manner as in Example 1, in-plane with respect to a glass disk substrate (φ2.5 inch) subjected to surface smoothing treatment by polishing until the surface roughness Ra becomes 0.2 nm or less. Magnetized soft magnetic layer (Co ₈₅ Zr _Ten Nb _Five , Thickness 150 nm), nonmagnetic layer (MgO, thickness 15 nm), and magnetic material film (Fe ₅₀ Pt ₅₀ , A thickness of 10 nm).
[0063]
Next, mask fine particles were formed on the magnetic material film. Specifically, first, iron carbonyl (Fe (CO) _Five ) 10 g and platinum acetylacetonate (Pt (acac)) ₂ ) A solution in which 10 g was dissolved or dispersed in 100 ml of ethylene glycol was applied onto the magnetic material film by spin coating. At this time, the rotation speed of the application target was 2500 rpm. Thereafter, the liquid component was evaporated by drying at 150 ° C. for 60 minutes to form mask fine particles on the magnetic material film. The mask fine particles are made of FePt. When the particle size of the mask fine particles formed in this way was examined using a TEM, the particle size was about 4 to 6 nm, and the average particle size was 5 nm. Further, when the surface of the magnetic material film was examined using AFM after forming the mask fine particles, the average surface roughness Ra was 0.23 nm. Thus, it was confirmed that fine particles were formed on the magnetic material film.
[0064]
In the manufacture of the magnetic recording medium of this example, a magnetic column was then formed in the same manner as in Example 1 using the mask fine particles as an etching mask. Subsequently, a nonmagnetic region between the magnetic columns was formed in the same manner as in Example 1. Thereby, the recording magnetic layer was formed. Next, a protective film was formed on the recording magnetic layer in the same manner as in Example 1. As described above, the magnetic recording medium of this example was manufactured. When the magnetic characteristics of the recording magnetic layer in the magnetic recording medium of this example were examined using VSM, the same magnetic characteristics as those of the magnetic recording medium of Example 1 were shown.
[0065]
<Recording and playback characteristics>
With respect to the magnetic recording medium of this example, in the same manner as in Example 1, the reproduction output of each recording signal having a linear recording density of 20 kFCI, 300 kFCI, and 800 kFCI was detected, and the reproduction signal amplitude and medium noise were examined. As a result, a value approximately the same as in Example 1 was obtained.
[0066]
[Example 3]
<Preparation of magnetic recording medium>
A magnetic recording medium of this example was manufactured as a magnetic disk having the stacked configuration shown in FIG. Specifically, first, in the same manner as in Example 1, in-plane with respect to a glass disk substrate (φ2.5 inch) subjected to surface smoothing treatment by polishing until the surface roughness Ra becomes 0.2 nm or less. Magnetized soft magnetic layer (Co ₈₅ Zr _Ten Nb _Five , Thickness 150 nm), nonmagnetic layer (MgO, thickness 15 nm), magnetic material film (Fe ₅₀ Pt ₅₀ , Thickness 10 nm), and mask fine particles (multilayer structure) were sequentially formed. Subsequently, in the same manner as in Example 1, a magnetic column was formed using the mask fine particles as an etching mask.
[0067]
Next, a nonmagnetic region was formed between the magnetic columns by depositing SiN, which is a nonmagnetic material, from above the magnetic columns formed as described above by DC sputtering. In this sputtering, the gas pressure was 0.32 Pa, the deposition rate was 13.6 nm / min, and the substrate temperature was room temperature. In this process performed under such conditions, it is considered that SiN having a relatively small surface energy fills between the magnetic columns with good wettability with respect to the magnetic column having a relatively large surface energy. After forming the recording magnetic layer composed of the magnetic column and the nonmagnetic region in this way, the cross-sectional structure of the recording magnetic layer was examined using TEM. The average cross-sectional diameter of the plurality of magnetic columns was 5 nm. The average separation distance between the magnetic columns was 2 nm.
