JP2010097680A - Vertical magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical magnetic recording medium which improves SNR by reducing noise coming from a subsidiary recording layer and achieves higher recording density. <P>SOLUTION: A representative configuration of the vertical magnetic recording medium 100 includes on a base substance at least: a granular structure magnetic recording layer 122 which forms a non-magnetic grain boundary between crystal grains grown in a columnar shape; a non-magnetic segmented layer 124 including Ru and oxygen on the magnetic recording layer 122; and the subsidiary magnetic recording layer 126 almost magnetically continuous in the in-plane direction of the main surface of the base substance 110 on the segmented layer 124. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, 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 GBytes 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 system 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 a granular structure in which a nonmagnetic grain boundary portion in which SiO ₂ is segregated is formed between magnetic grains in which Co hcp structure (hexagonal close-packed crystal lattice) crystals are continuously grown in a columnar shape in a magnetic recording layer. The magnetic particles are made finer 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).

  However, when a strong magnetic field is applied to the magnetic recording layer, the leakage magnetic field to the adjacent track also increases, so that recorded information disappears over several μm centering on the WAIT (Wide Area Track Erasure), that is, the track to be written. The phenomenon becomes a problem. As a technique for reducing WATE, it is important to make the reverse domain nucleation magnetic field Hn of the magnetic recording layer negative and further increase its absolute value. In order to obtain high (large absolute value) Hn, a CGC (Coupled Granular Continuous) medium in which a thin film exhibiting high perpendicular magnetic anisotropy is formed above or below a magnetic recording layer having a granular structure has been devised. (Patent Document 2).

  In general, if the coercive force Hc of the magnetic recording layer is improved, a higher recording density can be achieved, but writing with a magnetic head tends to be difficult. Therefore, the auxiliary recording layer also has a role of improving the ease of writing, that is, the overwrite characteristic by improving the saturation magnetization Ms. In other words, the purpose of providing the auxiliary recording layer on the magnetic recording layer is to improve the reverse domain nucleation magnetic field Hn to reduce noise, to improve the saturation magnetization Ms, and to improve the overwrite characteristics. The auxiliary recording layer may be called a continuous layer or a cap layer.

JP 2006-024346 A JP 2003-346315 A

T. Oikawa et.al., IEEE Trans. Magn, vol.38, 1976-1978 (2002)

  Although the magnetic recording medium has a higher recording density as described above, further improvement in the recording density is required in the future. Important factors for achieving high recording density include improved magnetostatic characteristics such as coercivity Hc and reverse domain nucleation magnetic field Hn, overwrite characteristics (OW characteristics), and SNR (Signal to Noise Ratio). ) And improved electromagnetic conversion characteristics such as narrowing of the track width. Among them, the improvement of the coercive force Hc and the improvement of the SNR are important for reading and writing accurately and at high speed even in a recording bit having a small area.

  The SNR is improved mainly by reducing the magnetization transition region noise of the magnetic recording layer. Factors effective for noise reduction include improvement of the crystal orientation of the magnetic recording layer, refinement of the particle size of the magnetic particles, and isolation of the magnetic particles. Above all, when the isolation of the magnetic particles is promoted, the magnetic interaction with the adjacent magnetic particles is blocked, so that the noise can be greatly reduced and the SNR can be remarkably improved. In the above-mentioned granular structure perpendicular magnetic recording medium, the grain boundary is formed by an oxide, thereby isolating and miniaturizing the magnetic particles to improve the SNR.

  However, the auxiliary recording layer does not have a granular structure, and has a structure that is magnetically continuous in the in-plane direction. For this reason, although the overwrite characteristics can be improved by the auxiliary recording layer, noise is increased. In particular, since the auxiliary recording layer is positioned above the medium, the influence on the increase in noise is large. However, without the auxiliary recording layer, the OW characteristics become extremely low, and the current magnetic recording layer having a high coercive force can no longer be written. For this reason, it was necessary to tolerate a certain amount of noise.

