JP2011096307A - Method for manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a perpendicular magnetic recording medium by which a recording density is made further higher by narrowing a track width and simultaneously improving an SNR. <P>SOLUTION: The method for manufacturing includes: a step to deposit at least an underlayer 150 including an Ru alloy as a main component on a substrate; and a step to deposit a plurality of magnetic layers (a first recording layer 161, a second recording layer 162) having a granular structure composed of a magnetic particle with a column-grown CoCrPt alloy as a main component and a non-magnetic grain boundary part with an oxide as a main component on the upper side of the underlayer, wherein, among the plurality of magnetic layers, at least a magnetic layer (the first recording layer 161) in contact with the underlayer is deposited without applied bias voltage, and at least a magnetic layer (the second recording layer 162) of one or a plurality of magnetic layers deposited closer to the surface layer side than the magnetic layer deposited without the applied bias voltage is deposited while applying the bias voltage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like.

Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 320 GB / platter has been required for a 2.5-inch diameter magnetic recording medium used for HDDs and the like, and in order to meet such a request, 500 GB / inch is required. It is required to realize an information recording density exceeding ² .

  In recent years, a perpendicular magnetic recording system has been proposed in order to achieve a high recording density in a magnetic recording medium used for an HDD or the like. The perpendicular magnetic recording medium used for the perpendicular magnetic recording system is adjusted so that the easy axis of magnetization of the magnetic recording layer is oriented in the direction perpendicular to the substrate surface. Compared with the conventional in-plane magnetic recording system, the perpendicular magnetic recording system can suppress the so-called thermal fluctuation phenomenon in which the thermal stability of the recording signal is lost due to the superparamagnetic phenomenon and the recording signal disappears. It is suitable for increasing the recording density.

  In order to achieve higher recording density in a perpendicular magnetic recording medium, various techniques for improving the characteristics of the medium (electromagnetic conversion characteristics, magnetostatic characteristics, etc.) have been proposed and disclosed. For example, Patent Document 1 discloses a method of manufacturing a perpendicular magnetic recording medium in which a direct current bias is applied to the substrate surface when each of the orientation adjustment layer (underlayer) and the magnetic recording layer is formed. According to Patent Document 1, since the film surface of the magnetic recording layer can be flattened, the isolation of magnetic particles can be promoted, and a granular structure with good orientation can be formed. It can be realized.

JP 2008-90918 A

However, in the perpendicular magnetic recording medium, in order to realize the information recording density exceeding 500 GBit / Inch ² described above, it is necessary to further improve the characteristics of the medium (static magnetic characteristics, electromagnetic conversion characteristics). In particular, since high TPI (Track per Inch) is required, it is necessary to improve the SNR after realizing narrowing of the track width.

It is known that crystallinity can be improved by forming a film while applying a bias as in Patent Document 1 described above. However, the inventors have confirmed that it is insufficient to achieve a track width and SNR of 500 GBit / Inch ² level.

  Accordingly, an object of the present invention is to provide a method of manufacturing a perpendicular magnetic recording medium that can achieve further higher recording density by reducing the track width and simultaneously improving the SNR.

  In order to solve the above-mentioned problems, the inventors have intensively studied. When forming a film while applying a bias, the degree of mixing with the lower layer becomes stronger than that during normal film formation, and the upper and lower layers I thought that a “mixing layer” in which these materials were mixed would occur. That is, when a bias is applied when a magnetic layer containing CoCrPt is formed on the Ru underlayer, a mixing layer made of a material in which CoCrPt and Ru are mixed is generated, and as a result, a crystal in the initial growth stage of the magnetic layer is generated. We thought that the magnetic properties would be deteriorated due to the disorder of the magnetic properties and the fine structure. Therefore, when applying a bias, if the composition of the base layer (outermost surface layer) and the layer formed while applying the bias are similar, the inventors may generate a mixing layer. It was predicted that the disorder of crystallinity and microstructure would not occur, and the present invention was completed by further research.

