JP2005141825A - Magnetic recording medium and magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium, having high magnetostatic characteristics and capable of recording with low medium noise and high-density, and to provide a magnetic recording device equipped with the same. <P>SOLUTION: This high-density magnetic recording medium is constructed, in such a manner that an adhesive layer provided on a nonmagnetic substrate, a soft magnetic layer and a foundation layer are formed, and then a CoPtCr alloy magnetic film containing an oxide and a protective layer are formed sequentially on the nonmagnetic substrate. A recording layer is constituted of a CoPtCr alloy magnetic film containing an oxide, in which oxide concentration in the magnetic film is continuously reduced from a substrate direction toward the film surface direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing information, and more particularly to a magnetic recording medium and a magnetic recording apparatus suitable for high-density recording.

  There is a remarkable development in the information society, and a magnetic recording device mounted on a computer or the like is known as one of devices capable of processing not only character information but also sound and image information at high speed. At present, development is progressing in the direction of downsizing the magnetic recording apparatus while improving the recording density of the magnetic recording apparatus. A typical magnetic recording apparatus has a plurality of magnetic disks rotatably mounted on a spindle. Each magnetic disk includes a substrate and a magnetic film formed thereon, and information recording is performed by forming a magnetic domain having a specific magnetization direction in the magnetic film. Conventionally, the direction of magnetization to be recorded is in the plane of the magnetic film, which is called an in-plane recording method. High-density recording of the in-plane recording type magnetic recording apparatus reduces the film thickness of the magnetic film, reduces the size of the magnetic crystal grains, and reduces the magnetic interaction between the grains. Has been achieved. However, miniaturization of crystal grains and reduction of the magnetic interaction between the grains are problematic in that the thermal stability of magnetization constituting the recorded bit is lowered.

  In order to alleviate this problem, a perpendicular magnetic recording method has been proposed, which makes the direction of recorded magnetization perpendicular to the substrate. As a result, the adjacent bits are magnetostatically stable and the recording transition area becomes sharp. Furthermore, by adding a layer made of a soft magnetic material (soft magnetic backing layer) between the recording layer and the substrate, the magnetic field at the time of recording can be sharpened. Recording becomes possible and the thermal stability of magnetization is improved, so that higher density recording is possible.

  Currently, a CoPtCr-based alloy (hereinafter referred to as a CoPtCr-based alloy medium) is used for the above-mentioned recording medium of the in-plane recording system, and the same CoPtCr-based alloy medium is mainly studied as a perpendicular magnetic recording system recording medium. It has been. The feature of this medium is that it is composed of crystal grains with high Co concentration having ferromagnetism and non-magnetic grain boundary portions with high Cr concentration, and the magnetic interaction between the crystal grains is reduced by the non-magnetic grain boundary portions. It is. This effect has realized the low noise characteristics of the medium necessary for high recording density. However, to cope with higher density recording, it is required to further reduce the magnetic interaction between crystal grains and at the same time further increase the magnetic thermal stability of the bit. As a method for this, there is a method in which oxygen is added to the recording layer to oxidize the crystal grain boundaries. This is obtained by adding an oxide to the target or forming a film in an oxygen gas atmosphere, and has a granular structure in which the magnetic crystal grains of the recording layer are surrounded by the oxide. It is called a CoPtCr-based alloy medium containing. In the case of a CoPtCr-based alloy medium containing an oxide, since separation between crystal grains can be performed by an oxide, phase separation by heating as in the case of a conventional CoPtCr-based alloy medium is not required. It has a feature that it can be controlled more than before and can be easily controlled to fine crystal grains. As a technical report of a CoPtCr-based alloy medium containing an oxide, for example, there is Document 1. In Reference 1, since the CoPtCr-based alloy medium containing an oxide can improve the magnetocrystalline anisotropy while reducing the magnetic interaction between crystal grains than the CoPtCr-based alloy medium, It is disclosed that the S / N ratio in a high recording density state is higher and the thermal stability of the bit can be improved.

