JP2008276912A - Vertical magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical magnetic recording medium enhancing durability such as wear resistance and impact resistance and avoiding problems such as high fly write even when a film thickness of a medium protection layer is limited to ≤3 nm. <P>SOLUTION: A vertical magnetic recording disk 100 includes a base 10, a magnetic recording layer 22, and the medium protection layer 26. The medium protection layer 26 contains nitrogen (N) and carbon (C) with an atomic mass ratio (N/C) in a range from 0.050 to 0.150. In a Raman spectrum in 900 to 1,800 cm<SP>-1</SP>wave number obtained by exciting the medium protection layer 26 by argon ion laser light of wavelength 514.5 nm, from which a fluorescence is removed, the peak ratio Dh/Gh is in a range from 0.70 to 0.95, when a D peak Dh appearing in the vicinity of 1,350 cm<SP>-1</SP>and G peak Gh appearing in the vicinity of 1,520 cm<SP>-1</SP>are waveform-separated by the Gauss function. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  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 GB.

  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 hindrance factor, in recent years, a perpendicular magnetic recording type magnetic disk (perpendicular magnetic recording disk) has 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.

  As the information recording density increases, both the circumferential linear recording density (BPI: Bit Per Inch) and the radial track recording density (TPI: Track Per Inch) continue to increase. Yes. Further, a technique for improving the S / N ratio by narrowing the gap (magnetic spacing) between the magnetic layer of the magnetic disk and the recording / reproducing element of the magnetic head has been studied. In recent years, the flying height of a magnetic head desired is 10 nm or less.

  As one technique for reducing the magnetic spacing, the head element generates heat during the operation of the magnetic head element, and the magnetic head is thermally expanded by the heat to move in the ABS (The air bearing surface) direction. A DFH (Dynamic Flying Height) head that slightly protrudes has been proposed. As a result, the gap between the magnetic head and the magnetic disk can be adjusted, and the magnetic head can always fly stably and with a narrow magnetic spacing.

  The perpendicular magnetic recording disk is provided with a medium protective layer that protects the surface of the magnetic recording layer from being damaged when the magnetic head collides with the perpendicular magnetic recording disk. The medium protective layer forms a high hardness film by a carbon overcoat (COC), that is, a carbon film. Some medium protective layers include a mixture of a hard diamond-like bond (amorphous bond) of carbon and a soft graphite bond (for example, Patent Document 1). Also disclosed is a technique for manufacturing a diamond-like bond protective film by a CVD (Chemical Vapor Deposition) method (for example, Patent Document 2). Furthermore, a technique for improving the durability of the medium protective layer is also disclosed (for example, Patent Document 3).

On the medium protective layer, a lubricating layer is formed to protect the medium protective layer and the magnetic head when the magnetic head collides. The lubricating layer is formed, for example, by applying perfluoropolyether and sintering.
Japanese Patent Laid-Open No. 10-11734 JP 2006-114182 A JP 2005-149553 A

  In order to achieve the magnetic spacing of, for example, 10 nm or less as described above, a thin film of 3 nm or less is required for the medium protective layer of the perpendicular magnetic recording disk. However, if the medium protective layer is simply made thin, durability such as wear resistance and impact resistance of the medium protective layer itself deteriorates.

  Various methods for forming a medium protective layer are conventionally known. However, since the conventional medium protective layer does not have sufficient durability, magnetic recording is performed in a LUL (Load Unload) type perpendicular magnetic recording disk apparatus. Due to the impact when the head is loaded on the perpendicular magnetic recording disk, a slight scratch or the like is generated on the perpendicular magnetic recording disk, and the reproduction signal is lowered.

  Even when the above-described DFH head is used, when the magnetic head comes into contact with the magnetic disk and the adhesion of the lubricating layer is weak, the lubricating layer may be transferred to the magnetic head. As a result, the magnetic head is covered, which may cause a read / write defect, or may cause the magnetic head to become unstable and cause a high fly write phenomenon. The high fly write phenomenon is a phenomenon in which data that should have been written is not written because the magnetic head is separated from the magnetic disk, and a read error occurs even if the hardware does not necessarily fail.

  The above Patent Document 3 also describes a technique for improving the durability of such a medium protective layer, but specific means for reducing the problem of the high flylight and the thickness of the medium protective layer to 3 nm or less. Is not mentioned.

  The present invention has been made in view of the above-mentioned problems of the configuration of the conventional medium protective layer, and an object of the present invention is to improve durability such as wear resistance and impact resistance, and to provide a lubricating layer. The perpendicular magnetic recording medium capable of avoiding various problems such as high fly write even if the thickness of the medium protective layer is limited to 3 nm or less by preventing the transfer of the magnetic head to the magnetic head and a method for manufacturing the same are provided. That is.

  As a result of extensive studies by the inventors to solve the above-mentioned problems, the property of the medium protective layer changes immediately after the magnetic layer is heat-treated immediately before the formation of the medium protective layer, and the heat treatment temperature. Adjusting the Raman spectrum of the medium protective layer, and the adhesion of the lubricating layer is affected by the amount of nitrogen on the outermost surface of the medium protective layer, and the nitrogen on the outermost surface of the medium protective layer. The present inventors have found that the atomic weight ratio (N / C) of carbon and carbon depends on the change in the nitrogen flow rate of the surface treatment layer, and further research has been completed to complete the present invention.

