WO2010134612A1

WO2010134612A1 - Perpendicular magnetic recording medium

Info

Publication number: WO2010134612A1
Application number: PCT/JP2010/058673
Authority: WO
Inventors: 猛伯梶原; 藤吉郎佐藤; 貴弘尾上
Original assignee: ダブリュディ・メディア・シンガポール・プライベートリミテッド
Priority date: 2009-05-21
Filing date: 2010-05-21
Publication date: 2010-11-25

Abstract

A perpendicular magnetic recording medium (100) comprises, on a substrate, a magnetic recording layer (122) for recording signals; a foundation layer (118), which is disposed underneath the magnetic recording layer (122) and is formed from Ru or an Ru compound; and a prefoundation layer (116), which is disposed underneath the foundation layer (118), is formed from a non-magnetic crystalline material, and serves to control the crystal orientation of the foundation layer (118). The prefoundation layer (116) comprises Ni as the primary component, W as a second element, and further, Al, Zr, or Si as a third element.

Description

Perpendicular magnetic recording medium

The present invention relates to a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like.

With the recent increase in information processing capacity, various information recording technologies have been developed. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, a 2.5-inch diameter magnetic recording medium used for HDDs or the like has been required to have an information recording capacity exceeding 200 GB per sheet. In order to meet such a demand, one square is required. It is required to realize an information recording density exceeding 400 GB per inch.

In recent years, a perpendicular magnetic recording method has been proposed in order to achieve a high recording density in a magnetic recording medium used for an HDD or the like. The perpendicular magnetic recording medium used for the perpendicular magnetic recording system is adjusted so that the easy axis of magnetization of the magnetic recording layer is oriented in the direction perpendicular to the substrate surface. Compared to the conventional in-plane recording method, the perpendicular magnetic recording method can suppress the so-called thermal fluctuation phenomenon in which the thermal stability of the recording signal is lost due to the superparamagnetic phenomenon, and the recording signal disappears. Suitable for higher recording density.

As a magnetic recording medium used in the perpendicular magnetic recording system, a CoCrPt—SiO ₂ perpendicular magnetic recording medium (see Non-Patent Document 1) has been proposed because it exhibits high thermal stability and good recording characteristics. This is because the magnetic recording layer has a granular structure in which nonmagnetic grain boundary portions in which SiO ₂ is segregated are formed between magnetic particles in which crystals of Co hcp crystal structure (hexagonal close-packed crystal lattice) are continuously grown in a columnar shape. The structure is formed, and the magnetic particles are miniaturized and the coercive force Hc is improved. It is known that an oxide is used for a nonmagnetic grain boundary (a nonmagnetic portion between magnetic grains). For example, any one of SiO ₂ , Cr ₂ O ₃ , TiO, TiO ₂ , and Ta ₂ O ₅ is used. Has been proposed (Patent Document 1).

By the way, as an important factor for increasing the recording density of the magnetic recording medium, improvement of the magnetostatic characteristics such as the above-mentioned coercive force Hc and reverse domain nucleation magnetic field Hn, overwriting characteristics (OW characteristics) and SNR ( Signal Noise 電磁 Ratio) and improvement of electromagnetic conversion characteristics such as narrowing of track width. Several methods for improving these characteristics are known. For example, increasing the film thickness of the magnetic recording layer, improving the crystal orientation of the magnetic recording layer (increasing perpendicular magnetic anisotropy), etc. The method is known.

In particular, a method of providing a Ru underlayer in order to increase the crystal orientation of the magnetic recording layer or a pre-underlayer (seed layer) to further improve the crystal orientation of the Ru underlayer has been conventionally known. ing. For example, Patent Document 2 proposes a perpendicular magnetic recording medium using an alloy containing NiW as a seed layer (pre-underlayer). In Patent Document 2, it is described that the seed layer is formed using a sputtering target containing Ni, and the grain size of the underlayer or the granular magnetic layer deposited subsequently to the seed layer is reduced to reduce lattice mismatch. Yes.

JP 2006-024346 A JP 2007-179598 A

Although the magnetic recording medium has a higher recording density as described above, further improvement of the recording density is demanded in the future. Therefore, in order to achieve further higher recording density of the magnetic recording medium, it is necessary to establish a new method that can further improve the minimization of the OW characteristics, SNR, and track width.

Of the above, the OW characteristic is a characteristic indicating the ease of rewriting the signal of the magnetic recording medium. The OW characteristic and the coercive force Hc are basically in a trade-off relationship, and a strong coercive force Hc means that the magnetization direction is difficult to reverse, so that rewriting is difficult. In order to achieve both the high coercivity and the OW characteristics, it has been considered to further improve the performance of the magnetic head.

However, although the performance of the current magnetic head is evolving, it has not been able to smoothly follow the rapid improvement in coercive force Hc of recent magnetic disks. On the magnetic head side, low power consumption is one of the major issues, and there has been a demand for rewriting without applying a large output.

