JP4207769B2 - Perpendicular magnetic recording medium and manufacturing method thereof - Google Patents

Description

  The present invention relates to a perpendicular magnetic recording medium mounted on various magnetic recording devices including an external recording device of a computer and a method for manufacturing the same.

  The recording density of magnetic recording media is increasing with tremendous growth, and this trend cannot be seen to weaken. In the conventional longitudinal recording system, it is considered that there is a limit to the recording density due to the problem of thermal disturbance of magnetization accompanying the miniaturization of magnetic particles necessary for increasing the recording density and the thinning of the magnetic layer thickness. In recent years, research on perpendicular magnetic recording media has been progressing rapidly in order to solve the problem. However, in these perpendicular magnetic recording media, it is indispensable to reduce noise and improve thermal stability in order to further increase the density. For this purpose, it is necessary to increase the perpendicular magnetic anisotropy energy Ku. In addition, since it is indispensable to reduce the thickness of the recording layer, it is important to select a material having a high perpendicular magnetic anisotropy energy Ku even with a thin recording layer thickness.

  In a conventional alloy thin film mainly composed of CoCr, particularly in a granular alloy in which a nonmagnetic material such as an oxide is precipitated at the grain boundary, magnetic particles are almost completely magnetically insulated by the interposition of the nonmagnetic material. ing. In the alloy, each magnetically insulated particle becomes the minimum magnetization unit, and a remarkable noise reduction effect is confirmed by suppressing the formation of coarse clusters.

  However, in the above-described granular type magnetic recording medium, the extremely small particles are almost completely isolated by the non-magnetic substance, so that the volume of the magnetic particles becomes extremely small and the magnitude of the magnetic anisotropy energy is large. Is close to the magnitude of thermal energy. Considering the case where the magnitudes of magnetic anisotropy energy and thermal energy are about the same, the spin direction is always fluctuated due to thermal disturbance, and the recording state can no longer be kept stable. For this reason, in a medium using a granular alloy, the thermal stability and long-term storage stability of recorded information become problems, and its practical use is regarded as difficult.

  In order to solve these problems, it is necessary to increase the magnetic anisotropy energy of the magnetic substance, and as a method therefor, a rule having a high crystal magnetic anisotropy of an L10 type (CuAu type) structure such as CoPt or FePt. Studies using alloys are underway. However, these materials have an irregular fcc structure as a metastable phase. For example, in the case of FePt, it is necessary to form an L10 type ordered structure by ordering by heat treatment at about 600 ° C. or higher. In particular, when the film thickness of the magnetic recording layer is reduced in response to an increase in recording density, the ordering process is important because the crystallinity of the alloy decreases as the film thickness decreases. This high-temperature heat treatment process is not suitable for mass production, and there is a problem that the intergranular interaction increases due to the coarsening of crystal grains in the process of heat treatment at high temperature, and it is important to reduce the ordering temperature. It is a problem.

  Currently, regarding the lowering of the ordering temperature of such an ordered alloy thin film, a substrate having an underlayer having an NaCl type crystal structure or an LiCl type crystal structure is heated to 500 ° C., and an L10 ordered alloy film is laminated. Has been reported (see Patent Document 1). In addition, by using a sputtering method in which the Ar gas pressure and the distance between the target substrates are regulated within a specific range on a base layer whose crystal face of the Miller index (100) is parallel to the substrate, a substrate at 400 to 500 ° C. A method of forming an L10 ordered alloy (FePt) film by using temperature has been reported (see Patent Document 2).

  Furthermore, it has been reported that the ordering temperature is reduced by adding a metal element to the ordered alloy film, such as adding MgO to the FePt film (see Patent Document 3). By adding these metal elements, the ordering temperature is reduced to around 400 ° C., but there is a problem that the magnetic anisotropy energy Ku value is lowered. In the future, the reduction of the synthesis temperature of the ordered alloy will be a problem while suppressing the decrease of the Ku value, and is now being studied actively.

