JP2008276916A - Magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which can obtain a high throughput, a high coercive force and S/N ratio at the same time, not requiring to largely change the existing facilities, and its manufacturing method. <P>SOLUTION: The typical configuration of the magnetic recording medium has an orientation control layer 16, a non-magnetic under layer 18, and a magnetic recording layer 22 all formed on a base plate, wherein the orientation control layer 16 is mainly made of nickel or an element having a smaller ionization tendency than nickel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium mounted on a magnetic recording type HDD (hard disk drive) or the like and a method for 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 100 GB has been required for a 2.5-inch diameter magnetic disk used for HDDs and the like. In order to meet such a demand, per 1 inch. It is required to realize an information recording density exceeding 150 Gbits.

  In order to achieve a high recording density in a magnetic disk used for an HDD or the like, it is necessary to refine the magnetic crystal particles constituting the magnetic recording layer for recording information signals and to reduce the layer thickness. It was. However, in the case of a magnetic disk of the in-plane magnetic recording method (also called longitudinal magnetic recording method or horizontal magnetic recording method) that has been commercialized conventionally, as a result of the progress of miniaturization of magnetic crystal grains, superparamagnetic phenomenon The thermal stability of the recording signal is impaired, and the so-called thermal fluctuation phenomenon that the recording signal disappears has occurred, which has been an impediment to increasing the recording density of the magnetic disk. In order to solve this obstacle, a perpendicular magnetic recording type magnetic disk has recently been proposed.

  Unlike the case of the in-plane magnetic recording method, the perpendicular magnetic recording method is adjusted so that the easy axis of magnetization of the magnetic recording layer is oriented in the direction perpendicular to the substrate surface. The perpendicular magnetic recording method can suppress the thermal fluctuation phenomenon as compared with the in-plane recording method, and is suitable for increasing the recording density.

  Also in the perpendicular magnetic recording system, higher recording density is required. In order to increase the recording density, a high coercive force Hc is required because the signal written in the minimized recording bit is not lost, and it is high in order to read the signal level that decreases with the minimization without error. An S / N ratio (Signal Noise Ratio) is required. In the perpendicular magnetic recording method, the magnetic recording layer has a granular structure in which a non-magnetic substance (mainly oxide) is segregated between magnetic grains (magnetic grains) to form grain boundaries, and the magnetic grains are isolated and refined. Thus, the S / N ratio and the coercive force Hc can be improved. Patent Document 1 (Japanese Patent Laid-Open No. 2003-217107) describes a configuration in which magnetic grains are epitaxially grown to form a columnar granular structure.

Magnetic disks are composed of multiple layers, including a magnetic recording layer for recording signals, an underlayer for improving the crystal orientation of the magnetic recording layer, and an orientation control layer for improving the crystal orientation of the underlayer. Is done. These layers are formed by sputtering, but an in-line type sputtering apparatus is often used from the viewpoint of productivity. The in-line type is a system in which a plurality of film forming chambers for performing sputtering are connected, and film formation is performed in each film forming chamber while sequentially transporting the disk substrate. For example, Patent Document 2 (Japanese Patent Laid-Open No. 2001-207258) describes an in-line type sputtering apparatus.
JP 2003-217107 A JP 2001-207258 A

  A magnetic disk requires a high recording density as described above, but at the same time, has a side that it must be mass-produced at low cost. Therefore, productivity is also an important factor, and it is required to have a configuration that is easy to make.

  However, it has been found that the coercive force Hc tends to decrease when the throughput (processing amount per unit time) is increased in an in-line type sputtering apparatus in order to improve productivity. Therefore, conventionally, it is difficult to improve the throughput, and the production amount has been secured by increasing the number of lines (sputtering apparatus) or increasing the operation time.

  Accordingly, an object of the present invention is to provide a magnetic recording medium capable of achieving both high throughput, high coercive force, and S / N ratio without greatly changing the conventional apparatus, and a method for manufacturing the same.

  As a result of intensive studies by the present inventors to solve the above-mentioned problems, when the throughput is increased in an in-line type sputtering apparatus, the crystal orientation of the magnetic recording layer is disturbed, which causes the coercive force Hc and the S / N ratio. Was found to have declined. Further research showed that the disorder of orientation started from the orientation control layer under the underlayer. As a result of various investigations on the orientation control layer, it was confirmed that the oxidation of the orientation control layer is the cause of disorder of orientation, and this was confirmed by experiments to complete the present invention.