  Therefore, since it is difficult to further improve the SNR using the above-described technique, a new recording medium that can further improve the SNR of the magnetic recording layer can be achieved to achieve a higher recording density of the magnetic recording medium. Establishing a method has been an issue.

  In view of such problems, the present invention provides a perpendicular magnetic recording medium that can reduce noise considered to be caused by an auxiliary recording layer to improve SNR and achieve higher recording density. With the goal.

  As a result of extensive studies by the inventors in order to solve the above problems, the inventors have focused on the fact that the magnetic recording layer and the auxiliary recording layer have extremely different structures. That is, the magnetic recording layer has a granular structure, whereas the auxiliary recording layer has a uniform film structure in the in-plane direction. Therefore, it was considered that forming the auxiliary recording layer on the magnetic recording layer may affect the fine structure of the auxiliary recording layer. Further, through further research, the auxiliary recording layer can be reduced in noise by interposing a nonmagnetic dividing layer containing Ru and oxygen between the magnetic recording layer and the auxiliary recording layer, and the above problems can be solved. As a result, the present invention has been completed.

  That is, in order to solve the above problems, a typical configuration of the perpendicular magnetic recording medium according to the present invention has a granular structure in which a nonmagnetic grain boundary is formed at least between crystal grains grown in a columnar shape on a substrate. A magnetic recording layer; a nonmagnetic dividing layer containing Ru and oxygen provided on the magnetic recording layer; and an auxiliary recording layer provided on the dividing layer and substantially magnetically continuous in the in-plane direction of the main surface of the substrate. It is characterized by providing.

  According to the above configuration, it is possible to improve the SNR by reducing noise considered to be caused by the auxiliary recording layer. This is presumably because the exchange coupling between the auxiliary recording layer and the magnetic recording layer is appropriately adjusted by providing a dividing layer containing Ru and oxygen between the magnetic recording layer and the auxiliary recording layer. In addition, when oxygen is included in the dividing layer, it has a high affinity with the oxide that constitutes the grain boundary of the magnetic recording layer, so that oxygen atoms in the dividing layer are selectively deposited and unevenly distributed on the grain boundary. . Thereby, separation of the auxiliary recording layer is promoted, and noise caused by the auxiliary recording layer is suppressed. Also, the Co crystal orientation of the auxiliary recording layer as a whole is improved by the effect of Ru.

  The dividing layer can be made of Ru and oxide as one of specific means for containing Ru and oxygen. This is because, when sputtering is performed using a target including Ru and an oxide, oxygen dissociated from the oxide is contained in the film, and thus the same effect as that of addition of oxygen is achieved.

The oxide may be WO ₃ , TiO ₂ , or RuO. Various oxides can be considered, and in particular, by using oxides of W (tungsten), Ti (titanium), and Ru (ruthenium), electromagnetic conversion characteristics (SNR) can be improved. Among them, WO ₃ can obtain a high effect. This is because WO ₃ is an unstable oxide, so that more oxygen is dissociated during sputtering and the effect of oxygen addition is more effectively exhibited.

  The thickness of the dividing layer may be 2 to 10 mm (0.2 to 1 nm). If the thickness of the dividing layer is 10 mm or more, the magnetic recording layer and the auxiliary recording layer are completely separated from each other, so that a desired SNR cannot be obtained. On the other hand, if the film thickness is 2 mm or less, the film cannot be formed. Here, the film does not necessarily have to be a continuous film. For example, even if the film is deposited in an island shape, there is no problem if the function can be exhibited.

  The magnetic recording layer may contain two or more kinds of oxides. As a result, the characteristics of a plurality of oxides can be obtained, noise can be reduced by further miniaturization and isolation of the magnetic particles in the magnetic recording layer, and SNR can be improved to increase the recording density. Can be obtained.

The magnetic recording layer may contain SiO ₂ and TiO ₂ as oxides. SiO ₂ promotes miniaturization and isolation of magnetic particles, and TiO ₂ has a characteristic of improving electromagnetic conversion characteristics (especially SNR). By combining these oxides and segregating at the grain boundaries of the magnetic recording layer, both benefits can be obtained.