In order to solve the above problems, according to one aspect of the present invention, there is provided a perpendicular magnetic recording medium including a magnetic recording layer on a substrate and a medium protective layer on the magnetic recording layer, wherein the medium protective layer is made of carbon. Nitrogen is impregnated into the surface layer of the film mainly containing N, the atomic weight ratio (N / C) of nitrogen (N) to carbon (C) is 0.050 to 0.150, and the wavelength is 514. appearing near 1350 cm ^-1 of the spectrum excluding the fluorescence from the Raman spectrum in a wave number 900 cm ^-1 ~ wavenumber 1800 cm ^-1 obtained by exciting the medium protective layer with argon ion laser light .5Nm D peak Dh (Disordered-peaks- height) and G peak Gh (Graphite-peaks-height) appearing in the vicinity of 1520 cm ⁻¹ when the waveform is separated by a Gaussian function, the peak ratio Dh / Gh is 0.70 to 0.95. A perpendicular magnetic recording medium is provided.

  With the configuration in which the magnetic layer is heated immediately before the formation of the medium protective layer, the peak ratio Dh / Gh by Raman spectrum can be set to 0.70 to 0.95, and durability such as impact resistance, wear resistance, and corrosion resistance can be achieved. Can be improved. Further, by setting the atomic weight ratio (N / C) to 0.050 to 0.150, it is possible to avoid the problem of high flylight and the crash with the magnetic head.

  The perpendicular magnetic recording medium is formed with an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at% of iron (Fe), and a soft magnetic layer having a saturation magnetization Ms of 1.2 T or more is provided below the magnetic recording layer. You may prepare. The soft magnetic layer is separated into two layers with a spacer layer therebetween, and the direction of magnetization is configured to be parallel to the disk surface of the perpendicular magnetic recording medium and opposite to each other. The antiferromagnetic exchange coupling (AFC) structure thus configured has an antiferromagnetic coupling force between two upper and lower layers arranged in antiparallel by heat of a predetermined temperature or more. Will fall. In the present invention, by mixing iron when forming the soft magnetic layer, a heat-resistant AFC structure is formed, and heating immediately before the formation of the medium protective layer is enabled. Further, the saturation magnetization Ms affects the ease of writing to the recording medium, that is, the overwrite characteristic, and the overwrite characteristic is improved as the saturation magnetization Ms is increased. Therefore, the required overwrite characteristic can be maintained by the configuration in which the saturation magnetization Ms is 1.2 T or more.

  The soft magnetic layer may have an exchange coupling magnetic field Hex of 40 Oe or more. The coupling strength of the AFC structure is determined based on the exchange coupling magnetic field Hex. Therefore, the larger Hex, the stronger the coupling of AFC. If Hex is less than 40 Oe, the function as the AFC structure cannot be maintained.

  The magnetic recording layer may be formed in a granular structure, and an auxiliary recording layer may be provided on the magnetic recording layer. With this configuration, it is possible to reduce the size of the magnetic particles in the magnetic recording layer and improve the coercive force Hc. Therefore, it is possible to improve the high density recording property and low noise property of the magnetic recording layer. Further, by providing the auxiliary recording layer on the magnetic recording layer, it is possible to further add high thermal fluctuation resistance to the perpendicular magnetic recording medium.

  The composition of the auxiliary recording layer may be CoCrPtB. Thereby, it is possible to form a thin film exhibiting perpendicular magnetic anisotropy and to improve the high thermal fluctuation resistance of the perpendicular magnetic recording medium.

In order to solve the above problems, according to another aspect of the present invention, a perpendicular magnetic recording medium comprising a magnetic recording layer on a substrate and a medium protective layer comprising a coating composed mainly of carbon on the magnetic recording layer. of a manufacturing method to form a magnetic recording layer, after the medium protective layer formed, a wavelength 514.5nm of argon ion laser beam to the medium protective layer excited obtained wavenumbers 900 cm ^-1 ~ wavenumber 1800 cm ^- and D peak Dh appearing near 1350 cm ^-1 of the spectrum excluding the fluorescence from the Raman spectrum in ^1, the peak ratio Dh / Gh when the waveform separated by a Gaussian function and a G peak Gh appearing near 1520 cm ^-1, 0. The perpendicular magnetic recording medium is heated to 70 to 0.95, a medium protective layer is formed by a CVD method, and nitrogen (N) and carbon (C) are further formed. Molecular weight ratio (N / C) characterized in that the exposure to nitrogen so that 0.050 to 0.150, method of manufacturing the perpendicular magnetic recording medium is provided.

  By forming the perpendicular magnetic recording medium so that the peak ratio Dh / Gh according to Raman spectrum is 0.70 to 0.95 and the atomic weight ratio (N / C) is 0.050 to 0.150, wear resistance and Even if the durability such as impact resistance is improved and the film thickness of the medium protective layer is limited to 3 nm or less, various problems such as high flylight can be avoided.

  Heating may be done at a temperature of 110-210 ° C. When the heat treatment is performed immediately before the formation of the medium protective layer, the carbon atoms decomposed by the plasma can reach the substrate while maintaining high energy. Since carbon atoms maintaining this high energy are formed on the substrate on the magnetic film, a dense and durable medium protective layer can be formed. In addition, the adhesion between the magnetic layer and the medium protective layer is improved by heating the magnetic layer at a high temperature.

  After the medium protective layer is formed, the medium protective layer may be subjected to surface treatment by exposure to a nitrogen atmosphere having a flow rate of 100 to 350 sccm. When exposed to a nitrogen atmosphere with a flow rate of 100 to 350 sccm, the atomic weight ratio (N / C) of nitrogen (N) and carbon (C) becomes 0.050 to 0.150, and a medium protective layer and a lubricating layer formed by CVD Adhesiveness and hardness are suitable.

  Furthermore, a lubricating layer containing a perfluoropolyether compound having a hydroxyl group at the terminal group may be formed.