  That is, a typical configuration of the present invention is a magnetic recording medium including an orientation control layer, a nonmagnetic underlayer, and a magnetic recording layer on a substrate. The orientation control layer mainly contains nickel or an element having a smaller ionization tendency than nickel. It is characterized by being a component.

  According to the above configuration, since the alignment control layer is not easily affected by oxidation, even if the throughput is improved, the alignment control layer is not easily disturbed, and the coercive force Hc and the S / N ratio can be prevented from being lowered. Thereby, both high throughput, high coercive force and S / N ratio can be achieved.

  The orientation control layer is mainly composed of Ni (nickel), and includes at least one of Ti (titanium), V (vanadium), Ta (tantalum), Cr (chromium), Mo (molybdenum), and W (tungsten). It is preferably made of an alloy containing an additive element. Ni is preferable because it is resistant to oxidation. However, Ni is a ferromagnetic material, and if a magnetic layer made of a ferromagnetic material exists under the nonmagnetic underlayer, the magnetic disk will not perform a desired operation. Therefore, it is preferable to add another element in which Ni does not have magnetism, and specifically, it is preferable to mix the above metal at 5 at% (atomic%) or more. On the other hand, the orientation control layer needs to have an fcc structure (face-centered cubic lattice), and if the amount of the additive becomes too large, the crystal structure cannot be maintained and becomes amorphous. is there. Specifically, the additive preferably contains the above metal at 15 at% or less.

  The nonmagnetic underlayer and magnetic recording layer are characterized by having an hcp structure (hexagonal close-packed structure). When the underlayer and the magnetic recording layer have the hcp structure, the crystal orientation can be controlled by the orientation control layer having the fcc structure, and a high coercive force Hc and S / N ratio can be realized.

  An onset layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between crystal grains grown in a columnar shape on the surface side of the magnetic recording medium from the underlayer, and is made nonmagnetic as a whole. It is characterized by. The underlayer has a substantially uniform crystal structure with an hcp structure. When forming a magnetic recording layer with a granular structure, the separation of the granular (magnetic crystal grains) of the magnetic recording layer is promoted by forming a non-magnetic granular layer. In addition, the S / N ratio can be improved. Providing an onset layer tends to lower the orientation instead of improving the separation, but the orientation of the onset layer is further improved by providing an orientation control layer that is resistant to oxidation, especially under the orientation control layer. In addition, the orientation of the magnetic recording layer can be further improved to achieve a high coercive force Hc and S / N ratio.

  The crystal particles of the onset layer may contain at least Co and Cr, and the nonmagnetic substance may contain an oxide. By including Co, the granular structure of the magnetic crystal grains of the magnetic recording layer formed thereon can be epitaxially grown without impairing the orientation.

  A magnetic recording layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between magnetic crystal grains containing at least Co (cobalt) and growing in a columnar shape on the surface side of the magnetic recording medium from the onset layer. You may have. By using the magnetic recording layer having such a configuration, the orientation is inherited from the orientation control layer. Therefore, as described above, the orientation control layer is not easily affected by oxidation, and even if the throughput is improved, the orientation control layer is not easily disturbed, so that the coercive force Hc and the S / N ratio can be prevented from being lowered. Thereby, both high throughput, high coercive force and S / N ratio can be achieved.

  A typical configuration of the method for manufacturing a magnetic recording medium according to the present invention is a magnetic recording medium in which an orientation control layer is formed on a substrate, a nonmagnetic underlayer is formed, and a magnetic recording layer is formed. In the manufacturing method, the orientation control layer is mainly composed of nickel or an element having a smaller ionization tendency than nickel, and the orientation control layer, the nonmagnetic underlayer, and the magnetic recording layer are formed using an in-line type sputtering apparatus. It is characterized by filming. This is because high throughput can be realized because sputtering is performed continuously using a plurality of deposition chambers.

  According to the present invention, it is possible to provide a magnetic recording medium capable of achieving both high throughput, high coercive force, and S / N ratio without greatly changing the conventional apparatus, and a method for manufacturing the same.

  Embodiments of a magnetic recording medium and a manufacturing method thereof according to the present invention will be described. In the present embodiment, the magnetic recording medium will be described as a perpendicular magnetic recording medium, but the present invention is not limited to this and can be applied to an in-plane magnetic recording medium. 1 is a diagram for explaining an in-line type sputtering apparatus, FIG. 2 is a diagram for explaining the configuration of a magnetic recording medium, FIG. 3 is a diagram for explaining the relationship between throughput and coercive force Hc, and FIG. 4 is a diagram showing throughput and S / N ratio. It is a figure explaining the relationship. Note that dimensions, materials, and other specific numerical values shown in the following examples are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified.