  However, according to experiments by the present inventors, even in the case of a CoPtCr-based alloy medium containing an oxide, if the oxide concentration is further increased in order to increase the recording density and the crystal grains are refined, the magnetic properties of the medium are increased. The characteristics deteriorated, and when the magnetization curve in the direction perpendicular to the film surface, which is the direction of the axis of easy magnetization of the medium, was measured, it was found that the squareness ratio was greatly degraded. In a medium with a low squareness ratio, the low frequency component of the medium noise is greatly increased, so that the bit error rate at the time of random recording deteriorates and cannot be used as a recording medium. Therefore, in order to realize a higher recording density, it is required to avoid deterioration of magnetic characteristics.

  In order to improve the deteriorated magnetic properties, the oxide concentration of the recording layer is higher than that of the layer in contact with the base layer in order to increase the oxide concentration of the recording layer first to make the crystal grain of the recording layer finer. It has been found that by forming a lower recording layer, it is possible to suppress deterioration of the magnetic characteristics of the entire recording layer due to magnetic coupling with the upper layer (Japanese Patent Application No. 2003-30905). As a result, a medium having fine crystal grains and excellent magnetic properties can be obtained.

T. T. et al. Oikawa et. al, IEEE Trans. Magn. , Vol. 38, pp. 1976-1978, 2002

  However, when a recording layer is formed with a plurality of oxide concentrations, the crystal growth of the recording layer may be disturbed if the oxide concentration is too different at the interface between layers having different oxide concentrations in the recording layer. I understood it. In that case, the magnetic characteristics of the low oxide concentration layer, which originally plays a role of improving the magnetic characteristics of the recording layer due to the high magnetic characteristics, deteriorates, and the magnetic characteristics of the entire recording layer also deteriorate.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a method and a medium for manufacturing a novel magnetic recording medium having high magnetic characteristics and low medium noise.

  According to a first aspect of the present invention, a soft magnetic backing layer made of a soft magnetic material, an underlayer, and a recording layer are formed in this order on a nonmagnetic substrate, and the recording layer is mainly composed of CoPtCr containing an oxide. In a perpendicular magnetic recording type recording medium in which the residual magnetization is higher in the direction perpendicular to the film surface than in the in-plane direction, the oxide concentration of the recording layer is from the substrate side in contact with the underlayer. The present invention relates to a magnetic recording medium that continuously decreases in the film thickness direction.

  As a result of film formation while continuously changing the oxide concentration of the recording layer, the crystal growth of the recording layer is less likely to be disturbed, the crystallinity of the recording layer is improved, and the crystal grain size is not increased, compared to the conventional case. It has been found that the magnetic properties of the recording layer can be improved. As a result, it was found that the recording / reproducing characteristics can be further improved.

  The film thickness of the recording layer is preferably 20 nm or less in order to perform recording under the condition that the magnetic field gradient is steep and to improve the resolution.

In the magnetic recording medium of the present invention, the oxide content in the CoPtCr-based oxide film containing the oxide forming the recording layer is preferably 5 to 20 mol%. A CoPtCr-based alloy magnetic film containing an oxide is formed by using a mixed gas of argon and oxygen as a sputtering gas. By appropriately adjusting this mixing ratio, 5 to 20 mol% of the CoPtCr-based alloy magnetic film is formed. The oxide can be introduced in a dispersed state. Alternatively, argon can be used as the sputtering gas, and the oxide content in the CoPtCr-based alloy magnetic film can be changed by adjusting the amount of oxygen contained in the target. For example, a simultaneous sputtering method using a CoPtCr target and a target such as SiO ₂ or MgO can be used. By using a CoPtCr alloy magnetic film containing 5 to 20 mol% of an oxide, the magnetic interaction between magnetic crystal grains can be reduced, and a medium with low medium noise can be provided. When the oxide content in the CoPtCr alloy magnetic film is more than 5 mol%, the separation between the magnetic particles proceeds and the magnetic interaction between the magnetic particles decreases, so the medium noise begins to decrease and the oxide content decreases. If it exceeds 20 mol%, oxygen is taken into the magnetic crystal grains and the magnetic characteristics are remarkably deteriorated, and the magnetic characteristics necessary for the recording layer are hardly exhibited.

