JP2011076693A - Perpendicular magnetic recording medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium that achieves higher recording density by improving an SNR while maintaining high coercive force Hc and a narrow track width, and to provide a method for manufacturing the same. <P>SOLUTION: The perpendicular magnetic recording medium at least includes: a plurality of granular magnetic layers; a partition layer 170 containing an Ru alloy as a main component; and an auxiliary recording layer 180 containing a CoCrPt alloy as a main component, in this order on a substrate. Each of the plurality of granular magnetic layers has a granular structure having a grain boundary section formed by segregating a nonmagnetic material containing an oxide as a main component around a magnetic particle containing a CoCrPt alloy grown in a columnar shape as a main component. In any adjacent two layers of the plurality of granular magnetic layers, the granular magnetic layer of the surface layer side has saturation magnetization Ms lower than that of the granular magnetic layer of the substrate side, and has film thickness larger than that of the substrate side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

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, etc. In order to meet such a demand, 450 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 to the conventional in-plane recording method, the perpendicular magnetic recording method 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. Suitable for higher recording density.

  Here, as important factors for further increasing the recording density of the perpendicular magnetic recording medium, the improvement of the magnetostatic characteristics such as the coercive force Hc and the reverse domain nucleation magnetic field Hn, the overwrite characteristic (OW characteristic), and the SNR There are improvements in electromagnetic conversion characteristics such as (Signal Noise Ratio) and narrowing of track width. Several methods for improving these characteristics are known. For example, a method of increasing the thickness of the magnetic recording layer, improving the crystal orientation of the magnetic recording layer, increasing the perpendicular magnetic anisotropy, etc. It has been known.

  For example, Patent Document 1 discloses a perpendicular magnetic recording medium that includes a recording layer having a plurality of ferromagnetic layers and whose magnetic anisotropy gradually decreases from the lower ferromagnetic layer to the upper ferromagnetic layer. Is disclosed. In this perpendicular magnetic recording medium, the lower ferromagnetic layer is formed of CoPt-oxide, and the upper ferromagnetic layer is formed of CoCrPt-oxide. Further, the Pt content is decreased from the lower to the upper ferromagnetic layer, and the magnetic anisotropy energy Ku is gradually decreased from the lower to the upper ferromagnetic layer. Yes. According to Patent Document 1, it is possible to realize a high-density perpendicular magnetic recording medium that is thermally stable and has high magnetic anisotropy energy Ku.

JP 2009-70540 A

  By the way, a magnetic recording medium exceeding 320 GByte / platter, which has been required in recent years, requires further measures against high frequency noise than a conventional magnetic recording medium of 250 GByte / platter. In other words, even with a medium that can be read and written without any trouble if the recording density is conventional, if the read / write frequency of the signal increases with the increase in recording density and speed, the signal becomes weak due to insufficient writing. Also, there is a problem that the signal at the time of reading becomes unclear due to noise, and as a result, reading and writing cannot be performed. Therefore, a higher SNR is required.

  In order to increase the recording density, it is necessary to narrow the track width. The track width here is not the track width (write interval) when the magnetic head is mechanically controlled, but the output profile (signal intensity fluctuation) when linear writing is read in the perpendicular direction. The width of the track determined from

  In order to reduce the track width, it is necessary to increase the coercive force Hc because it is necessary to reduce the bleeding. In order to increase the coercive force Hc, it is conceivable to first increase the film thickness of the magnetic recording layer. In this case, however, there is a trade-off that the SNR and OW characteristics decrease. Conventionally, in order to reduce the track width, the film thickness is reduced using a material having high Ku, and the spacing loss (distance from the magnetic head to the soft magnetic layer) is reduced to increase the coercive force Hc while increasing the coercive force Hc. The characteristics were maintained. However, when a material having a high Ku is used, the SNR is lowered, so that eventually high recording density has not been promoted.

  In view of such problems, the present invention aims to improve the SNR while maintaining a high coercive force Hc and keeping the track width narrow, thereby making it possible to realize a higher recording density and its manufacture. It aims to provide a method.

  In order to solve the above-described problems, a typical configuration of a perpendicular magnetic recording medium according to the present invention includes a plurality of granular magnetic layers, a dividing layer mainly composed of a Ru alloy, and a CoCrPt alloy as a major component on a substrate. The plurality of granular magnetic layers are segregated by a non-magnetic substance mainly composed of oxide around magnetic grains mainly composed of CoCrPt alloy each grown in a columnar shape. Further, in any two layers in contact with each other, the plurality of granular magnetic layers have a saturation magnetization Ms in which the granular magnetic layer on the surface layer side is more saturated than the granular magnetic layer on the substrate side. Is low and the film thickness is large.