  A sputtering apparatus 200 shown in FIG. 1 is a DC magnetron sputtering type in-line type sputtering apparatus. The sputtering apparatus 200 includes, for example, 12 film forming chambers 202. Each film forming chamber 202 can be connected to or equipped with a sputtering apparatus, a vacuum control apparatus, a gas supply apparatus for supplying an arbitrary gas, and the like, and a plurality of processes can be performed on the disk substrate 100. Two of the deposition chambers 202 are used for loading (introducing the disk substrate 100 into the sputtering apparatus 200) and unloading (discharging the disk substrate 100 from the sputtering apparatus 200).

The sputtering apparatus 200 includes a preliminary exhaust chamber 204. The disk substrate 100 (mainly glass or aluminum) is loaded into a pre-evacuation chamber after cleaning and pre-evacuated using a vacuum pump for a certain time. Thereafter, after reaching a certain back pressure (about 10 ⁻³ Pa), the substrate is loaded into the film formation chamber 202 (back pressure about 10 ⁻⁵ to 10 ⁻⁶ ), and film formation is started. After the film formation is completed, the film is unloaded from the sputtering apparatus via the preliminary exhaust chamber 204 again.

  In general, an in-line type sputtering apparatus loads and unloads the disk substrate 100 via the preliminary exhaust chamber as described above, thereby forming a film on the disk substrate 100 in order and realizing high throughput. However, on the other hand, since the back pressure of the preliminary exhaust chamber is higher than the back pressure of the film forming chamber, it is considered that impurities such as gas adsorbed on the disk substrate 100 are brought into the film forming chamber 202.

  That is, the individual film forming chambers 202 are sealed during the sputtering process, but all the film forming chambers 202 are opened simultaneously when the disk substrate 100 is transported. Therefore, if there is a difference in back pressure (atmospheric pressure), the gas will circulate in all the deposition chambers 202 in an instant.

  As described above, when the throughput (processing amount per unit time) is increased in the in-line type sputtering apparatus in order to improve the productivity, the coercive force Hc tends to decrease. This indicates that the crystal orientation of the magnetic recording layer is disturbed, and the coercive force Hc and the S / N ratio are thereby reduced. Further investigation by the inventors has revealed that the disorder of orientation starts from the orientation control layer below the underlayer. This was presumed to occur because gas was adsorbed or oxidized on the surface of the orientation control layer. As one means for solving this, it is conceivable to increase (lower pressure) the back pressure of the preliminary exhaust chamber 204, but in order to achieve a higher back pressure, it is necessary to take a long time for evacuation, This is contrary to increasing the throughput.

  As a result of various investigations on the orientation control layer, it was confirmed that the oxidation of the orientation control layer is the cause of disorder of orientation, and this was confirmed by experiments to complete the present invention.

  That is, as will be described later, in a magnetic recording medium having an orientation control layer, a nonmagnetic underlayer, and a magnetic recording layer on a substrate, the orientation control layer is mainly composed of nickel or an element having a smaller ionization tendency than nickel. According to the above configuration, since the alignment control layer is not easily affected by oxidation, even if the throughput is improved, the alignment control layer is not easily disturbed, and the coercive force Hc and the S / N ratio can be prevented from being lowered. Thereby, both high throughput, high coercive force and S / N ratio can be achieved.

  The orientation control layer is mainly composed of Ni (nickel), and includes at least one of Ti (titanium), V (vanadium), Ta (tantalum), Cr (chromium), Mo (molybdenum), and W (tungsten). An alloy containing an additive element can be preferably used. Ni is preferable because it is resistant to oxidation.

  However, Ni is a ferromagnetic material, and if a magnetic layer made of a ferromagnetic material exists under the nonmagnetic underlayer, the magnetic disk will not perform a desired operation. Therefore, it is preferable to add another element in which Ni does not have magnetism, and specifically, it is preferable to mix the above metal at 5 at% (atomic%) or more. On the other hand, the orientation control layer needs to have an fcc structure, and if the amount of the additive becomes too large, the crystal structure cannot be maintained and becomes amorphous. Specifically, the additive preferably contains the above metal at 15 at% or less.

