JP2004022138A - Vertical magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform recording with a steeper magnetic field of a head by reducing the thickness of an underlayer to obtain a favorable magnetic characteristic, and reducing the gap between a magnetic head and a soft magnetic layer. <P>SOLUTION: The vertical magnetic recording medium has a structure in which at least the underlayer 2, a magnetic recording layer 3, and a protective film 4 are formed in order on a non-magnetic substrate 1. The magnetic recording layer 3 comprises crystal grains having ferromagnetism and a non-magnetic crystal grain field of oxides or nitrides surrounding them, and the surface layer part is formed at a higher gas pressure than the initial layer part by varying the gas pressure when forming the underlayer. As for a method for forming the underlayer 2, the initial layer part is deposited at a low gas pressure, and the surface layer is deposited at a higher gas pressure than the initial layer part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a perpendicular magnetic recording medium and a manufacturing method thereof, and more particularly to a perpendicular magnetic recording medium mounted on various magnetic recording apparatuses and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, a perpendicular magnetic recording method in which the recording magnetization is perpendicular to the in-plane direction of the recording medium is attracting attention as a technique for realizing high density magnetic recording instead of the conventional longitudinal magnetic recording method. A perpendicular magnetic recording medium mainly includes a magnetic recording layer of a hard magnetic material, an underlayer for orienting the magnetic recording layer in a target direction, a protective film for protecting the surface of the magnetic recording layer, and the magnetic recording It is composed of a backing layer of a soft magnetic material that plays a role of concentrating a magnetic flux generated by a magnetic head used for recording on the layer.
[0003]
A medium having a soft magnetic backing layer improves the performance of the medium, but recording is possible without it, so the structure may be omitted. Those without such a soft magnetic underlayer are called single-layer perpendicular magnetic recording media, and those with two layers are called double-layer perpendicular magnetic recording media. In the perpendicular magnetic recording medium as well as the longitudinal magnetic recording medium, it is essential to achieve both high thermal stability and low noise in order to increase the recording density.
[0004]
In conventional longitudinal magnetic recording media, various magnetic recording layer compositions, structures, and nonmagnetic underlayer materials have been proposed and put to practical use. The magnetic recording layer uses an alloy made of CoCr (hereinafter referred to as CoCr) and segregates Cr at the crystal grain boundaries to obtain isolated magnetic particles. As other magnetic recording layer materials, magnetic layers using non-magnetic non-metallic substances such as oxides and nitrides as grain boundary phases called granular magnetic recording layers have been proposed.
[0005]
In CoCr, raising the substrate temperature at the time of film formation to 200 ° C. or more is indispensable for sufficient segregation of Cr. On the other hand, in the case of a granular magnetic recording layer, the nonmagnetic and nonmetallic properties of the film can be formed even without heating. Substances have the characteristic of causing segregation. The above-described CoCr or granular magnetic recording layer can also be applied to a perpendicular magnetic recording medium by causing perpendicular anisotropy by using, for example, a method of controlling crystal orientation with an underlayer.
[0006]
[Problems to be solved by the invention]
In the studies conducted by the inventors so far, when a granular magnetic recording layer is used as the magnetic recording layer of the perpendicular magnetic recording medium, it is easier to obtain a segregation structure than the CoCr described above, and as a result, the magnetic interaction between grains is reduced. It has been found to be low noise because of its reduced effect.
[0007]
In addition, before the formation of the granular magnetic recording layer, the substrate is O ₂ Or N ₂ A method of exposing in the atmosphere has been found, thereby forming a separation structure of ferromagnetic particles from the initial layer of the magnetic recording layer, and further reducing the medium noise and making the magnetic recording layer thinner.
[0008]
This effect is ₂ Or N ₂ Is attached to the crystal grain boundary on the surface of the underlayer, and the nonmagnetic nonmetal is preferentially formed by using it as a nucleus. Therefore, when the surface of the underlayer has a very dense structure and the grain boundary width is small, O ₂ Or N ₂ Is less likely to adhere and its effect is less likely to appear.