In the magnetic recording medium of the present invention, it is preferable to use Si oxide or Mg oxide as the oxide. In both cases, it is particularly desirable to use a Si oxide that is easy to obtain fine crystal grains. As a method of mixing Si oxide or Mg oxide in the recording layer, there is a method of sputtering using a target in which 5 to ₂₀ mol% of SiO ₂ or MgO is mixed in a CoPtCr target. In this method, the oxide content can be easily adjusted, and the formed thin film has a structure in which the oxide SiO ₂ and MgO surround the CoPtCr-based alloy magnetic crystal grains.

  In the magnetic recording medium of the present invention, it is preferable to use an underlayer formed of an alloy mainly composed of CoCrRu. By using this underlayer, the crystallinity of the recording layer is improved and high magnetic properties can be obtained.

  In the magnetic recording medium of the present invention, the soft magnetic underlayer has a role of focusing magnetic flux leaking from the magnetic head on the recording layer when information is recorded on and reproduced from the recording layer using the magnetic head. As a material for the soft magnetic underlayer, a soft magnetic material having a large saturation magnetization, a small coercive force, and a high magnetic permeability is preferable, and for example, a CoTaZr film is preferable. The film thickness of the soft magnetic backing layer is preferably in the range of 50 to 500 nm.

  According to the second aspect of the present invention, the magnetic recording medium of the present invention is magnetized in the direction perpendicular to the film surface of the recording layer, and the film surface of the soft magnetic backing layer is provided. A magnetic head that provides parallel magnetization and forms a magnetic circuit in cooperation with a recording layer and a soft magnetic underlayer; and a drive device for driving the magnetic recording medium relative to the head. A magnetic recording apparatus is provided.

  According to the magnetic recording medium of the present invention, the recording layer is composed of the CoPtCr alloy magnetic film containing at least two oxides whose oxide concentration in the magnetic film decreases from the substrate direction to the film surface direction. Accordingly, it is possible to provide a magnetic recording medium capable of high density recording with high magnetostatic characteristics and low medium noise, and a magnetic recording apparatus including the magnetic recording medium.

Hereinafter, the magnetic recording medium and the magnetic recording apparatus of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
(Example 1)

  A schematic cross-sectional view of the magnetic disk manufactured in Example 1 is shown in FIG. As shown in FIG. 1, the magnetic disk 10 has a structure in which an adhesion layer 2, a soft magnetic backing layer 3, an underlayer 4, a recording layer 5, and a protective layer 6 are sequentially laminated on a substrate 1. The adhesion layer 2 is a layer for preventing separation between the substrate 1 and a film laminated thereon, and the soft magnetic backing layer 3 is for focusing a magnetic field applied to the recording layer during information recording. Is a layer. The underlayer 4 is a layer for improving the orientation of the recording layer 5. The recording layer 5 is a layer in which information is recorded as magnetization information, and the oxide concentration is continuously changing in the film thickness direction. The magnetization direction is a direction perpendicular to the film surface. The protective layer 6 is a layer for protecting the laminated films 2 to 5 sequentially laminated on the substrate 1. A method for manufacturing the magnetic disk manufactured in this example will be described below.

  As the substrate 1, a disc-shaped glass substrate having a diameter of 2.5 inches (6.5 cm) was used. A Ti film as an adhesion layer 2 was formed on the substrate 1 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and a target of Ti. The film thickness of the adhesion layer 2 was 5 nm.

Next, a CoTaZr film as a soft magnetic backing layer 3 was formed on the adhesion layer 2 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 400 W, and the target composition was Co ₈₈ Ta ₁₀ Zr ₂ (at%). The film thickness of the soft magnetic backing layer 3 was 200 nm.