  The orientation control layer, the nonmagnetic underlayer, and the magnetic recording layer are preferably formed using an inline sputtering apparatus. Since sputtering is continuously performed using a plurality of deposition chambers, high throughput can be realized.

  The present invention is particularly effective when the nonmagnetic underlayer and magnetic recording layer have an hcp structure (hexagonal close-packed structure). When the underlayer and the magnetic recording layer have the hcp structure, the crystal orientation can be controlled by the orientation control layer having the fcc structure. Therefore, as described above, the orientation control layer is not easily affected by oxidation, and even if the throughput is improved, the orientation control layer is not easily disturbed, so that the coercive force Hc and the S / N ratio can be prevented from being lowered. Thereby, both high throughput, high coercive force and S / N ratio can be achieved.

[Example]
The magnetic recording disk shown in FIG. 2 includes a disk substrate 10, a soft magnetic layer 14, an orientation control layer 16, an underlayer 18, an onset layer 20, a magnetic recording layer 22, an auxiliary recording layer 24, a medium protective layer 26, and a lubricating layer 28. Is provided.

  The soft magnetic layer 14 has AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 14b between the first soft magnetic layer 14a and the second soft magnetic layer 14c. It was configured as follows. Thereby, the magnetization directions of the first soft magnetic layer and the second soft magnetic layer can be aligned antiparallel with high accuracy, and noise generated from the soft magnetic layer 14 can be reduced. Specifically, the composition of the first soft magnetic layer 14a and the second soft magnetic layer 14c can be CoTaZr (cobalt-tantalum-zirconium) or CoFeTaZr (cobalt-iron-tantalum-zirconium). The composition of the spacer layer 14b was Ru (ruthenium).

  The orientation control layer 16 has an action of protecting the soft magnetic layer 14 and an action of promoting alignment of crystal grains of the underlayer 18. The orientation control layer 16 may be a Pt (platinum), NiW (nickel-tungsten), or NiCr (nickel-chromium) layer having an fcc structure.

  The underlayer 18 has a two-layer structure made of Ru. When forming the second underlayer 18b on the upper layer side, the Ar gas pressure is made higher than when forming the first underlayer 18a on the lower layer side, so that the crystal orientation and the magnetic grains of the magnetic recording layer 22 are increased. Separation can be improved at the same time.

The onset layer 20 is a nonmagnetic granular layer. By forming a nonmagnetic granular layer on the hcp crystal structure of the underlayer 18 and growing the magnetic recording layer 22 thereon, the magnetic recording layer 22 has an action of separating from the initial stage (rise). is doing. The composition of the onset layer 20 was nonmagnetic CoCrRu—SiO ₂ (SiO ₂ : silicon oxide).

The magnetic recording layer 22 formed an hcp crystal structure by using a hard magnetic target made of CoCrPt (cobalt-chromium-platinum) containing titanium oxide (TiO ₂ ), which is a nonmagnetic substance.

  The auxiliary recording layer 24 forms a thin film (continuous layer) exhibiting high perpendicular magnetic anisotropy on the magnetic recording layer 22 and constitutes an exchange energy control layer. Thereby, in addition to the high density recording property and low noise property of the magnetic recording layer 22, the high heat resistance of the auxiliary recording layer 24 can be added. The composition of the auxiliary recording layer 24 was CoCrPtB.

  The medium protective layer 26 was formed by depositing carbon by a CVD method while maintaining a vacuum. The medium protective layer 26 is a protective layer for protecting the magnetic recording layer from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness as compared with that deposited by the sputtering method, so that the magnetic recording layer can be more effectively protected against the impact from the magnetic head.

  The lubricating layer 28 was formed by dip coating using PFPE (perfluoropolyether). The film thickness of the lubricating layer 28 is about 1 nm.

[Evaluation]
In the same sputtering apparatus, the orientation control layer 16 was composed of Pt and NiW as Examples 1 and 2, and composed of Ta as a comparative example. Then, several types of magnetic recording media were created while changing the throughput. Then, the magnetostatic characteristics were measured using a Polar Kerr effect measuring device, and the coercive force Hc was evaluated. The results are shown in FIGS. In the figure, the unit of throughput is pph (Piece per hour), and the unit of coercive force Hc is Oe (Oersted: represents magnetic field strength).