[0009]
In general, such an increase in the grain boundary width is caused by crystal growth accompanying an increase in film thickness, and usually has a separation structure on the surface from a film thickness of several tens of nm or more. Although there is a method of forming a film with a high gas pressure at the time of film formation as a method of taking a separation structure even if it is thin, the film does not fulfill its original role because the crystal orientation deteriorates.
[0010]
In the above-described double-layered perpendicular magnetic recording medium having a soft magnetic underlayer, recording can be performed with a steeper head magnetic field as the distance between the magnetic head and the soft magnetic layer becomes smaller. In order to improve the characteristics of the medium, it is necessary to reduce the thickness of the nonmagnetic underlayer provided between the layers as much as possible. Also, from the viewpoint of cost, it is preferable that the film thickness of the underlayer is thin, and this has been a problem of high recording density and low cost.
[0011]
The present invention has been made in view of such a problem, and an object of the present invention is to obtain good magnetic characteristics even when the thickness of the underlayer is reduced and to obtain a magnetic head and a soft magnetic layer. Is a perpendicular magnetic recording medium capable of recording with a steeper head magnetic field and a method for manufacturing the same.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the invention according to claim 1 is a vertical structure in which at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate. In the method of manufacturing a magnetic recording medium, the magnetic recording layer is composed of ferromagnetic crystal grains and oxide or nitride nonmagnetic crystal boundaries surrounding the ferromagnetic grains, and changes the gas pressure when forming the underlayer. The surface layer portion is formed at a higher gas pressure than the initial layer portion.
[0013]
According to a second aspect of the present invention, in the first aspect of the present invention, the gas pressure at the time of forming the initial layer portion of the underlayer is 30 mTorr or less.
[0014]
According to a third aspect of the present invention, there is provided a method for manufacturing a perpendicular magnetic recording medium in which at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate. Is composed of crystal grains having ferromagnetism and nonmagnetic crystal grain boundaries surrounding oxide or nitride, and at the time of forming the underlayer, at least the interface layer with the magnetic recording layer, which is the surface layer, is used as a rare gas. O ₂ Or N ₂ It is formed using a mixed gas to which is added.
[0015]
According to a fourth aspect of the present invention, in the first, second, or third aspect of the present invention, the substrate is placed after the underlayer is formed and before the magnetic recording layer is formed. ₂ Or N ₂ O in atmosphere or noble gas ₂ Or N ₂ The magnetic recording layer is formed after exposure to a mixed gas atmosphere to which is added.
[0016]
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the underlayer is made of at least Ru or RuW, RuTi, RuAl, RuCu, RuSi, RuC, RuB, RuCoCr, or the like. It is an alloy containing Ru.
[0017]
The invention according to claim 6 is the Ni-based alloy of NiFe, NiFeNb, NiFeSi, NiFeB, NiFeNbB, NiFeCr or the like directly under the underlayer in the invention according to any one of claims 1 to 5. A sheet layer is provided.
[0018]
The invention according to claim 7 is a perpendicular magnetic recording medium manufactured by the manufacturing method according to any one of claims 1 to 6.
[0019]
Thus, the present invention proposes two solutions. First, the high gas pressure film formation that makes it easy to create a separation structure is not used from the beginning, but it is applied only to the surface layer portion, so that the crystallinity is maintained even when the underlayer is thin, and only the surface layer is moderately intergranular. Is a means of creating a separate structure. Second, a small amount of O is present at the surface grain boundary of the underlayer. ₂ Or N ₂ In this case, a nonmagnetic nonmetallic formation site of the magnetic recording layer is formed even if the surface does not have a separation structure. Specifically, the following two methods are used.
(1) A method is used in which the film formation process of the underlayer is performed stepwise, the initial layer portion of the underlayer is formed at a low gas pressure, and the surface portion is formed at a gas pressure higher than that of the initial layer portion. That is, the initial layer has a dense structure to ensure crystallinity and orientation, the surface layer has a sparser structure than the initial layer, and a structure having a large grain boundary width so that gas molecules are easily adsorbed.