  According to the above configuration, first, the granular magnetic layer is multilayered to suppress the enlargement of the magnetic particles, and the magnetic particles are separated and isolated and refined to improve the SNR while keeping the track width narrow. Yes. Further, by lowering the saturation magnetization Ms toward the surface layer side, while maintaining the coercive force Hc in the lower granular magnetic layer, noise is reduced in the upper granular magnetic layer close to the magnetic head, and the SNR is improved. Yes. Further, by increasing the thickness of the granular magnetic layer as the layer having less noise, the coercive force Hc is maintained while suppressing an increase in noise. Furthermore, from these facts, the SNR can be improved while maintaining a high coercive force Hc and keeping the track width narrow. Therefore, it is possible to provide a magnetic recording medium having high resistance to high frequency noise and capable of increasing the recording density.

The “main component” means that at least 50% or more is contained when the total composition is at% (or mol%). For example, when a composition of 90 (Co—Cr—Pt) -10 (SiO ₂ ) is considered, the CoCrPt alloy is the main component because it accounts for 90% of the total.

  Conventionally, the saturation magnetization Ms of the granular magnetic layer is set low in consideration of preventing the SNR from being lowered. However, with the above configuration, the saturation magnetization Ms of the plurality of granular magnetic layers as a whole is set high. Is possible. As a result, the signal strength can be increased and the SNR can be improved.

  Furthermore, it is preferable that the granular magnetic layer on the surface layer side has a higher magnetization film thickness product Ms · t, which is the product of the saturation magnetization Ms and the film thickness t, than the granular magnetic layer on the substrate side. By disposing a layer having a low saturation magnetization Ms and a high magnetization film thickness product Ms · t near the magnetic head, the SNR can be effectively improved.

  Furthermore, by interposing a dividing layer between the plurality of granular magnetic layers and the auxiliary recording layer, the strength of the magnetic interaction that the plurality of granular magnetic layers receives from the auxiliary recording layer can be adjusted. Therefore, the track width can be kept narrow while maintaining the OW characteristics.

  The plurality of granular magnetic layers may have a total film thickness of 12 nm or less. This is because if the thickness is 12 nm or more, the spacing loss becomes too large, and the OW characteristics deteriorate. In addition, since the film thickness can be reduced by increasing the saturation magnetization Ms in the layer on the substrate side of the granular magnetic layer, such a total film thickness can be realized.

  In order to solve the above problems, a typical configuration of a method for manufacturing a perpendicular magnetic recording medium according to the present invention is to oxidize at least around magnetic particles mainly composed of a CoCrPt alloy each grown in a columnar shape on a substrate. A step of forming a plurality of granular magnetic layers having a granular structure in which a non-magnetic substance containing a substance as a main component is segregated to form a grain boundary, and a Ru alloy as a main component above the plurality of granular magnetic layers And a step of forming an auxiliary recording layer mainly composed of a CoCrPt alloy above the dividing layer, and the plurality of granular magnetic layers are in contact with each other. Also in the layer, the granular magnetic layer on the surface layer side is formed of a material having a higher saturation magnetization Ms and a thick film than the granular magnetic layer on the substrate side.

  The components corresponding to the technical idea of the perpendicular magnetic recording medium and the description thereof can be applied to the method for manufacturing the perpendicular magnetic recording medium.

  According to the present invention, it is possible to provide a perpendicular magnetic recording medium capable of realizing further higher recording density by maintaining a high coercive force Hc and maintaining a narrow track width, and a method for manufacturing the same. Is possible.

It is a figure explaining the structure of a perpendicular magnetic recording medium. It is a figure explaining the structure of a perpendicular magnetic recording medium. It is a figure explaining an Example and a comparative example.

  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.

In the following description, the “main component” means that at least 50% or more is contained when the total composition is at% (or mol%). For example, when a composition of 90 (Co—Cr—Pt) -10 (SiO ₂ ) is considered, the CoCrPt alloy is the main component because it accounts for 90% of the total.
(First embodiment)

[Perpendicular magnetic recording medium and manufacturing method thereof]
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 first soft magnetic layer 131, a spacer layer 132, a second soft magnetic layer 133, a pre-underlayer 140, an underlayer 150, and a first magnetic recording layer. 161, a second magnetic recording layer 162, a dividing layer 170, an auxiliary recording layer 180, a protective layer 190, and a lubricating layer 200. The first soft magnetic layer 131, the spacer layer 132, and the second soft magnetic layer 133 together constitute the soft magnetic layer 130. Together with the first magnetic recording layer 161 and the second magnetic recording layer 162, a main recording layer 160 is formed.