Further, although paradoxically, if high OW characteristics can be obtained, rewriting is possible even if the coercive force Hc is high, so that it is allowed to increase the coercive force Hc without changing the performance of the magnetic head. . If a film having a high coercive force Hc is used, the thickness of the magnetic recording layer can be reduced. Then, the spacing loss from the magnetic head to the soft magnetic layer can be reduced (narrowed), so that the density can be increased by preventing the diffusion of magnetic flux, and the recording bits can be miniaturized, resulting in a high recording density. Can contribute. Therefore, in order to achieve high recording density, improvement of OW characteristics has become a very important issue as well as development of a film having a high coercive force Hc and improvement of SNR.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a perpendicular magnetic recording medium that can improve OW characteristics and achieve higher recording density.

In order to solve the above problems, the inventors diligently studied and reviewed the substances constituting the pre-underlayer. The experiment was repeated and attention was paid to the fact that the addition of another metal element to the pre-underlayer composed of the NiW alloy changes the OW characteristics while suppressing the decrease in the coercive force Hc. Further, by further research, it was found that a desired state can be derived by adding Al, Zr or Si to the layer, and the present invention has been completed.

That is, in order to solve the above-described problem, a typical configuration of the perpendicular magnetic recording medium according to the present invention includes a magnetic recording layer for recording a signal on a substrate, and a Ru or Ru compound provided below the magnetic recording layer. And an underlayer for controlling the crystal orientation of the underlayer made of a nonmagnetic crystalline material provided under the underlayer, the preunderlayer having Ni as a main component, It is characterized by containing W as the second element and further containing Al, Zr or Si as the third element.

According to the above configuration, the strength ratio of the (111) plane to the (200) plane of the fcc crystal structure of the Ni crystal of the previous underlayer is improved by containing Al, Zr or Si, and the OW characteristics are also improved accordingly. This makes it possible to provide a perpendicular magnetic recording medium that can achieve a higher recording density. Note that the strength ratio between the (111) plane and the (200) plane of the fcc crystal structure of the Ni crystal is improved, so that the Ru crystal orientation of the underlying layer is improved. As a result, the crystal grains of the magnetic recording layer It is presumed that the crystal orientation is improved.

The content of the third element may be 1 at% to 5 at%. With this configuration, the OW characteristics of the perpendicular magnetic recording medium can be improved. On the other hand, if it is 1 at% or less, the desired effect of improving the OW characteristics cannot be obtained, and if it is 5 at% or more, the Ni content is low. The crystal orientation is reduced due to the decrease.

The total content of the second element and the third element may be 3 at% to 20 at%. According to this configuration, when 3 at% or less, Ni becomes magnetic (soft magnetism) and becomes a noise source. On the other hand, when 20 at% or more, Ni becomes amorphous, The crystal orientation cannot be improved. As a result, when the total content of W and Al is 3 at% to 20 at%, the OW characteristics of the perpendicular magnetic recording medium can be improved.

According to the present invention, it is possible to provide a perpendicular magnetic recording medium capable of improving the OW characteristics while maintaining the coercive force Hc and SNR and achieving further higher recording density.

It is a figure explaining the structure of a perpendicular magnetic recording medium. It is the figure which showed the relationship between MEW of Example 1 and SNm. It is the figure which showed the relationship between MEW and SN2 of Example 1. It is the figure which showed the relationship between Hc and Hn of Example 1. It is a figure for demonstrating the result in FIG. 4 of Example 1. FIG. It is a figure for demonstrating the test result of the influence by 3rd element addition. It is a figure which shows the effectiveness of each Example.

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording medium 110 ... Disk base | substrate 112 ... Adhesion layer 114 ... Soft magnetic layer 114a ... Soft magnetic layer 114b ... Soft magnetic layer 116 ... Pre-underlayer 118 ... Underlayer 118a ... Underlayer 118b ... Underlayer 120 ... Nonmagnetic Granular layer 122 ... magnetic recording layer 122a ... magnetic recording layer 122b ... magnetic recording layer 122c ... magnetic recording layer 122d ... magnetic recording layer 124 ... divided layer 126 ... auxiliary recording layer 128 ... media protective layer 130 ... lubricating layer

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

[Perpendicular magnetic recording medium]
A first embodiment of a perpendicular magnetic recording medium according to the present invention will be described. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 according to the present embodiment.

The perpendicular magnetic recording medium 100 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, a pre-underlayer 116, a first underlayer 118a, a second underlayer 118b, The non-magnetic granular layer 120, the lower recording layer 122 a, the intervening layer 122 b, the first main recording layer 122 c, the second main recording layer 122 d, the dividing layer 124, the auxiliary recording layer 126, the medium protective layer 128, and the lubricating layer 130. Yes. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The lower recording layer 122a, the intervening layer 122b, the first main recording layer 122c, and the second main recording layer 122d together constitute the magnetic recording layer 122.

The disk substrate 110 may be a glass disk obtained by forming amorphous aluminosilicate glass into a disk shape by direct pressing. The type, size, thickness, etc. of the glass disk are not particularly limited. Examples of the material of the glass disk include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or glass ceramic such as crystallized glass. It is done. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth non-magnetic disk base 110 made of a chemically strengthened glass disk.

