JP2009099197A - Perpendicular magnetic recording medium, and perpendicular magnetic recording reproducing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium having excellent heat stability and recording/reproducing characteristics, with high recording density, and to provide a perpendicular magnetic recording unit using the same. <P>SOLUTION: On a non-magnetic substrate, the magnetic recording medium at least includes a backing layer, an underlayer and a magnetic recording layer. The perpendicular magnetic recording medium is configured by laminating a perpendicular magnetic recording layer having a granular structure at least including Co and Pt, and the magnetic recording layer formed thereon, in which two or more in-plane magnetic recording layers are antiferromagnetically coupled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a perpendicular magnetic recording medium and a perpendicular magnetic recording / reproducing apparatus using the perpendicular magnetic recording medium.

  In recent years, the range of application of magnetic recording devices such as magnetic disk devices, flexible disk devices, and magnetic tape devices has been remarkably increased, and the importance has increased, and the recording density of magnetic recording media used in these devices has increased. Significant improvements are being made. Particularly in HDD (hard disk drive), since the introduction of MR head and PRML technology, the increase in surface recording density has become more intense, and in recent years, GMR heads, TuMR heads, etc. have also been introduced and the pace is about 100% per year. Continues to increase.

  On the other hand, as a magnetic recording system for HDDs, the so-called perpendicular magnetic recording system has been rapidly used in recent years as a technique replacing the conventional in-plane magnetic recording system (the magnetization direction is parallel to the substrate surface). In the perpendicular magnetic recording system, crystal grains of a recording layer for recording information have an easy magnetization axis in a direction perpendicular to the substrate. This easy magnetization axis means a direction in which the magnetization is easily oriented, and in the case of a commonly used Co alloy, it is an axis (c axis) parallel to the normal line of the (0001) plane of the Co hcp structure. . As a result, even when the high recording density is advanced, the influence of the demagnetizing field between the recording bits is small, and there is a feature that it is stable magnetostatically.

  A perpendicular magnetic recording medium is generally formed on a nonmagnetic substrate in the order of an underlayer, an intermediate layer (orientation control layer), a magnetic recording layer, and a protective layer. In many cases, a lubricating layer is applied to the surface after forming a protective layer. In many cases, a magnetic film called a soft magnetic backing layer is provided under the underlayer. The underlayer and the intermediate layer are formed for the purpose of improving the characteristics of the magnetic recording layer. Specifically, it functions to adjust the crystal orientation of the magnetic recording layer and simultaneously control the shape of the magnetic crystal.

In order to increase the recording density of the perpendicular magnetic recording medium, it is necessary to realize low noise while maintaining thermal stability. Two methods are generally used for noise reduction. The first is a method of reducing the magnetic interaction between the magnetic crystal grains by magnetically separating and isolating the magnetic crystal grains in the recording layer. The second method is to reduce the size of the magnetic crystal grains. Specifically, for example, there is a method of forming a perpendicular magnetic recording layer having a so-called granular structure in which SiO ₂ or the like is added to the recording layer and magnetic crystal grains are surrounded by a grain boundary region containing a large amount of SiO ₂ or the like. . However, when noise reduction is performed by such a method, it is necessary to increase the magnetic anisotropic energy (Ku) of the magnetic crystal grains in order to ensure thermal stability. However, when the magnetocrystalline anisotropy energy is increased, Hc and Hco increase, and writing with the recording head becomes insufficient, resulting in a problem that the reproduction characteristics deteriorate.

  As a method for solving this problem, so-called composite media in which a magnetic recording layer made of soft magnetic particles is provided on or below the perpendicular magnetic recording layer (recording layer) made of the above granular structure has been proposed (for example, Non-patent document 1, Patent document 1). According to this method, since the hard magnetic film, which is a magnetic recording layer having a granular structure containing at least Co and Pt, and the soft magnetic film, which is an in-plane magnetic recording layer, are exchange-coupled, a surface is applied when a magnetic field is applied from the head. Since the inner perpendicular magnetic recording layer portion first starts the magnetization reversal, it can be reversed with a lower applied magnetic field than the conventional perpendicular magnetic recording medium. Also, by providing a nonmagnetic film between the magnetic recording layer having a granular structure containing at least Co and Pt and the in-plane magnetic recording layer, the magnetic recording layer having a granular structure containing at least Co and Pt and the in-plane magnetic recording are provided. By controlling the magnetostatic coupling of the layers, it is possible to design a perpendicular magnetic recording medium having optimum characteristics.