Perfluoropolyether has a linear structure and exhibits moderate lubrication performance for perpendicular magnetic recording media, as well as high adhesion performance to the media protective layer by having a hydroxyl group (OH) at the end group. can do. In particular, in the configuration of the present invention provided with a surface treatment layer containing nitrogen on the surface of the medium protective layer, (N ⁺ ) and (OH ⁻ ) have high affinity, so that a high lubricating layer adhesion rate can be obtained. it can.

  As described above, according to the perpendicular magnetic recording medium of the present invention, it is possible to improve durability such as wear resistance and impact resistance and to prevent the lubricant layer from being transferred to the magnetic head. Even if the thickness of the protective layer is limited to 3 nm or less, various problems such as high flylight can be avoided.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 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.

  FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording disk 100 as a perpendicular magnetic recording medium according to the present embodiment. A perpendicular magnetic recording disk 100 shown in FIG. 1 includes a disk substrate 10, an adhesion layer 12, a first soft magnetic layer 14a, a spacer layer 14b, a second soft magnetic layer 14c, an orientation control layer 16, a first underlayer 18a, and a second layer. The underlayer 18b, the onset layer 20, the first magnetic recording layer 22a, the second magnetic recording layer 22b, the auxiliary recording layer 24, the medium protective layer 26, and the lubricating layer 28 are formed. The first soft magnetic layer 14a, the spacer layer 14b, and the second soft magnetic layer 14c together constitute the soft magnetic layer 14. The first base layer 18a and the second base layer 18b together constitute the base layer 18. The first magnetic recording layer 22a and the second magnetic recording layer 22b constitute the magnetic recording layer 22 together.

  First, an amorphous aluminosilicate glass was formed into a disk shape by direct pressing to produce a glass disk. The glass disk was subjected to grinding, polishing, and chemical strengthening in order to obtain a smooth non-magnetic disk base 10 made of a chemically strengthened glass disk.

  Since the aluminosilicate glass is smooth and has high rigidity, the magnetic spacing, particularly the flying height of the magnetic head, can be more stably reduced. Aluminosilicate glass can obtain high rigidity and strength by chemical strengthening.

  On the disk base 10 obtained, a film forming apparatus that has been evacuated is used to sequentially form a film from the adhesion layer 12 to the auxiliary recording layer 24 in an Ar atmosphere by a DC magnetron sputtering method, thereby protecting the medium protective layer. No. 26 was formed by CVD. Thereafter, the lubricating layer 28 was formed by dip coating. Note that it is also preferable to use an in-line film forming method in that uniform film formation is possible. Hereinafter, the configuration and manufacturing method of each layer will be described in detail.

  The adhesion layer 12 was formed using a Ti alloy target so as to be a 10 nm Ti alloy layer. By forming the adhesion layer 12, the adhesion between the disk base 10 and the soft magnetic layer 14 can be improved, so that the soft magnetic layer 14 can be prevented from peeling off. As a material of the adhesion layer 12, for example, a CrTi alloy can be used. From the practical viewpoint, the thickness of the adhesion layer is preferably 1 nm to 50 nm.

  The soft magnetic layer 14 is configured to include AFC by interposing a nonmagnetic spacer layer 14b between the first soft magnetic layer 14a and the second soft magnetic layer 14c. As a result, the magnetization direction of the soft magnetic layer 14 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and noise generated from the soft magnetic layer 14 can be reduced by extremely reducing the perpendicular component of magnetization. it can.

  FIG. 2 is an explanatory diagram for explaining the magnetization characteristics of the AFC structure. Referring to such magnetization characteristics, a soft magnetic layer having no AFC structure maintains a positive or negative magnetization state when a magnetic field H is not applied, whereas a soft magnetic layer having an AFC structure has a magnetic field H applied thereto. When no voltage is applied, a magnetic flux is formed between the first soft magnetic layer 14a and the second soft magnetic layer 14c as shown in (b), and the magnetization M becomes zero. When the magnetic field H is applied in either direction, the magnetic fluxes of both soft magnetic layers 14a and 14c are oriented in the same direction as shown in (a) and (c).

  The coupling strength of the AFC structure is determined based on the exchange coupling magnetic field Hex shown in FIG. 2, and the larger the Hex, the stronger the coupling of AFC. The Hex is set so as to be magnetized with respect to the magnetic field for writing of the corresponding magnetic recording layer 22 and not to react with the magnetic field for writing of the adjacent magnetic recording layer 22. Hex can be increased if the film thickness is reduced. However, if the film thickness is simply reduced, it becomes impossible to absorb all the magnetic flux from the magnetic head, so it is necessary to reduce the thickness according to the magnetic flux from the magnetic head. .

  Further, as the magnetic field H is applied, the magnetization M of the soft magnetic layer having the AFC structure increases to a certain value and becomes saturated. The value at which the magnetization M is in a saturated state in this way is referred to as saturation magnetization Ms. By improving the saturation magnetization Ms, the ease of writing to the recording medium, that is, the overwrite characteristic is improved. The saturation magnetization Ms is preferably 1.2T or more. This is because the required overwrite characteristic can be maintained.

  The magnetic moment representing the strength of the magnet of the magnetic film is represented by Ms · t, which is the product of the saturation magnetization Ms and the film thickness t. Therefore, when it is desired to obtain a magnetic moment Ms · t having a desired strength, if the saturation magnetization Ms is weak, it is necessary to increase the film thickness. However, as the film thickness increases, it is necessary to increase the magnetic field of the magnetic head in order to reach the lines of magnetic force. For this reason, even if the same magnetic moment Ms · t is obtained, it is preferable that the saturation magnetization Ms and the thin film thickness t be as high as possible.