On the disk substrate 110, a film is sequentially formed from the adhesion layer 112 to the auxiliary recording layer 126 by a DC magnetron sputtering method, and the medium protective layer 128 can be formed by a CVD (Chemical Vapor Deposition) method. Thereafter, the lubricating layer 130 can be formed by a dip coating method. Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration and manufacturing method of each layer will be described.

The adhesion layer 112 is formed in contact with the disk substrate 110, has a function of increasing the peel strength between the soft magnetic layer 114 formed on the disk substrate 110 and the disk substrate 110, and a crystal of each layer formed on the soft magnetic layer 114. It has a function to make grains finer and uniform. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous (amorphous) alloy film so as to correspond to the amorphous glass surface.

The adhesion layer 112 can be selected from, for example, a CrTi amorphous layer, a CoW amorphous layer, a CrW amorphous layer, a CrTa amorphous layer, or a CrNb amorphous layer. The adhesion layer 112 may be a single layer made of a single material, or may be formed by laminating a plurality of layers. For example, a CoW layer or a CrW layer may be formed on the CrTi layer. These adhesion layers 112 are preferably formed by sputtering with a material containing carbon dioxide, carbon monoxide, nitrogen, or oxygen, or the surface layer is exposed with these gases.

The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to pass magnetic flux in a direction perpendicular to the recording layer in the perpendicular magnetic recording method. The soft magnetic layer 114 can be configured to have AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 114b between the first soft magnetic layer 114a and the second soft magnetic layer 114c. . As a result, the magnetization direction of the soft magnetic layer 114 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 114 is reduced. Can do. The compositions of the first soft magnetic layer 114a and the second soft magnetic layer 114c include cobalt alloys such as CoTaZr, Co—Fe alloys such as CoCrFeB and CoFeTaZr, and Ni such as [Ni—Fe / Sn] n multilayer structure. An Fe-based alloy or the like can be used.

The pre-underlayer 116 is a non-magnetic alloy layer that protects the soft magnetic layer 114 and the easy magnetization axis of the hexagonal close-packed structure (hcp crystal structure) included in the underlayer 118 formed thereon. Has a function of orienting the disk in the vertical direction of the disk. The pre-underlayer 116 preferably has the (111) plane of the fcc crystal structure parallel to the main surface of the disk substrate 110. Further, the pre-underlayer 116 may have a configuration in which an fcc crystal structure and another structure or an amorphous structure are mixed.

As the material of the pre-underlayer 116 in this embodiment, an alloy containing Ni as a main component, W as the second element, and Al, Zr or Si as the third element is desirable. By including the third element in the pre-underlayer 116 as described above, the OW characteristics can be improved as compared with the conventional pre-underlayer 116 that does not contain the third element.

The coercive force Hc is improved by increasing the Ni content of the NiW alloy in the pre-underlayer 116. This is because the (111) plane of the Ni fcc crystal structure corresponds to (0001) of the hcp crystal structure of the underlayer, thereby improving the crystal orientation of the film above it and improving the coercive force Hc as a whole. It is thought to do. On the other hand, when the ratio of Ni decreases, when the predetermined ratio is exceeded, the crystal structure of the alloy containing Ni becomes amorphous.

That is, the more Ni in the pre-underlayer 116, the better the crystal orientation of the layer above it, and the addition of W promotes the refinement of crystals. Further, when Al, Zr or Si is further added as the third element, the OW characteristics are improved. This is improved by the inclusion of the third element in the intensity ratio between the (111) plane and the (200) plane of the fcc crystal structure of the Ni crystal, and thereby the orientation of the underlayer 118 and the magnetic recording layer 122 thereon. It is presumed that this has led to an improvement.

The pre-underlayer 116 may have a third element content of 1 at% to 5 at%. As described above, the OW characteristics can be improved by adding the third element to NiW. This is because if it is 1 at% or less, the desired effect of improving the OW characteristics cannot be obtained. On the other hand, if the content is 5 at% or more, the Ni content decreases and the crystal orientation deteriorates.

The ratio of the second element W and the third element Al, Zr, or Si in the pre-underlayer is preferably between 3 at% and 20 at%, which is the peak of the OW characteristics. With this configuration, the required performance can be realized. If it is 3 at% or less, Ni becomes magnetized and the front ground layer 116 becomes a noise source. On the other hand, if it is 20 at% or more, Ni becomes amorphous, and the crystal orientation of the layer above it cannot be improved, which is not preferable.

The underlayer 118 has an hcp crystal structure, and has a function of growing a crystal of the Co hcp crystal structure of the magnetic recording layer 122 as a granular structure. Therefore, the higher the crystal orientation of the underlayer 118, that is, the more the (0001) plane of the crystal of the underlayer 118 is parallel to the main surface of the disk substrate 110, the more the orientation of the magnetic recording layer 122 is improved. Can do. Ru is a typical material for the underlayer 118, but in addition, it can be selected from RuCr and RuCo. Since Ru has an hcp crystal structure and the crystal lattice spacing is close to Co, the magnetic recording layer 122 containing Co as a main component can be well oriented.