In the above method of providing a nonmagnetic film between a magnetic recording layer having a granular structure containing at least Co and Pt and an in-plane magnetic recording layer, if the film thickness is insufficient, it is used for the magnetic recording layer Due to the low Ku of the material, the magnetic recording layer having a granular structure containing at least Co and Pt and the in-plane magnetic recording layer are integrated, so that the squareness ratio (RS) of the hysteresis loop deteriorates to less than 1. Therefore, the improvement of the thermal fluctuation resistance becomes insufficient, which is not preferable. On the other hand, when the thickness of the nonmagnetic film is increased, the in-plane magnetic recording layer undergoes magnetization reversal with a smaller magnetic field, which causes a deterioration in recording by reacting to a minute leakage magnetic field from the head. Unfavorable to bring.
Further, in Patent Document 2, the magnetic recording layer includes a magnetic recording layer having an exchange-coupled granular structure including at least Co and Pt and an in-plane magnetic recording layer, and has a granular structure including at least Co and Pt. The magnetic recording layer is composed of magnetic particles and a non-magnetic material surrounding the magnetic particle, has perpendicular magnetic anisotropy, and the in-plane magnetic recording layer is composed of a material having negative magnetocrystalline anisotropy. Is described.
The methods of these documents 1 and 2 have a problem that they react to a minute magnetic field from the head.
IEEE Transactions in Magnetics, vol. 41, pp. 537 Japanese Patent Application No. 2005-172601 Japanese Patent Application No. 2006-351058

  The present invention has been made in view of the above circumstances, and provides a perpendicular magnetic recording medium having both good thermal stability and recording / reproducing characteristics and capable of high recording density, and a magnetic recording apparatus using the same. With the goal.

In order to achieve the above object, the present invention has the following configuration.
(1) In a magnetic recording medium having at least a backing layer, an underlayer and a magnetic recording layer on a nonmagnetic substrate, the magnetic recording layer has a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt, A perpendicular magnetic recording medium comprising at least two in-plane magnetic recording layers, wherein the two or more in-plane magnetic recording layers are antiferromagnetically coupled to each other.
(2) The perpendicular magnetic recording medium as described in (1) above, wherein the in-plane magnetic recording layer has magnetic anisotropy in the circumferential direction of the substrate.
(3) The perpendicular magnetic recording medium according to (1) or (2), wherein a Ru film is provided between the in-plane magnetic recording layers.

(4) The perpendicular magnetic recording medium according to any one of (1) to (3) above, wherein a nonmagnetic coupling control layer is provided between the perpendicular magnetic recording layer and the in-plane magnetic recording layer.
(5) The magnetic recording layer having a granular structure included in the perpendicular magnetic recording layer is composed of ferromagnetic crystal grains containing Pt and Co and grain boundary constituent materials such as Si oxide, Ti oxide, W oxide, and Cr oxide. The perpendicular magnetic recording medium according to any one of (1) to (4) above, comprising at least one of Co oxide, Ta oxide, and Ru oxide.
(6) The total thickness of the magnetic layers included in the in-plane magnetic recording layer is ½ or less of the total thickness of the magnetic layers included in the perpendicular magnetic recording layer. 5. The perpendicular magnetic recording medium according to any one of 5).

(7) The perpendicular magnetic recording medium according to any one of (1) to (6) above, wherein the saturation magnetic flux density of the in-plane magnetic recording layer is 400 memu / cc or more.
(8) The in-plane magnetic recording layer has a granular structure, and the grain boundary constituent materials include Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, and Ru oxide. The perpendicular magnetic recording medium according to any one of (1) to (7), including at least one of the above.
(9) The perpendicular magnetic recording medium according to any one of (1) to (8) above, wherein the total thickness of the magnetic layers included in the perpendicular magnetic recording layer is in the range of 5 nm to 15 nm. .
(10) The perpendicular magnetic recording medium according to any one of (4) to (9), wherein the thickness of the coupling control layer is not less than 0.3 nm and not more than 3 nm.