  As the substrate 110, a glass disk in which amorphous aluminosilicate glass is formed 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. Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration of each layer will be described.

  The adhesion layer 120 is formed in contact with the substrate 110, has a function of increasing the peel strength between the soft magnetic layer 130 formed on the substrate 110 and the substrate 110, and refines the crystal grain of each layer formed thereon. Has the function to make uniform. When the substrate 110 is made of amorphous glass, the adhesion layer 120 is preferably an amorphous (amorphous) alloy film so as to correspond to the amorphous glass surface. The film thickness of the adhesion layer 120 can be set to about 7 nm, for example.

  The composition of the adhesion layer 120 can be selected from, for example, a CrTi amorphous layer, a CoW amorphous layer, a CrW amorphous layer, a CrTa amorphous layer, and a CrNb amorphous layer. Among these, a CoW alloy film is particularly preferable because it forms an amorphous metal film containing microcrystals. The adhesion layer 120 may be a single layer made of a single material, or may be formed by laminating a plurality of layers. For example, a CoW layer or a CrW layer may be formed on the CrTi layer. These adhesion layers 120 are preferably formed by sputtering with a material containing carbon dioxide, carbon monoxide, nitrogen, or oxygen, or the surface layer is exposed with these gases.

  The soft magnetic layer 130 is a layer that temporarily forms a magnetic path during recording in order to allow magnetic flux to pass through the main recording layer 160 in the perpendicular direction in the perpendicular magnetic recording method. The soft magnetic layer 130 has AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 132 between the first soft magnetic layer 131 and the second soft magnetic layer 133. Can be configured. As a result, the magnetization direction of the soft magnetic layer 130 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 130 is reduced. Can do. The thickness of the soft magnetic layer 130 can be about 20 nm for the first soft magnetic layer 114a and the second soft magnetic layer 114c, respectively, and about 0.7 nm for the spacer layer 132, for example. The compositions of the first soft magnetic layer 131 and the second soft magnetic layer 133 include cobalt-based alloys such as CoTaZr, Co-Fe-based alloys such as CoCrFeB and CoFeTaZr, and Ni such as a [Ni—Fe / Sn] n multilayer structure. A Fe alloy or the like can be used.

  The pre-underlayer 140 (also referred to as a seed layer) is a nonmagnetic alloy layer that protects the soft magnetic layer 130 and a hexagonal close-packed structure (hcp) included in the underlayer 150 formed thereon. The crystal structure has a function of orienting the easy axis of magnetization in the direction perpendicular to the disk. The pre-underlayer 140 preferably has a (111) plane of a face-centered cubic structure (fcc structure) parallel to the main surface of the substrate 110. The pre-underlayer 140 may have a configuration in which these crystal structures and amorphous are mixed. The film thickness of the pre-underlayer 140 can be about 8 to 11 nm. The material of the front ground layer 140 can be selected from Ni, Cu, Pt, Pd, Zr, Hf, Nb, and Ta. Furthermore, it is good also as an alloy which has these metals as a main component and contains any one or more additional elements of Ti, V, Cr, Mo, and W. For example, NiTa, NiW, NiWAl, NiWAlSi, CuW, or CuCr can be suitably selected as an alloy having an fcc structure. Further, the pre-underlayer 140 may have a two-layer structure.

  The underlayer 150 has an hcp crystal structure and has a function of growing a crystal of the Co hcp crystal structure of the main recording layer 160 as a granular structure. Therefore, the higher the crystal orientation of the underlayer 150, that is, the more the (0001) plane of the crystal of the underlayer 150 is parallel to the main surface of the substrate 110, the more the orientation of the main recording layer 160 is improved. it can. The film thickness of the underlayer 150 can be, for example, about 20 nm. Ru is a typical material for the underlayer 150. Since Ru has an hcp crystal structure and the crystal lattice spacing is close to Co, the main recording layer 160 containing Co as a main component can be well oriented.

  The main recording layer 160 has a granular structure in which a non-magnetic substance is segregated around a magnetic particle of a CoCrPt alloy continuously grown in a columnar shape to form a grain boundary part. In the present embodiment, a plurality of granular magnetic layers having different compositions and film thicknesses are constituted by a first magnetic recording layer 161 and a second magnetic recording layer 162.

The first magnetic recording layer 161 has a columnar granular structure in which a nonmagnetic substance is segregated around a magnetic particle of a hard magnetic material selected from a Co-based alloy, an Fe-based alloy, and a Ni-based alloy to form a grain boundary. ing. In the present embodiment, by forming a film by using a target which contains SiO ₂ and TiO ₂ to CoCrPt, the SiO ₂ and TiO ₂ is a non-magnetic material around the magnetic particles made of CoCrPt alloy (grains) segregation Thus, a grain boundary was formed, and a granular structure in which magnetic particles grew in a columnar shape was formed. The magnetic particles of the first magnetic recording layer 161 can be epitaxially grown continuously from the crystal structure of Ru contained in the underlayer.