[0068]
Next, a protective film (amorphous carbon, thickness 3 nm) was formed on the recording magnetic layer in the same manner as in Example 1. As described above, the magnetic recording medium of this example was manufactured. When the magnetic characteristics of the recording magnetic layer in the magnetic recording medium of this example were examined using VSM, the same magnetic characteristics as those of the magnetic recording medium of Example 1 were shown.
[0069]
<Recording and playback characteristics>
With respect to the magnetic recording medium of this example, in the same manner as in Example 1, the reproduction output of each recording signal having a linear recording density of 20 kFCI, 300 kFCI, and 800 kFCI was detected, and the reproduction signal amplitude and medium noise were examined. As a result, a value approximately the same as in Example 1 was obtained.
[0070]
[Example 4]
<Preparation of magnetic recording medium>
The magnetic recording medium of this example was manufactured as another magnetic disk having the stacked configuration shown in FIG. Specifically, first, in the same manner as in Example 1, in-plane with respect to a glass disk substrate (φ2.5 inch) subjected to surface smoothing treatment by polishing until the surface roughness Ra becomes 0.2 nm or less. Magnetized soft magnetic layer (Co ₈₅ Zr _Ten Nb _Five , Thickness 150 nm), nonmagnetic layer (MgO, thickness 15 nm), and magnetic material film (Fe ₅₀ Pt ₅₀ , A thickness of 10 nm).
[0071]
Next, in the same manner as in Example 2, mask fine particles were formed on the magnetic material film. Next, in the same manner as in Example 1, a magnetic column was formed using the mask fine particles as an etching mask. Next, in the same manner as in Example 3, a nonmagnetic region was formed between the magnetic columns. Thus, the recording magnetic layer of this example was formed. When the cross-sectional structure of the recording magnetic layer was examined using a TEM, the average cross-sectional diameter of the plurality of magnetic columns was 6 nm, and the average separation distance between the magnetic columns was 2 nm.
[0072]
Next, a protective film (amorphous carbon, thickness 3 nm) was formed on the recording magnetic layer in the same manner as in Example 1. As described above, the magnetic recording medium of this example was manufactured. When the magnetic characteristics of the recording magnetic layer in the magnetic recording medium of this example were examined using VSM, the same magnetic characteristics as those of the magnetic recording medium of Example 1 were shown.
[0073]
<Recording and playback characteristics>
With respect to the magnetic recording medium of this example, in the same manner as in Example 1, the reproduction output of each recording signal having a linear recording density of 20 kFCI, 300 kFCI, and 800 kFCI was detected, and the reproduction signal amplitude and medium noise were examined. As a result, a value approximately the same as in Example 1 was obtained.
[0074]
[Comparative example]
<Preparation of magnetic recording medium>
A magnetic recording medium of this comparative example was manufactured as a magnetic disk having the stacked configuration shown in FIG. Specifically, first, in the same manner as in Example 1, in-plane with respect to a glass disk substrate (φ2.5 inch) subjected to surface smoothing treatment by polishing until the surface roughness Ra becomes 0.2 nm or less. Magnetized soft magnetic layer (Co ₈₅ Zr _Ten Nb _Five , Thickness 150 nm), nonmagnetic layer (MgO, thickness 15 nm), and magnetic material film (Fe) constituting the recording magnetic layer of this comparative example ₅₀ Pt ₅₀ , A thickness of 10 nm). Next, a protective film (amorphous carbon, thickness 3 nm) was formed on the recording magnetic layer in the same manner as in Example 1. The magnetic recording medium of this comparative example was produced as described above.
[0075]
<Recording and playback characteristics>
For the magnetic recording medium of this comparative example, in the same manner as in Example 1, the reproduction output of each recording signal with a linear recording density of 20 kFCI and 300 kFCI was detected, and the reproduction signal amplitude and medium noise were examined. As a result, the reproduction signal amplitude with a linear recording density of 20 kFCI was 0.70 mV, and the medium noise at this time was about 3 μVrms. At a linear recording density of 300 kFCI, the reproduction signal amplitude was 0.18 mV, and the medium noise was 49.7 μVrms. Further, no signal could be recorded on the magnetic recording medium of this comparative example at a linear recording density of 800 kFCI.