  The magnetic recording layer may contain 5 mol% or more of an oxide constituting the grain boundary part. When the content is 5 mol% or more, high magnetostatic characteristics and electromagnetic conversion characteristics can be obtained, and in such a range, the characteristics of the auxiliary recording layer are deteriorated to a degree that cannot be ignored. This is because improvement of the above can be obtained.

  The magnetic recording layer may include a first main recording layer that does not include a Co oxide and a second main recording layer that is provided on the first main recording layer and includes at least a Co oxide.

  As described above, in the magnetic recording layer, a granular structure having a grain boundary portion between magnetic grains is formed, and the grain boundary portion is formed by precipitating an oxide contained in the magnetic recording layer. . In such a magnetic recording layer containing an oxide, the element as a simple substance tends to be taken into the magnetic particles (oxygen vacancies are generated) by desorption of oxygen from the oxide. When such a phenomenon occurs, the crystallinity and crystal orientation of the magnetic particles are lowered, and the coercive force Hc is lowered.

  Therefore, at least a Co oxide (Co oxide) is used as the oxide constituting the grain boundary portion. Co oxide has a large Gibbs liberalization energy ΔG, and Co ions and oxygen ions are easily separated. For this reason, oxygen is desorbed preferentially from the Co oxide, and oxygen vacancies generated in the oxide included in the magnetic recording layer can be compensated. Therefore, it is possible to prevent the elements constituting the oxide from being mixed into the magnetic particles and improve the crystallinity and crystal orientation of the magnetic particles.

  However, when Co oxide is contained in the entire magnetic recording layer, the SNR is lowered. Therefore, in the above configuration, the magnetic recording layer is composed of the first main recording layer and the second main recording layer, and only the second main recording layer contains Co oxide. This makes it possible to obtain a high coercivity Hc with the second main recording layer while securing a high SNR with the first main recording layer. As described above, when oxygen is desorbed from the Co oxide, Co ions are generated. However, since the magnetic particles are a Co alloy, even if such Co ions are mixed into the magnetic particles, the magnetic properties are not deteriorated. Absent.

  The perpendicular magnetic recording medium further includes an underlayer made of Ru or a Ru compound provided below the magnetic recording layer, and the dividing layer is formed by a Ru having a gas pressure lower than the gas pressure at the time of forming the underlayer. A layer consisting of

  A film formed by sputtering has a low density (coarse state) as the gas pressure during film formation is increased, and becomes a high density (dense state) as the gas pressure is decreased. Therefore, according to the above configuration, the dividing layer is a coating with a higher density than the underlayer. When the density of the film is low, the metal deposited from below the layer formed on the perpendicular magnetic recording medium passes through the film and reaches the surface of the medium, causing corrosion. In other words, if the density of the film is high, the film can prevent the deposited metal from reaching the medium surface. In addition, since the magnetic recording layer has a granular structure in which an oxide is precipitated at the grain boundary (grain boundary part), the film density is rough and corrosion resistance cannot be expected. On the other hand, corrosion resistance can be improved by interposing the metal layer which does not contain an oxide like the said structure. In addition, if the density is increased by forming the metal layer at a low gas pressure, it is possible to prevent the deposited metal from reaching the surface of the medium very effectively and to prevent the occurrence of corrosion.

  In order to solve the above problems, another configuration of the perpendicular magnetic recording medium according to the present invention includes a granular magnetic recording layer in which a nonmagnetic grain boundary portion is formed between crystal grains grown at least on a substrate. A nonmagnetic dividing layer containing Ru and oxygen provided on the magnetic recording layer, and an auxiliary recording layer provided on the dividing layer and substantially magnetically continuous in the in-plane direction of the main surface of the substrate. The magnetic recording layer includes a first magnetic recording layer that is provided above the substrate and includes an oxide that forms a grain boundary portion, and a larger amount of oxide provided on the first magnetic recording layer than the first magnetic recording layer. A second magnetic recording layer including the first main recording layer provided on the first magnetic recording layer and not including the Co oxide; and the second magnetic recording layer provided on the first main recording layer. And a second main recording layer containing at least a Co oxide.