  That is, in order to solve the above-described problems, a typical configuration of a method for manufacturing a perpendicular magnetic recording medium according to the present invention includes a step of forming a base layer containing at least a Ru alloy as a main component on a substrate, Forming a plurality of magnetic layers having a granular structure composed of magnetic particles mainly composed of columnar-grown CoCrPt alloy and non-magnetic grain boundary portions mainly composed of oxides above the base layer; A plurality of magnetic layers, at least a magnetic layer that is in contact with the underlayer is formed without applying a bias voltage (on the substrate), and on the surface layer side of the magnetic layer formed without applying a bias voltage. At least one magnetic layer among the one or more magnetic layers to be formed is formed while applying a bias voltage (to the substrate).

  According to the above configuration, the crystallinity of the magnetic layer can be improved by forming the film while applying a bias voltage to the substrate. At this time, a bias voltage is not applied to the substrate when the magnetic layer immediately above the underlayer is formed, and a bias voltage is applied to the substrate when the magnetic layer is formed thereon. Generation of a mixing layer mixed with a CoCrPt alloy or the like can be prevented. As a result, the crystallinity of the magnetic particles of the magnetic layer to which the bias voltage is applied is not disturbed. Therefore, the SNR can be improved while narrowing the track width, and the recording density can be further increased.

  In the above configuration, the magnetic layer formed without applying a bias voltage to the substrate is not limited to the magnetic layer directly above the base layer. In other words, the magnetic layer formed without applying a bias voltage is one or a plurality of magnetic layers including the magnetic layer immediately above the base layer. Therefore, the plurality of magnetic layers having the above-described granular structure include one or more magnetic layers formed without applying a bias voltage, and one or more magnetic layers formed while applying a bias voltage thereon. Including.

As used herein, the term “main component” refers to a component that is contained most when the overall composition is at% (or mol%). For example, when considering a composition of 90 (70Co-10Cr-20Pt) -10 (SiO ₂ ), it is assumed that the CoCrPt alloy is the main component because it accounts for 90% of the total. Further, since Co accounts for 70% in the CoCrPt alloy, Co is assumed to be the main component of the CoCrPt alloy.

  The bias voltage is preferably applied within a range of −50 to −200V. Within this range, the crystallinity of the magnetic layer can be preferably improved. This is because if the bias voltage is too small, the crystallinity improving effect may not be sufficiently obtained, and if it is too high, the granular structure may be disturbed and the magnetic characteristics may be deteriorated.

  The magnetic layer formed without applying a bias voltage is preferably formed with a total film thickness of 1 nm or more. Thereby, it is possible to reliably prevent the generation of a mixing layer in which the Ru alloy or the like of the underlayer and the CoCrPt alloy or the like of the magnetic layer are mixed.

  According to the present invention, it is possible to provide a method of manufacturing a perpendicular magnetic recording medium capable of achieving further higher recording density by reducing the track width and simultaneously improving the SNR.

It is a figure explaining the structure of a perpendicular magnetic recording medium. It is a figure explaining an Example and a comparative example. It is a figure which compares the Example from which the film thickness of a 1st recording layer differs.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Perpendicular magnetic recording medium)
FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 according to the first embodiment. A perpendicular magnetic recording medium 100 shown in FIG. 1 includes a substrate 110, an adhesion layer 120, a soft magnetic layer 130, a pre-underlayer 140, an underlayer 150, a first recording layer 161, a second recording layer 162, a dividing layer 170, and auxiliary recording. The layer 180, the protective layer 190, and the lubricating layer 200 are included. The first recording layer 161 and the second recording layer 162 together constitute the main recording layer 160.