[0076]
[Evaluation]
Regarding the medium noise when reproducing a recording signal with a linear recording density of 300 kFCI, the magnetic recording medium of Example 1 was about one-tenth of the magnetic recording medium of the comparative example, and was well reduced. Further, while the signal could be properly recorded on the magnetic recording medium of Example 1 at a recording density of 800 kFCI, the signal could not be recorded on the magnetic recording medium of the comparative example at such a high density. It was.
[0077]
In the magnetic recording medium of the comparative example, since the magnetic particles constituting the recording magnetic layer are not isolated, the magnetic interaction between the magnetic particles is strong. Therefore, a single magnetic domain (magnetic) formed by the recording process is strong. It is considered that the medium noise increases as the unit) becomes relatively large and the linear recording density increases. On the other hand, in the magnetic recording medium of Example 1, each magnetic particle (each magnetic column) expressing the magnetic property of the recording magnetic layer is isolated, so that a single magnetic domain (magnetic unit) formed by the recording process is used. Therefore, it is considered that the recording / reproducing characteristics are excellent even at a high linear recording density.
[0078]
Thus, the magnetic recording medium of Example 1 has higher recording resolution and lower medium noise than the magnetic recording medium of the comparative example. Therefore, in the magnetic recording medium of Example 1 according to the present invention and the magnetic recording media of Examples 2 to 4 showing the same recording / reproducing characteristics, the recording density is higher than that of the magnetic recording medium of the comparative example. Can be achieved.
[0079]
As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.
[0080]
(Appendix 1) Recording including a plurality of magnetic columns made of a magnetic material and having parallel perpendicular magnetic anisotropy, and a nonmagnetic region made of a nonmagnetic material and interposed between the plurality of magnetic columns A magnetic recording medium comprising a magnetic layer.
(Additional remark 2) The magnetic recording medium of Additional remark 1 which has the laminated structure which consists of the said recording magnetic layer, a soft magnetic layer, and the nonmagnetic layer between these.
(Appendix 3) The average diameter of the cross section of the plurality of magnetic columns and the average separation distance between adjacent magnetic columns in the plurality of magnetic columns are smaller than the thickness of the recording magnetic layer. Magnetic recording medium.
(Supplementary note 4) The magnetic recording medium according to any one of supplementary notes 1 to 3, wherein a ratio of an average separation distance of the plurality of magnetic columns to a cross-sectional average diameter of the plurality of magnetic columns is 1 or less.
(Supplementary note 5) The magnetic recording medium according to any one of supplementary notes 1 to 4, wherein the magnetic column is made of an ordered alloy or a rare earth-transition metal amorphous alloy.
(Supplementary note 6) The magnetic recording medium according to supplementary note 5, wherein the ordered alloy is FePt or CoPt.
(Additional remark 7) The said nonmagnetic layer is a magnetic recording medium of Additional remark 5 or 6 which consists of a nonmagnetic oxide for controlling the crystal orientation of the said ordered alloy.
(Supplementary Note 8) To manufacture a magnetic recording medium including a recording magnetic layer including a plurality of magnetic columns arranged in parallel with perpendicular magnetic anisotropy and a nonmagnetic region interposed between the plurality of magnetic columns. The method of
A step for forming a magnetic material film by depositing a magnetic material on a substrate;
A mask forming step for forming an etching mask for masking the magnetic column forming region on the magnetic material film;
Etching the magnetic material film through the etching mask to form a plurality of parallel and spaced magnetic columns;
A nonmagnetic region forming step for forming a nonmagnetic region interposed between the plurality of magnetic columns by filling a nonmagnetic material between the plurality of magnetic columns, A method of manufacturing a magnetic recording medium.