  The magnetic particles of the first magnetic recording layer 161 are initial growth layers of magnetic particles that continuously grow up to the second magnetic recording layer 162. Therefore, by making the first magnetic recording layer 161 thin, the enlargement of the entire magnetic particles is suppressed.

The second magnetic recording layer 162 is provided on the first magnetic recording layer 161, and similarly to the first magnetic recording layer 161, the magnetic property of a hard magnetic material selected from a Co-based alloy, an Fe-based alloy, and a Ni-based alloy is used. It has a columnar granular structure in which grain boundaries are formed by segregating nonmagnetic substances around the particles. In the present embodiment, by forming a film by using a target which contains the _SiO 2, TiO ₂ in CoCrPt, _{SiO 2,} TiO 2 (composite oxide around the magnetic particles made of CoCrPt (grains) is a non-magnetic material The material) segregated to form grain boundaries, and a granular structure in which magnetic particles grew in a columnar shape was formed. In this embodiment, the crystal grains of the second magnetic recording layer 162 continue to grow from the crystal grains of the first magnetic recording layer 161, thereby achieving miniaturization and improvement of crystal orientation.

  By multilayering the main recording layer 160 as described above, the enlargement of the magnetic particles can be suppressed, and the magnetic particles can be isolated and isolated and refined. As a result, the SNR is improved while keeping the track width narrow.

  In the present embodiment, the second magnetic recording layer 162 on the surface layer side has a lower saturation magnetization Ms than the first magnetic recording layer 161 on the substrate side. Thus, while maintaining the coercive force Hc in the lower granular magnetic layer, the upper granular magnetic layer close to the magnetic head reduces noise and improves the SNR. Conventionally, when the saturation magnetization Ms of the granular magnetic layer is set low in consideration of preventing the SNR from being lowered, the saturation magnetization Ms as a whole of the plurality of granular magnetic layers (main recording layer 160) as in the above configuration. It becomes possible to set Ms high. As a result, the signal strength can be increased and the SNR can be improved.

In order to increase the saturation magnetization Ms, it is conceivable to reduce the Cr content and increase the Co content. Specifically, the first magnetic recording layer 161 is 90 (74Co-10Cr-16Pt) -5 (SiO ₂ ) -5 (TiO ₂ ), and the second magnetic recording layer 162 is 90 (72Co-12Cr-16Pt) −. 5 (SiO ₂ ) -5 (TiO ₂ ). By adjusting these components, the first magnetic recording layer 161 is configured to prioritize the improvement of the saturation magnetization Ms over the second magnetic recording layer 162 in the material.

  In the present embodiment, the second magnetic recording layer 162 on the surface layer side is thicker than the first magnetic recording layer 161 on the substrate side. For example, the first magnetic recording layer 161 can be 3.3 nm, and the second magnetic recording layer 162 can be 7.1 nm. Thus, by increasing the film thickness of the layer with lower saturation magnetization Ms and less noise, the coercive force Hc is maintained while suppressing increase in noise.

  For these reasons, the SNR can be improved while maintaining a high coercive force Hc and keeping the track width narrow. Therefore, it is possible to provide a magnetic recording medium having high resistance to high frequency noise and capable of increasing the recording density.

  The main recording layer 160 includes the plurality of granular magnetic layers (the first magnetic recording layer 161 and the second magnetic recording layer 162). In this embodiment, the total film thickness is 12 nm or less. This is because if the thickness is 12 nm or more, the spacing loss becomes too large, and the OW characteristics deteriorate. In addition, since the film thickness can be reduced by increasing the saturation magnetization Ms in the layer on the substrate side of the granular magnetic layer (first magnetic recording layer 161), such a total film thickness can be realized.

  Further, in the main recording layer 160, the second magnetic recording layer 162 on the surface side of the first magnetic recording layer 161 on the substrate side has a magnetization film thickness product Ms · t that is the product of the saturation magnetization Ms and the film thickness t. Is preferably high. This is because the SNR can be effectively improved by disposing a layer (second magnetic recording layer 162) having a low saturation magnetization Ms and a high magnetization film thickness product Ms · t in the vicinity of the magnetic head. .

  As for the amount of oxide, since the second magnetic recording layer 162 wants to have a higher SNR than the first magnetic recording layer 161 as described above, the oxide content of the second magnetic recording layer 162 is the first magnetic recording layer 162. The recording layer 161 is preferably the same as or slightly more than the recording layer 161.