Japanese Patent Laid-Open No. 2001-189010 Japanese Patent Laid-Open No. 11-353648 JP 2002-123920 A

  In the current situation where a material for a magnetic recording layer having a film thickness of 3 nm to 15 nm is required to increase the density of the magnetic recording medium, the high magnetic anisotropy energy Ku necessary for both improving the thermal stability and reducing the noise is obtained. There is a strong demand for a method of forming the L10-type ordered alloy at a lower temperature. More specifically, a method that enables ordering of the L10 type ordered alloy at a lower temperature (for example, 400 ° C. or lower) in order to eliminate the restriction of the substrate material due to the high temperature heat treatment and suppress the increase in intergranular interaction. There is a strong demand to provide.

  As a result of diligent investigation, we have alternated Co (or Fe) and Pt by sputtering at a monoatomic layer thickness (Co = about 1.77 mm, Fe = about 1.43 mm, Pt = about 1.96 mm). It was possible to solve the problem of reducing the ordering temperature of the above ordered alloy. More specifically, the conversion from the metastable fcc structure to the L10 type ordered fct structure by atomic diffusion was promoted even in a low temperature region, and the ordering temperature could be greatly lowered without significantly degrading the magnetic properties. . That is, conventionally, a temperature treatment of 600 ° C. or higher has been required, but by using the method of the present invention, it is possible to order at temperatures from room temperature to 400 ° C.

  As a result, it is possible to suppress the enlargement of crystal grains due to high-temperature heat treatment and to set the ordering temperature to 400 ° C. or less. Absent. Furthermore, the method for producing a magnetic recording medium of the present invention can be carried out at a low temperature that does not cause a problem in mass production. Further, when a nonmagnetic seed layer having a preferential crystal orientation plane of (100) is provided between the nonmagnetic substrate and the nonmagnetic underlayer, there is a further effect. Examples of the nonmagnetic seed layer include MgO, NiO, TiO, or Ti carbide or nitride having a NaCl type structure.

  By using the ordered alloy laminating method of the present invention described in detail below, the ordering temperature of CoPt or FePt or the like can be changed by a conventional sputtering method using a CoPt or FePt alloy target, or Co (or Fe) and Pt. Compared with the co-sputter method by simultaneous sputtering with, it was possible to greatly reduce. From this, it is possible to eliminate restrictions on the substrate material and suppress grain growth (increase in inter-grain interaction) due to the thermal process.

  Further, when heat treatment at 300 ° C. is performed using the present invention, the coercive force Hc and the perpendicular magnetic anisotropy energy Ku value can be obtained even when the magnetic recording layer is as thin as 5 nm, for example. A value much larger than that of the CoCrPt-based magnetic layer perpendicular medium used in the above is obtained. Therefore, it is possible to sufficiently satisfy the thinning of the recording layer and the securing of a high Ku value, which will be indispensable for higher recording density in the future. Furthermore, a magnetic recording medium having excellent characteristics can also be obtained by using heating at the time of forming a magnetic recording layer, which is advantageous for mass production instead of post-heating treatment.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium of the present invention. FIG. 1A is a cross-sectional view of a perpendicular magnetic recording medium of the present invention, in which a nonmagnetic seed layer 2, a nonmagnetic underlayer 3, a magnetic recording layer 4, and a protective film 5 are sequentially formed on a nonmagnetic substrate 1. The liquid lubricating layer 6 is formed thereon.

  FIG. 1B is a cross-sectional view for explaining a method of laminating the magnetic recording layer 4 in which Co (or Fe) and Pt, each having a single atomic layer thickness, are the greatest feature of the present invention. It is. In FIG. 1B, as an example, the magnetic recording layer 4 in which four layers are laminated is shown, but the desired film thickness of the magnetic recording layer can be controlled by appropriately changing the number of laminated layers. it can.

  As the non-magnetic substrate 1, it is possible to use a NiP-plated Al alloy, tempered glass, crystallized glass, surface-oxidized Si wafer, fused quartz substrate, etc., which are used for ordinary magnetic recording media, and polycarbonate. A plastic resin substrate produced by injection molding of polyolefin or other plastic resins can also be used.