Next, a CoCrRu film was formed as a base layer 4 on the soft magnetic backing layer 3 by DC sputtering. The sputtering conditions were a gas pressure of 4.2 Pa and an input power of 500 W, and the target composition was Co ₅₅ Cr ₂₅ Ru ₂₀ (at%).
The film thickness of the underlayer 4 was 20 nm.

Further, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the recording layer 5 on the underlayer 4. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the input power to the SiO ₂ target was 400 W at the beginning of recording layer formation, and continuously changed to 100 W. As a result, the oxide concentration of the recording layer was changed. The film thickness of the recording layer 5 was 15 nm.

Finally, an amorphous carbon film was formed as a protective layer 6 on the recording layer 5 by DC sputtering. The sputtering conditions were such that the gas pressure was 0.20 Pa, the input power was 300 W, and the thickness of the protective layer 6 was 3 nm.
(Comparative Example 1)

  A schematic cross-sectional view of the magnetic disk produced in Comparative Example 1 is shown in FIG. As shown in FIG. 2, the magnetic disk 10 is formed by sequentially laminating an adhesion layer 2, a soft magnetic backing layer 3, an underlayer 4, a first recording layer 7, a second recording layer 8, and a protective layer 6 on a substrate 1. Has the structure. The adhesion layer 2 is a layer for preventing separation between the substrate 1 and a film laminated thereon, and the soft magnetic backing layer 3 is for focusing a magnetic field applied to the recording layer during information recording. Is a layer. The underlayer 4 is a layer for improving the orientation of the first recording layer 5 and the second recording layer 6. The first recording layer 5 and the second recording layer 6 are layers in which information is recorded as magnetization information, and the magnetization directions of the first recording layer 5 and the second recording layer 6 are perpendicular to the film surface. The protective layer 7 is a layer for protecting the laminated films 2 to 6 sequentially laminated on the substrate 1. A method for manufacturing the magnetic disk manufactured in this example will be described below.

  As the substrate 1, a disc-shaped glass substrate having a diameter of 2.5 inches (6.5 cm) was used. A Ti film as an adhesion layer 2 was formed on the substrate 1 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and a target of Ti. The film thickness of the adhesion layer 2 was 5 nm.

Next, a CoTaZr film as a soft magnetic backing layer 3 was formed on the adhesion layer 2 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 400 W, and the target composition was Co ₈₈ Ta ₁₀ Zr ₂ (at%). The film thickness of the soft magnetic backing layer 3 was 200 nm.

Next, a CoCrRu film was formed as a base layer 4 on the soft magnetic backing layer 3 by DC sputtering. The sputtering conditions were a gas pressure of 4.2 Pa and an input power of 500 W, and the target composition was Co ₅₅ Cr ₂₅ Ru ₂₀ (at%). The film thickness of the underlayer 4 was 20 nm.

Further, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the first recording layer 7 on the underlayer 4. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the input power to the SiO ₂ target was 400 W. The first recording layer 5 was 5 nm.

Further, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the second recording layer 8 on the first recording layer 7. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the power input to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the power input to the SiO ₂ target was 100 W. The second recording layer 6 was 10 nm.

Finally, an amorphous carbon film was formed as the protective layer 7 on the second recording layer 6 by DC sputtering. The sputtering conditions were such that the gas pressure was 0.20 Pa, the input power was 300 W, and the thickness of the protective layer 7 was 3 nm.
(Comparative Example 2)

  A schematic cross-sectional view of the magnetic disk produced in Comparative Example 2 is shown in FIG. The substrate 1 has a structure in which an adhesion layer 2, a soft magnetic backing layer 3, an underlayer 4, a first recording layer 7, a second recording layer 8, a third recording layer 9, and a protective layer 7 are sequentially laminated. Hereinafter, a method of manufacturing the magnetic disk 10 manufactured in this example will be described.