  As the substrate 110, for example, a glass disk obtained by forming amorphous aluminosilicate glass into a disk shape by direct pressing can be used. The type, size, thickness, etc. of the glass disk are not particularly limited. Examples of the material of the glass disk include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or glass ceramic such as crystallized glass. It is done. The glass disk can be ground, polished, and chemically strengthened in order to obtain a smooth nonmagnetic substrate 110 made of the chemically strengthened glass disk.

  On the substrate 110, a film is sequentially formed from the adhesion layer 120 to the auxiliary recording layer 180 by a DC magnetron sputtering method, and the protective layer 190 can be formed by a CVD method. Thereafter, the lubricating layer 200 can be formed by a dip coating method. Hereinafter, the configuration of each layer will be described.

  The soft magnetic layer 130 serves to help the signal writing to the magnetic recording layer and increase the density by converging the write magnetic field from the head when recording a signal in the perpendicular magnetic recording system. As the soft magnetic material, in addition to cobalt-based alloys such as CoTaZr, FeCo-based alloys such as FeCoCrB, FeCoTaZr, and FeCoNiTaZr, and materials exhibiting soft magnetic properties such as NiFe-based alloys can be used. In addition, by interposing a spacer layer made of Ru substantially in the middle of the soft magnetic layer 130, it can be configured to have AFC (Antiferro-magnetic exchange coupling). By doing so, the perpendicular component of magnetization can be extremely reduced, so that noise generated from the soft magnetic layer 130 can be reduced. When the spacer layer is interposed, the thickness of the soft magnetic layer 130 can be about 0.3 to 0.9 nm for the spacer layer and about 10 to 50 nm for the upper and lower layers of the soft magnetic material. .

  The pre-underlayer 140 has a function of promoting crystal orientation of the underlayer 150 formed thereabove and a function of controlling a fine structure such as a grain size. The pre-underlayer 140 may have an hcp structure, but preferably has a face-centered cubic structure (fcc structure) oriented so that the (111) plane is parallel to the main surface of the substrate 110. Examples of the material of the pre-underlayer 140 include Ni, Cu, Pt, Pd, Ru, Co, Hf, and one or more of V, Cr, Mo, W, Ta, and the like mainly containing these metals. It can be an added alloy. Specifically, NiV, NiCr, NiTa, NiW, NiVCr, CuW, CuCr and the like can be suitably selected. The film thickness of the pre-underlayer 140 can be about 1 to 20 nm. Further, the pre-underlayer 140 may have a multi-layer structure.

  The underlayer 150 has an hcp structure, and has a function of promoting the crystal orientation of the magnetic crystal grains of the hcp structure of the main recording layer 160 formed thereabove and a function of controlling a fine structure such as a grain size. In other words, it is a layer that becomes the basis of the granular structure of the main recording layer 160. Since Ru has the same hcp structure as Co and the lattice spacing of the crystal is close to Co, magnetic grains mainly composed of Co can be well oriented. Therefore, the higher the crystal orientation of the under layer 150, the more the crystal orientation of the main recording layer 160 can be improved. Further, by reducing the particle size of the under layer 150, the particle size of the main recording layer can be reduced. It can be miniaturized. Ru is a typical material for the underlayer 150, but metals such as Cr and Co, and oxides can also be added. The film thickness of the underlayer 150 can be, for example, about 5 to 40 nm.

  Further, the base layer 150 may have a two-layer structure by changing the gas pressure during sputtering. Specifically, when forming the upper layer side of the underlayer 150, if the Ar gas pressure is set higher than when forming the lower layer side, the crystal orientation of the upper main recording layer 160 is maintained well, It is possible to reduce the particle size of the magnetic particles.

The first recording layer 161 has a columnar granular structure in which a grain boundary is formed by segregating a non-magnetic substance mainly composed of an oxide around a ferromagnetic magnetic particle composed mainly of a Co—Pt alloy. A magnetic layer having In the present embodiment, by forming a film by using a target which contains the _SiO 2, TiO ₂ to CoCrPt-based alloy, SiO ₂ and a non-magnetic material around the magnetic particles (grains) composed of a CoCrPt alloy, TiO ₂ segregates to form a grain boundary, and a granular structure in which magnetic particles grow in a columnar shape can be formed. Further, the magnetic particles of the first recording layer 161 can be continuously epitaxially grown from the crystal structure of Ru contained in the underlayer.