Note that the materials used for the first magnetic recording layer 161 and the second magnetic recording layer 162 described above are examples, and the present invention is not limited thereto. Examples of nonmagnetic substances for forming grain boundaries include titanium oxide (TiO ₂ ), silicon oxide (SiO _x ), chromium oxide (Cr _X O _Y ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O). ₅ ), oxides such as iron oxide (Fe ₂ O ₃ ) and boron oxide (B ₂ O ₃ ). Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used. Furthermore, in this embodiment, three types of oxides are used in the first magnetic recording layer 161 and the second magnetic recording layer 162, but the present invention is not limited to this, and one type of oxide is used in any layer. Or a composite of two or more kinds of oxides.

  The dividing layer 170 is provided above the second magnetic recording layer 162 and below the auxiliary recording layer 180, and substantially separates the magnetic properties of these layers. The dividing layer 170 is preferably non-magnetic, but may have weak magnetism if slightly.

  As an effect on the magnetism of the dividing layer 170, the magnetism of the second magnetic recording layer 162 and the auxiliary recording layer 180 is divided, and the strength of exchange coupling between them is adjusted. This weakens the magnetic connection between the second magnetic recording layer 162 and the auxiliary recording layer 180 and between adjacent magnetic particles of the second magnetic recording layer 162, while maintaining the coercive force Hc and the overwrite characteristics. SNR can be improved and the track width can be reduced.

  Further, as an effect on the crystal structure of the dividing layer 170, the separation of the crystal particles of the auxiliary recording layer 180 is promoted. As will be described later, the auxiliary recording layer 180 is a magnetic layer that is magnetically continuous in the in-plane direction. However, the grain boundaries (not oxides) of the crystal grains become clear, the unit of magnetization reversal becomes smaller, and the domain wall also becomes smaller. Narrow. Thereby, the SNR can be improved. In order to obtain good exchange coupling strength, it is preferable that the dividing layer 170 has a film thickness of 0.3 to 0.9 nm.

  The split layer 170 is preferably a layer containing a Ru alloy as a main component in order not to lower the inheritance of crystal orientation. The Ru alloy is obtained by adding another metal element to Ru.

  As described above, the strength of the magnetic interaction received by the second magnetic recording layer 162 from the auxiliary recording layer 180 is adjusted by interposing the dividing layer 170 between the second magnetic recording layer 162 and the auxiliary recording layer 180. can do. Therefore, the track width can be narrowed while maintaining the OW characteristics of the perpendicular magnetic recording medium 100.

  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. The auxiliary recording layer 180 needs to be adjacent or close to the main recording layer 160 so as to have a magnetic interaction. The film thickness of the auxiliary recording layer can be 5 to 7 nm, for example. As the material of the auxiliary recording layer 180, for example, CoCrPt, CoCrPtB, or a small amount of oxides can be contained in these.

  The auxiliary recording layer 180 has a magnetic interaction (performs exchange coupling) with the magnetic particles of the main recording layer 160, thereby adjusting the reverse domain nucleation magnetic field Hn and adjusting the coercive force Hc. It aims at improving the OW characteristics and SNR. In order to achieve this object, the auxiliary recording layer 180 is preferably made of a material having high perpendicular magnetic anisotropy Ku and saturation magnetization Ms. In addition, since the crystal particles connected to the granular magnetic particles (crystal particles having magnetic interaction) have a larger area than the cross-section of the granular magnetic particles, it is easy to reverse the magnetization by receiving a large amount of magnetic flux from the magnetic head. It is considered that the OW characteristics are improved.

  Note that “magnetically continuous” means that magnetism is continuous and the magnetic particles are not miniaturized (separated and isolated) by a nonmagnetic substance such as an oxide. “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 across the recording bits composed of an aggregate of a plurality of granular magnetic particles. As long as this condition is satisfied, Cr may be segregated in the auxiliary recording layer 180, or a small amount of oxide may be contained and segregated.

  The protective layer 190 can be formed by depositing carbon by a CVD method while maintaining a vacuum. The protective layer 190 is a layer for protecting the perpendicular magnetic recording medium 100 from the impact of the magnetic head. The film thickness of the protective layer 190 can be 4 to 6 nm, for example. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording medium 100 can be more effectively protected against the impact from the magnetic head.

  The lubricating layer 200 can be formed of PFPE (perfluoropolyether) by dip coating. PFPE has a long chain molecular structure and binds with high affinity to N atoms on the surface of the protective layer 190. Due to the action of the lubricating layer 136, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100, damage or loss of the protective layer 190 can be prevented. The film thickness of the lubricating layer 136 can be, for example, about 1 nm.