(2) A small amount of O in a rare gas for the formation of the underlayer ₂ Or N ₂ Is performed in an atmosphere to which O is added. ₂ Or N ₂ Are segregated to the crystal grain boundaries of the underlayer to form nonmagnetic non-metal formation sites that become the crystal grain boundaries of the magnetic recording layer. In this case, O ₂ Or N ₂ It is important to use a material that has low reactivity and does not deteriorate crystal orientation.
[0020]
When a seed layer is provided directly under the underlayer, the seed layer is similarly O ₂ Or N ₂ It is preferable to use a material having low reactivity with the seed layer. ₂ Or N ₂ When the reactivity is high, epitaxial growth of the underlayer may be hindered. On the other hand, O ₂ Or N ₂ Is present only at the interface with the magnetic recording layer. Therefore, the initial layer portion of the underlayer is formed using only a rare gas, and O 2 is formed when the surface layer portion is formed. ₂ Or N ₂ If added, the seed layer is O ₂ Or N ₂ Therefore, the range of material selection can be expanded.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an embodiment of the perpendicular magnetic recording medium of the present invention. In the figure, reference numeral 1 denotes a nonmagnetic substrate, 2 denotes an underlayer, 2a denotes high gas pressure film formation, and 2b denotes low gas pressure formation. A film 3, a magnetic recording layer 4, a protective film 4, and a liquid lubricant layer 5. This perpendicular magnetic recording medium has a structure in which at least an underlayer 2, a magnetic recording layer 3, and a protective film 4 are sequentially formed on a nonmagnetic substrate 1, and a liquid lubricant layer 5 is further formed thereon. Is formed.
[0022]
As the nonmagnetic substrate 1, there can be used Al alloy plated with NiP, tempered glass, crystallized glass, etc., which are used for ordinary magnetic recording media. When the substrate heating temperature is suppressed to 100 ° C. or less, a plastic substrate made of a resin such as polycarbonate or polyolefin can be used.
[0023]
As the underlayer 2, for example, a metal having a hexagonal close packed structure or an alloy material thereof, or a metal having a face-centered cubic lattice structure or an alloy material thereof is preferably used. Examples of the metal having the hexagonal close packed structure described above include Ti, Zr, Ru, Zn, Tc, Re, and the like, and examples of the metal having a face-centered cubic lattice structure include Cu, Rh, Pd, Ag, Ir, Pt, Examples include Au, Ni, Co and the like. In the case of providing a soft magnetic backing layer, which will be described later, the distance between the magnetic head and the soft magnetic layer needs to be as small as possible. Therefore, the film thickness of the underlayer is preferably as small as possible.
[0024]
As a method for forming the underlayer 2, as shown in FIG. 1, there is a method in which the initial layer portion is formed at a lower gas pressure and the surface layer is formed at a higher gas pressure than the initial layer portion. The optimum value of the pressure varies depending on the underlayer material and the magnetic recording layer composition, but the gas pressure during the initial layer deposition is preferably 30 mTorr or less.
[0025]
For example, a thin film mainly composed of carbon is used as the protective film 4. In addition, the liquid lubricant layer 5 can use, for example, a perfluoropolyether lubricant.
[0026]
FIG. 2 is a schematic cross-sectional view showing another embodiment of the perpendicular magnetic recording medium of the present invention, in which reference numeral 12 denotes an underlayer and 12a denotes O. ₂ Or N ₂ Additional gas film formation, 12b shows Ar gas film formation. In addition, the component which has the same function as FIG. 1 is attached | subjected the same code | symbol.
[0027]
In this embodiment, as shown in FIG. 2, the underlayer 12 is formed by using a rare gas with O 2 when forming the underlayer. ₂ Or N ₂ Is a method using a mixed gas containing. O ₂ And N ₂ Is preferably selected according to the nonmagnetic nonmetal of the magnetic recording layer. When the seed layer is provided directly under the underlayer, the seed layer material is O ₂ Or N ₂ If the reactivity of the seed layer is large, the surface of the seed layer becomes O when the mixed layer is formed from the initial layer. ₂ Or N ₂ May interfere with the epitaxial growth of the underlayer. In order to broaden the choice of seed layer material, the initial layer of the underlayer is formed only with a rare gas and O during the formation of the surface layer. ₂ Or N ₂ What is necessary is just to take the method using the mixed gas containing.