  As shown in FIG. 3, when Ta is used for the orientation control layer 16 (comparative example), it can be seen that the coercive force Hc tends to decrease as the throughput increases. On the other hand, when Pt is used for the orientation control layer 16 (Example 1), it can be seen that even if the throughput is high, a coercive force Hc equivalent to that of Ta and a low throughput is obtained. In the case of using Pt, the coercive force Hc is rather improved when the throughput is increased. When NiW was used for the orientation control layer 16 (Example 2), the coercive force Hc was the highest, and the coercive force was only slightly reduced even when the throughput was increased.

  As shown in FIG. 4, the S / N ratio has a similar tendency, and Pt and NiW have a significantly higher S / N ratio than Ta. In addition, Pt and NiW showed only a slight decrease in the S / N ratio even when the throughput was increased.

  From these facts, it is possible to achieve both high throughput, high coercive force and high S / N ratio without making major changes to the conventional device by using as a main component an element that is not easily oxidized as the orientation control layer 16. It was confirmed that there was.

[Second Embodiment]
A second embodiment of the method for manufacturing a perpendicular magnetic recording medium according to the present invention will be described. Note that dimensions, materials, and other specific numerical values shown in the following embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  FIG. 5 is a diagram for explaining the configuration of the perpendicular magnetic recording medium 102 according to the second embodiment. The perpendicular magnetic recording medium 102 shown in FIG. 5 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, an orientation control layer 116, a first underlayer 118a, and a second layer. The underlayer 118b, the onset layer 120, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the auxiliary recording layer 124, the medium protective layer 126, and the lubricating layer 128 are included. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

  As will be described below, the perpendicular magnetic recording medium 102 shown in the present embodiment has a plurality of types of oxides (one or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b of the magnetic recording layer 122). Hereinafter, the composite oxide is segregated at the nonmagnetic grain boundaries by containing “composite oxide”.

  As the disk base 110, 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 substrate are not particularly limited. Examples of the glass substrate material include glass ceramics such as aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or crystallized glass. It is done. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth nonmagnetic disk base 10 made of a chemically strengthened glass disk.

  On the disk substrate 110, the adhesion layer 112 to the auxiliary recording layer 124 are sequentially formed by DC magnetron sputtering, and the medium protective layer 126 can be formed by CVD. Thereafter, the lubricating layer 128 can be formed by dip coating. Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration and manufacturing method of each layer will be described.

  The adhesion layer 112 is an amorphous underlayer, which is formed in contact with the disk substrate 110 and has a function of increasing the peel strength between the soft magnetic layer 114 and the disk substrate 110 formed thereon. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous alloy film so as to correspond to the amorphous glass surface.

  As the adhesion layer 112, for example, a CrTi-based amorphous layer can be selected.

  The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to pass magnetic flux in a direction perpendicular to the recording layer in the perpendicular magnetic recording method. The soft magnetic layer 114 is provided with AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 114b between the first soft magnetic layer 114a and the second soft magnetic layer 114c. Can be configured. As a result, the magnetization direction of the soft magnetic layer 114 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 114 is reduced. Can do. The compositions of the first soft magnetic layer 114a and the second soft magnetic layer 114c include a Co-based alloy such as CoTaZr, a Co-Fe based alloy such as CoCrFeB, and a Ni-Fe such as a [Ni-Fe / Sn] n multilayer structure. A system alloy or the like can be used.

  The orientation control layer 116 is a nonmagnetic alloy layer, and acts to protect the soft magnetic layer 114 and the easy magnetization axis of the hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon is a disk. A function for aligning in the vertical direction is provided. In the orientation control layer 116, the (111) plane of the face-centered cubic structure (fcc structure) or the (110) plane of the body-centered cubic structure (bcc structure) is preferably parallel to the main surface of the disk substrate 110. Further, the orientation control layer 116 may have a configuration in which these crystal structures and amorphous are mixed.

  The orientation control layer is mainly composed of Ni (nickel), and includes at least one of Ti (titanium), V (vanadium), Ta (tantalum), Cr (chromium), Mo (molybdenum), and W (tungsten). It is preferably made of an alloy containing an additive element. Ni is preferable because it is resistant to oxidation. However, Ni is a ferromagnetic material, and if a magnetic layer made of a ferromagnetic material exists under the nonmagnetic underlayer, the magnetic disk will not perform a desired operation. Therefore, it is preferable to add another element in which Ni does not have magnetism, and specifically, it is preferable to mix the above metal at 5 at% (atomic%) or more. On the other hand, the orientation control layer needs to have an fcc structure (face-centered cubic lattice), and if the amount of the additive becomes too large, the crystal structure cannot be maintained and becomes amorphous. is there. Specifically, the additive preferably contains the above metal at 15 at% or less.