The perpendicular magnetic recording medium 100 according to the first embodiment and the manufacturing method thereof have been described above. As described above, in the present embodiment, the first magnetic recording layer 161 and the second magnetic recording layer 162 are provided in the main recording layer 160. Furthermore, the second magnetic recording layer 162 on the surface layer side has a lower saturation magnetization Ms and a larger film thickness than the first magnetic recording layer 161 on the substrate side. Therefore, the SNR can be improved while maintaining a high coercive force Hc and keeping the track width narrow. . As a result, it is possible to provide a magnetic recording medium that has high resistance to high-frequency noise and can achieve high recording density.
(Second Embodiment)

[Perpendicular magnetic recording medium and manufacturing method thereof]
A second embodiment of the present invention will be described. FIG. 2 is a diagram illustrating the configuration of the perpendicular magnetic recording medium 202 according to the second embodiment. As shown in FIG. 2, the second embodiment is different from the first embodiment in that it includes a main recording layer 260 composed of three granular magnetic layers.

  In the present embodiment, the main recording layer 260 is composed of three granular magnetic layers, a first magnetic recording layer 261, a second magnetic recording layer 262, and a third recording layer 263. The three granular magnetic layers have a structure in which the granular magnetic layer on the surface layer side has a lower saturation magnetization Ms and is thicker than the granular magnetic layer on the substrate side.

  The first magnetic recording layer 261 is a granular magnetic layer located on the lowermost side (substrate side) among the plurality of granular magnetic layers included in the main recording layer 260. Since the magnetic particles of the first magnetic recording layer 261 are formed on the underlayer 118, they can be epitaxially grown continuously from the crystal structure of Ru contained in the underlayer.

  The first magnetic recording layer 261 has the highest saturation magnetization Ms among the plurality of granular magnetic layers included in the main recording layer 260. Further, the first magnetic recording layer 261 has the smallest thickness among the plurality of granular magnetic layers included in the main recording layer 260.

  The second magnetic recording layer 262 is a granular magnetic layer formed on the first magnetic recording layer 261. The magnetic particles of the second magnetic recording layer 262 continuously grow on the magnetic particles of the first magnetic recording layer 261 therebelow. The saturation magnetization Ms of the second magnetic recording layer 262 is larger than that of the first magnetic recording layer 261 and smaller than that of the third recording layer 263. The second magnetic recording layer 262 is thicker than the first magnetic recording layer 261 and thinner than the third recording layer 263.

  The third recording layer 263 is a granular magnetic layer formed on the second magnetic recording layer 262. The saturation magnetization Ms of the third recording layer 263 has the lowest saturation magnetization Ms among the plurality of granular magnetic layers included in the main recording layer 260. Further, the third recording layer 263 has the largest thickness among the plurality of granular magnetic layers included in the main recording layer 260. The magnetic particles are also grown continuously on the magnetic particles of the first magnetic recording layer 261 and the second magnetic recording layer 262 therebelow.

  The main recording layer 260 includes a plurality of granular magnetic layers. In this embodiment, the total film thickness is 12 nm or less. This is because if the thickness is 12 nm or more, the spacing loss becomes too large, and the OW characteristics deteriorate. Since the film thickness can be reduced by increasing the saturation magnetization Ms in the substrate side layer of the granular magnetic layer, it is possible to realize the thin total film thickness as described above while maintaining the saturation magnetization Ms as a whole. it can.

  As described above, in the present embodiment, first, the main recording layer 260 is multilayered to suppress the enlargement of the magnetic particles, and by separating and miniaturizing the magnetic particles, the SNR is maintained while keeping the track width narrow. We are trying to improve. Further, by lowering the saturation magnetization Ms toward the surface layer side, while maintaining the coercive force Hc in the lower granular magnetic layer, noise is reduced in the upper granular magnetic layer close to the magnetic head, and the SNR is improved. Yes. Further, by increasing the thickness of the granular magnetic layer as the layer having less noise, the coercive force Hc is maintained while suppressing an increase in noise. Accordingly, the main recording layer 260 can improve the SNR while maintaining a high coercive force Hc and keeping the track width narrow.

  Conventionally, when the saturation magnetization Ms of the granular magnetic layer is set low in consideration of prevention of a decrease in SNR, the saturation magnetization of the plurality of granular magnetic layers (main recording layer 260) as a whole is configured as described above. It becomes possible to set Ms high. As a result, the signal strength can be increased and the SNR can be improved.