(11) Any one of (5) to (10) above, wherein the total amount of oxides in the magnetic layer included in the perpendicular magnetic recording layer is in the range of 3 mol% to 15 mol%. Perpendicular magnetic recording media.
(12) The perpendicular magnetic recording medium according to any one of (8) to (11) above, wherein the total amount of oxides in the in-plane magnetic recording layer is 15 mol% or less.
(13) A magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on / from the magnetic recording medium, wherein the magnetic recording medium is any one of (1) to (12) above. A perpendicular magnetic recording / reproducing apparatus according to claim 1, wherein the perpendicular magnetic recording medium is a perpendicular magnetic recording medium.

  According to the present invention, a perpendicular magnetic recording medium with improved medium SNR, excellent OW characteristics, and good thermal stability can be obtained, and a high recording density can be achieved.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1A is a sectional view showing an example of a magnetic recording medium according to the present invention, and FIG. 1B is a detailed view of the magnetic recording layer 5.
The perpendicular magnetic recording medium 10 according to the present invention includes at least a soft magnetic backing layer 2 on a nonmagnetic substrate 1, an orientation control layer 3 and an underlayer 4, a magnetic recording layer 5, and a protective layer 6 that control the orientation of the film immediately above the nonmagnetic substrate 1. Are stacked in order. 7 is a lubricating layer and 8 is an adhesion layer. The magnetic recording layer 5 has a configuration in which a perpendicular magnetic recording layer and an in-plane magnetic recording layer are laminated in this order, and the perpendicular magnetic recording layer is composed of a magnetic recording layer 5-1 having a granular structure containing at least Co and Pt. . The in-plane magnetic recording layer (reference numeral 5-3) is composed of two or more in-plane magnetic recording layers (reference numerals 5-3-1 and 5-3-3). For ferromagnetic coupling, for example, a nonmagnetic layer (reference numeral 5-3-2) such as Ru can be provided. Further, it is preferable to provide a coupling control layer 5-2 made of a nonmagnetic material between the perpendicular magnetic recording layer and the in-plane magnetic recording layer.

Examples of the nonmagnetic substrate used in the perpendicular magnetic recording medium of the present invention include an Al alloy substrate such as an Al-Mg alloy containing Al as a main component, ordinary soda glass, aluminosilicate glass, amorphous glass, silicon Any nonmagnetic substrate such as a substrate made of titanium, ceramics, sapphire, quartz, or various resins can be used. Of these, glass substrates such as Al alloy substrates, crystallized glass, and amorphous glass are often used. In the case of a glass substrate, a mirror-polished substrate or a low Ra substrate such as Ra <1 (Å) is preferable. If it is mild, it may have a texture.
In the manufacturing process of the magnetic disk, the substrate is usually first cleaned and dried. In the present invention, it is desirable to perform cleaning and drying before formation from the viewpoint of ensuring the adhesion of each layer. Cleaning includes not only water cleaning but also cleaning by etching (reverse sputtering). Also, the substrate size is not particularly limited.

  A soft magnetic underlayer is provided on many perpendicular magnetic recording media. When recording a signal on the medium, the recording magnetic field from the head is guided and the perpendicular component of the recording magnetic field is efficiently applied to the magnetic recording layer. As the material, any material having so-called soft magnetic characteristics such as an FeCo alloy, a CoZrNb alloy, and a CoTaZr alloy can be used. It is particularly preferable that the soft magnetic underlayer has an amorphous structure. By using an amorphous structure, it is possible to prevent the surface roughness Ra from being increased, to reduce the flying height of the head, and to further increase the recording density. In addition to the single soft magnetic layer, a structure in which an extremely thin nonmagnetic thin film such as Ru is sandwiched between two layers and antiferromagnetic coupling is provided between the soft magnetic layers is preferable. The total film thickness of the backing layer is about 20 (nm) to 120 (nm), but is appropriately determined depending on the balance between the recording / reproducing characteristics and the writing characteristics.

In the present invention, it is preferable to provide an orientation control layer for controlling the orientation of the magnetic recording layer on the backing layer. As the material for the orientation control layer, a Ni alloy such as Ni, Ni—Nb, Ni—Ta, Ni—V, Ni—W or the like oriented with Ta or fcc (111) crystal plane is preferable.
Even when the soft magnetic underlayer has an amorphous structure, the surface roughness Ra may increase depending on the material and film formation conditions. Therefore, a nonmagnetic amorphous layer is formed between the underlayer and the orientation control layer. By doing so, Ra can be lowered and the orientation of the magnetic recording layer can be improved.
An underlayer is provided on the backing layer or the orientation control layer. The material of the underlayer is preferably Ru, Re, or an alloy thereof having an hcp structure like the magnetic recording layer. Since the function of the intermediate layer (orientation control layer) is to control the orientation of the magnetic recording layer, any material that can control the orientation of the magnetic recording layer without adopting the hcp structure can be used. The total thickness of the underlayer is preferably 5 (nm) or more and 20 (nm) or less from the balance between the recording / reproducing characteristics and the writing characteristics.