  The nonmagnetic seed layer 2 is made of MgO, NiO, TiO, or Ti controlled so that the Miller index (100) of the crystal lattice plane is parallel to the substrate (that is, the preferential crystal orientation plane is the (100) plane). It consists of carbide or nitride. These materials are materials in which the (100) plane becomes the preferential crystal orientation plane by laminating under normal conditions, but by further optimizing the film thickness or film formation process (film formation pressure, etc.) (100 ) It is possible to improve the orientation. On this nonmagnetic seed layer 2, the layer structure in the present invention, that is, the nonmagnetic underlayer 3 and the magnetic recording layer 4 are sequentially formed, so that the mirror of the crystal lattice plane of the L10 type ordered alloy phase in the magnetic recording layer 4 is formed. The index (001) can be controlled to be parallel to other adjacent layers and the substrate. The nonmagnetic seed layer 2 has an optimum film thickness that varies depending on the material, but is desirably 3 nm or more and 15 nm or less. The nonmagnetic seed layer 2 can be laminated by a method commonly used in the art such as vapor deposition, sputtering, ion plating, laser ablation, or ion beam vapor deposition.

  Next, the nonmagnetic underlayer 3 is used mainly for the purpose of controlling the crystal orientation and crystal grain size of the magnetic recording layer. Accordingly, any film having an appropriate material and structure suitable for the desired orientation plane in the ordered alloy film of the magnetic recording layer may be used. For example, a metal or alloy containing at least one of Ag, Al, Au, Cu, Ir, Ni, Pt, and Pd having an fcc structure, or Cr or Cr alloy having a bcc structure can be used as appropriate. By using these metals or alloys, the surface of the nonmagnetic underlayer 3 becomes the (200) plane, and the preferential crystal orientation plane of the L10 type ordered alloy of the magnetic recording layer 4 laminated thereon is defined as the (001) plane. It becomes possible to do. In addition, in order to control the crystal grain size of the L10 type ordered alloy of the magnetic recording layer 4 to 5 nm or less, it is necessary to optimize the film thickness and the film forming process of the nonmagnetic underlayer and the magnetic recording layer. This can be achieved by means such as thinning the underlayer. The film thickness of the nonmagnetic underlayer is not particularly limited, but is generally preferably about 5 nm or more and about 50 nm or less for controlling the structure of the magnetic recording layer. The nonmagnetic underlayer 3 can be laminated by a method commonly used in the art such as vapor deposition, sputtering, ion plating, laser ablation, or ion beam vapor deposition.

  The magnetic recording layer 4 includes a Co (or Fe) layer and a Pt layer, each having a thickness corresponding to a monoatomic layer thickness (Co = about 1.77 mm, Fe = about 1.43 mm, Pt = about 1.96 mm). It is formed by alternately laminating. Each layer constituting the magnetic recording layer 4 of the present invention is preferably a continuous layer in which atoms are arranged over the entire area to be coated. However, it may be a discontinuous layer including an area where atoms are not arranged on condition that the magnetic properties of the layer are not deteriorated. Alternatively, two atoms may be deposited on part of the layer, provided that the magnetic properties of the layer are not degraded. For the formation of the magnetic recording layer 4, vapor deposition, sputtering, ion plating, laser ablation, ion beam vapor deposition, or the like can be used, and particularly preferably, a DC magnetron sputtering method can be used. As a method of alternately laminating these separate elements in one chamber, for example, a sputtering method using a rotary cathode composed of these elements can be cited, and a desired laminated film can be suitably formed by this method.

  The film thickness in the present specification means an average film thickness that can be measured by a method known in the art such as ellipsometry or stylus method. For each of Co, Fe, and Pt, the following film thickness should be regarded as “a film thickness corresponding to a monoatomic layer film thickness”. When the Co layer is laminated, the film thickness of one layer should be 0.1 nm or more and 0.3 nm or less, preferably 0.17 nm or more and 0.20 nm or less. Similarly, in the case of laminating an Fe layer, the thickness of a single laminated layer should be 0.1 nm to 0.3 nm, preferably 0.14 nm to 0.16 nm. On the other hand, when the Pt layer is laminated, the thickness of the laminated film at one time should be 0.15 nm or more and 0.35 nm or less, preferably 0.19 nm or more and 0.21 nm or less. The total film thickness of the magnetic recording layer 4 can be appropriately controlled by the number of lamination of these elements. The total thickness of the magnetic recording layer 4 is 3 nm to 15 nm, preferably 3 nm to 5 nm.