  In the AFC structure configured as described above, the easy axis of magnetization of the upper and lower layers arranged in antiparallel due to heat of a predetermined temperature or more is usually broken, and the S / N ratio is lowered. In this embodiment, iron is mixed during the formation of the soft magnetic layer to form an AFC structure that is resistant to heat, and heating immediately before the formation of the medium protective layer described later is enabled. Therefore, the composition of the first soft magnetic layer 14a and the second soft magnetic layer 14c is CoCrFeB, and the composition of the spacer layer 14b is 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 is a NiW or NiCr layer having an fcc structure.

  The underlayer 18 has a two-layer structure made of Ru. When forming the upper second base layer 18b, the crystal orientation can be improved by making the Ar gas pressure higher than when forming the lower first base layer 18a.

The onset layer 20 is a nonmagnetic granular layer. A nonmagnetic granular layer is formed on the hcp crystal structure of the underlayer 18, and the granular layer of the first magnetic recording layer 22 a is grown thereon to separate the magnetic granular layer from the initial stage (rise). Has an effect. The composition of the onset layer 20 was nonmagnetic CoCr—SiO ₂ .

  The magnetic recording layer 22 includes a thin first magnetic recording layer 22a and a thick second magnetic recording layer 22b.

The first magnetic recording layer 22a is a 2 nm CoCrPt—Cr ₂ O ₃ hcp crystal structure using a hard magnetic target made of CoCrPt containing chromium oxide (Cr ₂ O ₃ ) as an example of a nonmagnetic substance. Formed. The nonmagnetic material segregated around the magnetic material to form grain boundaries, and the magnetic particles (magnetic grains) formed a columnar granular structure. The magnetic grains were epitaxially grown continuously from the granular structure of the onset layer.

The second magnetic recording layer 22b was formed using a CoCrPt—TiO ₂ hcp crystal structure of 10 nm using a hard magnetic target made of CoCrPt containing titanium oxide (TiO ₂ ) as an example of a nonmagnetic substance. Also in the second magnetic recording layer 22b, the magnetic grains formed a granular structure.

  The auxiliary recording layer 24 forms a CGC structure (Coupled Granular Continuous) by forming a thin film (continuous layer) showing high perpendicular magnetic anisotropy on the granular magnetic layer. Thereby, in addition to the high density recording property and low noise property of the granular layer, the high thermal fluctuation resistance of the continuous film can be added. The composition of the auxiliary recording layer 24 was CoCrPtB.

  The medium protective layer 26 is a medium protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head. The medium protective layer 26 is formed immediately after the auxiliary recording layer 24 is formed and immediately after the perpendicular magnetic recording disk 100 is preheated.

  Thus, if the magnetic layer is heat-treated immediately before the formation of the medium protective layer 26, the properties of the medium protective layer 26 immediately after it change. In the present embodiment, in particular, the Raman spectrum (ratio of diamond-like bond and graphite-like bond) changes, and the resistance of the medium protective layer 26 is improved as the diamond-like bond increases. Such heat treatment is performed in a range where the peak ratio Dh / Gh of the medium protective layer 26 to be formed later is 0.70 to 0.95.

Here, the peak ratio Dh / Gh is a Raman spectrum was measured at a wave number 900 cm ^-1 ~ wavenumber 1800 cm ^-1 obtained by exciting the medium protective layer by argon ion laser beam having a wavelength of 514.5 nm, the background due to fluorescence corrected by linear approximation, Dh and Gh when the waveform separated by low wave number side (1350 cm ^-1) D peak Dh and high frequency side which appears in the vicinity of (1520 cm ^-1) Gaussian function and a G peak Gh appearing near the spectrum And the ratio.

  The reason why Dh / Gh is set to 0.70 to 0.95 is that when Dh / Gh is less than 0.70, the adhesion to the lubricating layer may be impaired, and Dh / Gh is 0.95. This is because the hardness of the medium protective layer may decrease in the above case. By setting Dh / Gh within the range of 0.70 to 0.95, adhesion and hardness between the medium protective layer and the lubricating layer formed through CVD become suitable, and sufficient durability can be obtained. It becomes.

  The specific heating temperature for setting the peak ratio Dh / Gh to 0.70 to 0.95 is, for example, a temperature range of 110 to 210 ° C. The temperature of the perpendicular magnetic recording disk 100 after forming the magnetic layer immediately before forming the medium protective layer 26 is set to 110 to 210 ° C. because the kinetic energy of carbon atoms is low when the film forming temperature is less than 110 ° C. This is because the denseness of the protective layer is lost, and when the temperature exceeds 210 ° C., the magnetic layer itself diffuses and the magnetic properties deteriorate. Therefore, a dense and high-hardness medium protective layer can be formed by heat-treating the magnetic layer at 110 to 210 ° C.

  When the heat treatment is performed immediately before the medium protective layer 26 is formed as described above, the perpendicular magnetic recording disk 100 maintains the high energy of the carbon atoms decomposed by the plasma when the medium protective layer 26 is formed. Thus, the dense and durable medium protective layer 26 can be formed. Further, by heating the magnetic layer at a high temperature, the adhesion between the magnetic layer and the medium protective layer is also improved.

  After such heat treatment is performed, carbon is deposited by plasma CVD, and the medium protective layer 26 is formed. When a hydrocarbon medium protective layer is formed by plasma CVD, it is desirable to form a diamond-like bond using only a hydrocarbon gas as a reactive gas. This is because when an inert gas (such as Ar) or a carrier gas such as hydrogen gas is mixed with a hydrocarbon gas, these impure gases are taken into the medium protective layer and the film density is lowered. Because it will end up.

