JP2008276913A - Vertical magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise a heat resistant temperature of a vertical magnetic recording disc by making an AFC (Antiferro-magnetic exchange coupling) have a structure strong in against heat to suppress the generation of corrosion without impairing a function of the AFC. <P>SOLUTION: The vertical magnetic recording disc 100 includes a soft magnetic layer 14, a magnetic recording layer 22, and a medium protection layer 26 in this order on a base 10. The soft magnetic layer 14 is formed in an AFC structure containing Fe of 30 to 70 at%. The magnetic recording layer 22 is a ferromagnetic layer having a granular structure including a non-magnetic substance forming a grain boundary between crystal grains containing at least Co, wherein the medium protection layer 26 has a peak ratio Dh/Gh of a Raman spectrum of 0.60 to 1.05. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 100 GB has been required for a 2.5-inch diameter perpendicular magnetic recording disk used for HDDs and the like, and in order to meet such a demand, one square is required. It is required to realize an information recording density exceeding 150 Gbits per inch.

  In order to achieve a high recording density in a perpendicular magnetic recording disk used for an HDD or the like, it is necessary to refine the magnetic crystal grains constituting the magnetic recording layer for recording information signals and reduce the layer thickness. was there. 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, a perpendicular magnetic recording disk of a perpendicular magnetic recording system 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.

  In such a perpendicular magnetic recording system, a single pole type perpendicular head is used and a magnetic field perpendicular to the magnetic recording layer is generated. However, simply using a single magnetic pole type vertical head makes it impossible to apply a sufficiently strong magnetic field to the magnetic recording layer because the magnetic flux exiting the single magnetic pole end immediately returns to the return magnetic pole on the opposite side. Therefore, a strong magnetic field in the perpendicular direction can be applied to the magnetic recording layer by providing a soft magnetic layer under the magnetic recording layer of the perpendicular magnetic recording disk and using the soft magnetic layer as a path for magnetic flux.

Further, such a soft magnetic layer is separated into two layers with a spacer layer therebetween, and the magnetization direction is parallel to the perpendicular magnetic recording disk surface and opposite to each other, so-called AFC (Antiferro-magnetic exchange coupling). There is also known a technology that suppresses the generation of huge magnetic domains in the horizontal direction in the soft magnetic layer by adopting a (magnetic exchange coupling) structure and prevents the occurrence of spike noise due to the vertical leakage magnetic flux generated from the domain wall ( For example, Patent Document 1).
JP 2002-358618 A

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

  Media protection that protects the surface of the magnetic recording layer from scratching in order to narrow the magnetic spacing, that is, to achieve a recording density exceeding 150 Gbits per square inch with a flying height of the magnetic head of 10 nm or less. The layer needs to be 3 nm or less. 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.

  By the way, one of the problems existing in the magnetic media is corrosion. Corrosion is typically a phenomenon in which a metal such as cobalt (Co) is deposited from the lower layer to form an oxide on the surface of the medium protective layer. When the corrosion occurs, the data recorded at that position is lost, and the magnetic head has a low flying height, which causes a crash failure, which may lead to a failure of the disk drive.

  The medium protective layer forms a high hardness film by a carbon overcoat (COC), that is, a carbon film. In the medium protective layer, a hard diamond-like bond of carbon and a soft graphite bond are mixed. The inventors of the present application increase the diamond-like bond by the structure in which the magnetic layer is heated immediately before forming the medium protective layer, and improve durability such as wear resistance and impact resistance of the medium protective layer. And it discovered that generation | occurrence | production of corrosion could be suppressed.

  However, the soft magnetic layer has already been formed before the above-described medium protective layer is formed. The AFC structure described above is used for the soft magnetic layer. This AFC structure is weak to heat, and when heated to a high temperature, the antiferromagnetic coupling force between the two upper and lower layers arranged in antiparallel is lowered, and finally the function as the AFC structure is not performed. If the AFC structure of the soft magnetic layer is broken, noise from the soft magnetic layer increases and it becomes difficult to achieve a high recording density.