  The second recording layer 162 is a magnetic layer provided on the first recording layer 161 and having a granular structure like the first recording layer 161. The description of the composition is omitted because it overlaps with the first recording layer 161.

  In this embodiment, the first recording layer 161 in contact with the base layer 150 is formed without applying a bias voltage to the substrate 110, and the second recording layer 162 is formed on the surface layer side of the first recording layer 161. A film is formed while applying a bias voltage to the substrate 110. Thereby, the crystallinity of the magnetic particles of the second recording layer 162 can be improved without disturbing the fine structure (granular structure). Therefore, the SNR can be improved in a narrow track width.

  The bias voltage is preferably applied within a range of −50 to −200V. Within this range, the crystallinity of the second recording layer 162 can be preferably improved. This is because if the bias voltage is too small, the crystallinity improving effect may not be sufficiently obtained, and if it is too high, the granular structure may be disturbed and the magnetic characteristics may be deteriorated.

  In general, it is known that by forming a metal film while applying a bias voltage to the substrate 110, the crystallinity of the metal film can be improved. However, this time, simply by applying a bias voltage to the main recording layer 160, the expected effect could not be obtained. This is because the application of a bias voltage generates a mixing layer containing both the Ru alloy of the underlayer 150 and the CoCrPt alloy of the first recording layer 161, and the crystallinity of the magnetic particles above the mixing layer and This is probably because the fine structure has been disturbed.

  However, according to the configuration of the present embodiment, since the first recording layer 161 is formed without applying a bias voltage to the substrate 110, there is no possibility that Ru or the like of the underlayer 150 mixes with the first recording layer 161. . Further, since the first recording layer 161 and the second recording layer 162 have similar compositions, even if mixing occurs between them, the crystallinity and fine structure of the magnetic particles are not disturbed. Therefore, it is considered that the effect of improving the crystallinity by applying the bias voltage could be obtained effectively.

The material used for the main recording layer 160 described above is an example, and the present invention is not limited to this. As the CoCrPt-based alloy, one or more kinds of B, Ta, Cu, etc. may be added to CoCrPt. Examples of nonmagnetic materials for forming grain boundaries include silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), chromium oxide (Cr ₂ O ₃ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta). An oxide such as ₂ O ₅ ) can be exemplified. Further, not only one kind of oxide but also two or more kinds of oxides can be used in combination.

  The dividing layer 170 is provided on the main recording layer 160 and below the auxiliary recording layer 180, and is a layer for adjusting the magnetic connection between the upper and lower layers. The dividing layer 170 is preferably non-magnetic, but may have weak magnetism.

  The dividing layer 170 is provided between the main recording layer 160 and the auxiliary recording layer 180 and has an effect of adjusting the strength of exchange coupling between these layers. As a result, the strength of the magnetic coupling acting between the main recording layer 160 and the auxiliary recording layer 180 and between the adjacent magnetic particles in the main recording layer 160 can be adjusted, so that thermal fluctuations such as Hc and Hn occur. The recording / reproducing characteristics such as the overwrite characteristic and the SNR characteristic can be improved while maintaining the magnetostatic value related to the durability.

The split layer 170 is preferably a layer mainly composed of Ru or Co having an hcp crystal structure so as not to lower the inheritance of crystal orientation. As the Ru-based material, in addition to Ru, a material obtained by adding other metal element, oxygen, or oxide to Ru can be used. As the Co-based material, a CoCr alloy or the like can be used. Specific examples include Ru, RuCr, RuCo, Ru—SiO 2, Ru—WO ₃ , Ru—TiO ₂ , CoCr, CoCr—SiO ₂ , and CoCr—TiO ₂ . In addition, although the non-magnetic material is normally used for the dividing layer 170, it may have weak magnetism. In order to obtain good exchange coupling strength, the thickness of the dividing layer 170 is preferably in the range of 0.2 to 1.0 nm.