  First, a disc-shaped glass substrate having a diameter of 2.5 inches (6.5 cm) was used as the substrate 1, and a Ti film was formed as an adhesion layer 2 on the substrate 1 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and a target of Ti. The film thickness of the adhesion layer 2 was 5 nm.

Next, a CoTaZr film as a soft magnetic backing layer 3 was formed on the adhesion layer 2 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and the target composition was Co ₈₈ Ta ₁₀ Zr ₂ (at%). The film thickness of the soft magnetic backing layer 3 was 200 nm.

Next, a CoCrRu film was formed as a base layer 4 on the soft magnetic backing layer 3 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and the target composition was Co ₅₅ Cr ₂₅ Ru ₂₀ (at%). The film thickness of the underlayer 4 was 10 nm.

Further, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the first recording layer 7 on the underlayer 4. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the input power to the SiO ₂ target was 400 W. The first recording layer 7 was 5 nm.

Next, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the second recording layer 8 on the first recording layer 7. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the input power to the SiO ₂ target was 250 W. The film thickness of the second recording layer 8 was 5 nm.

Next, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the third recording layer 9 on the second recording layer 8. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the power input to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the power input to the SiO ₂ target was 100 W. The film thickness of the third recording layer 9 was 5 nm.

  Finally, an amorphous carbon film as a protective layer 10 was formed on the third recording layer 9 by DC sputtering. The sputtering conditions were such that the gas pressure was 0.20 Pa, the input power was 300 W, and the thickness of the protective layer 10 was 3 nm.

For these examples, the oxide concentration of the recording layer was determined by Auger electron spectroscopy. The result is shown in FIG. In the case of Example 1, it can be seen that the oxide concentration continuously decreases from 15 mol% to 5 mol%. On the other hand, it can be seen that Comparative Example 1 discontinuously changes from 15 mol% to 5 mol%, and Comparative Example 2 discontinuously changes from 15 mol% to 10 mol%, from 10 mol% to 5 mol%. From these results, it was possible to continuously change the oxide concentration of the recording layer by continuously reducing the input power to the SiO ₂ target when forming the recording layer.

  Next, the magnetic characteristics of these examples were measured using a polar Kerr effect measuring apparatus and a sample resonance magnetometer. Table 1 shows the results of the magnetic characteristics.

As shown in Table 1, the magnetic characteristics of Example 1 were the most excellent. In order to investigate this cause, the X-ray diffraction measurement of Example 1, Comparative Example 1 and Comparative Example 2 is performed, and the Δθ ₅₀ of the (002) plane of the recording layer is obtained from the rocking curve, whereby the orientation of the recording layer is determined. evaluated. The results are shown in Table 2.

The value of Δθ ₅₀ reflects the crystal orientation, and the smaller the value, the higher the orientation. Comparing the example and the comparative example, it can be seen that the value of Example 1 is the smallest, and the orientation is improved accordingly. The high orientation means that the crystal growth of the recording layer is proceeding favorably, and as a result, it is presumed that the magnetic characteristics are improved.

  Next, after applying a 1 nm thick lubricant on the protective layer of the magnetic disk produced in these examples, the magnetic disk is mounted in the magnetic recording apparatus 60 shown in FIG. Evaluated. FIG. 5A is a schematic plan view of the magnetic recording device 60, and FIG. 5B is a schematic cross-sectional view of the magnetic recording device 60 taken along a broken line AA ′ in FIG. As shown in FIG. 5B, the magnetic disk 10 is coaxially attached to the spindle 52 of the rotational drive system and is rotated by the spindle 52.

  When recording information on the magnetic disk 10 with this magnetic recording device 60, a thin-film magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1T is used. A spin valve type magnetic head having a resistance effect was used. The thin film magnetic head for recording and the spin valve type magnetic head for reproduction are integrated, and are shown as a magnetic head 53 in FIG. This integrated magnetic head 53 is controlled by a magnetic head drive system 54. The distance between the magnetic head surface of the magnetic recording device 60 and the magnetic disk surface was kept at 5 nm.