  As the reactive gas, it is preferable to use hydrocarbons (hydrogenated carbon), particularly lower hydrocarbons, and it is more preferable to use linear lower saturated hydrocarbons or linear lower unsaturated hydrocarbons. As the linear lower saturated hydrocarbon, methane, ethane, propane, butane, pentane, hexane, heptane, octane, or the like may be used. Further, as the linear lower unsaturated hydrocarbon, ethylene, propylene, butylene, acetylene or the like may be used. Here, the term “lower” refers to a hydrocarbon having 1 to 10 carbon atoms per molecule.

  The linear lower hydrocarbon is preferably used because it becomes difficult to vaporize the hydrocarbon as a gas and supply it to the film forming apparatus as the number of carbon atoms increases, and decomposition during plasma discharge It will be difficult.

  In addition, when the number of carbon atoms increases, the component of the formed medium protective layer is likely to contain a large amount of high molecular hydrocarbons, leading to a decrease in the density and hardness of the medium protective layer. Furthermore, in the case of cyclic hydrocarbons, it may be difficult to decompose during plasma discharge compared to straight chain hydrocarbons. Accordingly, it is preferable to use a straight chain lower hydrocarbon as the hydrocarbon. In particular, by using ethylene, a dense and high-hardness medium protective layer can be formed.

  In general, carbon deposited by the CVD method has improved film hardness as compared with that deposited by the sputtering method, so that the perpendicular magnetic recording layer can be more effectively protected against an impact from the magnetic head.

  Further, after film formation by the CVD method, the medium protective layer 26 is exposed to a nitrogen atmosphere having a flow rate of 100 to 350 sccm, and the atomic weight ratio (N / C) of nitrogen (N) to carbon (C) is 0.050. The surface treatment is performed so as to be ˜0.150. Here, the reason why N / C is set to 0.05 to 0.15 is that when N / C is less than 0.05, high flylight frequently occurs and an error occurs in the recording / reproducing process. If the value exceeds .150, the possibility of a crash increases. Therefore, when N / C is in the range of 0.05 to 0.15, the adhesion and hardness between the medium protective layer and the lubricating layer formed by CVD are suitable.

  Here, the atomic weight ratio (N / C) of nitrogen / carbon can be measured using X-ray photoelectron spectroscopy (hereinafter referred to as ESCA (Electron Spectroscopy for Chemical Analysis)). Specifically, the atomic weight ratio of nitrogen / carbon is obtained from the intensities of the N1s spectrum and C1s spectrum measured by ESCA.

  In the present embodiment, the thickness of the medium protective layer 26 is preferably 1 nm or more. If the thickness is less than 1 nm, the coverage of the medium protective layer 26 is reduced, so that it may not be sufficient to prevent migration of metal ions in the magnetic layer, and there may be a problem in wear resistance. In addition, although it is not necessary to provide an upper limit for the thickness of the medium protective layer formed by CVD, it is preferably 3 nm or less for practical use so as not to hinder the improvement of magnetic spacing.

  Furthermore, it is preferable to apply a bias voltage of −300 to −50 V when forming the medium protective layer 26. The applied voltage is set to -300 to -50V. If the applied voltage is less than -300V, excessive energy is applied to the substrate to cause arcing, causing particles and contamination. If the applied voltage exceeds -50V, bias is applied. This is because the effect is lost.

  Then, after the medium protective layer 26 is formed, the surface quality of the perpendicular magnetic recording disk 100 can be improved by washing with ultrapure water and isopropyl alcohol.

  With the above-described medium protective layer 26, in the conventional manufacturing method, when the medium protective layer is formed to 3 nm or less, durability abnormalities such as scratches occur, and deterioration of the reproduction signal or the like occurs in the high flylight is 3 nm or less. Even so, there was no problem with load unload (hereinafter simply referred to as LUL) durability and the like.

The lubricating layer 28 was formed of PFPE (perfluoropolyether) by dip coating. The film thickness of the lubricating layer 28 is about 1 nm. Due to the action of the lubricating layer 28, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording disk 100, damage or loss of the medium protective layer 26 can be prevented. This perfluoropolyether has a linear structure, exhibits an appropriate lubrication performance for a perpendicular magnetic recording disk, and has a hydroxyl group (OH) as a terminal group, thereby providing high adhesion performance to the medium protective layer 26. Can be demonstrated. In particular, in the configuration of this embodiment provided with a surface treatment layer containing nitrogen on the surface of the medium protective layer, (N ⁺ ) and (OH ⁻ ) have high affinity, so that a high lubricating layer adhesion rate is obtained. This is preferable.

  In addition, as a perfluoropolyether compound which has a hydroxyl group in a terminal group, it is good that the number of hydroxyl groups of one molecule is 2-4. This is because if the number is less than 2, the adhesion rate of the lubricating layer may decrease, and if the number exceeds 4, the lubrication performance may be deteriorated as a result of the adhesion rate being excessively improved. The film thickness of the lubricating layer may be appropriately adjusted within the range of 0.5 to 1.5 nm. This is because if the thickness is less than 0.5 nm, the lubrication performance may be lowered, and if it exceeds 1.5 nm, the adhesion rate of the lubricating layer may be lowered.

  The roughness of the surface of the perpendicular magnetic recording disk 100 generated as described above is preferably 2.5 nm or less in terms of Rmax. This is because if it exceeds 2.5 nm, magnetic spacing reduction may be inhibited. The surface roughness is defined in Japanese Industrial Standard (JIS) BO601.

  Through the above manufacturing process, the perpendicular magnetic recording disk 100 was obtained. The basis of the above parameters is shown below.