  Ordering of the CoPt or FePt alloy formed as the magnetic recording layer 4 can be achieved by heating the nonmagnetic substrate during film formation, or by heat treatment after lamination or after formation of a protective film and a liquid lubricant layer described later. it can. When ordering is performed by heating during film formation, film formation and ordering are performed at any non-magnetic substrate temperature, provided that the other layers already formed on the magnetic recording medium are not adversely affected. can do. The nonmagnetic substrate temperature that can be used is 400 ° C. or lower, preferably 200 ° C. or higher and 400 ° C. or lower, more preferably 300 ° C. or higher and 400 ° C. or lower. Alternatively, when an Al substrate plated with NiP is used as the nonmagnetic substrate, in order to prevent crystallization of NiP, it is 300 ° C. or lower, preferably 200 ° C. or higher and 300 ° C. or lower, more preferably 250 ° C. or higher and 300 ° C. or lower. It is preferable to use the non-magnetic substrate temperature. By forming the film at the nonmagnetic substrate temperature as described above, a sufficiently ordered L10 type ordered alloy layer can be formed. When ordering is performed by heat treatment after laminating the magnetic recording layer or after forming a protective film and a liquid lubricating layer described later, the film is formed at an arbitrary nonmagnetic substrate temperature such as 200 ° C. or lower. Also good.

  When ordering CoPt or FePt alloy after laminating the magnetic recording layer or after forming a protective film and a liquid lubricating layer, which will be described later, 400 ° C. or lower, preferably 200 ° C. or higher and 400 ° C. or lower, more preferably 300 ° C. The heat treatment is performed at a temperature of 400 ° C. or lower for 0.5 to 2 hours, preferably 0.5 to 1 hour. By this heat treatment, the magnetic recording layer formed without heating the nonmagnetic substrate can be made into a well-ordered L10 type ordered alloy layer. When an Al substrate plated with NiP is used as the nonmagnetic substrate, this heat treatment is performed at 300 ° C. or lower, preferably 200 ° C. or higher and 300 ° C. or lower, more preferably 250 ° C. or higher, in order to prevent NiP crystallization. You may implement at the temperature of 300 degrees C or less.

The CoPt ordered alloy obtained by heat treatment is preferably 7 × 10 ⁵ J / m ³ or more and 3 × 10 ⁶ J / m ³ or less (7 × 10 ⁶ erg / cm ³ or more and 3 × 10 ⁷ erg / cm ³ or less), preferably Indicates a perpendicular magnetic anisotropy energy Ku of 1 × 10 ⁶ J / m ³ or more and 3 × 10 ⁶ J / m ³ or less (1 × 10 ⁷ erg / cm ³ or more and 3 × 10 ⁷ erg / cm ³ or less). On the other hand, the FePt ordered alloy obtained by the heat treatment is 7 × 10 ⁵ J / m ³ or more and 7 × 10 ⁶ J / m ³ or less (7 × 10 ⁶ erg / cm ³ or more and 7 × 10 ⁷ erg / cm ³ or less). Preferably, the perpendicular magnetic anisotropy energy Ku is 1 × 10 ⁶ J / m ³ or more and 7 × 10 ⁶ J / m ³ or less (1 × 10 ⁷ erg / cm ³ or more and 7 × 10 ⁷ erg / cm ³ or less). Show. By having such a high Ku value, the magnetic recording layer 4 maintains high thermal stability and recording with less noise even when the volume of each particle is reduced by thinning and crystal grain refinement. Can be performed.

  The structure of the crystal grains constituting the magnetic recording layer 4 and the degree of ordering can be confirmed with a general X-ray diffractometer. If one of the peaks representing the fct- (001), (002), or (003) plane can be observed, it can be said that the fct structure exists and the c-axis is oriented perpendicular to the film surface. The intensity of the peak representing the fct- (001), (002) or (003) plane may be an intensity observed as a significant peak with respect to the background level. Further, even if the fct- (111) peak indicating in-plane orientation is observed, if the peak representing the fct- (001), (002) or (003) plane can be observed with higher intensity, the c-axis is the film surface. It can be said that it is oriented perpendicularly to. When the alloy crystal grains are completely irregular, the ratio I (001) / I (111) between the peak intensity I (001) of fct- (001) and the peak intensity I (111) of fct- (111). ) Is about 0.3. In the present invention, if the value of I (001) / I (111) is 1.0 or more, it is considered that the c-axis of the crystal grain is oriented perpendicular to the film surface. More preferably, the value of I (001) / I (111) is 10 or more.