  The magnetic head 53 of the magnetic recording device 60 provides magnetization in the direction perpendicular to the film surfaces of the first recording layer 5 and the second recording layer 6 of the magnetic disk 10, and the film surface of the soft magnetic backing layer 3. On the other hand, it is possible to form a magnetic circuit in cooperation with the recording layer and the soft magnetic backing layer 3 by giving magnetization in a parallel direction. Further, the magnetic recording device 60 includes a driving device 54 for driving the magnetic disk 10 relative to the magnetic head 53.

This magnetic disk 10 is used as a reproduction output (Slf) when a signal having a linear recording density of 20 kFCI is recorded, and the ratio with the noise (Nd) at each linear recording density is a recording / reproduction characteristic (Slf / Nd ratio) of the magnetic disk. ). FIG. 6 shows the dependence of the Slf / Nd ratio on the linear recording density. In all, it can be seen that the Slf / Nd ratio decreases as the linear recording density increases. However, in each linear recording density, the Slf / Nd ratio of Example 1 shows the highest value, and it can be seen that Example 1 has the best recording / reproducing characteristics. Further, when Comparative Example 1 and Comparative Example 2 are compared, Comparative Example 2 has a higher Slf / Nd ratio than Example 1 in the whole-line recording density region. Considering the results of magnetization measurement and X-ray diffraction measurement, this reflects the result of the best crystallinity of Example 1, and can be interpreted as being excellent in magnetic characteristics and recording / reproduction characteristics. it can. That is, it is important to form the recording layer while controlling the crystal growth of the recording layer with a fine crystal grain size.
(Example 2)

  A schematic cross-sectional view of the magnetic disk produced in Example 2 is shown in FIG. In Example 2, unlike Example 1, MgO was used as the oxide added to the recording layer. A method for manufacturing the magnetic disk manufactured in this example will be described below.

  As the substrate 1, a disc-shaped glass substrate having a diameter of 2.5 inches (6.5 cm) was used. A Ti film as an adhesion layer 2 was formed on the substrate 1 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and a target of Ti. The film thickness of the adhesion layer 2 was 5 nm.

Next, a CoTaZr film as a soft magnetic backing layer 3 was formed on the adhesion layer 2 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 400 W, and the target composition was Co ₈₈ Ta ₁₀ Zr ₂ (at%). The film thickness of the soft magnetic backing layer 3 was 200 nm.

Next, a CoCrRu film was formed as a base layer 4 on the soft magnetic backing layer 3 by DC sputtering. The sputtering conditions were a gas pressure of 4.2 Pa and an input power of 500 W, and the target composition was Co ₅₅ Cr ₂₅ Ru ₂₀ (at%).
The film thickness of the underlayer 4 was 20 nm.

Further, a CoPtCr—MgO alloy magnetic film containing an oxide was formed as the recording layer 5 on the underlayer 4. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, MgO was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions are as follows: the gas pressure is 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target is 200 W, and the input power to the MgO target is 400 W at the beginning of recording layer formation and continuously changed to 100 W. As a result, the oxide concentration of the recording layer was changed. The film thickness of the recording layer 5 was 15 nm.

  Finally, an amorphous carbon film was formed as a protective layer 6 on the recording layer 5 by DC sputtering. The sputtering conditions were such that the gas pressure was 0.20 Pa, the input power was 300 W, and the thickness of the protective layer 6 was 3 nm.

The recording / reproducing characteristics of Example 2 were measured. The results are shown in FIG.
Although the recording / reproducing characteristics of Example 2 are superior to those of the comparative example, it can be seen that each recording density is inferior to that of Example 1. In order to examine the difference between the two, the planar image of the recording layer was observed using a transmission electron microscope (TEM). As a result, the average crystal grain size of Example 1 was 7.1 nm, whereas the average of Example 2 was It was found that the crystal grain size was as large as 8.3 nm. Since this difference in particle size appears as a noise difference in the bit transition region during high-density recording, the recording / reproducing characteristics of Example 2 are considered to be slightly inferior. From the above results, it can be seen that the crystal grain size becomes finer when SiO ₂ is used as the oxide.