[0028]
In both of the above-described methods for forming the underlying layer, the film thickness ratio between the initial layer and the surface layer is not particularly limited. However, since it is important to sufficiently perform crystal growth in the initial layer, this region is It is preferable that it is 2 nm or more.
[0029]
3 and 4 are schematic cross-sectional views showing still another embodiment of the perpendicular magnetic recording medium of the present invention, in which reference numeral 21 denotes a soft magnetic backing layer and 22 denotes a seed layer. In addition, the component which has the same function as FIG.1 and FIG.2 is attached | subjected the same code | symbol.
[0030]
In order to improve the orientation of the underlayers 2 and 12, the seed layer 22 can be provided immediately below the underlayers 2 and 12. Materials similar to those listed for the underlayers 2 and 12 can be used. A non-magnetic material may be used, but when the seed layer is a two-layer perpendicular medium, a material that exhibits soft magnetic properties so as to function as a part of the soft magnetic layer is preferable. Examples of the seed layer 22 exhibiting soft magnetic properties include Ni-based alloys such as NiFe, NiFeNb, NiFeSi, NiFeB, NiFeCr, and NiFeNbB.
[0031]
In the case of providing a dual-layer perpendicular magnetic recording medium, when the seed layer 22 is provided below the underlayers 2 and 12, the soft magnetic backing layer 21 that plays a role of concentrating the magnetic flux generated by the magnetic head is provided below the seed layer 22. Can be provided. As the soft magnetic backing layer 21, for example, crystalline NiFe alloy, Sendust (FeSiAl) alloy, or the like, microcrystalline FeTaC or CoTaZr, amorphous Co alloy CoZrNb, or the like can be used. The optimum value of the film thickness of the soft magnetic backing layer 21 varies depending on the structure and characteristics of the magnetic head used for recording, but is preferably about 10 nm or more and 500 nm or less in view of productivity.
[0032]
The magnetic recording layer 3 has a structure having crystal grains having ferromagnetism and a nonmagnetic grain boundary surrounding the crystal grain, and a granular magnetic recording layer in which the nonmagnetic grain boundary is a nonmagnetic metal is used. As the crystals having ferromagnetism, for example, CoPt and FePt alloys, and alloys obtained by adding elements such as Cr, Ni, Nb, Ta, and B to them are preferable.
[0033]
As the nonmagnetic nonmetal of the nonmagnetic grain boundary, an oxide or nitride is preferable. For example, an oxide or nitride of Cr, Co, Si, Al, Ti, Ta, Hf, Zr, Y, or Ce is preferably used. It is done. For use as a perpendicular magnetic recording medium, the ferromagnetic crystal grains must have perpendicular anisotropy with respect to the film surface.
[0034]
In order to further improve the characteristics, as shown in FIGS. 3 and 4, the surface of the substrate before the formation of the magnetic recording layer 3, that is, the surface of the underlayer 2 is changed to O 2. ₂ Or N ₂ O in atmosphere or noble gas ₂ Or N ₂ A method of exposing in a mixed gas atmosphere to which is added can be used. Thereafter, by forming the magnetic recording layer 3, ferromagnetic crystal grains and nonmagnetic nonmetallic grain boundaries are formed from the initial layer, and a magnetic recording layer having a good segregation structure can be formed.
[0035]
Specific examples of the present invention will be described below. In addition, this invention is not limited to those Examples, It can change variously in the range which does not deviate from the summary of this invention.
[0036]
[Example 1]
A chemically strengthened glass substrate (for example, N-5 glass substrate manufactured by HOYA) having a smooth surface is used as a nonmagnetic substrate, which is introduced into a sputtering apparatus after cleaning, and Ni which is a nonmagnetic Ni-based alloy. ₅₈ Fe ₁₅ Cr ₂₇ Using a target, a NiFeCr seed layer having a thickness of 15 nm was formed under an Ar gas pressure of 5 mTorr.