When the underlayer 118 is made of Ru, a two-layer structure made of Ru can be obtained by changing the gas pressure during sputtering. Specifically, when forming the first underlayer 118a on the lower layer side, the Ar gas pressure is set to a predetermined pressure, that is, a low pressure, and when forming the second underlayer 118b on the upper layer side, the first lower layer 118b on the lower layer side is formed. The gas pressure of Ar is set higher than when forming the first underlayer 118a, that is, the pressure is increased. Thereby, the crystal orientation of the magnetic recording layer 122 can be improved by the first underlayer 118a, and the grain size of the magnetic particles of the magnetic recording layer 122 can be reduced by the second underlayer 118b.

Further, when the gas pressure is increased, the mean free path of the plasma ions to be sputtered is shortened, so that the film formation rate is slow and the film becomes rough, so that separation and refinement of Ru crystal particles can be promoted, Co crystal grains can also be made finer.

Furthermore, a small amount of oxygen may be contained in Ru of the base layer 118. As a result, the separation and refinement of the Ru crystal grains can be further promoted, and the magnetic recording layer 122 can be further isolated and refined. Therefore, in the present embodiment, oxygen is included in the second underlayer formed immediately below the magnetic recording layer in the underlayer 118 constituted by two layers. That is, the second underlayer is made of RuO. Thereby, said advantage can be acquired most effectively. Note that oxygen may be contained by reactive sputtering, but it is preferable to use a target containing oxygen at the time of sputtering film formation.

The nonmagnetic granular layer 120 is a nonmagnetic layer having a granular structure. A nonmagnetic granular layer 120 is formed on the hcp crystal structure of the underlayer 118, and a granular layer of the lower recording layer 122a (that is, the entire magnetic recording layer 122) is grown thereon, thereby initial growth of the magnetic granular layer. It has an action of separating from the stage (rise). Thereby, isolation of the magnetic particles of the magnetic recording layer 122 can be promoted. The composition of the nonmagnetic granular layer 120 can be a granular structure by forming a grain boundary by segregating a nonmagnetic substance between nonmagnetic crystal grains made of a Co-based alloy.

In this embodiment, CoCr—SiO ₂ is used for the nonmagnetic granular layer 120. As a result, SiO ₂ (nonmagnetic substance) segregates between Co-based alloys (nonmagnetic crystal grains) to form grain boundaries, and the nonmagnetic granular layer 120 has a granular structure. Note that CoCr—SiO ₂ is an example, and the present invention is not limited to this. In addition, CoCrRu—SiO ₂ can be preferably used, and Rh (rhodium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Au (gold) can be used instead of Ru. Can also be used. A non-magnetic substance is a substance that can form a grain boundary around magnetic particles so that exchange interaction between magnetic particles (magnetic grains) is suppressed or blocked, and cobalt (Co). Any non-magnetic substance that does not dissolve in solution can be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (Cr ₂ O ₃ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

In this embodiment, the nonmagnetic granular layer 120 is provided on the underlayer 188 (second underlayer 188b). However, the present invention is not limited to this. The recording medium 100 can also be configured.

The magnetic recording layer 122 has a columnar granular structure in which a nonmagnetic substance is segregated around a magnetic particle of a hard magnetic material selected from a Co alloy, an Fe alloy, and a Ni alloy to form a grain boundary. Yes. By providing the nonmagnetic granular layer 120, the magnetic particles can be epitaxially grown continuously from the granular structure. In this embodiment, the magnetic recording layer 122 includes a lower recording layer 122a, an intervening layer 122b, a first main recording layer 122c, and a second main recording layer 122d. Thereby, small crystal grains of the first main recording layer 122c and the second main recording layer 122d continue to grow from the crystal grains (magnetic particles) of the lower recording layer 122a, and the main recording layer can be miniaturized. SNR can be improved.

In this embodiment, CoCrPt—Cr ₂ O ₅ —SiO ₂ is used for the lower recording layer 122a. In CoCrPt—Cr ₂ O ₅ —SiO ₂ , Cr ₂ O ₅ and SiO ₂ (oxide), which are nonmagnetic substances, segregate around magnetic particles (grains) made of CoCrPt to form grain boundaries, and magnetic A granular structure is formed in which particles grow in a columnar shape. The magnetic particles were epitaxially grown continuously from the granular structure of the nonmagnetic granular layer 120.

The intervening layer 122b is a non-magnetic thin film, and is interposed between the lower recording layer 122a and the first main recording layer 122c, so that the magnetic continuity between them is divided. At this time, by setting the thickness of the intervening layer 122b to a predetermined thickness (0.7 to 0.9 nm), antiferromagnetic exchange coupling (AFC) is established between the lower recording layer 122a and the first main recording layer 122c. ) Occurs. As a result, magnetization is attracted between the upper and lower layers of the intervening layer 122b and acts to fix the magnetization directions to each other, so that fluctuations in the magnetization axis can be reduced and noise can be reduced.