  The present invention has been made in view of the above-mentioned problems caused by the idea of the corrosion suppression technique, and an object of the present invention is to increase the heat resistance temperature of the perpendicular magnetic recording medium by making the AFC heat resistant structure. An object of the present invention is to provide a perpendicular magnetic recording medium capable of suppressing the occurrence of corrosion without impairing the function of AFC and a method for manufacturing the same.

In order to solve the above problems, according to an aspect of the present invention, there is provided a perpendicular magnetic recording medium including a soft magnetic layer, a magnetic recording layer, and a medium protective layer in this order on a substrate, wherein the soft magnetic layer includes iron ( Fe) is formed with an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at%, and the magnetic recording layer is a grain made of a nonmagnetic substance between crystal grains grown at least in a columnar shape containing cobalt (Co). a ferromagnetic layer of a granular structure in which the field unit is formed, the medium protective layer, Raman the 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 514.5nm The D peak Dh (Disordered-peaks-height) appearing near 1350 cm ⁻¹ and the G peak Gh (Graphite−) appearing near 1520 cm ^{−1 of} the spectrum excluding fluorescence from the spectrum. The perpendicular magnetic recording medium is characterized in that the peak ratio Dh / Gh when the waveforms are separated from each other by a Gaussian function is 0.60 to 1.05.

  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. In the AFC (Antiferro-magnetic exchange coupling) structure configured in this way, the antiferromagnetic coupling force of the upper and lower two layers arranged in antiparallel due to heat of a predetermined temperature or more is reduced. 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. Accordingly, the peak ratio Dh / Gh of the Raman spectrum in the medium protective layer can be set to 0.60 to 1.05, and the occurrence of corrosion can be suppressed without impairing the AFC function.

  The soft magnetic layer preferably has a saturation magnetization Ms of 1.3 T or more. The saturation magnetization Ms affects the ease of writing on the recording medium, that is, the overwrite characteristic. The larger the saturation magnetization Ms, the better the overwrite characteristic. Therefore, the required overwrite characteristic can be maintained with this configuration.

  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 is preferably 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, there is provided a method of manufacturing a perpendicular magnetic recording medium comprising a soft magnetic layer, a magnetic recording layer, and a medium protective layer in this order on a substrate, the soft magnetic layer Is formed with an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at% of iron (Fe), and the magnetic recording layer is nonmagnetic between crystal grains grown in a columnar shape containing at least cobalt (Co). A ferromagnetic layer having a granular structure in which a grain boundary portion made of a material is formed, and a wave number of 900 cm obtained by exciting the medium protective layer with an argon ion laser beam having a wavelength of 514.5 nm of a medium protective layer to be formed later. ^{-1-wavenumber} 1800cm appearing near 1350 cm ^-1 of the spectrum excluding the fluorescence from the Raman spectrum in ^-1 D peak Dh and 1520cm appears in the vicinity of ^-1 G peak G The perpendicular magnetic recording medium is heated so that the peak ratio Dh / Gh when the waveforms are separated by a Gaussian function is 0.60 to 1.05, and the medium protective layer is formed by the CVD method. A method for manufacturing a perpendicular magnetic recording medium is provided.

  Like the perpendicular magnetic recording medium, in the present invention, by forming a soft magnetic layer containing 30 to 70 at% of iron, an AFC structure that can withstand subsequent heating can be formed. By improving durability such as impact resistance and forming it densely, the occurrence of corrosion can be suppressed.

  Heating may be done at a temperature of 135-220 ° 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. Thus, the peak ratio Dh / Gh of the Raman spectrum can be set to 0.60 to 1.05.

  As described above, according to the perpendicular magnetic recording medium of the present invention, by making the AFC resistant to heat, the heat resistance temperature of the perpendicular magnetic recording medium can be increased, and corrosion can be generated without impairing the function of the AFC. It becomes possible to suppress.