[0037]
Subsequently, a Ru underlayer is formed using a Ru target. The initial layer 5 nm is formed under an Ar gas pressure of 30 mTorr, the surface layer 5 nm is formed under 80 mTorr, and the total film thickness is 10 nm. . Then 92 (Co ₇₅ Cr ₁₀ Pt ₁₅ ) -8SiO ₂ CoCrPt-SiO with target ₂ A magnetic recording layer was formed to a thickness of 20 nm under an Ar gas pressure of 30 mTorr.
[0038]
Finally, a protective film 6 nm made of carbon was formed using a carbon target, and then taken out from the vacuum apparatus. Thereafter, a liquid lubricant layer 2 nm made of perfluoropolyether was formed by a dip method to obtain a single layer perpendicular magnetic recording medium. RF sputtering was used to form the magnetic recording layer, and all other layers were formed by DC magnetron sputtering.
[0039]
[Example 2]
After forming the Ru underlayer, CoCrPt-SiO ₂ Before film formation of the magnetic recording layer, 5% O in Ar ₂ A single-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 1 except that the exposure was performed in an atmosphere containing 10 seconds. Ar + O at this time ₂ The pressure was 5 mTorr and the flow rate was 60 sccm.
[0040]
[Example 3]
When the Ru underlayer is formed, the initial layer is formed with a thickness of 5 nm under Ar gas of 30 mTorr, and the surface layer of 5 nm is formed with 0.5% O in Ar. ₂ A single-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 1 except that a film was formed using a mixed gas to which a gas was added under a gas pressure of 10 mTorr.
[0041]
[Example 4]
After forming the Ru underlayer, CoCrPt-SiO ₂ Before film formation of the magnetic recording layer, 5% O in Ar ₂ A single-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 3 except that the exposure was performed in an atmosphere containing 10 seconds. Ar + O at this time ₂ The pressure was 5 mTorr and the flow rate was 60 sccm.
[0042]
[Comparative Example 1]
As a comparative example of Examples 1 and 3, single-layer perpendicular magnetic recording was performed in the same manner as Example 1 except that the Ar gas pressure during Ru film formation was constant at 30 mTorr and the film thickness was 10 nm or 20 nm. Two types of media were produced.
[0043]
[Comparative Example 2]
As a comparative example of Examples 2 and 4, after forming a Ru underlayer, CoCrPt-SiO ₂ Before film formation of the magnetic recording layer, 5% O in Ar ₂ Two types of single-layer perpendicular magnetic recording media were produced in the same manner as in Comparative Example 1 except that the exposure was performed in an atmosphere containing 10 seconds. Ar + O at this time ₂ The pressure was 5 mTorr and the flow rate was 60 sccm.
[0044]
[Example 5]
A chemically strengthened glass substrate (for example, N-5 glass substrate manufactured by HOYA) having a smooth surface is used as a nonmagnetic substrate, and this is introduced into a sputtering apparatus after cleaning. ₈₆ Zr ₅ Nb ₉ After forming 300 nm of CoZrNb under an Ar gas pressure of 5 mTorr using a target, Ni is a soft magnetic Ni-based alloy. ₈₀ Fe ₁₂ Nb ₃ B ₅ Using a target, a NiFeNbB soft magnetic seed layer was formed to a thickness of 30 nm under an Ar gas pressure of 5 mTorr.
[0045]
Further, using a Ru target, an initial layer of 6 nm was formed under an Ar gas pressure of 10 mTorr, and then a 2 nm surface layer was formed under an Ar gas pressure of 80 mTorr to form a total of 8 nm. Subsequently, 5% O in Ar ₂ For 10 seconds in an atmosphere containing Ar + O at this time ₂ The pressure was 5 mTorr and the flow rate was 60 sccm. Then 92 (Co ₇₅ Cr ₁₀ Pt ₁₅ ) -8SiO ₂ CoCrPt-SiO with target ₂ A magnetic recording layer was formed to a thickness of 12 nm under an Ar gas pressure of 30 mTorr.