  Also in the perpendicular magnetic recording medium having such a configuration, the above-described advantages can be obtained, and further higher recording density can be achieved.

  According to the present invention, it is possible to provide a perpendicular magnetic recording medium that can reduce noise considered to be caused by the auxiliary recording layer, improve the SNR, and achieve a higher recording density.

It is a figure explaining the structure of a perpendicular magnetic recording medium. It is a figure which shows the Example and comparative example by the composition of a division | segmentation fault. It is a figure which shows the Example by the combination of the oxide of a magnetic layer, and a comparative example. It is a TEM photograph of an auxiliary recording layer of an example and a comparative example. It is a figure explaining the structure of the perpendicular magnetic recording medium concerning 2nd Embodiment. It is a figure explaining SNR in the perpendicular magnetic recording medium in which the 2nd magnetic recording layer is comprised from several layers.

  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.

(Embodiment)
In the first embodiment, the first embodiment of the perpendicular magnetic recording medium according to the present invention will be described first, and then the dividing layer provided between the magnetic recording layer and the auxiliary recording layer will be described in detail.

[Perpendicular magnetic recording medium]
FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 according to the first embodiment. The perpendicular magnetic recording medium 100 shown in FIG. 1 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, and a second layer. The underlayer 118b, the nonmagnetic granular layer 120, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the dividing layer 124, the auxiliary recording layer 126, the medium protective layer 128, and the lubricating layer 130 are formed. 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 first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

  As the disk substrate 110, a glass disk obtained by forming amorphous aluminosilicate glass into a disk shape by direct pressing can be used. 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 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 of each layer will be described.

  The adhesion layer 112 is formed in contact with the disk substrate 110, and 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 the crystal grains of each layer formed thereon are finely divided. It has a function to make it uniform 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, and a CrNb amorphous layer. Among these, a CoW alloy film is particularly preferable because it forms an amorphous metal film containing microcrystals. 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 allow magnetic flux to pass through the magnetic recording layer 122 in the perpendicular direction in the perpendicular magnetic recording method. The soft magnetic layer 114 is provided with 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. Can be configured. 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 composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c is as follows. Co-based alloys such as CoTaZr, Co-Fe based alloys such as CoCrFeB, and Ni-Fe such as [Ni-Fe / Sn] n multilayer structure. A system alloy or the like can be used.

  The pre-underlayer 116 is a nonmagnetic alloy layer that protects the soft magnetic layer 114 and the easy axis of magnetization of the hexagonal close-packed structure (hcp 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 a (111) plane of a face-centered cubic structure (fcc structure) parallel to the main surface of the disk substrate 110. Further, the pre-underlayer 116 may have a configuration in which these crystal structures and amorphous are mixed. The material of the pre-underlayer 116 can be selected from Ni, Cu, Pt, Pd, Zr, Hf, Nb, and Ta. Furthermore, it is good also as an alloy which has these metals as a main component and contains any one or more additional elements of Ti, V, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected as an alloy having an fcc structure.

  The underlayer 118 has an hcp structure, and has a function of growing a Co hcp crystal 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 structure and the lattice spacing of crystals 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.

  Further, 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. 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 non-magnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and a granular layer of the first magnetic recording layer 122a (or magnetic recording layer 122) is grown thereon, whereby the magnetic granular layer is initially formed. It has the effect of separating from the growth 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 the present 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 nonmagnetic substance is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is 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 (CrO ₂ ), 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, and the nonmagnetic granular layer 120 is not provided. 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-based alloy, an Fe-based alloy, and a Ni-based alloy to form a grain boundary. Yes. By providing the nonmagnetic granular layer 120, the magnetic grains can be continuously epitaxially grown from the granular structure. Although the magnetic recording layer 122 may be a single layer, in this embodiment, the magnetic recording layer 122 includes a first magnetic recording layer 122a and a second magnetic recording layer 122b having different compositions and film thicknesses. As a result, small crystal grains of the second magnetic recording layer 122b continue to grow from the crystal grains of the first magnetic recording layer 122a, and the second magnetic recording layer 122b, which is the main recording layer, can be miniaturized. Can be improved.