The magnetic recording medium in the present invention is composed of a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt, and an in-plane orientation magnetic recording layer antiferromagnetically coupled. A nonmagnetic coupling control layer is preferably provided between the perpendicular magnetic recording layer having a granular structure and the in-plane oriented magnetic recording layer.
A perpendicular magnetic recording layer having a granular structure containing at least Co and Pt is a layer on which signals are actually recorded. This layer has a granular structure composed of ferromagnetic crystal grains and nonmagnetic oxide crystal grain boundaries.

  As the ferromagnetic material in the perpendicular magnetic recording layer, it is preferable to use a material containing Co and Pt as essential components and added with an oxide for forming a granular structure. The oxide preferably contains at least one of Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, and Ru oxide. Examples of ferromagnetic materials to which these oxides are added include CoCrPt—Si oxide, CoCrPt—Ti oxide, CoCrPt—W oxide, CoCrPt—Cr oxide, CoCrPt—Co oxide, CoCrPt—Ta oxide, Examples thereof include CoCrPt—Ru oxide, CoRuPt—Si oxide, and CoCrPtRu—Si oxide. Two or more of these oxides can be added.

The average grain size of magnetic crystal grains forming a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt is preferably 3 nm or more and 12 nm or less. The average grain boundary width is preferably 0.3 nm or more and 2.0 nm or less. The average crystal grain size and the average grain boundary width can be calculated using a planar TEM observation image.
The total thickness of the magnetic layers included in the perpendicular magnetic recording layer is preferably 5 nm to 15 nm.
The total amount of oxides present in the perpendicular magnetic recording layer having a granular structure containing at least Co and Pt is preferably 3 to 15 mol%, more preferably 5 to 15 mol%. When the total amount of oxide added is within this range, a good granular structure can be formed.

The perpendicular magnetic recording layer may have a multilayer structure of two or more layers. In that case, at least one layer should just have the above-mentioned granular structure.
As the coupling control layer, a non-magnetic material such as Pd, Ru, CoCr or a material obtained by adding an oxide to these can be used. The material is appropriately determined. The thickness of the coupling control layer is optimal for coercive force (Hc), saturation magnetization (Ms), film thickness, etc. of the perpendicular magnetic recording layer having a granular structure mainly containing at least Co and Pt and the in-plane magnetic recording layer. Is determined. In this invention, it is preferable that it is the range of 0.3-3 nm.

  The in-plane magnetic recording layer of the present invention has a structure in which, for example, an in-plane magnetic recording layer (A), a Ru film, and an in-plane magnetic recording layer (B) are stacked. The in-plane magnetic recording layer (A) and the in-plane magnetic recording layer (B) must be antiferromagnetically coupled. Therefore, the film thickness of the Ru film is preferably 0.3 nm or more and 1.3 nm or less.

In the present invention, it is preferable to provide magnetic anisotropy in the circumferential direction of the substrate for two or more in-plane magnetic recording layers that are antiferromagnetically coupled. By adopting such a configuration, it is possible to satisfy all of thermal stability, writing characteristics, and recording / reproducing characteristics. This is estimated as follows.
When no magnetic field is applied from the outside, the in-plane magnetic recording layer (A) and the in-plane magnetic recording layer (B) constituting the in-plane magnetic recording layer are antiferromagnetically coupled and thus magnetically stable. It is a state. Therefore, a signal recorded in a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt can also have thermal stability. When the in-plane magnetic recording layer is not antiferromagnetically coupled, the perpendicular magnetic recording layer having a granular structure containing at least Co and Pt is also affected by the low Ku of the in-plane magnetic recording layer. Stability is inferior. On the other hand, at the time of recording, the in-plane magnetic recording layer functions as a conventional soft magnetism by a magnetic field from the head, so that it can have writing characteristics and recording / reproducing characteristics. Further, since antiferromagnetic coupling is performed at the time of recording and reproduction, noise from the in-plane magnetic recording layer does not leak, so that SNR can be improved.