The intervening layer 122b may be made of Ru or a Ru compound. This is because Ru has an atomic interval close to that of Co constituting the magnetic particles, and thus it is difficult to inhibit the epitaxial growth of Co crystal particles even if it is interposed between the magnetic recording layers 122. In addition, even if the intervening layer 122b is extremely thin, it is difficult to inhibit the epitaxial growth.

Here, the lower recording layer 122a is a magnet that is continuous with the first main recording layer 122c and the second main recording layer 122d without the intervening layer 122b. Become. Further, by reducing the film thickness of the lower recording layer 122a, the aspect ratio of the granular magnetic particles is shortened (in the perpendicular magnetic recording medium, the film thickness direction corresponds to the longitudinal direction of the easy axis of magnetization). The demagnetizing field generated inside becomes stronger. For this reason, although the lower recording layer 122a is hard magnetic, the magnetic moment to be exposed to the outside becomes small and it is difficult to be picked up by the magnetic head. That is, by adjusting the film thickness of the lower recording layer 122a, the magnetic moment (magnet strength) is such that the magnetic flux does not easily reach the magnetic head and has a magnetic interaction with the first main recording layer 122c. ), A magnetic recording layer with low noise while exhibiting a high coercive force can be obtained.

In the present embodiment, the first main recording layer 122c is made of CoCrPt—SiO ₂ —TiO ₂ . As a result, also in the first main recording layer 122c, nonmagnetic materials such as SiO ₂ and TiO ₂ (composite oxide) are segregated around the magnetic grains (grains) made of CoCrPt to form grain boundaries, and the magnetic grains Formed a granular structure with columnar growth.

In the present embodiment, the second main recording layer 122d is continuous with the first main recording layer 122c, but the composition and film thickness are different. The second main recording layer 122d is made of CoCrPt—SiO ₂ —TiO ₂ —Co ₃ O ₄ . As a result, also in the second main recording layer 122d, nonmagnetic materials such as SiO ₂ , TiO ₂ , and Co ₃ O ₄ (composite oxide) are segregated around the magnetic grains (grains) made of CoCrPt to form grain boundaries. As a result, a granular structure in which magnetic grains were grown in a columnar shape was formed.

As described above, in the present embodiment, the second main recording layer 122d includes a larger amount of oxide than the first main recording layer 122c. Thereby, separation of crystal grains can be promoted stepwise from the first main recording layer 122c to the second main recording layer 122d.

Further, as described above, the second main recording layer 122d contains Co oxide. When SiO ₂ or TiO ₂ is mixed as an oxide, there is a fact that oxygen deficiency occurs, Si ions or Ti ions are mixed into the magnetic particles, the crystal orientation is disturbed, and the holding force Hc is reduced. Therefore, by containing Co oxide, it can function as an oxygen carrier for compensating for this oxygen deficiency. Co ₃ O ₄ is exemplified as the Co oxide, but CoO may be used.

Co oxide has Gibbs liberalization energy ΔG larger than that of SiO ₂ or TiO ₂ , and Co ions and oxygen ions are easily separated. Therefore, oxygen is preferentially separated from the Co oxide, and oxygen vacancies generated in SiO ₂ and TiO ₂ are compensated to complete Si and Ti ions as oxides, which can be precipitated at grain boundaries. Thereby, it can prevent that foreign materials, such as Si and Ti, mix in a magnetic particle, and can prevent disordering the crystallinity of a magnetic particle by the mixing. At this time, surplus Co ions are considered to be mixed in the magnetic particles, but since the magnetic particles are a Co alloy in the first place, the magnetic properties are not impaired. Accordingly, the crystallinity and crystal orientation of the magnetic particles are improved, and the coercive force Hc can be increased. Further, since the saturation magnetization Ms is improved, there is an advantage that the overwrite characteristic is also improved.

However, when Co oxide is mixed in the magnetic recording layer, there is a problem that the SNR is lowered. Therefore, by providing the first main recording layer 122c not mixed with Co oxide as described above, a high SNR is secured in the first main recording layer 122c, while a high holding force Hc and overload are achieved in the second main recording layer 122d. Light characteristics can be obtained. The second main recording layer 122d is preferably thicker than the first main recording layer 122c. As a preferred example, the first main recording layer 122c is 2 nm and the second main recording layer 122d is 8 nm. be able to.

The materials used for the lower recording layer 122a, the first main recording layer 122c, and the second main recording layer 122d described above are merely examples, and the present invention is not limited thereto. Examples of nonmagnetic substances for forming grain boundaries include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and oxidation. Examples of the oxide include tantalum (Ta ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), and boron oxide (B ₂ O ₃ ). Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used.