  An embodiment of a perpendicular magnetic recording medium according to the present invention will be described. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium according to this embodiment. 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. In the following description, a disk-shaped perpendicular magnetic recording disk 100 is used as the perpendicular magnetic recording medium. However, the present invention is not limited to this, and recording media of other shapes are naturally included.

  FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording disk 100 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 terms of high mass productivity. 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 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. 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. Such saturation magnetization Ms is preferably 1.3 T 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, when the film thickness is increased, the AFC coupling is weakened and Hex is reduced. 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 coupling of the easy magnetization axes of the upper and lower two layers arranged in antiparallel with 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 containing 30 to 70 at% Fe, 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 protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head.

  In the medium protective layer 26, a metal such as cobalt (Co) is precipitated from the lower layer, and so-called corrosion occurs in which an oxide is formed on the surface of the medium protective layer. When the corrosion occurs, the data recorded at that position is lost, and the magnetic head has a low flying height, which causes a crash failure, which may lead to a failure of the disk drive.

  In this embodiment, the structure in which the magnetic layer is heated immediately before forming the medium protective layer 26 increases the diamond-like bond, thereby improving the durability of the medium protective layer 26 such as wear resistance and impact resistance. Suppresses the occurrence of corrosion. Conventionally, the AFC structure of the soft magnetic layer already formed before the formation of the medium protective layer 26 is weak against heat, and by heating the magnetic layer, the upper and lower two layers of easy-magnetization axis cups are arranged in parallel. The ring collapsed, and finally it failed to function as an AFC structure. In the present embodiment, as described above, the magnetic layer immediately before film formation of the medium protective layer 26 can be heated by configuring the AFC structure containing Fe and having excellent heat resistance.

  If the magnetic layer is heat-treated immediately before the medium protective layer 26 is formed, the properties of the medium protective layer 26 immediately after that 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 0.60 to 1.05.

FIG. 3 is an explanatory diagram for explaining an image of a Raman spectrum. Here, by the 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, correcting the background by fluorescence in linear approximation Spectral characteristics as shown in FIG. 3 can be obtained. The ratio of Dh and Gh when the D peak Dh appearing near the low wavenumber side (1350 cm ⁻¹ ) of the spectrum and the G peak Gh appearing near the high wavenumber side (1520 cm ⁻¹ ) are separated by a Gaussian function. The peak ratio is calculated as Dh / Gh.

  Here, Dh / Gh was set to 0.60 to 1.05 when Dh / Gh was less than 0.60, the medium protective film had insufficient hardness, and Dh / Gh was 1.05. In the above case, the medium protective layer is too brittle and brittle, and conversely, wear resistance may be reduced. By setting Dh / Gh within the range of 0.60 to 1.05, the hardness of the medium protective layer formed through CVD becomes suitable, and sufficient durability can be obtained.

  A specific heating temperature for setting the peak ratio Dh / Gh to 0.60 to 1.05 is, for example, a temperature range of 135 to 220 ° C. The temperature of the perpendicular magnetic recording disk 100 after film formation immediately before film formation of the medium protective layer 26 is set to 135 to 220 ° C. because the kinetic energy of carbon atoms is low when the film formation temperature is less than 135 ° C. This is because the denseness of the protective layer is lost, and when the temperature exceeds 220 ° 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 135 to 220 ° 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.

  The lubricating layer 28 was formed by dip coating using PFPE (perfluoropolyether). 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.

  It should be noted that it is possible to subject the surface of the medium protective layer 26 to a nitriding treatment before the lubricating layer 28 is formed. Such a nitriding treatment can be performed using a CN (nitrogen carbide) gas by a CVD method. Further, nitrogen (N atoms) may be infiltrated into the surface layer by exposing the carbon film formed using CH (hydrogenated carbon) gas as described above to nitrogen. As a result, N atoms are introduced into the surface of the medium protective layer 26, and these N atoms bind with high affinity to the PFPE having the long chain molecular structure of the lubricating layer 28. Therefore, the adhesion between the medium protective layer 26 and the lubricating layer 28 can be improved.

  Through the above manufacturing process, the perpendicular magnetic recording disk 100 was obtained. In the following, an embodiment as a basis for the above-described parameters is shown.