[0046]
Finally, a protective film 6 nm made of carbon was formed using a carbon target, and then taken out from the vacuum apparatus. Thereafter, a liquid lubricant layer 2 nm made of perfluoropolyether was formed by a dipping method to obtain a two-layer perpendicular magnetic recording medium. RF sputtering was used to form the magnetic recording layer, and all other layers were formed by DC magnetron sputtering.
[0047]
[Example 6]
When the Ru underlayer is formed, the initial layer 6 nm is formed under Ar gas 10 mTorr, and the surface layer 2 nm is formed with 0.5% O in Ar. ₂ A double-layered perpendicular magnetic recording medium was obtained in the same manner as in Example 5 except that a film with a gas added was used to form a film at a gas pressure of 10 mTorr.
[0048]
[Example 7]
A chemically strengthened glass substrate (for example, N-5 glass substrate manufactured by HOYA) having a smooth surface is used as a nonmagnetic substrate, and this is introduced into a sputtering apparatus after cleaning. ₉₂ Ta ₃ Zr ₅ After forming 300 nm of CoTaZr under an Ar gas pressure of 5 mTorr using a target, Ni is a soft magnetic Ni-based alloy. ₈₀ Fe ₁₂ Nb ₈ Using a target, an NiFeNb seed layer was formed to a thickness of 30 nm under an Ar gas pressure of 5 mTorr.
[0049]
Ru ₇₅ W ₂₅ Using a target, a RuW underlayer was formed with an initial layer of 6 nm under an Ar gas pressure of 10 mTorr, and then a 2 nm surface layer was formed under an Ar gas pressure of 80 mTorr to form a total of 8 nm. Subsequently, 3% N ₂ For 10 seconds in an Ar atmosphere to which was added. Ar + N at this time ₂ The pressure was 5 mTorr and the flow rate was 60 sccm. Then 92 (Co ₇₃ Cr ₁₀ Pt ₁₇ ) A CoCrPt-SiN magnetic recording layer was formed to a thickness of 12 nm under an Ar gas pressure of 30 mTorr using a -8 SiN target.
[0050]
Finally, a protective film 6 nm made of carbon was formed using a carbon target, and then taken out from the vacuum apparatus. Thereafter, a liquid lubricant layer 2 nm made of perfluoropolyether was formed by a dipping method to obtain a two-layer perpendicular magnetic recording medium. RF sputtering was used to form the magnetic recording layer, and all other layers were formed by DC magnetron sputtering.
[0051]
[Example 8]
When the RuW underlayer is formed, the initial layer 6 nm is formed under Ar gas 10 mTorr, and the surface layer 2 nm is 0.5% N in Ar. ₂ A double-layered perpendicular magnetic recording medium was obtained in the same manner as in Example 7 except that the film was formed under a gas pressure of 10 mTorr using a mixed gas to which was added.
[0052]
[Comparative Example 3]
As a comparative example of Examples 5 and 6, a dual-layer perpendicular magnetic recording medium was obtained in the same manner as Example 5 except that the Ru underlayer was formed with the Ar gas pressure during Ru film formation being constant at 30 mTorr. At this time, two types with a Ru film thickness of 8 nm and 20 nm were prepared.
[0053]
[Comparative Example 4]
As a comparative example of Examples 7 and 8, a dual-layer perpendicular magnetic recording medium was obtained in the same manner as in Example 7 except that the RuW underlayer was formed with the Ar gas pressure during RuW film formation being constant at 30 mTorr. At this time, two types with a RuW film thickness of 8 nm and 20 nm were produced.
[0054]
First, Examples 1-4 and Comparative Examples 1-2 in the present invention will be described. FIG. 5 shows the magnetic property measurement results performed for each example and comparative example. Magnetic property evaluation was performed using VSM, and the coercive force Hc and the inclination α of the magnetization curve were obtained from the obtained MH loop. α is a value obtained by multiplying (dM / dH) by 4π at H = Hc. The larger the value, the larger the magnetization reversal unit of the magnetic recording layer. You may think that the unit is small. Since the smaller the magnetization reversal unit, the smaller bits can be written, the density can be increased.