  In the above-described embodiment, an example in which a CoPtCr alloy magnetic film containing an oxide is used as a recording layer of a magnetic disk has been described. However, the present invention is not limited to this. The CoPtCr alloy magnetic film containing an oxide is crystalline and has a structure including an alloy containing Co as a main component in crystal grains and an oxide between particles. In addition to Cr and Pt, elements such as Ta, Nb, Ti, Si, B, Pd, V, Mg, and Gd, or combinations thereof may be included as long as the hexagonal close-packed structure is adopted.

  In the above embodiment, an example in which glass is used as the substrate material of the magnetic disk has been described, but the present invention is not limited to this. In some cases, a plastic such as aluminum or polycarbonate, or a resin may be used.

This technique is applicable not only to magnetic disks but also to tape media. Hereinafter, examples in which the present technology is applied to a tape will be described.
(Example 3)

  A schematic cross-sectional view of the magnetic tape produced in Example 3 is shown in FIG. As shown in FIG. 8, the magnetic tape 20 has a structure in which an adhesion layer 2, a soft magnetic backing layer 3, an underlayer 4, a recording layer 5, and a protective layer 6 are sequentially laminated on a base film 11 having a thickness of 3 μm. Have. The adhesion layer 2 is a layer for preventing peeling between the base film 11 and the film laminated thereon, and the soft magnetic backing layer 3 is for focusing a magnetic field applied to the recording layer during information recording. Of layers. The underlayer 4 is a layer for improving the orientation of the recording layer 5. The recording layer 5 is a layer in which information is recorded as magnetization information. The recording layer 5 is a layer in which the oxide concentration continuously changes, and the magnetization direction thereof is perpendicular to the film surface. The protective layer 6 is a layer for protecting the laminated films 2 to 5 sequentially laminated on the base film 11. A method for producing the magnetic tape produced in this example will be described below.

  The base film 11 was a PEN film having a thickness of 3 μm. A Ti film as an adhesion layer 2 was formed on the base film 1 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 500 W, and a target of Ti. The film thickness of the adhesion layer 2 was 5 nm.

Next, a CoTaZr film as a soft magnetic backing layer 3 was formed on the adhesion layer 2 by DC sputtering. The sputtering conditions were a gas pressure of 0.28 Pa, an input power of 400 W, and the target composition was Co ₈₈ Ta ₁₀ Zr ₂ (at%). The film thickness of the soft magnetic backing layer 3 was 200 nm.

Next, a CoCrRu film was formed as a base layer 4 on the soft magnetic backing layer 3 by DC sputtering. The sputtering conditions were a gas pressure of 4.2 Pa and an input power of 500 W, and the target composition was Co ₅₅ Cr ₂₅ Ru ₂₀ (at%).
The film thickness of the underlayer 4 was 20 nm.

Further, a CoPtCr—SiO ₂ alloy magnetic film containing an oxide was formed as the recording layer 5 on the underlayer 4. As a target, Co ₆₄ Pt ₂₀ Cr ₁₆ was a DC sputtering method, SiO ₂ was an RF sputtering method, and a simultaneous sputtering method using these two types of targets was used. The sputtering conditions were such that the gas pressure was 4.2 Pa, the input power to the Co ₆₄ Pt ₂₀ Cr ₁₆ target was 200 W, and the input power to the SiO ₂ target was 400 W at the beginning of recording layer formation, and continuously changed to 100 W. As a result, the oxide concentration of the recording layer was changed. The film thickness of the recording layer 5 was 30 nm.

  Finally, an amorphous carbon film was formed as a protective layer 6 on the recording layer 5 by DC sputtering. The sputtering conditions were such that the gas pressure was 0.20 Pa, the input power was 300 W, and the thickness of the protective layer 6 was 3 nm.