The protective film 5 is a thin film mainly composed of carbon, such as diamond-like carbon (DLC). Various thin film materials generally used as a protective film of a magnetic recording medium such as silicon carbide (SiC), zirconium oxide (ZrO ₂ ), or carbon nitride (CN) may be used. The protective film 5 can be laminated by a method commonly used in the art, such as vapor deposition, sputtering, ion plating, laser ablation, CVD, or ion beam vapor deposition. The protective film 5 preferably has a thickness of 1 to 5 nm, more preferably 2 to 4 nm.

  The liquid lubricant layer 6 can be formed using a fluorocarbon lubricant, for example, a perfluoropolyether lubricant. In addition, various lubricating materials that are generally used as liquid lubricating layer materials for magnetic recording media may be used. The liquid lubricating layer 6 can be laminated by a method commonly used in the art such as dip coating, spraying, spin coating, knife coating and the like. The liquid lubricating layer 6 has a thickness of 0.5 to 5 nm, preferably 1 to 2 nm.

  A tempered glass disk substrate having a diameter of 2.5 inches was used as the nonmagnetic substrate. This was introduced into a sputtering apparatus after cleaning, and a nonmagnetic seed layer having a thickness of 5 nm was formed by RF sputtering using MgO as a target under an Ar gas pressure of 0.67 Pa (5 mTorr). Subsequently, a nonmagnetic underlayer having a thickness of 20 nm was formed by DC sputtering made of Pt and targeting Pt under an Ar gas pressure of 0.67 Pa (5 mTorr). Thereafter, in a DC magnetron sputtering apparatus under an Ar gas pressure of 2 Pa (15 mTorr), using a Co target and a Pt target alternately, at a target potential of 400 V, an RF output of 200 W, and a target substrate distance of 8 cm, respectively, a monoatomic layer film The magnetic recording layer 4 was formed by alternately stacking Co layers having a thickness (0.177 nm) and Pt layers having a monoatomic layer thickness (0.196 nm).

  Here, a medium in which the magnetic recording layer thickness δ was changed from δ = 5 nm to 30 nm by adjusting the number of laminations was produced. -On the other hand, a magnetic recording made of an FePt ordered alloy by alternately laminating an Fe layer having a monoatomic layer thickness (0.143 nm) and a Pt layer having a monoatomic layer thickness (0.196 nm) by the same method. A magnetic recording medium having a layer was formed.

  Thereafter, a carbon protective film having a thickness of 5 nm was formed by DC sputtering using carbon as a target under an Ar gas pressure of 0.67 Pa (5 mTorr). Finally, a perfluoropolyether lubricant was dip coated to form a 5 nm thick liquid lubricant layer. After all the layers were formed, heat treatment was performed by maintaining the substrate temperature at 300 ° C. for 1 hour.

  Table 1 shows the intensity ratio (I (001) between the fct- (001) diffraction peak and the fct- (111) diffraction peak of the CoPt and FePt ordered alloy media thus prepared, measured by a thin film X-ray diffractometer. ) / I (111)). As can be seen from Table 1, the peak intensity ratio, that is, the degree of ordering tends to increase as the recording layer thickness increases. This is presumably because the crystallinity improves as the recording layer thickness increases. It was found that the peak intensity ratio in each of the magnetic recording layer thicknesses in this example was approximately 100, and sufficient ordering could be achieved even at a heat treatment temperature of 300 ° C. From the above, it can be said that the ordering temperature of the L10 type ordered alloy could be significantly reduced by alternately laminating the constituent atoms with a film thickness corresponding to the monoatomic layer film thickness.

FIG. 2 is a graph showing the dependence of the coercive force Hc and the perpendicular magnetic anisotropy energy Ku on the magnetic recording layer thickness in the CoPt ordered alloy medium of this example. Hc was measured by a sample vibration type magnetometer (VSM), and Ku value was measured by a magnetic torque meter. As can be seen from the graph, both the Hc and Ku values increase as the film thickness increases, as with the change in the peak intensity ratio. Ku = 7.8 × 10 ⁵ J / m ³ (7.8 × 10 ⁶ erg / cc), and a very large value was obtained.