  The auxiliary recording layer 180 is a magnetic layer that is substantially magnetically continuous in the in-plane direction of the main surface of the substrate. Since the auxiliary recording layer 180 has a magnetic interaction (exchange coupling) with the main recording layer 160, it is possible to adjust the magnetostatic characteristics such as the coercive force Hc and the reverse domain nucleation magnetic field Hn. Therefore, it is intended to improve thermal fluctuation resistance, OW characteristics, and SNR. As a material for the auxiliary recording layer 180, a CoCrPt-based alloy can be used, and an additive such as B, Ta, or Cu may be added. Specifically, CoCrPt, CoCrPtB, CoCrPtTa, CoCrPtCu, CoCrPtCuB, or the like can be used. The film thickness of the auxiliary recording layer 180 can be set to 3 to 10 nm, for example.

  Note that “magnetically continuous” means that magnetism is connected without interruption. “Substantially continuous” means that the entire auxiliary recording layer 180 is not necessarily a single magnet but may be partially discontinuous in magnetism. That is, the auxiliary recording layer 180 only needs to be continuous in magnetism so as to straddle (cover) an aggregate of a plurality of magnetic particles. As long as this condition is satisfied, the auxiliary recording layer 180 may have a structure in which, for example, Cr is segregated.

  The protective layer 190 is a layer for protecting the perpendicular magnetic recording medium 100 from the impact of the magnetic head. The protective layer 190 can be formed by forming a film containing carbon by a CVD method. In general, carbon film formed by the CVD method has a higher film hardness than that formed by the sputtering method, so that the perpendicular magnetic recording medium 100 can be more effectively protected against the impact from the magnetic head. Is preferred. The film thickness of the protective layer 190 can be 2-6 nm, for example.

  The lubricating layer 200 is formed to prevent the protective layer 190 from being damaged when the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100. For example, PFPE (perfluoropolyether) can be applied by dip coating to form a film. The film thickness of the lubricating layer 200 can be set to 0.5 to 2.0 nm, for example.

  The method for manufacturing the perpendicular magnetic recording medium 100 according to the present embodiment has been described above. As described above, in the present embodiment, the second recording layer 162 is formed by applying a bias voltage to the substrate 110 on the surface layer side of the first recording layer 161 formed without applying a bias voltage to the substrate 110. Is done. Therefore, the SNR can be improved while narrowing the track width. Thus, a magnetic recording medium capable of achieving further higher recording density can be provided.

(Example)
In order to confirm the effectiveness of the manufacturing method of the perpendicular magnetic recording medium having the above-described configuration, description will be made using the following examples and comparative examples.

As an example, film formation was sequentially performed on the substrate 110 from the adhesion layer 120 to the auxiliary recording layer 180 in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated. Unless otherwise noted, the Ar gas pressure during film formation is 0.6 Pa. The adhesion layer 120 was formed by depositing 10Cr of 50Cr-50Ti. As the soft magnetic layer 130, a film of 92 (40Fe-60Co) -3Ta-5Zr was formed to a thickness of 40 nm. When a Ru layer is interposed between the soft magnetic layers 130, Ru can be formed to a thickness of 0.7 nm. As a result, the soft magnetic layer 130 can have a two-layer structure of 20 nm above and below. As the pre-underlayer 140, 95Ni-5W was deposited to 8 nm. The underlayer 150 was formed by depositing 10 nm of Ru at 0.6 Pa and then depositing 10 nm of Ru at 5 Pa. The first recording layer 161 was formed by depositing 90 (70Co-10Cr-20Pt) -5 (SiO ₂ ) -5 (TiO ₂ ) at 3 Pa. The second recording layer 162 was formed by depositing 90 (72Co-10Cr-18Pt) -5 (SiO ₂ ) -5 (TiO ₂ ) at 3 Pa. For the first recording layer 161 and the second recording layer 162, the following examples and comparative examples were created and compared. The composition of the dividing layer 170 was 0.3 nm of Ru. The auxiliary recording layer 180 was formed of 62 nm of 18 Co-18Cr-15Pt-5B having a thickness of 5.5 nm. The protective layer 190 was formed by depositing C ₂ H ₄ with a thickness of 5 nm by a CVD method and treating the surface layer with nitrogen. The lubricating layer 200 was formed to 1 nm using PFPE by a dip coating method.