In this embodiment, CoCrPt—Cr ₂ O ₃ is used for the first magnetic recording layer 122a. In CoCrPt—Cr ₂ O ₃ , Cr and Cr ₂ O ₃ (oxide), which are nonmagnetic substances, segregate around magnetic grains (grains) made of CoCrPt to form grain boundaries, and the magnetic grains are columnar. A grown granular structure was formed. The magnetic grains were epitaxially grown continuously from the granular structure of the nonmagnetic granular layer.

Also, CoCrPt—SiO ₂ —TiO ₂ is used for the second magnetic recording layer 122b. Also in the second magnetic recording layer 122b, Cr, SiO ₂ and TiO ₂ (composite oxide), which are nonmagnetic substances, segregate around the magnetic grains (grains) made of CoCrPt to form grain boundaries. A granular structure grown in a columnar shape was formed.

The materials used for the first magnetic recording layer 122a and the second magnetic recording layer 122b described above are merely examples, and the present invention is not limited thereto. In the present embodiment, the first magnetic recording layer 122a and the second magnetic recording layer 122b are made of different materials (targets). However, the present invention is not limited to this, and materials having the same composition and type may be used. Examples of the nonmagnetic substance for forming the nonmagnetic region include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), Examples thereof include oxides such as tantalum oxide (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 this embodiment, one type of nonmagnetic material (oxide) is used in the first magnetic recording layer 122a and two types of nonmagnetic substances (oxides) in the second magnetic recording layer 122b. However, the present invention is not limited to this. It is also possible to use a composite of two or more kinds of nonmagnetic substances in either or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b. 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 magnetic recording layer 122 is composed of only one layer, the magnetic recording layer 122 is preferably made of CoCrPt—SiO ₂ —TiO ₂ .

  The dividing layer 124 is a nonmagnetic layer provided between the magnetic recording layer 122 (second magnetic recording layer 122 b) and the auxiliary recording layer 126. In the present embodiment, the dividing layer 124 is a thin film containing Ru and oxygen. When the dividing layer 124 contains oxygen, the dividing layer 124 is formed on the magnetic recording layer 122 containing a large amount of oxide, and the auxiliary recording layer 126 containing no oxygen is formed thereon. And a structural bridge.

  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 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.

  Note that “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 operation of the auxiliary recording layer 126 are not necessarily clear, it has a magnetic interaction with the granular magnetic grains of the magnetic recording layer 122 (performs exchange coupling), so that Hn and Hc can be adjusted, and heat resistance It is thought that fluctuation characteristics and SNR are improved. In addition, since the crystal grains connected to the granular magnetic grains (crystal grains having magnetic interaction) have a larger area than the cross section of the granular magnetic grains, 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.

  Through the above manufacturing process, the perpendicular magnetic recording medium 100 was obtained. Next, the dividing fault 124 that is a feature of the present invention will be described in more detail.

  As described above, the dividing layer 124 is a nonmagnetic layer containing Ru and oxygen provided between the magnetic recording layer 122 and the auxiliary recording layer 126. By providing such a dividing layer 124, it is possible to reduce the noise considered to be caused by the auxiliary recording layer 126 and improve the SNR. This is presumably because the fine structure inherited from the magnetic recording layer 122 can be adjusted when the auxiliary recording layer 126 is crystal-grown. The portion of the dividing layer 124 positioned on the magnetic particle of the magnetic recording layer 122 causes Ru to inherit the Co crystal structure of the magnetic recording layer 122 up to Co of the auxiliary recording layer 126. The portion of the dividing layer 124 positioned above the grain boundary of the magnetic recording layer 122 has no significant inheritance of crystal orientation because the lattice constants of the oxide forming the grain boundary and Ru are greatly different. Atoms form a film (crystal) while freely migrating. By forming the auxiliary recording layer 126 on the Ru crystal, the Co particles of the auxiliary recording layer 126 are further separated and the noise is reduced. Therefore, the crystal orientation of the auxiliary recording layer 126 is improved as a whole.