Furthermore, in the present embodiment, two types of nonmagnetic substances (oxides) are used in the lower recording layer 122a and the first main recording layer 122c, and three types of nonmagnetic substances (oxides) are used in the second main recording layer 122d. Absent. For example, in any or all of the lower recording layer 122a to the second main recording layer 122d, one type of nonmagnetic material may be used, or two or more types of nonmagnetic materials may be used in combination. . Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to contain SiO ₂ and TiO ₂ as in this embodiment. Therefore, unlike the present embodiment, when the second recording layer 122d is composed of only one layer from the lower recording layer 122a (when the intervening layer 122b is not provided), the magnetic recording layer is CoCrPt—SiO ₂ —TiO _2. ₂ is preferable.

The dividing layer 124 is a nonmagnetic layer provided between the magnetic recording layer 122 (second main recording layer 122d) and the auxiliary recording layer 126. However, the dividing layer 124 is formed thicker than the intervening layer 122b. Thereby, not the antiferromagnetic exchange coupling but the ferromagnetic exchange coupling occurs as a magnetic effect between the magnetic recording layer 122 and the auxiliary recording layer 126. Thereby, the magnetic recording layer 122 acts as a pinned layer (magnetization direction fixed layer) with respect to the auxiliary recording layer 126, and noise caused by the auxiliary recording layer 126 can be reduced and SNR can be improved.

In the present embodiment, the dividing layer 124 can be constituted by a thin film containing Ru, a Ru compound, Ru and oxygen, or Ru and an oxide. This can also reduce noise caused by the auxiliary recording layer 126. When the dividing layer 124 is formed, oxygen contained in the dividing layer 124 is segregated on the oxide of the magnetic recording layer 122, and Ru is segregated on the magnetic particles. This is because the crystal structure of the auxiliary recording layer 126 can be inherited to Co.

Various oxides are conceivable as the oxide contained in Ru of the split layer 124. In particular, by using oxides of W, Ti, and Ru, electromagnetic conversion characteristics (SNR) can be improved. For example, the dividing layer 124 may be RuO, RuWO ₃ , or RuTiO ₂ . Among them, WO ₃ can obtain a high effect.

This is presumably because oxygen contained in Ru is dissociated during sputtering, and the dissociated oxygen also exhibits the effect of oxygen addition. That is, the use of WO ₃ is preferable because it can have both the effect of adding oxygen and the effect of adding oxide. Other examples of the oxide include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O). ₅ ), oxides such as iron oxide (Fe ₂ O ₃ ) and boron oxide (B ₂ O ₃ ). Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used.

The auxiliary recording layer 126 is a magnetic layer that is substantially magnetically continuous in the in-plane direction of the main surface of the substrate. The auxiliary recording layer 126 needs to be adjacent or close to the magnetic recording layer 122 so as to have a magnetic interaction. As the material of the auxiliary recording layer 126, for example, CoCrPt, CoCrPtB, or a small amount of oxides can be contained in these. The purpose of the auxiliary recording layer 126 is to adjust the reverse domain nucleation magnetic field Hn and the coercive force Hc, thereby improving the heat-resistant fluctuation characteristics, the OW characteristics, and the SNR. In order to achieve this object, it is desirable that the auxiliary recording layer 126 has high perpendicular magnetic anisotropy Ku and saturation magnetization Ms. In this embodiment, the auxiliary recording layer 126 is provided above the magnetic recording layer 122, but may be provided below.

In addition, “magnetically continuous” means that magnetism is continuous. “Substantially continuous” means that the magnetism may be discontinuous due to grain boundaries of crystal grains, etc., instead of a single magnet when observed in the entire auxiliary recording layer 126. The grain boundaries are not limited to crystal discontinuities, and Cr may be segregated, and further, a minute amount of oxide may be contained and segregated. However, even when a grain boundary containing an oxide is formed in the auxiliary recording layer 126, it is preferable that the area is smaller than the grain boundary of the magnetic recording layer 122 (the content of the oxide is small). Although the function and action of the auxiliary recording layer 126 are not necessarily clear, Hn and Hc can be adjusted by having a magnetic interaction (perform exchange coupling) with the granular magnetic particles of the magnetic recording layer 122, and heat resistance. It is thought that fluctuation characteristics and SNR are improved. In addition, since the crystal particles (crystal particles having magnetic interaction) connected to the granular magnetic particles have a larger area than the cross-section of the granular magnetic particles, the magnetization is easily reversed by receiving a large amount of magnetic flux from the magnetic head. It is thought to improve the characteristics.

The medium protective layer 128 can be formed by depositing carbon by a CVD method while maintaining a vacuum. The medium protective layer 128 is a layer for protecting the perpendicular magnetic recording medium 100 from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording medium 100 can be more effectively protected against the impact from the magnetic head.

The lubricating layer 130 can be formed of PFPE (perfluoropolyether) by dip coating. PFPE has a long chain molecular structure and binds with high affinity to N atoms on the surface of the medium protective layer 128. Due to the action of the lubricating layer 130, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100, the medium protective layer 128 can be prevented from being damaged or lost.

In addition, the perpendicular magnetic recording medium 100 according to the present embodiment can improve the OW characteristics by adding Al, Zr, or Si as the third element to the pre-underlayer 116 as described above. This is because the intensity ratio between the (111) plane and the (200) plane of the fcc crystal structure of the Ni crystal of the pre-underlayer 116 is improved by containing Al, Zr or Si. It is presumed that this leads to an improvement in the orientation of the recording layer 122.