  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. 4 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. 4, 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. 5 is an explanatory diagram showing the relationship between the Fe concentration and the blocking temperature (boundary temperature). Referring to FIG. 5, it can be understood that the blocking temperatures of CoTaZr, FeCoTaZr, and FeCoBCr described above can be linearly approximated, and that the perpendicular magnetic recording disk 100 can be heated to a temperature that is substantially proportional to the increased 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. 6 is an explanatory diagram showing the relationship between the Fe concentration and the saturation magnetization Ms. Referring to FIG. 6, even when the soft magnetic layer 14 contains 30 to 70 at% of Fe, the soft magnetic layer 14 has a saturation magnetization Ms of 1.3 T or more. Further, when the soft magnetic layer 14 contains 65% Fe, the peak of the saturation magnetization Ms has a maximum value of 1.60. This indicates that the soft magnetic layer 14 containing 30 to 70 at% Fe has sufficient overwrite characteristics.

  Next, the relationship between the heat treatment immediately before the formation of the medium protective layer 26 and the peak ratio Dh / Gh after the heating will be described.

  FIG. 7 is an explanatory diagram showing the relationship between the substrate temperature immediately before the formation of the medium protective layer 26 and the peak ratio Dh / Gh after heating. As can be understood with reference to FIG. 7, the peak ratio Dh / Gh is a gradually increasing function with respect to the substrate temperature. When the substrate temperature is increased, the peak ratio Dh / Gh is increased, that is, the diamond-like bond is increased. The resistance of the protective layer 26 is improved.

  A suitable value of the peak ratio Dh / Gh in the present embodiment is 0.60 to 1.05 as described above, and refer to FIG. 7 for the substrate temperature for forming such a peak ratio Dh / Gh. Then, it can be understood that the temperature is 135 to 220 ° C.

  FIG. 8 is an explanatory diagram showing the relationship between the substrate temperature immediately before the formation of the medium protective layer 26, the peak ratio Dh / Gh after heating, and the reliability. Here, the reliability is the durability of the perpendicular magnetic recording disk 100, and the reliability is determined by the result of a scratch test using a needle. In the above scratch test, ◎ indicates that the wear scar depth of the perpendicular magnetic recording disk 100 is less than 0.5 nm, ○ indicates that the wear mark depth is 0.5 nm or more and less than 1.0 nm, and 1.0 nm or more and less than 3.0 nm. The evaluation was made on a four-point scale, with Δ when it was, and x when it was 3.0 nm or more. In the scratch test, the disk base 10 immediately before the formation of the medium protective layer 26 was heated at each substrate temperature Ts, and the perpendicular magnetic recording disk 100 as the final product manufactured through the subsequent manufacturing process was used. .

  Referring to FIG. 8, when heat treatment is performed at 116 ° C., the peak ratio Dh / Gh is 0.55, and the reliability of the perpendicular magnetic recording disk 100 is “x”. This is probably because the ratio of diamond-like bonds in the medium protective layer 26 is low because the heat treatment temperature is low. As a result, the medium protective layer 26 cannot obtain sufficient hardness, and the perpendicular magnetic recording disk 100 is deeply scratched in the scratch test.

  As the heat treatment temperature increases, the peak ratio Dh / Gh increases, and the reliability of the perpendicular magnetic recording disk 100 is improved accordingly. However, when the heat treatment temperature is 228 ° C., the peak ratio Dh / Gh is 1.10, but the reliability is lowered, and the evaluation is “x”. This is probably because the medium protective layer 26 is too hard because the ratio of diamond-like bonds in the medium protective layer 26 is too high. As a result, the medium protective layer 26 becomes fragile, and the medium protective layer 26 is considered to be deeply damaged by breaking.