  Here, even if the dividing layer 124 is made of only Ru, the OW characteristics and the like are improved. However, by including Ru and oxygen, the SNR is drastically improved. This is because a high coercive force cannot be obtained even if a film made of only Ru is formed on a grain boundary containing a large amount of oxygen. On the other hand, by including Ru and oxygen in the dividing layer 124 as in the present invention, the contained oxygen atoms have a high affinity with the oxygen atoms contained in the grain boundaries and are selectively deposited. That is, by allowing oxygen to be contained in the dividing layer 124 in a proportion smaller than that of the oxide contained in the magnetic recording layer 122, the grain boundary of the magnetic recording layer 122 containing a large amount of oxygen and the auxiliary recording layer 126 containing no oxygen It is assumed that it was possible to bridge.

  The oxygen contained in Ru in the dividing layer 124 includes one or both of an oxygen atom as a simple substance and an oxygen atom as an oxide. In order to contain a very small amount of oxygen in Ru, there are a method of previously containing oxygen in the target and a reactive sputtering method of adding oxygen to the atmospheric gas during sputtering. The reactive sputtering method is a method in which an active gas is added to an atmospheric gas supplied into a sputtering chamber to form a compound film or mixed film of target atoms and active gas atoms. Therefore, oxygen can be contained in the dividing layer 124 by adding oxygen gas as an active gas during sputtering of the dividing layer 124.

  However, in the reactive sputtering method, since the amount of oxygen gas added to the atmospheric gas is small, it is very difficult to adjust the amount of oxygen contained in the dividing layer 124 to a desired amount. In addition, since it is difficult to adjust the active gas to be uniformly distributed in the atmospheric gas, the oxygen distribution in the dividing layer 124 becomes non-uniform. Further, since it is difficult to completely degas oxygen gas mixed in the layer when the dividing layer 124 is formed, the oxygen gas remaining in the chamber forms a layer after the dividing layer 124. It will enter the filming chamber. Therefore, it is preferable to perform sputtering on the dividing layer 124 using a target made of Ru and an oxide because oxygen can be uniformly contained in the entire film.

The oxide contained in the dividing layer 124 may be WO ₃ , TiO ₂ , or RuO. As described above, it is preferable to include oxygen in the dividing layer 124 by including an oxide in the sputtering target. Various oxides are conceivable. In particular, by using oxides of W, Ti, and Ru, electromagnetic conversion characteristics (SNR) can be improved. Among them, WO ₃ can obtain a high effect. This is because WO ₃ is an unstable oxide, so that oxygen is dissociated during sputtering, and the dissociated oxygen also exhibits the effect of oxygen addition. In addition, 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. Examples thereof include oxides such as (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.

  The dividing layer 124 may have a film thickness of 2 mm to 10 mm (0.2 nm to 1 nm). By making such a thin film, the dividing layer 124 does not form a complete film, and the inheritance of crystal orientation from the crystal grains of the magnetic recording layer 122 to the auxiliary recording layer 126 is not hindered. If the thickness of the dividing layer 124 is 10 mm or more, the magnetic recording layer 122 and the auxiliary recording layer 126 are completely separated magnetically, and a desired SNR cannot be obtained. On the other hand, if the film thickness is 2 mm or less, a film cannot be formed.

  The magnetic recording layer 122 may contain two or more kinds of oxides. As a result, characteristics of a plurality of oxides can be obtained, noise is reduced by further miniaturization and isolation of the magnetic particles of the magnetic recording layer 122, and SNR is improved to increase the recording density. Can be obtained.