  FIG. 2 is a diagram illustrating an example and a comparative example. In Examples 1 to 4 and Comparative Examples 1 to 3, the first recording layer 161 and the second recording layer 162 were formed by applying bias voltages of different conditions to the substrate 110. The first recording layer 161 is formed to a thickness of 2 nm, and the second recording layer 162 is adjusted in thickness (approximately 12 nm) to adjust the magnetostatic characteristics (coercive force Hc) so that the MWW approaches a constant value. The SNR values of each Example and Comparative Example were compared.

  2, in Examples 1 to 4, no bias voltage is applied to the substrate 110 when the first recording layer 161 is formed, and −50 V, −100 V, −200 V, −− are applied when the second recording layer 162 is formed. A bias voltage of 250 V is applied to the substrate 110.

  In Comparative Example 1, the first recording layer 161 and the second recording layer 162 are formed on the substrate 110 without applying a bias voltage. In Comparative Example 2, the first recording layer 161 and the second recording layer 162 were formed by applying a bias voltage of −100 V to the substrate 110 at the time of film formation. In Comparative Example 3, a bias voltage of −100 V is applied to the substrate 110 only when the first recording layer 161 is formed, and the second recording layer 162 is formed on the substrate 110 without applying a bias voltage.

  When Examples 1 to 4 are compared with Comparative Example 1, it can be seen that SNR is improved in Examples 1 to 4. This is presumably because the crystallinity of the magnetic particles was improved by applying a bias voltage to the substrate 110 during the formation of the magnetic layer (second recording layer 162).

  Here, when the film thickness is increased as a general method for improving the coercive force Hc, the coercive force Hc and the SNR are in a trade-off relationship. However, as described above, in Examples 1 to 4 according to the present invention, it can be understood that the SNR can be improved without reducing the coercive force Hc.

  In addition, as described above, Examples 1 to 4 achieve a high SNR value with an MWW substantially equivalent to that of Comparative Example 1. In other words, Examples 1 to 4 are substantially equivalent to Comparative Example 1. SNR can be achieved with a thicker film thickness. Therefore, it is possible to improve the coercive force Hc and reduce the track width.

  In Comparative Example 2 and Comparative Example 3, the SNR is lower than that in Comparative Example 1. This is a result of the generation of a mixing layer in which the Ru alloy or the like of the underlayer 150 and the CoCrPt alloy or the like of the first recording layer 161 are mixed due to the application of a bias voltage when forming the first recording layer 161. It is believed that there is. That is, in Comparative Example 2 and Comparative Example 3, Ru is mixed into the magnetic particles of the first recording layer 161 in the initial growth stage by mixing, and the crystallinity and fine structure (granular structure) of the first recording layer 161 are in Comparative Example 1. It is thought that it was more disturbed.