Through the above manufacturing process, the perpendicular magnetic recording medium 100 could be obtained. Next, Example 1 according to the present embodiment will be described.

Example 1
On the disk substrate 110, a film was formed in order from the adhesion layer 112 to the auxiliary recording layer 126 in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated. The adhesion layer 112 was made of CrTi. In the soft magnetic layer 114, the composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c was CoFeTaZr, and the composition of the spacer layer 114b was Ru.

The pre-underlayer 116 was formed using a target containing Ni, W, and Al as the third element while applying a DC bias (−300 V to −500 V) to the substrate. In Example 1, two samples of 95Ni-4W-1Al and 93Ni-4W-3Al were prepared.

As the first underlayer 118a, a Ru film was formed in an Ar atmosphere at a predetermined pressure (low pressure: for example, 0.6 to 0.7 Pa). As the second underlayer 118b, a Ru (RuO) film containing oxygen is formed in an Ar atmosphere at a pressure higher than a predetermined pressure (high pressure: for example, 4.5 to 7 Pa) using a target containing oxygen. did. The composition of the nonmagnetic granular layer 120 was nonmagnetic CoCr—SiO ₂ . The lower recording layer 122a contains Cr ₂ O ₅ and SiO ₂ as examples of oxides in the grain boundary portion, and formed a hcp crystal structure of CoCrPt—Cr ₂ O ₅ —SiO ₂ . The intervening layer 122b was formed from Ru. The first main recording layer 122c contained SiO ₂ and TiO ₂ as examples of complex oxides (plural types of oxides) at the grain boundary portion, and formed an hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ . The second main recording layer 122d contains SiO ₂ , TiO _2, and Co ₃ O ₄ as examples of complex oxides (plural types of oxides) at the grain boundary, and CoCrPt—SiO ₂ —TiO ₂ —Co _3. An O ₄ hcp crystal structure was formed. The dividing 124 formed from RuWO _3. The composition of the auxiliary recording layer 126 was CoCrPtB. The medium protective layer 128 was formed using C ₂ H ₄ and CN by the CVD method, and the lubricating layer 130 was formed using PFPE by the dip coating method.

(Evaluation test)
Below, the effectiveness of this embodiment is evaluated using 95Ni-4W-1Al among the two samples of Example 1 according to the above embodiment, and the test results are shown in FIG. 2, FIG. 3, FIG. This will be described with reference to FIG. In Comparative Example 1, the pre-underlayer 116 was 95Ni-5W. The configuration described above is used except for the pre-underlayer 116.

FIG. 2 shows the relationship between MEW (Magnet Erase Width) and SNm (Write / Read at a medium frequency) by changing the composition ratio of the pre-underlayer 116. Note that MEW is a track width including an erase width, and SNm is an SNR (Signal Noise Ratio) when a write / read test is performed at a medium frequency. When Example 1 and Comparative Example 1 shown in FIG. 2 are compared, although Example 1 has a tendency that SNm is slightly lower than that of Comparative Example 1, MEW is significantly smaller (narrower). From this, it can be seen that, as in Example 1, the addition of Al to the pre-underlayer 116 promotes the narrowing of the track width.

FIG. 3 shows the relationship between MEW and SN2 by changing the composition ratio of the pre-underlayer 116. SN2 is an SNR when a write / read test is performed at a predetermined high frequency (2T). When Example 1 and Comparative Example 1 shown in FIG. 3 are compared, Example 1 has a tendency that the MEW becomes narrower than Comparative Example 1, and SN2 is also greatly improved. From this, it can be seen that the addition of Al to the pre-underlayer 116 as in Example 1 promotes the narrowing of the track width and the improvement of the SNR in the high frequency region. From this, it can be seen that high recording density of the magnetic recording medium can be achieved by adding Al to the pre-underlayer 116.

FIG. 4 shows the relationship between the coercive force Hc and the reverse domain nucleation magnetic field Hn (hereinafter, simply referred to as “Hn”) by changing the composition ratio of the pre-underlayer 116. When Example 1 and Comparative Example 1 shown in FIG. 5 are compared, the coercive force Hc of Example 1 shows a value in the almost same range as Comparative Example 1, but Example 1 has an improvement in Hn over Comparative Example 1. You can confirm that The results shown in FIG. 4 will be described below with reference to FIG.

FIG. 5 is a diagram showing the result shown in FIG. 4 as a hysteresis curve. In Example 1, compared with Comparative Example 1, Hc is almost equal, while Hn is improved. Therefore, the slope of the hysteresis curve drawn from Example 1 is higher than that of Comparative Example 1 (changes in the direction in which the hysteresis curve stands). Thus, when the hysteresis curve stands, it means that the saturation magnetic field Hs becomes small, and it is proved that the OW characteristics are improved.