However, the mechanism of effect is not simple and is not clear at this time.
By adopting the configuration of the present invention, the reason why thermal stability, writing characteristics and recording / reproducing characteristics can be compatible is not simple, and is not clear at present.
Examples of the material for the in-plane magnetic recording layer include a Co alloy, a Ni alloy, and an Fe alloy. For example, Co-Ta-Cr-Ni, Ni-Fe-Ta, Ni-Fe-Mo, etc. An oxide can be added to these alloys to form a granular structure. The oxide preferably contains at least one of Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, and Ru oxide. These oxides are 15 mol% or less, preferably 3 mol% or more and 15 mol% or less in the in-plane magnetic recording layer.

The in-plane magnetic recording layer in the present invention preferably has anisotropy (magnetization direction) in the circumferential direction of the substrate.
The total film thickness (not including the film thickness of Ru) of the in-plane magnetic recording layer is preferably 1.0 nm or more, and more preferably 1.5 nm or more. When the total film thickness of the in-plane magnetic recording layer is less than 1.0 nm, the effect as the in-plane magnetic recording layer is insufficient. The total film thickness of the in-plane magnetic recording layer is preferably less than half that of the perpendicular magnetic recording layer having a granular structure containing at least Co and Pt. When the total thickness of the in-plane magnetic recording layer exceeds half of the thickness of the perpendicular magnetic recording layer having a granular structure including at least Co and Pt, noise in the low frequency band from the in-plane magnetic recording layer itself increases. As a result, the recording / reproducing characteristics deteriorate, which is not preferable. The saturation magnetic flux density of the in-plane magnetic recording layer is preferably 400 memu / cc or more.
A sputtering method is usually used for manufacturing a magnetic recording medium. In this case, whether the magnetic recording layer is a perpendicular magnetic recording layer or an in-plane magnetic recording layer is mainly determined by the material.

The protective layer is for protecting the medium from damage due to contact between the head and the medium, and a carbon film, a SiO ₂ film, or the like is used. In many cases, a carbon film is used. A sputtering method, a plasma CVD method, or the like is used to form the film, but in recent years, a plasma CVD method is often used. A magnetron plasma CVD method is also possible. The film thickness is about 1 (nm) to 10 (nm), preferably about 2 (nm) to 6 (nm), more preferably 2 (nm) to 4 (nm).

FIG. 2 shows an example of a magnetic recording / reproducing apparatus using the magnetic recording medium. A magnetic recording / reproducing apparatus shown in FIG. 2 includes a perpendicular magnetic recording medium 100 configured as shown in FIG. 1, a medium driving unit 101 that rotationally drives the magnetic recording medium 100, and a magnetic head 102 that records and reproduces information on the magnetic recording medium 100. And a head drive unit 103 for moving the magnetic head 102 relative to the magnetic recording medium 100, and a recording / reproducing signal processing system 104.
The recording / reproducing signal processing system 104 can process data input from the outside and send the recording signal to the magnetic head 102, and can process the reproducing signal from the magnetic head 102 and send the data to the outside. It is like that.
For the magnetic head 102 used in the magnetic recording / reproducing apparatus of the present invention, a magnetic head suitable for higher recording density having a GMR element utilizing the giant magnetoresistive effect (GMR), a TuMR element utilizing the tunnel effect, etc. Can be used.

Hereinafter, the present invention will be specifically described with reference to examples. The unit of the film composition is mol%.
Example 1
A 2.5-inch hard disk-shaped glass substrate (MEL3 manufactured by Konica Minolta) was introduced into a vacuum chamber of a C-3040 type sputtering apparatus manufactured by ANELVA. After evacuating the vacuum degree of the sputtering apparatus to 1 × 10 ⁻⁵ Pa or less, as the adhesion layer, Cr film is 10 nm, as the backing layer, 70Co-20Fe-5Ta-5Zr is 30 nm, Ru film is 0.8 nm, 70Co— A film of 20Fe-5Ta-5Zr was formed to a thickness of 30 nm. Next, 90Ni-10W of 5 nm was formed as an orientation control film, and Ru was formed as a base film of 15 nm. At the time of sputtering, Ar gas was used, the backing layer and Ni-10W had a gas pressure of 0.8 Pa, and the Ru underlayer was 8 Pa.