[0055]
Compared with Comparative Examples 1 and 2 in which Ru is formed at a constant Ar gas pressure of 30 mTorr, Hc decreases and α also increases when the Ru film thickness is small. Further, the larger the Ru film thickness, the more Ar + O. ₂ The effect of exposure, ie, an increase in Hc and a decrease in α, is noticeable. Comparing Examples 1 and 3 with Comparative Example 1, when compared with the same Ru film thickness of 10 nm, Hc increases and α decreases, and even when compared with the Comparative Example 1 Ru film thickness of 20 nm, Example 1 In Example 3, substantially the same characteristics are obtained, and in Example 3, characteristics exceeding the same are obtained.
[0056]
Ar + O ₂ Comparing the exposed Examples 2 and 4 with Comparative Example 2, when compared with the same Ru film thickness of 10 nm, Hc increases and α decreases, and even when compared with the Ru film thickness of Comparative Example 2 of 20 nm. In the second embodiment, characteristics exceeding the above are obtained, and in the fourth embodiment, substantially the same characteristics are obtained.
[0057]
From the above, if the underlayer structure according to the present invention is used, it is possible to promote the segregation structure of the magnetic recording layer even if the underlayer thickness is thin, and a reduction in α is realized with an increase in Hc.
[0058]
Next, Examples 5 to 8 and Examples 3 to 4 in the present invention will be described. FIG. 6 shows the magnetic property evaluation results and electromagnetic conversion property evaluation results performed for each example and comparative example. The value of the coercive force Hc was obtained from the hysteresis loop of the Kerr effect measurement.
[0059]
The SNR (signal-to-noise ratio) in the electromagnetic conversion characteristic evaluation is such that the magnetic recording medium produced is rotated by a spin stand tester so that the relative speed with respect to the magnetic head is 14 m / sec, and the recording track width is 0. Recording was performed with a 6 μm single magnetic pole head, and the recorded signal was reproduced by a GMR head having a reproduction track width of 0.4 μm. Note that the values of SNR shown in the table of FIG. 6 are values at a linear recording density of 400 KLCI.
[0060]
In Examples 5 and 6 and Comparative Example 3, the nonmagnetic nonmetal of the magnetic recording layer is made of SiO. ₂ Ar + O before forming the magnetic recording layer ₂ Although these were exposed, when these were compared, Examples 5 and 6 had higher Hc and SNR than Comparative Example 3, and exhibited excellent characteristics. In Comparative Example 3, the Ru film thickness is 8 nm, since the Hc is significantly reduced as compared with Examples 5 and 6, the SNR is also reduced. In Comparative Example 3 where the Ru film thickness was 20 nm, Hc was the same as in Examples 5 and 6, but the SNR was small. This is because the distance between the magnetic head and the soft magnetic layer is larger in Comparative Example 3 than in Examples 5 and 6, and the transition width between the written bits is widened as the magnetic field gradient of the magnetic head is increased. This is because noise increased.
[0061]
In Examples 7 and 8 and Comparative Example 4, the nonmagnetic nonmetal of the magnetic recording layer was SiN, and Ar + N was formed before the magnetic recording layer was formed. ₂ As a result of exposure, Examples 7 and 8 compared with Comparative Example 4 had higher Hc and SNR and showed excellent characteristics. In Comparative Example 4, the Ru film thickness is 8 nm, since the Hc is significantly reduced as compared with Examples 7 and 8, the SNR is also reduced. In Comparative Example 4 where the Ru film thickness is 20 nm, Hc is the same as in Examples 7 and 8, but the SNR is small. This is because in Comparative Example 4, the distance between the magnetic head and the soft magnetic layer is larger than in Examples 7 and 8, and the transition width between the written bits is widened as the magnetic field gradient of the magnetic head is increased. This is because noise increased.