  As described above, in the AFC structure in the soft magnetic layer 14, the easy magnetization axes of the two upper and lower layers arranged in antiparallel due to heat of a predetermined temperature or more are usually broken, and the S / N ratio is lowered. However, by mixing Fe during the formation of the soft magnetic layer, a heat-resistant AFC structure is formed, and heating immediately before the formation of the medium protective layer described later is enabled.

  FIG. 3 is an explanatory diagram showing the relationship between the substrate temperature of the perpendicular magnetic recording disk 100 when the Fe concentration is changed and the strength of the exchange coupling magnetic field Hex by AFC. Referring to FIG. 3, it can be seen that when the substrate temperature exceeds a predetermined temperature, the strength of Hex decreases sharply and does not function as an AFC structure. The temperature at such a boundary point (blocking temperature described later) varies depending on the Fe concentration, and the higher the Fe concentration, the higher the boundary temperature.

  For example, the boundary temperature is about 177 ° C. for CoTaZr not containing Fe, about 197 ° C. for FeCoTaZr containing 40 at% Fe, and about 210 ° C. for FeCoBCr containing 65 at% Fe. This boundary temperature has a certain degree of regularity regardless of the composition of the material that binds to Fe.

  FIG. 4 is an explanatory diagram showing the relationship between the Fe concentration and the blocking temperature (boundary temperature). Referring to FIG. 4, it can be understood that the blocking temperatures of the above-described CoTaZr, FeCoTaZr, and FeCoBCr can be linearly approximated, and that the perpendicular magnetic recording disk 100 can be heated to a temperature approximately proportional to the Fe concentration. Here, the blocking temperature is a temperature at which Hex starts to decrease.

  In this embodiment, the blocking temperature can be raised to about 190 to 215 ° C. by containing 30 to 70 at% Fe in the soft magnetic layer 14.

  FIG. 5 is an explanatory diagram showing the relationship between the Fe concentration and the saturation magnetization Ms. Referring to FIG. 5, even when the soft magnetic layer 14 contains 30 to 70 at% Fe, the soft magnetic layer 14 has a saturation magnetization Ms of 1.2 T or more. Further, when the soft magnetic layer 14 contains 65% Fe, the peak of the saturation magnetization Ms becomes the maximum value. This indicates that the soft magnetic layer 14 containing 30 to 70 at% Fe has sufficient overwrite characteristics.

  The effectiveness of this embodiment will be described below using examples and comparative examples.

  FIG. 6 is an explanatory diagram showing parameters and effectiveness of the example and the comparative example. Here, 13 examples and 8 comparative examples are given, and the LUL durability test, the pin-on-disk test, and the high fly light test are executed for each, and the effectiveness thereof is evaluated.

  Here, an amorphous glass substrate was used as the substrate 10. Its composition is aluminosilicate. The glass substrate had a diameter of 65 mm, an inner diameter of 20 mm, and a disk thickness of 0.635 mm for a 2.5 inch type perpendicular magnetic recording disk substrate. Here, when the surface roughness of the obtained glass substrate was observed with an AFM (atomic force microscope), it was confirmed that the surface was smooth with Rmax of 2.18 nm and Ra of 0.18 nm.

  Next, the adhesion layer 12, the soft magnetic layer 14, the orientation control layer 16, the underlayer 18, the onset layer 20, and the like are sequentially formed on the substrate 10 by DC magnetron sputtering using a C3040 sputtering film forming apparatus manufactured by Canon Anelva. A magnetic recording layer 22 and an auxiliary recording layer 24 were formed. The degree of vacuum during film formation was 0.6 Pa. A detailed description of film formation is as follows.

  Pd was used as a sputtering target, and a Pd underlayer 18 having a thickness of 7 nm was formed on the orientation control layer 16 by sputtering. The degree of vacuum during film formation was 1.0 Pa.

Next, CoCrPt-TiO2 as a sputtering target (Cr: 12at%, Pt: 10at%, T i O 2: 9at%, balance Co) using a sputtering target made of an alloy, on the onset layer 20, CoCrPt-TiO2 alloy A 15 nm magnetic recording layer 22 made of the above was formed by sputtering. The degree of vacuum at the time of film formation was 3.5 Pa.

  Then, the surface of the perpendicular magnetic recording disk 100 after the auxiliary recording layer 24 was formed was preheated. For example, in Example 1, the perpendicular magnetic recording disk 100 was ripened using a heater heating method so that the temperature of the surface of the perpendicular magnetic recording disk 100 was 160 ° C. The heating time is about 5 seconds. The substrate temperature of the perpendicular magnetic recording disk 100 was confirmed using a radiation thermometer from the chamber window immediately after the magnetic layer was formed.

  Further, 250 sccm of ethylene gas was introduced onto the disk on which the magnetic recording layer 22 had been formed, and the medium protective layer 26 was formed by plasma CVD while applying a bias of −300 V under a pressure of 1 Pa. The film formation speed when the medium protective layer 26 was formed was 1 nm / sec.

  Further, after the medium protective layer 26 was formed, only the nitrogen gas was introduced into the plasma at 250 sccm, and the medium protective layer 26 was exposed to a nitrogen atmosphere under a pressure adjusted to a vacuum level of 3 Pa. In this way, the surface of the medium protective layer 26 was impregnated with nitrogen.

  After film formation up to the medium protective layer 26, the film thickness of the medium protective layer 26 was measured by cross-sectional observation with a transmission electron microscope (TEM). Then, the film thickness of the medium protective layer 26 was 3.0 nm.