  Except for fixing the film thickness of the magnetic recording layer to 10 nm and changing the heat treatment temperature Ts after the formation of all layers from room temperature (no heat treatment, ie, as-deposited) to 500 ° C., the same as in Example 1. A perpendicular magnetic recording medium was manufactured.

  Table 2 shows the heat treatment temperature dependence of I (001) / I (111) of the CoPt and FePt ordered alloy media thus prepared. The heat treatment time was 1 hour as in Example 1. As can be seen from Table 2, when either CoPt or FePt is used, the degree of ordering increases as the heat treatment temperature rises, and at 400 ° C., the peak of fct- (111) can be almost confirmed. lost.

  Further, at room temperature (25 ° C., as-deposited in Table 2), the fct- (001) peak was confirmed, and at the same time, the peak intensity ratio I (001) / I (111) was not so large. It can be said that the (001) plane is more preferentially oriented than the peak intensity ratio 0.3 in the random orientation. It is considered that the peak intensity ratio is small because the crystallinity is not so good and the entire film surface is not uniformly ordered, but it is possible to completely control the orientation of the seed layer and the underlayer, and in the magnetic recording layer It is considered that due to the optimization of the process, the ordering is sufficiently achieved even when the heat treatment temperature is 200 ° C. or lower.

FIG. 3 is a graph showing the heat treatment temperature dependence of the perpendicular magnetic anisotropy energy Ku and the coercive force Hc in the magnetic recording medium using the FePt ordered alloy of this example. Similar to the change in the peak intensity ratio, both the Hc and Ku values increase as the heat treatment temperature rises. Particularly at room temperature (as-deposited), Hc = 250 kA / m (3.2 kOe), Ku = 6 An extremely large value of 9.9 × 10 ⁵ J / m ³ (6.9 × 10 ⁶ erg / cc) was obtained.

FIG. 4 is a graph comparing the heat treatment temperature dependence of the Ku value for magnetic recording media using CoPt and FePt ordered alloys of this example. As can be seen from FIG. 4, both have a large Ku value at room temperature (as-deposited). In addition, the Ku values of CoPt and FePt ordered alloy media differ greatly in the high temperature heat treatment region because the Ku value is 3.0 × 10 ⁶ J / m ³ (3.0 × 10 ⁷ erg / bulk) in bulk in the CoPt ordered alloy. cc) On the other hand, the FePt ordered alloy has 7.0 × 10 ⁶ J / m ³ (7.0 × 10 ⁷ erg / cc) in the same bulk, and the FePt ordered alloy has higher perpendicular magnetic anisotropy. This is because.

  Instead of performing a heat treatment after the formation of all the layers forming the magnetic recording medium, the same procedure as in Example 1 was performed except that the nonmagnetic substrate was heated to 300 ° C. using a heater during the formation of the magnetic recording layer. A magnetic recording medium having a 10 nm thick magnetic recording layer made of a CoPt ordered alloy was formed. In addition, a magnetic recording medium having a 10 nm-thick magnetic recording layer made of an FePt ordered alloy was formed by the same method.

  The characteristics of the CoPt and FePt ordered alloy media produced as described above were compared with the media subjected to heat treatment at 300 ° C. for 1 hour after the formation of all layers. The results are shown in Table 3.

  The characteristics of the medium of this example that was ordered by heating the nonmagnetic substrate during the formation of the magnetic recording layer were as follows. The peak intensity ratio of the medium of Example 1 that was subjected to post-heating treatment for both ordered alloys of CoPt and FePt As for the magnetic anisotropy value Ku, although a slight decrease in the numerical value was observed, no significant deterioration was observed. From the above results, it was revealed that CoPt and FePt ordered alloy magnetic recording layers having excellent characteristics can be obtained by using heating during film formation without using post-heating treatment. The method of this embodiment is particularly useful for mass production of magnetic recording media.