Hereinafter, the effect of the third element addition will be evaluated using FIG. 6 and the test results will be described. The at% of Ni was appropriately changed according to the at% of other elements. In Example 1, 1 or 3 at% Al was added as a third element to Ni-4W as described above. In Example 2, 1, 3, 5, 10, 20 at% Al was added as a third element to Ni-5W. In Example 3, 1 or 3 at% of Zr was added as a third element to Ni-5W. In Example 4, 1, 3, 5 at% Si was added as a third element to Ni-5W. A comparative example is Ni-5W with no third element added. Other configurations are the same as those in the first embodiment.

FIG. 6 shows the relationship between the addition amount of the third element and the intensity ratio of the (111) plane and the (200) plane of the fcc crystal structure by X-ray diffraction. The (111) plane and the (200) plane are diffraction planes that satisfy the conditions of Bragg's law and cause diffraction, and (111) and (200) indicate the Miller index (hkl) of the diffraction plane. Comparing the comparative example with Examples 1 to 4, it can be confirmed that the strength ratio is improved by adding the third element. That is, the strength of the fcc (111) plane is increased, which indicates that the crystal orientation of the underlayer 118 having the hcp crystal structure can be improved. This is because a hexagonal shape is formed on the (111) plane of the fcc crystal structure of the pre-underlayer 116, so that the (0001) plane of the hcp crystal structure of the underlayer 118 is formed and the C axis is directed in the vertical direction. This is because it is considered that crystals grow in a state.

Further, in both Example 1 and Example 3, when the addition amount of the third element is 3 at%, the strength ratio is lower than when 1 at% is added. Therefore, the amount of the third element added is preferably about 1 at%. However, referring to Example 2, when Al is added to Ni-5W, the strength ratio decreases when the addition amount of the third element exceeds about 5 at%. Therefore, when the third element is Al, it can be seen that the addition amount is preferably 5 at% or less. Note that, as described above, if the total content of the second element and the third element exceeds 20 at%, Ni becomes amorphous and the fcc crystal structure cannot be maintained, so the contents of the second element and the third element Is preferably 3 at% to 20 at%.

From these facts, by adding the third element in the range of 1 at% to 5 at%, the strength ratio of the (111) plane to the (200) plane of the fcc crystal structure is improved, and accordingly, the underlying layer thereon The orientation of 118 and the magnetic recording layer 122 is also improved. This can contribute to the improvement of the OW characteristics of the perpendicular magnetic recording medium 100.

Hereinafter, the effect of the addition of the third element will be evaluated using FIG. 7 and the test results will be described. FIG. 7 is a diagram showing the effectiveness of each embodiment. FIG. 7A is a table showing the compositions of Examples and Comparative Examples and measured values in each measurement item, and FIG. 7B is a graph showing the relationship between MEW and SNR in FIG. 7B.

As shown in FIG. 7A, in Examples 5 to 7, two kinds of third elements are added in the range of 1 at% to 5 at%, respectively. In Example 5, 1 at% Al was added to Ni-4W as the first third element, and 1, 3, 5 at% Si was added as the other third element. In Example 6, 1 at% Si was added as the first third element to Ni-4W, and 1, 3, 5 at% Al was added as the other third element. In Example 7, 1 at% Al was added as the first third element to Ni-4W, and 1 at% Zr was added as the other third element. In addition, about the composition of Example 1 and a comparative example, it is the same as that of FIG.

Referring to the film thickness and the coercive force Hc in FIG. 7A, the coercive force Hc is comparable even though each example has a smaller film thickness than the comparative example. This indicates that the coercive force Hc is improved by the addition of the third element, so that the same coercive force Hc as that of the comparative example can be secured even if the film thickness is reduced. Further, referring to the item of Hn, the value of Hn in each embodiment is improved as compared with the comparative example. This indicates that the crystallinity is improved by the addition of the third element.

Refer to FIG. 7 (b). When the comparative example shown in FIG. 7D is compared with each embodiment, in each embodiment, the MEW is narrowed and the SNR is improved by the addition of the third element. In particular, Example 5 and Example 6 achieve good values for both MEW and SNR.

As described above, from FIG. 7B, it is possible to accurately promote the narrowing of the track width and the improvement of the SNR by adding two kinds of elements of Al and Si as the third element. I can see it. Therefore, it is possible to contribute to further improvement of the OW characteristics of the perpendicular magnetic recording medium 100.

As mentioned above, although the suitable Example of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

The present invention can be used for a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like.

Claims

On the substrate,
A magnetic recording layer for recording signals;
An underlayer made of Ru or a Ru compound provided below the magnetic recording layer;
A pre-underlayer for controlling the crystal orientation of the underlayer comprising a non-magnetic crystalline material provided under the underlayer;
With
2. The perpendicular magnetic recording medium according to claim 1, wherein the pre-underlayer includes Ni as a main component, W as a second element, and Al, Zr, or Si as a third element.
2. The perpendicular magnetic recording medium according to claim 1, wherein the content of the third element is 1 at% to 5 at%.
2. The perpendicular magnetic recording medium according to claim 1, wherein the total content of the second element and the third element is 3 at% to 20 at%.