(Supplementary Note 9) In the mask forming step, a first material film having a surface energy smaller than that of the magnetic material is formed on the magnetic material film to form a first material film, and the first material film is formed on the first material film. A plurality of second material grains are formed by depositing the second material in a granular form, and a mask particle as the etching mask is formed by depositing a third material on each of the second material grains. The method for manufacturing a magnetic recording medium according to appendix 8.
(Additional remark 10) After forming the first material film and before forming the second material grain, a base point on which the second material is deposited and grown is formed on the first material film. A method for producing the magnetic recording medium according to claim.
(Supplementary note 11) The magnetic recording according to supplementary note 8, wherein in the mask formation step, a mask particle solution is applied onto the magnetic material film, and mask particles as the etching mask are deposited from the applied solution. A method for manufacturing a medium.
(Supplementary Note 12) In the nonmagnetic region forming step, a nonmagnetic material is supplied between the plurality of magnetic columns by supplying the nonmagnetic material from above the plurality of magnetic columns while heating the magnetic column. The method for manufacturing a magnetic recording medium according to any one of appendices 8 to 11, wherein the magnetic recording medium is filled.
(Supplementary Note 13) In the non-magnetic region forming step, a non-magnetic material having a surface energy smaller than that of the magnetic material is supplied from above the plurality of magnetic columns, so that the non-magnetic region is formed between the plurality of magnetic columns. The method for manufacturing a magnetic recording medium according to any one of appendices 8 to 11, wherein the magnetic material is filled.
[0081]
【The invention's effect】
According to the present invention, it is possible to improve recording resolution and reduce medium noise in a recording magnetic layer of a perpendicular magnetic recording type magnetic recording medium. Therefore, the magnetic recording medium and the manufacturing method thereof according to the present invention are suitable for increasing the recording density in a perpendicular magnetic recording type magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic partial sectional view of a magnetic recording medium according to the present invention.
2 is a partially enlarged cross-sectional view of a recording magnetic layer in the magnetic recording medium shown in FIG.
FIG. 3 shows some steps in the method of manufacturing the magnetic recording medium shown in FIG.
4 shows a process of forming mask fine particles shown in FIG.
FIG. 5 shows a step that follows FIG.
FIG. 6 shows a laminated structure of magnetic recording media of Examples 1 and 2.
FIG. 7 shows a laminated structure of magnetic recording media of Examples 3 and 4.
FIG. 8 shows a laminated structure of a magnetic recording medium of a comparative example.
FIG. 9 is a partial perspective view of a conventional magnetic recording medium of a perpendicular magnetic recording system.
10 is a partially enlarged cross-sectional view of a recording magnetic layer in the magnetic recording medium shown in FIG.
[Explanation of symbols]
X1 magnetic recording medium
S substrate
11 Recording magnetic layer
11a Magnetic column
11a 'Magnetic material film
11b Nonmagnetic region
12 Soft magnetic layer
13 Nonmagnetic layer
14 Protective film
15 Mask fine particles
15a Material grain
15b Enhanced material
16 Underlayer

Claims (1)

A method for manufacturing a magnetic recording medium comprising a recording magnetic layer including a plurality of magnetic columns arranged in parallel with perpendicular magnetic anisotropy and a nonmagnetic region interposed between the plurality of magnetic columns. And
A step for forming a magnetic material film by depositing a magnetic material on a substrate;
A mask forming step for forming an etching mask for masking the magnetic column forming region on the magnetic material film;
Etching the magnetic material film through the etching mask to form a plurality of parallel and spaced magnetic columns;
A non-magnetic region forming step for forming a non-magnetic region interposed between the plurality of magnetic columns by filling a non-magnetic material between the plurality of magnetic columns,
In the mask forming step, a first material having a surface energy lower than that of the magnetic material is formed on the magnetic material film to form a first material film, and a first material having a surface energy higher than that of the first material is formed. A mask as the etching mask is formed by depositing two materials in a granular form on the first material film to form second material grains and depositing a third material on each of the second material grains. A method for producing a magnetic recording medium, wherein particles are formed .

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