  The underlayer 118 has an hcp structure, and has a function of growing a Co hcp crystal of the magnetic recording layer 22 as a granular structure. Therefore, the higher the crystal orientation of the underlayer 18, that is, the more the (0001) plane of the crystal of the underlayer 118 is parallel to the main surface of the disk substrate 110, the more the orientation of the magnetic recording layer 22 is improved. Can do. Ru is a typical material for the underlayer, but in addition, it can be selected from RuCr and RuCo. Since Ru has an hcp structure and the lattice spacing of crystals is close to Co, a magnetic recording layer containing Co as a main component can be well oriented.

  When the underlayer 118 is made of Ru, a two-layer structure made of Ru can be obtained by changing the gas pressure during sputtering. Specifically, when forming the second base layer 118b on the upper layer side, the Ar gas pressure is set higher than when forming the first base layer 118a on the lower layer side. When the gas pressure is increased, the free movement distance of the plasma ions to be sputtered is shortened, so that the film formation rate is reduced and the crystal orientation can be improved. Further, by increasing the pressure, the size of the crystal lattice is reduced. Since the size of the Ru crystal lattice is larger than that of the Co crystal lattice, if the Ru crystal lattice is made smaller, it approaches that of Co, and the crystal orientation of the Co granular layer can be further improved.

The onset layer 120 is a nonmagnetic granular layer. A nonmagnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and the granular layer of the first magnetic recording layer 122a is grown thereon, so that the magnetic granular layer can be grown from the initial growth stage (rise). Has the effect of separating. The composition of the onset layer 120 can be a granular structure by segregating nonmagnetic substances between nonmagnetic crystal grains made of a Co-based alloy to form grain boundaries. In particular, CoCr—SiO ₂ and CoCrRu—SiO ₂ can be preferably used, and Rh (rhodium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Au (in addition to Ru) Gold) can also be used. A nonmagnetic substance is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is cobalt (Co). Any non-magnetic substance that does not dissolve in solution can be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  By providing the onset layer on the surface side of the underlayer as described above, by providing the orientation control layer on the orientation control layer resistant to oxidation, the orientation of the onset layer is further improved, and the magnetic recording layer The coercive force Hc and S / N ratio can be realized by improving the orientation of the film. That is, the underlayer has a substantially uniform crystal structure of hcp structure, and when forming a magnetic recording layer of granular structure, by forming a non-magnetic granular layer, the granularity (magnetic crystal grains) of the magnetic recording layer is improved. It can promote and improve the S / N ratio.

  The crystal particles of the onset layer may contain at least Co and Cr, and the nonmagnetic substance may contain an oxide. By including Co, the granular structure of the magnetic crystal grains of the magnetic recording layer formed thereon can be epitaxially grown without impairing the orientation.

The magnetic recording layer 122 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. Yes. By providing the onset layer 20, the magnetic grains can be epitaxially grown continuously from the granular structure. The magnetic recording layer may be a single layer, but in this embodiment, the magnetic recording layer is composed of a first magnetic recording layer 122a and a second magnetic recording layer 122b having different compositions and film thicknesses. The first magnetic recording layer 122a and the second magnetic recording layer 122b are all non-magnetic materials such as oxides such as SiO ₂ , Cr ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Fe ₂ O ₃ , BN, etc. Nitride and carbides such as B ₄ C ₃ can be preferably used.

  By using the magnetic recording layer having such a configuration, the orientation is inherited from the orientation control layer. Therefore, as described above, the orientation control layer is not easily affected by oxidation, and even if the throughput is improved, the orientation control layer is not easily disturbed, so that the coercive force Hc and the S / N ratio can be prevented from being lowered. Thereby, both high throughput, high coercive force and S / N ratio can be achieved.

Furthermore, in this embodiment, two or more nonmagnetic substances are used in combination in either or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b. Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to include SiO ₂ and TiO ₂ , and Cr ₂ O ₃ can be suitably used instead of / in addition to either of them. For example, the first magnetic recording layer 22a contains Cr ₂ O ₃ and SiO ₂ as an example of a complex oxide (a plurality of types of oxides) at the grain boundary, and an hcp crystal of CoCrPt—Cr ₂ O ₃ —SiO ₂ . A structure can be formed. Further, for example, the second magnetic recording layer 22b contains SiO ₂ and TiO ₂ as an example of a composite oxide at the grain boundary portion, and can form an hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ .

  The auxiliary recording layer 124 is a layer (also called a continuous layer) that is magnetically continuous in the in-plane direction on the magnetic recording layer 122 having a granular structure. Although the auxiliary recording layer 124 is not necessarily required, by providing the auxiliary recording layer 124, in addition to the high density recording property and low noise property of the magnetic recording layer 122, the reverse domain nucleation magnetic field Hn is improved, the heat-resistant fluctuation characteristic is improved, and the overwrite is performed. The characteristics can be improved.

  The medium protective layer 126 can be formed by forming a carbon film by a CVD method while maintaining a vacuum. The medium protective layer 126 is a protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head. 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 layer can be protected more effectively against the impact from the magnetic head.

  The lubricating layer 128 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 medium protective layer 126. Due to the action of the lubricating layer 128, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 102, damage or loss of the medium protective layer 126 can be prevented.

  Through the above manufacturing process, the perpendicular magnetic recording medium 102 can be obtained.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. 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 magnetic recording medium mounted on a magnetic recording type HDD or the like and a manufacturing method thereof.

It is a figure explaining an in-line type sputtering device. It is a figure explaining the structure of a magnetic recording medium. It is a figure explaining the relationship between a throughput and the coercive force Hc. It is a figure explaining the relationship between a throughput and S / N ratio. It is a figure explaining the structure of the perpendicular magnetic recording medium concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Disk base | substrate 14 ... Soft-magnetic layer 14a ... 1st soft-magnetic layer 14b ... Spacer layer 14c ... 2nd soft-magnetic layer 16 ... Orientation control layer 18 ... Underlayer 18a ... 1st underlayer 18b ... 2nd underlayer 20 ... Onset layer 22 ... magnetic recording layer 24 ... auxiliary recording layer 26 ... medium protective layer 28 ... lubricating layer 100 ... disk substrate 102 ... perpendicular magnetic recording medium 110 ... disk substrate 112 ... adhesion layer 114 ... soft magnetic layer 114a ... first soft layer Magnetic layer 114b ... Spacer layer 114c ... Second soft magnetic layer 116 ... Orientation control layer 118 ... Underlayer 118a ... First underlayer 118b ... Second underlayer 120 ... Onset layer 122 ... Magnetic recording layer 122a ... First magnetic recording Layer 122b ... Second magnetic recording layer 124 ... Auxiliary recording layer 126 ... Medium protective layer 128 ... Lubricating layer 200 ... Sputtering device 202 ... Film forming channel 204 ... spare exhaust chamber

Claims (7)

In a magnetic recording medium comprising an orientation control layer, a nonmagnetic underlayer, and a magnetic recording layer on a substrate,
The magnetic recording medium according to claim 1, wherein the orientation control layer is mainly composed of nickel or an element having a smaller ionization tendency than nickel.   2. The magnetic recording medium according to claim 1, wherein the orientation control layer is made of an alloy containing Ni as a main component and containing at least one additive element of Ti, V, Ta, Cr, Mo, and W. .   2. The magnetic recording medium according to claim 1, wherein the nonmagnetic underlayer and the magnetic recording layer have an hcp structure (hexagonal close-packed structure).   An onset layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between crystal grains grown in a columnar shape on the surface side of the magnetic recording medium from the underlayer, and is made nonmagnetic as a whole. The magnetic recording medium according to claim 1.   The magnetic recording medium according to claim 4, wherein the crystal grains of the onset layer contain at least Co and Cr, and the nonmagnetic substance contains an oxide.   A magnetic recording layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between magnetic crystal grains containing at least Co (cobalt) and growing in a columnar shape on the surface side of the magnetic recording medium from the onset layer. The magnetic recording medium according to claim 1, comprising: An orientation control layer is formed on the substrate,
Deposit a non-magnetic underlayer,
In the method of manufacturing a magnetic recording medium for forming a magnetic recording layer,
The orientation control layer is mainly composed of nickel or an element having a smaller ionization tendency than nickel, and the orientation control layer, the nonmagnetic underlayer, and the magnetic recording layer are formed using an in-line type sputtering apparatus. A method of manufacturing a magnetic recording medium, comprising forming a film.

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