As the magnetic recording layer, 92 (70 Co-10 Cr-20 Pt) -8 (SiO ₂ ) is formed as a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt, and 12 nm is formed as a coupling control layer, and 1.0 nm is formed as Pd. did. Next, 66Co-5Ta-5Cr-20Ni-4 (SiO ₂ ) is 1.5 nm, Ru is 0.8 nm as the first magnetic recording layer which is the in-plane magnetic recording layer, and 66Co is used as the in-plane second magnetic recording layer. -5Ta-5Cr-20Ni-4 ( SiO 2) was 1.5nm deposition. Ar gas is used for sputtering, and the first and second magnetic recording layers of the perpendicular magnetic recording layer and the in-plane magnetic recording layer having a granular structure containing at least Co and Pt have a gas pressure of 2.0 Pa, Pd and Ru are 0.8 Pa. Next, a carbon protective film was formed to a thickness of 4 nm by a CVD method to produce a magnetic recording medium.

  The obtained magnetic recording medium was coated with a lubricant and evaluated for recording / reproducing characteristics using a read / write analyzer 1632 and spin stand S1701MP manufactured by Guzik, USA. The recording / reproduction characteristics include a signal-to-noise ratio (SNR, where S is an output at a linear recording density of 576 kFCI, N is an rms (root mean square) value at a linear recording density of 576 kFCI), and an OW value (a signal at a linear recording density of 576 kFCI). Then, the reproduction output ratio (attenuation rate) of the 576 kFCI signal before and after overwriting the signal with the linear recording density of 77 kFCI was evaluated.

  Thereafter, the magnetostatic characteristics were evaluated using a Kerr measuring device (manufactured by Neoarc). In order to investigate the crystal orientation of the CoCrPt magnetic crystal in the magnetic recording layer, the rocking curve of the magnetic layer was measured by an X-ray diffractometer (manufactured by Philips). It was confirmed that the film was small. Finally, planar TEM observation of the perpendicular magnetic recording layer having a granular structure containing at least Co and Pt of the magnetic recording layer was performed, and the crystal grain size of the magnetic crystal was observed. As a result, it was confirmed that it had a clear granular structure, an average crystal grain size of 7.5 nm, and an average grain boundary width of 0.8 nm.

VSM (manufactured by Riken Denshi) was used for evaluation of the saturation magnetization amount (Ms) of the in-plane magnetic recording layer, measurement and confirmation of antiferromagnetic coupling.
The evaluation results of Example 1 are shown in Table 1.

(Comparative Example 1)
A magnetic recording medium is manufactured according to Example 1 except that no Ru film is provided between the first and second magnetic recording layers, which are in-plane magnetic recording layers, and these two layers are not antiferromagnetically coupled. did. The results are shown in Table 1.
From Table 1, it can be seen that the perpendicular magnetic recording medium of Example 1 has superior SNR and thermal stability to the perpendicular magnetic recording medium of Comparative Example 1. Since there is no significant difference in write characteristics, it can be seen that the write characteristics are not deteriorated by antiferromagnetic coupling between the first and second magnetic recording layers.

(Examples 2 to 12)
Except that the film thickness and material of the magnetic recording layer having a granular structure containing at least Co and Pt are the conditions shown in Table 2, a soft magnetic backing layer, an orientation control layer, and an underlayer are formed on a glass substrate according to Example 1. As a magnetic recording layer, a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt, a coupling control layer, and an in-plane magnetic recording layer were sequentially formed. The results are shown in Table 2.

(Examples 13 to 24)
Except that the film thickness and material of the in-plane magnetic recording layer were set to the conditions shown in Table 3, according to Example 1, at least Co as a soft magnetic backing layer, orientation control layer, underlayer, and magnetic recording layer on the glass substrate. A perpendicular magnetic recording layer having a granular structure containing Pt, a coupling control layer, and an in-plane magnetic recording layer were sequentially formed. The results are shown in Table 3.

(Examples 25-32)
Except that the film thickness and material of the bond control layer are the conditions shown in Table 4, according to Example 1, at least Co and Pt are used as the soft magnetic backing layer, orientation control layer, underlayer, and magnetic recording layer on the glass substrate. A perpendicular magnetic recording layer having a granular structure, a coupling control layer, and an in-plane magnetic recording layer were sequentially formed. The results are shown in Table 4.