  As described above, also from the viewpoint of reliability, that is, the durability of the perpendicular magnetic recording disk 100, the hardness of the medium protective layer 26 is suitable when the peak ratio Dh / Gh is in the range of 0.60 to 1.05. It can be understood that the perpendicular magnetic recording disk 100 obtains sufficient durability. It can also be seen that the hardness for obtaining sufficient reliability, that is, the peak ratio Dh / Gh 0.60 cannot be obtained unless heat treatment is performed at a substrate temperature of 135 ° C. or higher.

  FIG. 9 is an explanatory diagram showing the relationship between the Fe concentration and the peak ratio Dh / Gh after heating. Referring to FIG. 9, when the Fe content of the soft magnetic layer 14 is less than 30 at%, the saturation magnetization Ms of the soft magnetic layer 14 is low and the saturation magnetization Ms1.3T cannot be satisfied. Therefore, the perpendicular magnetic recording disk 100 having such a soft magnetic layer 14 cannot maintain the required overwrite characteristics. Further, when the Fe content is 70% or more, the corrosion characteristics are remarkably deteriorated, so that it cannot be used as the perpendicular magnetic recording disk 100.

  On the other hand, when the peak ratio Dh / Gh is less than 0.60, the hardness of the medium protective layer 26 is too low, so that scratches are easily generated, and the reliability of the perpendicular magnetic recording disk 100 is lowered. Similarly, when the peak ratio Dh / Gh is greater than 1.05, the medium protective layer 26 is too hard and brittle, reducing the reliability of the perpendicular magnetic recording disk 100.

  Therefore, when the Fe content in the soft magnetic layer 14 is 30 to 70 at% and the peak ratio Dh / Gh of the medium protective layer 26 is in the range of 0.60 to 1.05, sufficient overwriting is achieved. The perpendicular magnetic recording disk 100 having characteristics and excellent reliability can be obtained.

  As described above, in the perpendicular magnetic recording medium (perpendicular magnetic recording disk) and the manufacturing method thereof according to the present embodiment, an AFC structure resistant to heat is formed by mixing iron when forming the soft magnetic layer, The substrate temperature immediately before the formation of the medium protective layer can be increased. Therefore, the peak ratio Dh / Gh of the Raman spectrum in the medium protective layer can be set to a suitable value, and the occurrence of corrosion can be suppressed without impairing the AFC function.

  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 for a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type 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 for demonstrating the image of a Raman spectrum. 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 relationship between the substrate temperature just before film formation of a medium protective layer, and the peak ratio Dh / Gh after a heating. It is explanatory drawing which showed the relationship between the substrate temperature just before film-forming of a medium protective layer, the peak ratio Dh / Gh after a heating, and reliability. It is explanatory drawing which showed the relationship between the density | concentration of Fe, and the peak ratio Dh / Gh after a heating.

Explanation of symbols

10 disk substrate 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 (7)

A perpendicular magnetic recording medium comprising a soft magnetic layer, a magnetic recording layer, and a medium protective layer in this order on a substrate,
The soft magnetic layer is formed of an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at% of iron (Fe),
The magnetic recording layer is a ferromagnetic layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between columnar crystal grains containing at least cobalt (Co).
The medium protective layer, the spectral 1350cm around ^-1 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 0.60 to 1.05 when the D peak Dh that appears and the G peak Gh that appears in the vicinity of 1520 cm ⁻¹ are separated by a Gaussian function. .   The perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic layer has a saturation magnetization Ms of 1.3 T or more.   The perpendicular magnetic recording medium according to claim 1, 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 of manufacturing a perpendicular magnetic recording medium comprising a soft magnetic layer, a magnetic recording layer, and a medium protective layer in this order on a substrate,
The soft magnetic layer is formed of an antiferromagnetic exchange coupling (AFC) structure containing 30 to 70 at% of iron (Fe),
As the magnetic recording layer, a ferromagnetic layer having a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between columnar crystal grains containing at least cobalt (Co),
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 0.60 to 1.05 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
A method of manufacturing a perpendicular magnetic recording medium, wherein the medium protective layer is formed by a CVD method.   The method of manufacturing a perpendicular magnetic recording medium according to claim 6, wherein the heating is performed at a temperature of 135 to 220 ° C. 8.

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