The magnetic recording layer 122 may contain SiO ₂ and TiO ₂ as oxides. SiO ₂ promotes miniaturization and isolation of magnetic particles, and TiO ₂ has a characteristic of improving electromagnetic conversion characteristics (especially SNR). By combining these oxides and segregating at the grain boundaries of the magnetic recording layer 122, both benefits can be enjoyed.

  The magnetic recording layer 122 may contain 5 mol% or more of an oxide constituting the grain boundary part. When the content is 5 mol% or more, high magnetostatic characteristics and electromagnetic conversion characteristics can be obtained. In such a range, the characteristics of the auxiliary recording layer 126 are deteriorated so as not to be ignored. This is because an improvement in characteristics can be obtained.

(Example)
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 composition of the pre-underlayer 116 was a NiW alloy having an fcc structure. 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 film containing oxygen was 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. The composition of the nonmagnetic granular layer 120 was nonmagnetic CoCr—SiO ₂ . The first magnetic recording layer 122a contained Cr ₂ O ₃ as an example of an oxide at the grain boundary part, and formed a hcp crystal structure of CoCrPt—Cr ₂ O ₃ . The second magnetic recording layer 122b contains SiO ₂ and TiO ₂ as examples of complex oxides (plural types of oxides) at the grain boundary part, and has a CoCrPt—SiO ₂ —TiO ₂ hcp crystal structure. The dividing layer 124 had a thickness of 3 mm, and the composition thereof was compared by creating the following examples and comparative examples. 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.

FIG. 2 is a diagram showing an example and a comparative example according to the composition of the dividing layer 124. The composition of the dividing layer 124 is RuWO ₃ in Example 1, RuSiO ₂ in Example ₂ , and Ru + O ₂ exposure (reactive sputtering) in Example 3. Comparative Example 1 is not provided with the dividing layer 124, Comparative Example 2 is only Ru, and Comparative Example 3 is only O ₂ exposure. The thickness of the dividing layer 124 is 3 mm except for Comparative Example 1 and Comparative Example 3. And about each Example and the comparative example, SNR was measured as a coercive force Hc and a reverse domain nucleation magnetic field Hn as a magnetostatic characteristic, and an electromagnetic conversion characteristic. Since the coercive force Hc and the reverse domain nucleation magnetic field Hn are better as the absolute values are larger, they are shown on the graph as absolute values on the same axis.

From FIG. 2, it can be seen that the SNR is significantly improved in Examples 1 to 3 as compared with the comparative example. Among them, the SNR was most improved in Example 1 in which the dividing layer 124 was formed with RuWO ₃ . Among the comparative examples, the comparative example 2 in which the dividing layer 124 made of Ru is formed has a good SNR, but does not reach the examples 1 to 3 that further contain oxygen. However, in Comparative Example 3 in which the magnetic recording layer 122 was exposed to oxygen, no improvement in SNR was observed, so that the effect was not achieved when oxygen was included in the magnetic recording layer 122, but oxygen was not present in the dividing layer 124. It turns out that an effect is show | played by including.

  The coercive force Hc was the largest in Comparative Example 1 in which the dividing layer 124 was not provided, and was lower in other cases. However, although it is low, the coercive force Hc is 4500 [Oe] or more at present, so there is no problem. Further, since the signal can be easily read if the SNR is high, the coercive force Hc may be low. Similarly, the reverse domain nucleation magnetic field Hn is slightly lower in the example than in the comparative example, but is in a range where there is no problem at all. Furthermore, the coercive force Hc and the reverse domain nucleation magnetic field Hn can be improved by other means such as increasing the thickness of the magnetic recording layer 122, reducing Cr, increasing Pt, or reducing oxide. That is, according to the present invention, it is understood that the SNR can be significantly improved without significantly reducing the coercive force Hc and the reverse domain nucleation magnetic field Hn.