  Further, a backcoat paint was applied as a backcoat layer 12 to the back surface on the side where the recording layer was formed.

When the signal corresponding to 5 Gbit / inch ² (500 kFCI, 9.8 kTPI) corresponding to the capacity of 10 TB tape was recorded on the magnetic tape of Example 3 and the S / N ratio was evaluated, the system was 25 dB. The required recording / playback characteristics are shown.

  In the above embodiments, the example in which the CoTaZr film is provided as the soft magnetic backing layer of the magnetic disk or magnetic tape has been described. However, the present invention is not limited to this. The soft magnetic backing layer may be FeTaC, FeTaN, FeAlSi, FeC, CoB, CoTaNb, NiFe, or a laminated film of these soft magnetic films and C films. However, the CoTaZr film is most desirable.

  In the above embodiment, when forming a CoPtCr alloy magnetic film containing an oxide as the recording layer, the content of the oxide in the recording layer is adjusted by using the simultaneous film formation method of the CoPtCr alloy target and the oxide target. However, the present invention is not limited to this. Sputtering may be performed using a mixed gas of oxide and argon on a target that does not contain an oxide to adjust the oxygen content in the recording layer, and a mixed gas of oxide and argon may be used as a sputtering gas. Further, the oxide content in the recording layer may be adjusted by sputtering using a target in which oxygen is mixed in a CoPtCr alloy.

  In the above embodiment, the magnetic disk and the magnetic tape in which the base layer and the recording layer are laminated on the substrate have been described, but the present invention is not limited to this. If the base layer itself has a function of supporting the recording layer, the substrate may not be provided.

1 shows a cross-sectional structure of a magnetic disk of Example 1. 2 shows a cross-sectional structure of a magnetic disk of Comparative Example 1. The cross-sectional structure of the magnetic disk of the comparative example 2 is shown. The Auger spectroscopic analysis result of Example 1, the comparative example 1, and the comparative example 2 is shown. FIG. 5A is a schematic view of a magnetic recording apparatus including a magnetic disk manufactured according to the present invention, FIG. 5A is a plan view, and FIG. 5B is a cross-sectional view taken along line AA ′ in FIG. is there. The dependence of linear recording density on the recording / reproducing characteristics of the magnetic disks of Example 1, Comparative Example 1 and Comparative Example 2 is shown. The dependence of the recording / reproduction characteristics of the magnetic disks of Example 1 and Example 2 on the linear recording density is shown. 6 shows a cross-sectional structure of a magnetic disk of Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Adhesion layer 3 Soft magnetic backing layer 4 Underlayer 5 Recording layer 6 Protective layer 7 First recording layer 8 Second recording layer 9 Third recording layer 10 Magnetic disk 11 Base film 12 Backcoat layer 60 Magnetic recording device 52 Spindle 53 Magnetic head 54 Magnetic head drive system

Claims (5)

  An underlayer and a recording layer are formed in this order on a nonmagnetic substrate, and the recording layer is an alloy magnetic material mainly composed of CoPtCr containing oxide, and the residual magnetization is perpendicular to the film surface from the in-film direction. A perpendicular magnetic recording type recording medium having a larger direction, wherein the oxide concentration of the recording layer continuously decreases in the film thickness direction from the substrate side in contact with the underlayer.   2. The magnetic recording medium according to claim 1, wherein the oxide content in the recording layer is 5 to 20 mol%.   The magnetic recording medium according to claim 1, wherein the oxide in the recording layer is a Si oxide.   The magnetic recording medium according to claim 1, wherein the recording layer has a thickness of 20 nm or less. 2. A magnetic head for applying magnetization in a direction perpendicular to the film surface of the recording layer to the magnetic recording medium according to claim 1, and driving for driving the magnetic recording medium relative to the magnetic head. And a perpendicular magnetic recording type magnetic recording apparatus.

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