  When Examples 1 to 4 are compared with each other, it can be confirmed that Example 2 in which a bias voltage of −100 V is applied to the substrate 110 achieves the highest SNR value. Further, Example 1 in which a bias voltage of −50 V is applied to the substrate 110 and Example 3 in which a bias voltage of −200 V is applied to the substrate 110 are not as large as Example 2, but have an SNR value higher than that of Comparative Example 1. It has improved. In Example 4 in which a bias voltage of −250 V was applied to the substrate 110, the SNR value was slightly improved as compared with Comparative Example 1, but the value was lower than in Examples 1 to 3. This is probably because the granular structure of the main recording layer 160 was disturbed because the bias voltage was too high. On the other hand, if the bias voltage is lower than −50 V, the crystallinity improvement effect cannot be obtained sufficiently, and thus the SNR may not be improved. Therefore, it can be understood that the bias voltage is preferably applied within the range of −50 to −200V.

  FIG. 3 is a diagram comparing Examples 2, 5, and 6 in which the thickness of the first recording layer 161 is different. In Examples 5 and 6, the bias application conditions were the same as Example 2 (first recording layer 161: 2.0 nm) that achieved the highest SNR value in FIG. 2, and the film of the first recording layer 161 was used. The thickness was fixed at 1.0 nm and 0.5 nm, respectively, and the film thickness of the second recording layer 162 was adjusted so that the MWW was equivalent, and the SNR values were compared.

  When Examples are compared, it can be confirmed that Example 2 in which the film thickness is set to 2.0 nm achieves the highest SNR. In addition, Example 5 in which the film thickness is set to 1.0 nm also achieves a high SNR value although not as much as Example 2. However, in Example 6 in which the film thickness is set to 0.5 nm, the SNR is lowered. This is because the film thickness of the first recording layer 161 is too thin, and the mixing layer generated between the first recording layer 161 and the second recording layer 162 having a similar composition by application of a bias voltage has a different composition. It is considered that the crystallinity and fine structure of the magnetic particles are disturbed due to the generation of a mixing layer in which CoCrPt and Ru are mixed as a result of reaching a certain underlayer 150. From these, it is understood that the first recording layer 161 (magnetic layer formed without applying a bias voltage) is preferably formed with a film thickness (total film thickness) of 1.0 nm or more. it can.

  In the above embodiment, the main recording layer has been described as having two layers. However, the main recording layer may be three layers or four layers. In this case, at least the magnetic layer in contact with the underlayer is formed without applying a bias voltage to the substrate, and at least one of the one or more magnetic layers is formed on the surface layer side of the magnetic layer. May be formed while applying a bias voltage to the substrate. Therefore, for example, when there are three magnetic layers, a bias voltage is not applied when the bottom magnetic layer is formed, and a bias voltage is applied when the second magnetic layer is formed. A configuration may be adopted in which a bias voltage is not applied during film formation. Also by doing in this way, the benefits of the present invention can be suitably enjoyed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD or the like and a method of manufacturing the same.

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording medium 110 ... Substrate 120 ... Adhesion layer 130 ... Soft magnetic layer 140 ... Pre-underlayer 150 ... Underlayer 160 ... Main recording layer 161 ... First recording layer 162 ... Second recording layer 170 ... Splitting layer 180 ... Auxiliary recording layer 190 ... protective layer 200 ... lubricating layer

Claims (3)

At least on the substrate,
Forming a base layer containing a Ru alloy as a main component;
A step of forming a plurality of magnetic layers having a granular structure composed of a magnetic particle mainly composed of a CoCrPt alloy grown in a columnar shape and a nonmagnetic grain boundary portion mainly composed of an oxide on the underlayer. When,
Including
The plurality of magnetic layers are formed at least on the magnetic layer in contact with the underlayer without applying a bias voltage, and are formed on the surface layer side of the magnetic layer formed without applying the bias voltage. A method of manufacturing a perpendicular magnetic recording medium, comprising forming at least one magnetic layer of a plurality of magnetic layers while applying a bias voltage.   The method of manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the bias voltage is applied within a range of −50 to −200V.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic layer formed without applying a bias voltage is formed with a total film thickness of 1 nm or more.

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