[0062]
【The invention's effect】
As described above, according to the present invention, in the method of manufacturing a perpendicular magnetic recording medium in which at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate, the magnetic recording layer is The surface layer portion is made to have a higher gas pressure than the initial layer portion by changing the gas pressure during the formation of the underlayer, which is composed of crystal grains having ferromagnetism and nonmagnetic crystal grain boundaries of oxide or nitride surrounding it. Therefore, good magnetic properties can be obtained even if the underlayer thickness is small. As a result of thinning the underlayer, the distance between the magnetic head and the soft magnetic layer is reduced. For this reason, recording can be performed with a steeper head magnetic field, and noise is reduced. Therefore, a high SNR can be obtained and a high recording density of the perpendicular magnetic recording medium can be realized. Further, the cost can be reduced by reducing the thickness of the underlayer.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing one embodiment of a perpendicular magnetic recording medium of the present invention.
FIG. 2 is a schematic cross-sectional view showing another embodiment of the perpendicular magnetic recording medium of the present invention.
FIG. 3 is a schematic cross-sectional view showing still another embodiment of the perpendicular magnetic recording medium of the present invention.
FIG. 4 is a schematic cross-sectional view showing still another embodiment of the perpendicular magnetic recording medium of the present invention.
5 is a diagram showing coercive force Hc and magnetization curve slope α obtained by magnetic characteristic evaluation according to Examples 1 to 4 and Comparative Examples 1 and 2. FIG.
6 is a diagram showing coercive force Hc obtained from magnetic characteristic evaluation and SNR obtained from electromagnetic conversion characteristic evaluation according to Examples 5 to 8 and Comparative Examples 3 to 4. FIG.
[Explanation of symbols]
1 Non-magnetic substrate
2 Underlayer
2a High gas pressure film formation
2b Low gas pressure film formation
3 Magnetic recording layer
4 Protective film
5 Liquid lubricant layer
12 Underlayer
12a O ₂ Or N ₂ Additive gas deposition
12b Ar gas deposition
21 Soft magnetic underlayer
22 Seed layer

Claims (7)

In a method for manufacturing a perpendicular magnetic recording medium in which at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate, the magnetic recording layer comprises ferromagnetic crystal grains and The vertical layer is characterized by comprising non-magnetic crystal grain boundaries of surrounding oxide or nitride and changing the gas pressure at the time of forming the underlayer to form the surface layer portion at a higher gas pressure than the initial layer portion. A method of manufacturing a magnetic recording medium. 2. The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein a gas pressure at the time of forming the initial layer portion of the underlayer is 30 mTorr or less. In a method of manufacturing a perpendicular magnetic recording medium in which at least an underlayer, a magnetic recording layer, a protective film, and a liquid lubricant layer are sequentially laminated on a nonmagnetic substrate, the magnetic recording layer comprises ferromagnetic crystal grains and A mixed gas in which O ₂ or N ₂ is added to a rare gas at the interface layer with the magnetic recording layer, which is the surface layer, is formed of the surrounding oxide or nitride nonmagnetic crystal grain boundary and at the time of forming the underlayer. A method of manufacturing a perpendicular magnetic recording medium, characterized by being used. After the formation of the underlayer, before the formation of the magnetic recording layer, the substrate is exposed to an O ₂ or N ₂ atmosphere or a mixed gas atmosphere in which O ₂ or N ₂ is added to a rare gas, and then the magnetic recording is performed. 4. The method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein a layer is formed. 5. The perpendicular magnetic recording according to claim 1, wherein the underlayer is made of Ru or an alloy containing at least Ru, such as RuW, RuTi, RuAl, RuCu, RuSi, RuC, RuB, and RuCoCr. A method for manufacturing a medium. 6. The perpendicular magnetic recording medium according to claim 1, wherein a sheet layer made of a Ni-based alloy such as NiFe, NiFeNb, NiFeSi, NiFeB, NiFeNbB, or NiFeCr is provided immediately below the underlayer. Production method. A perpendicular magnetic recording medium manufactured by the manufacturing method according to claim 1.

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