Moreover, after forming the medium protective layer 26, when the nitrogen / carbon atomic weight ratio (N / C) of the medium protective layer 26 was confirmed by ESCA, the value was 0.107. The measurement conditions for such ESCA analysis are as follows.
Apparatus: Quantum 2000 manufactured by ULVAC-PHI
X-ray excitation source: Al-Kα ray (1486.6 eV)
X-ray source 20W
Analysis room vacuum <2 × 10 −7 Pa
Pass energy 117.5eV
Photoelectron detection angle 45 °
Measurement target peak C1s, N1s
Analysis area 100umφ
The accumulated number of times was 10. Further, when the Raman spectroscopic analysis was performed after the medium protective layer 26 was formed, Dh / Gh was 0.80.

Incidentally, Raman spectroscopy, the surface of the medium protective layer 26, a wavelength was irradiated with Ar ion laser 514.5 ^nm, by observing the Raman spectrum by the Raman scattering appearing in waveband of 900cm ^-1 ~1800cm -1 It was done.

FIG. 7 is an explanatory diagram for explaining an image of a Raman spectrum. Here, in the range of 1800 cm ^-1 wave number 900 cm ^-1 of the Raman spectrum, correcting the background by fluorescence in linear approximation to determine the ratio of the peak heights of the D and G-peaks as Dh / Gh.

  The Raman spectroscopic analysis is usually performed before the lubricant layer 28 is applied, but may be measured after the lubricant is applied. When Raman spectroscopic analysis was performed before and after applying the lubricant, the Dh / Gh values showed exactly the same values both before and after, and the influence of the perfluoropolyether lubricant layer having a hydroxyl group at the end group on the Raman spectroscopic analysis. It became clear that there was no.

  After the medium protective layer 26 was formed, immersion cleaning was performed in pure water at 70 ° C. for 400 seconds, and further cleaning was performed with IPA for 400 seconds, followed by drying with IPA vapor as finish drying.

  Next, a lubricating layer 28 made of a PFPE (perfluoropolyether) compound was formed on the medium protective layer 26 that had been cleaned with ultrapure water and IPA by using a dipping method. Specifically, an alcohol-modified von purinette derivative manufactured by Augmont was used. This compound has 1 to 2 hydroxyl groups at both ends of the main chain of PFPE, that is, 2 to 4 hydroxyl groups per molecule. The film thickness of the lubricating layer 28 was 1.4 nm.

  As described above, when the surface roughness of the produced perpendicular magnetic recording disk 100 was observed with AFM, it was confirmed that the surface was smooth with Rmax of 2.30 nm and Ra of 0.22 nm. The glide height was measured and found to be 3.2 nm. When the flying height of the magnetic head is stably set to 10 nm or less, the glide height of the perpendicular magnetic recording disk 100 is desirably set to 4.0 nm or less.

  Various performances of the perpendicular magnetic recording disk 100 thus obtained were evaluated and analyzed as follows.

(LUL durability test)
The LUL durability test was performed using a 2.5 inch HDD rotating at 5400 rpm and a magnetic head having a flying height of 10 nm. The slider of the magnetic head was an NPAB (negative pressure type) slider, and the reproducing element was a TMR element equipped with a DFH mechanism. The perpendicular magnetic recording disk 100 was mounted on this HDD, and the LUL operation was continuously performed by the magnetic head described above.

  Then, the LUL durability of the perpendicular magnetic recording disk 100 was evaluated by measuring the number of LULs that were durable without causing the HDD to fail. The test environment was 70C / 80% RH. This is a severer condition than the normal HDD operating environment, and the durability reliability of the perpendicular magnetic recording disk 100 can be judged more accurately by performing it in an environment assuming an HDD used for applications such as car navigation. It is to do.

  In the LUL durability test, the perpendicular magnetic recording disks 100 of Examples 1 to 13 exceeded the number of LULs exceeding 1 million without causing the failure. Usually, in the LUL durability test, it is necessary that the number of LULs continuously exceed 400,000 times without failure. The number of LUL times of 400,000 is comparable to that for about 10 years in a normal HDD usage environment.

(Pin-on-disk test)
The pin-on-disk test was conducted as follows. That is, in order to evaluate the durability and wear resistance of the medium protective layer 26, a medium 2 mm diameter sphere made of Al ₂ O ₃ —TiC is loaded with a 15 g load on the perpendicular magnetic recording medium at a radius of 22 mm. By rotating the perpendicular magnetic recording disk 100 while pressing upward, the Al ₂ O ₃ —TiC sphere and the medium protective layer 26 are relatively rotated and slid at a speed of 2 m / sec. The number of sliding times until the protective layer 26 was broken was measured.

  In this pin-on-disk test, if the number of sliding times until the medium protective layer 26 is broken is 300 times or more, it is determined to pass. Since the normal magnetic recording head does not contact the perpendicular magnetic recording disk 100, this pin-on test is an endurance test in a harsh environment as compared to the actual use environment. For example, in the perpendicular magnetic recording disk 100 of Example 1, the number of sliding was 501 times, and in other examples, the value was over 300 times.

(High fly light test)
The high flylight test was conducted as follows. A 2.5-inch HDD rotating at 5400 rpm and a magnetic head with a flying height of 10 nm are used. The slider of the magnetic head was an NPAB (negative pressure type) slider, and the reproducing element was a TMR element equipped with a DFH mechanism. The perpendicular magnetic recording disk 100 was mounted on this HDD, the DFH mechanism was operated, and the head element was heated. With the heat, the magnetic head thermally expanded and protruded by 2 nm in the ABS direction, and recording / reproduction was performed for 1000 hours in this state to examine whether or not an error failure occurred. As a result, no error occurred in the recording / reproduction for 1000 hours in Examples 1 to 13.