  The first to third recording layers included in the main recording layer 260 have a magnetization film thickness product in which the granular magnetic layer on the surface layer side is the product of the saturation magnetization Ms and the film thickness t rather than the granular magnetic layer on the substrate side. It is preferable that Ms · t is high. This is because the SNR can be improved when the layer having the high magnetization film thickness product Ms · t (the third recording layer 263 in the present embodiment) is positioned near the magnetic head.

  The perpendicular magnetic recording medium 202 according to the second embodiment and the manufacturing method thereof have been described above. In the present embodiment, the main recording layer 260 is divided into three layers to suppress the enlargement of the magnetic particles, the saturation magnetization Ms is decreased toward the surface layer side, and the film thickness is increased to maintain a high coercive force Hc. Thus, the SNR can be improved while keeping the track width narrow. Accordingly, it is possible to provide the magnetic recording medium 202 that has high resistance to high frequency noise and can further increase the recording density.

(Example)
In order to confirm the effectiveness of the perpendicular magnetic recording medium having the above-described configuration and the manufacturing method thereof, description will be made using the following examples and comparative examples. FIG. 3 is a diagram illustrating an example and a comparative example.

As an example and a comparative example, a film was formed on the substrate 110 sequentially from the adhesion layer 120 to the auxiliary recording layer 180 in an Ar atmosphere by a DC magnetron sputtering method using a vacuum deposition apparatus. . Unless otherwise noted, the Ar gas pressure during film formation is 0.6 Pa. For the adhesion layer 120, 50Cr-50Ti was deposited to a thickness of 10 nm. For the soft magnetic layer 130, the first soft magnetic layer 131 and the second soft magnetic layer 133 were each formed by depositing 92 nm (40Fe-60Co) -3Ta-5Zr, and the spacer layer 132 was formed by depositing 0.7 nm Ru. The pre-underlayer 140 was formed with 8 nm of Ni-5W. The underlayer 150 was formed by depositing 10 nm of Ru and depositing 10 nm of Ru at 5 Pa. The main recording layer 160 and the main recording layer 260 including a plurality of granular magnetic layers were compared by creating Examples 1-2 and Comparative Examples 1-4 as shown in FIG. The composition of the dividing layer 170 was 0.3 nm of Ru. As the auxiliary recording layer 180, a film of 57Co-18Cr-15Pt-5B having a thickness of 5.5 nm was formed. The protective layer 190 was formed by depositing 1 nm of C ₂ H ₄ by a CVD method, and the surface layer was impregnated with N ₂ . The lubricating layer 200 was formed using PFPE by a dip coating method.

In Example 1, the main recording layer 160 has a two-layer structure with a total film thickness of 10.4 nm, and the first magnetic recording layer 161 is 90 (74Co-10Cr-16Pt) -5 (SiO ₂ ) -5 (TiO ₂ ). A layer having a coercive force Ms of 600 (emu / cm ³ ) is formed with a thickness of 3.3 nm using a target, and the second magnetic recording layer 162 is 90 (72 Co-12Cr-16Pt) -5 (SiO ₂ ). A layer of 550 (emu / cm ³ ) was formed to a thickness of 7.1 nm using a −5 (TiO ₂ ) target. That is, in Example 1, the second magnetic recording layer 162 on the surface layer side has a lower saturation magnetization Ms and a larger film thickness than the first magnetic recording layer 161 on the substrate side.

In Example 2, the main recording layer 260 has a three-layer structure with a total film thickness of 11.3 nm, and the first magnetic recording layer 261 is 90 (74Co-10Cr-16Pt) -5 (SiO ₂ ) -5 (TiO ₂ ). A layer having a coercive force Ms of 600 (emu / cm ³ ) is formed with a thickness of 1.2 nm using a target, and the second magnetic recording layer 262 is 90 (71 Co-13Cr-16Pt) -5 (SiO ₂ ). A layer having a coercive force Ms of 530 (emu / cm ³ ) is formed to a thickness of 4.1 nm using a target of −5 (TiO ₂ ), and the third recording layer is 90 (70 Co-14Cr-16 Pt) — A layer having a coercive force Ms of 510 (emu / cm ³ ) was formed to a thickness of 6 nm using a target of 5 (SiO ₂ ) -5 (TiO ₂ ). That is, in Example 2, the saturation magnetization Ms gradually decreases from the first magnetic recording layer 161 on the substrate side toward the third magnetic recording layer 163 on the surface layer side, and the film thickness gradually increases.

  With reference to FIG. 3, Examples 1-2 and Comparative Examples 1-4 are verified. In Examples and Comparative Examples, Hc, MEW, and SNR were evaluated.

  Comparative Example 1 is an example in which the granular magnetic layer is one layer. When Example 1 having two granular magnetic layers and Comparative Example 1 are compared with each other, Example 1 shows a higher SNR (0.4 dB difference).