(Examples 33 to 38)
Except that the film thickness and materials of the underlayer and orientation control layer were the conditions shown in Table 5, according to Example 1, at least Co as a soft magnetic backing layer, orientation control layer, underlayer, and magnetic recording layer was applied to the glass substrate. And a perpendicular magnetic recording layer having a granular structure containing Pt, a coupling control layer, and an in-plane magnetic recording layer were sequentially formed. The results are shown in Table 5.

  According to the present invention, since the medium SNR is improved, a magnetic recording medium having excellent OW characteristics and good thermal stability is obtained, and a high recording density is possible. Therefore, a magnetic disk device, a flexible disk device, It is suitable as a magnetic recording device having a high recording density such as a magnetic tape device.

(A) is sectional drawing which shows an example of the perpendicular magnetic recording medium of this invention, (b) is the detailed enlarged view of the magnetic-recording layer 5. FIG. 1 is a perspective view of a magnetic recording / reproducing apparatus using a magnetic recording medium of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Backing layer 3 Orientation control layer 4 Underlayer 5 Perpendicular magnetic recording layer 5-1 Perpendicular magnetic recording layer 502 Coupling control layer 5-3 In-plane magnetic recording layer 5-3-1 One layer of in-plane magnetic recording layer 5-3-2 Ru layer 5-3-3 Other layers of in-plane magnetic recording layer 6 Protective layer 7 Lubricating layer 8 Adhesion layer 100 Perpendicular recording medium 101 Vertical recording medium driving unit 102 Magnetic head 103 Magnetic head driving unit 104 Recording / playback signal processing system

Claims (13)

  In a magnetic recording medium having at least a backing layer, an underlayer and a magnetic recording layer on a nonmagnetic substrate, the magnetic recording layer has a perpendicular magnetic recording layer having a granular structure containing at least Co and Pt, and at least two layers thereon A perpendicular magnetic recording medium comprising the above in-plane magnetic recording layer, wherein the two or more in-plane magnetic recording layers are antiferromagnetically coupled to each other.   The perpendicular magnetic recording medium according to claim 1, wherein the in-plane magnetic recording layer has magnetic anisotropy in a circumferential direction of the substrate.   The perpendicular magnetic recording medium according to claim 1, further comprising a Ru film between the in-plane magnetic recording layers.   4. The perpendicular magnetic recording medium according to claim 1, further comprising a nonmagnetic coupling control layer between the perpendicular magnetic recording layer and the in-plane magnetic recording layer.   The magnetic recording layer having a granular structure contained in the perpendicular magnetic recording layer is composed of ferromagnetic crystal grains containing Pt and Co and grain boundary constituent materials such as Si oxide, Ti oxide, W oxide, Cr oxide, and Co oxidation. 5. The perpendicular magnetic recording medium according to claim 1, comprising at least one of an oxide, a Ta oxide, and a Ru oxide.   6. The total thickness of the magnetic layers included in the in-plane magnetic recording layer is ½ or less of the total thickness of the magnetic layers included in the perpendicular magnetic recording layer. Item 10. The perpendicular magnetic recording medium according to Item.   7. The perpendicular magnetic recording medium according to claim 1, wherein the in-plane magnetic recording layer has a saturation magnetic flux density of 400 memu / cc or more.   The in-plane magnetic recording layer has a granular structure, and any one of Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, and Ru oxide as a grain boundary constituent material The perpendicular magnetic recording medium according to claim 1, comprising at least one kind.   9. The perpendicular magnetic recording medium according to claim 1, wherein the total thickness of the magnetic layers included in the perpendicular magnetic recording layer is in a range of 5 nm to 15 nm.   10. The perpendicular magnetic recording medium according to claim 4, wherein the thickness of the coupling control layer is not less than 0.3 nm and not more than 3 nm.   11. The perpendicular magnetic recording medium according to claim 5, wherein the total amount of oxides in the magnetic layer contained in the perpendicular magnetic recording layer is in the range of 3 mol% to 15 mol%.   12. The perpendicular magnetic recording medium according to claim 8, wherein the total amount of oxides in the in-plane magnetic recording layer is 15 mol% or less.   A magnetic recording / reproducing apparatus comprising a magnetic recording medium and a magnetic head for recording / reproducing information on the magnetic recording medium, wherein the magnetic recording medium is a perpendicular magnetic recording according to any one of claims 1 to 12. A perpendicular magnetic recording / reproducing apparatus characterized by being a medium.

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