  Similar to the above-described examples, the LUL durability test, the pin-on-disk test, and the high flylight test were also performed on the comparative examples.

  For example, in Comparative Example 1, a perpendicular magnetic recording disk was formed in the same manner as in Example 1 except that the nitrogen gas exposed to the medium protective layer 26 was 90 sccm. However, since the amount of nitrogen introduced was too small, a failure that could not be recorded and reproduced after 12 hours occurred in the high flylight test.

  Further, in Comparative Example 2, since it was exposed to 360 sccm of nitrogen gas, the amount of nitrogen introduced was too large, and it did not reach the standard 300 times in the pin-on test disk test. And crashed after 300,000 times. In other comparative examples, one or more parameters are different from those of the example, and are not within a predetermined range, so that one or more acceptable values of the LUL durability test, the pin-on-disk test, and the high flylight test are not satisfied. I understand that.

  FIG. 8 is a plot diagram in which N / C and Dh / Gh of the example and the comparative example are plotted. Refer to the examples in the range of N / C = 0.050 to 0.150 and Dh / Gh = 0.70 to 0.95 and the comparative examples outside the range, indicated by the solid line in the figure. As can be seen, the perpendicular magnetic recording disk 100 in this embodiment can be applied to a DFH head, and can prevent high fly write failure and wear resistance even when the thickness of the medium protective layer is 3 nm or less. It is suitable for property and sliding characteristics. Needless to say, the perpendicular magnetic recording disk 100 of this embodiment can also be applied to an LUL HDD.

  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 is applicable to a perpendicular magnetic recording medium mounted on an HDD or the like and a manufacturing method thereof.

It is a figure explaining the structure of the perpendicular magnetic recording disk concerning this embodiment. It is explanatory drawing for demonstrating the magnetization characteristic by an AFC structure. It is explanatory drawing which showed the relationship between the substrate temperature of the perpendicular magnetic recording medium at the time of changing the density | concentration of Fe, and the intensity | strength of the exchange coupling magnetic field Hex by AFC. It is explanatory drawing which showed the relationship between the density | concentration of Fe and blocking temperature. It is explanatory drawing which showed the relationship between the density | concentration of Fe, and saturation magnetization Ms. It is explanatory drawing which showed the parameter and effectiveness of the Example and the comparative example. It is explanatory drawing for demonstrating the image of a Raman spectrum. It is the plot figure which plotted N / C and Dh / Gh of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Base body 12 Adhesion layer 14 Soft magnetic layer 16 Orientation control layer 18 Underlayer 20 Onset layer 22 Magnetic recording layer 24 Auxiliary recording layer 26 Medium protective layer 28 Lubricating layer 100 Perpendicular magnetic recording disk

Claims (9)

A perpendicular magnetic recording medium comprising a magnetic recording layer on a substrate and a medium protective layer on the magnetic recording layer,
The medium protective layer is formed by impregnating nitrogen into the surface layer of a film containing carbon as a main component, and the atomic weight ratio (N / C) of nitrogen (N) to carbon (C) contained is 0.050 to 0.150. , and the and appearing near 1350 cm ^-1 of the spectrum excluding the fluorescence from the Raman spectrum in a wave number 900 cm ^-1 ~ wavenumber 1800 cm ^-1 obtained by exciting the said medium protective layer by argon ion laser beam having a wavelength of 514.5nm A perpendicular magnetic recording medium having a peak ratio Dh / Gh of 0.70 to 0.95 when the D peak Dh and the G peak Gh appearing in the vicinity of 1520 cm ⁻¹ are separated by a Gaussian function.   A soft magnetic layer formed of an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at% of iron (Fe) and having a saturation magnetization Ms of 1.2 T or more is provided below the magnetic recording layer. The perpendicular magnetic recording medium according to claim 1.   The perpendicular magnetic recording medium according to claim 2, wherein the soft magnetic layer has an exchange coupling magnetic field Hex of 40 Oe or more.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer is formed in a granular structure, and an auxiliary recording layer is provided on the magnetic recording layer.   The perpendicular magnetic recording medium according to claim 4, wherein the composition of the auxiliary recording layer is CoCrPtB. A method for producing a perpendicular magnetic recording medium comprising a magnetic recording layer on a substrate, and a medium protective layer comprising a coating composed mainly of carbon on the magnetic recording layer,
Forming the magnetic recording layer;
After the medium protective layer formed, from the Raman spectrum in a wave number 900 cm ^-1 ~ wavenumber 1800 cm ^-1 obtained by exciting the said medium protective layer by argon ion laser beam having a wavelength 514.5nm spectral excluding the fluorescent 1350 cm ^{- The} perpendicular magnetic recording medium has a peak ratio Dh / Gh of 0.70 to 0.95 when the D peak Dh appearing near ¹ and the G peak Gh appearing near 1520 cm ⁻¹ are separated by a Gaussian function. Heat the
The medium protective layer is formed by a CVD method, and further exposed to nitrogen such that the atomic weight ratio (N / C) of nitrogen (N) to carbon (C) is 0.050 to 0.150. A method for manufacturing a perpendicular magnetic recording medium.   The method of manufacturing a perpendicular magnetic recording medium according to claim 6, wherein the heating is performed at a temperature of 110 to 210 ° C. 8.   8. The perpendicular magnetic recording according to claim 6, wherein after forming the medium protective layer, the medium protective layer is further subjected to surface treatment by exposure to a nitrogen atmosphere having a flow rate of 100 to 350 sccm. A method for manufacturing a medium.   9. The method of manufacturing a perpendicular magnetic recording medium according to claim 6, further comprising forming a lubricating layer containing a perfluoropolyether compound having a hydroxyl group at a terminal group.

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