The structure of the magnetic recording medium by this invention is shown, (a) is a schematic cross section of a magnetic recording medium, (b) is a schematic cross section which shows the laminated structure of a magnetic recording layer. It is a graph which shows the magnetic recording layer film thickness dependence of perpendicular magnetic anisotropy energy Ku and coercive force Hc in the medium which heat-processed for 1 hour after Ts = 300 degreeC after each layer formation. 6 is a graph showing the heat treatment temperature dependence of perpendicular magnetic anisotropy energy Ku and coercive force Hc in a medium with a magnetic recording layer thickness fixed at δ = 10 nm. It is a graph which shows the comparison of the heat treatment temperature dependence of perpendicular magnetic anisotropy energy Ku in a CoPt ordered alloy medium and a FePt ordered alloy medium in a medium in which the thickness of each magnetic recording layer is fixed at δ = 10 nm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonmagnetic base | substrate 2 Nonmagnetic seed layer 3 Nonmagnetic underlayer 4 Magnetic recording layer 5 Protective film 6 Liquid lubricating layer 11 Co (or Fe) layer 12 Pt layer

Claims (13)

In a perpendicular magnetic recording medium in which at least a nonmagnetic seed layer, a nonmagnetic underlayer, a magnetic recording layer, a protective film, and a liquid lubricating layer are sequentially formed on a nonmagnetic substrate.
The magnetic recording layer is formed by alternately stacking Fe having a thickness of 0.1 nm or more and 0.3 nm or less and Pt having a thickness of 0.15 nm or more and 0.35 nm or less. Ri Do an alloy mainly composed of FePt containing structure is a region,
The perpendicular characterized in that the nonmagnetic seed layer is MgO, NiO, TiO, or Ti carbide or nitride having a NaCl type structure, and the preferential crystal orientation plane is a (100) plane. Magnetic recording medium.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer has a thickness of 3 nm to 15 nm.   2. The perpendicular magnetic recording according to claim 1, wherein a (001) crystal lattice plane of a region having an L10 type regular structure in the magnetic recording layer is formed in parallel with a film surface of the magnetic recording layer. Medium.   The nonmagnetic underlayer is a metal or alloy containing at least one selected from the group consisting of Ag, Al, Au, Cu, Ir, Ni, Pt and Pd having an fcc structure, or Cr or Cr having a bcc structure 2. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is made of an alloy.   The perpendicular magnetic recording medium according to claim 1, wherein the nonmagnetic underlayer has a thickness of 5 nm to 50 nm. The perpendicular magnetic recording medium according to claim 1 , wherein the nonmagnetic seed layer has a thickness of 3 nm to 15 nm.   2. The perpendicular magnetic recording medium according to claim 1, wherein the nonmagnetic substrate is selected from the group consisting of an Al substrate, a surface-oxidized Si wafer, a fused quartz substrate, a glass substrate, and a plastic resin substrate. 2. The perpendicular magnetic recording according to claim 1, wherein the perpendicular magnetic anisotropy energy value Ku of the magnetic recording layer is 7 × 10 ⁵ J / m ³ or more and 7 × 10 ⁶ J / m ³ or less. Medium.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer is formed by a DC magnetron sputtering method. A step of providing a nonmagnetic seed layer on a nonmagnetic substrate , wherein the nonmagnetic seed layer is MgO, NiO, TiO, or Ti carbide or nitride having a NaCl type structure, and the preferred crystal orientation plane is A process which is a (100) plane;
A step of providing a nonmagnetic underlayer on the nonmagnetic seed layer ; and an Fe film having a thickness of 0.1 nm to 0.3 nm and a thickness of 0.15 nm to 0.35 nm on the nonmagnetic underlayer. A step of alternately stacking Pt and forming a magnetic recording layer made of an alloy mainly composed of FePt including a region having an L10 type regular structure;
Providing a protective film on the magnetic recording layer;
And a step of providing a liquid lubricant layer on the protective film. The method of manufacturing a perpendicular magnetic recording medium according to claim 10 , wherein the magnetic recording layer is formed by a DC magnetron sputtering method. The method of manufacturing a perpendicular magnetic recording medium according to claim 10 , further comprising a step of performing a heat treatment under a temperature condition of 400 ° C. or less after the formation of the magnetic recording layer. The method of manufacturing a perpendicular magnetic recording medium according to claim 10 , wherein in the step of forming the magnetic recording layer, the temperature of the nonmagnetic substrate is 400 ° C. or less.

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