  Further, in Example 1, the MEW (Magnet Erase Width) is 95 nm, which is a value (narrow value) smaller than MEW: 98 of Comparative Example 1. Here, MEW is the track width including the erase width. From these, it was confirmed that Example 1 has a high SNR while maintaining a high coercive force Hc and keeping the track width narrow.

  Comparative Example 2 is an example in which the saturation magnetization Ms is higher in the second magnetic recording layer 162 on the surface layer side than on the first magnetic recording layer 161 on the substrate side. When Example 1 and Comparative Example 2 are compared, the value of coercive force Hc is approximately the same in Example 1, but the SNR is slightly improved. From this measurement result, it can be confirmed that the SNR is improved by disposing a layer having a low saturation magnetization Ms on the surface layer side close to the magnetic head.

  Comparative Example 3 is an example in which the thickness of the second magnetic recording layer 162 on the surface layer side is smaller than that of the first magnetic recording layer 161 on the substrate side. Since Comparative Example 3 has a total film thickness of 9.9 nm, which is thinner than Example 1 having a total film thickness of 10.4 nm, the coercive force Hc has a high value of 5289 (Oe). There seems to be. However, in Comparative Example 3, compared with Example 1, the SNR is significantly lowered with a difference of 0.3 dB. This is considered to be a result of noise increase in Comparative Example 3 due to the thick layer having a high saturation magnetization Ms.

  Comparative Example 4 is an example in which the saturation magnetization Ms is higher and the film thickness is thinner on the surface layer side than on the substrate side. In this comparative example 4, the SNR is significantly reduced with a difference of 0.3 dB.

  From the above, in Example 1, the first magnetic recording layer 161 and the second magnetic recording layer 162 are stacked so that the film thickness increases toward the surface layer side and the saturation magnetization Ms decreases. It was confirmed that a high SNR could be achieved while keeping the high coercive force Hc and keeping the track width narrow without increasing the total film thickness of the main recording layer 160.

  Furthermore, it can be confirmed that Example 2 in which the main recording layer 260 has three layers has obtained good results in all items. For example, the SNR is 16.5 dB, which is a very good value compared to other examples and comparative examples. Further, MEW: 92 nm, which is a narrower track width than other examples and comparative examples. The coercive force Hc is also the highest value of 5314 (Oe).

  As described above, in Example 1 and Example 2, it was confirmed that the SNR can be improved while maintaining the coercive force Hc and keeping the track width narrow. Therefore, according to Example 1 and Example 2, it is possible to provide a magnetic recording medium having high resistance to high frequency noise and capable of increasing the recording density.

  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 131 ... First soft magnetic layer 132 ... Spacer layer 133 ... Second soft magnetic layer 140 ... Pre-underlayer 150 ... Underlayer 160 ... Main recording layer 161 ... first magnetic recording layer 162 ... second magnetic recording layer 170 ... dividing layer 180 ... auxiliary recording layer 190 ... protective layer 200 ... lubricating layer 202 ... perpendicular magnetic recording medium 260 ... main recording layer 261 ... first magnetic recording layer 262 ... 2nd magnetic recording layer 263 ... 3rd recording layer 270 ... Dividing fault

Claims (3)

On the substrate, a plurality of granular magnetic layers, a dividing layer mainly composed of a Ru alloy, and an auxiliary recording layer mainly composed of a CoCrPt alloy are provided at least in this order.
The plurality of granular magnetic layers each have a granular structure in which a grain boundary portion is formed by segregating a non-magnetic substance mainly composed of an oxide around a magnetic particle mainly composed of a CoCrPt alloy grown in a columnar shape. Have
Further, the plurality of granular magnetic layers are characterized in that in any two layers in contact with each other, the granular magnetic layer on the surface layer side has a lower saturation magnetization Ms and is thicker than the granular magnetic layer on the substrate side. Perpendicular magnetic recording medium.   The perpendicular magnetic recording medium according to claim 1, wherein the plurality of granular magnetic layers have a total film thickness of 12 nm or less. At least on the substrate,
A plurality of granular magnetic layers having a granular structure in which a non-magnetic substance mainly composed of an oxide segregates around magnetic particles each composed mainly of a CoCrPt alloy grown in a columnar shape to form grain boundaries. Forming a film;
Forming a dividing layer mainly composed of a Ru alloy above the plurality of granular magnetic layers;
Forming an auxiliary recording layer mainly composed of a CoCrPt alloy above the dividing layer;
Including
In any two layers in contact with each other, the plurality of granular magnetic layers are formed with a material having a higher saturation magnetization Ms and a thicker film thickness than the granular magnetic layer on the substrate side. A perpendicular magnetic recording medium.

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