Furthermore, it can be seen that, among the examples, the coercive force Hc is highest in Example 1 in which the dividing layer 124 is formed of RuWO ₃ . That is, RuWO ₃ has the highest SNR and coercive force Hc among Examples 1 to 3, indicating that it is an optimal composition.

FIG. 3 is a diagram showing an example and a comparative example using a combination of oxides in the magnetic layer. The composition of the dividing layer 124 was all RuWO ₃ and the film thickness was 3 mm. In Example 4, the magnetic recording layer 122 contained a composite of SiO ₂ and TiO ₂ as a plurality of oxides. Comparative Example 4 contained SiO ₂ and Comparative Example 5 contained only TiO ₂ as an oxide. In Example 4, Comparative Example 4, and Comparative Example 5, the total amount of oxide was equally 10 mol%.

Comparing Comparative Example 4 and Comparative Example 5, it can be seen that SiO ₂ has a high coercive force Hc and TiO ₂ has a high SNR. Then, referring to Example 4, it can be seen that both the coercive force Hc and the SNR are greatly improved. In particular, when comparing the SNR when the dividing layer 124 is not provided with the SNR when the dividing line 124 is provided, the improvement is about 0.4 in the comparative example 4 and the comparative example 5, whereas the improvement is about 0.6 in the example 4. You can see that From this, it can be seen that the benefits of the present invention can be further effectively obtained by incorporating a plurality of oxides in the magnetic recording layer 122.

FIG. 4 is a TEM photograph of the auxiliary recording layer 126 of Example 1 (when the dividing layer 124 made of RuWO ₃ is provided) and Comparative Example 1 (when the dividing layer 124 is not provided). Referring to FIG. 4, it can be seen that in Comparative Example 1, the fine structure of the auxiliary recording layer 126 is blurred, but in Example 1, separation between particles is clearly promoted. Thereby, it can be confirmed that the noise of the auxiliary recording layer 126 can be reduced by the dividing layer 124.

  As described above, according to the perpendicular magnetic recording medium 100 according to the first embodiment, it is possible to reduce the noise considered to be caused by the auxiliary recording layer and improve the SNR. As a result, the recording density of the perpendicular magnetic recording medium 100 can be further increased.

(Second Embodiment)
The second embodiment of the perpendicular magnetic recording medium according to the present invention will be described below. In the perpendicular magnetic recording medium 100 according to the first embodiment described above, the second magnetic recording layer 122b is composed of one layer. On the other hand, the perpendicular magnetic recording medium according to the second embodiment includes the second magnetic recording layer. Is composed of two layers. In addition, about the element which has the same function and structure as 1st Embodiment, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Perpendicular magnetic recording medium]
FIG. 5 is a diagram illustrating the configuration of the perpendicular magnetic recording medium 200 according to the second embodiment. The perpendicular magnetic recording medium 200 shown in FIG. 5 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, and a second layer. Consists of an underlayer 118b, a non-magnetic granular layer 120, a first magnetic recording layer 122a, a first main recording layer 222c, a second main recording layer 222d, a dividing layer 124, an auxiliary recording layer 126, a medium protective layer 128, and a lubricating layer 130. Has been. 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 first main recording layer 222c and the second main recording layer 222d together constitute a second magnetic recording layer 222a, and the first magnetic recording layer 122a and the second magnetic recording layer 222a together constitute a magnetic recording layer 222. .

  In the present embodiment, the second magnetic recording layer 222a includes a first main recording layer 222c provided on the first magnetic recording layer 122a (on the disk substrate 110 side), and a first main recording layer 222c (on the perpendicular magnetic recording medium). And a second main recording layer 222d provided on the main surface side 200).

The first main recording layer 222c is made of CoCrPt—SiO ₂ —TiO ₂ . Thereby, in the first main recording layer 222c, SiO ₂ and TiO ₂ (composite oxide), which are nonmagnetic substances, segregate around the magnetic particles (grains) made of CoCrPt to form grain boundaries, and the magnetic particles A granular structure grown in a columnar shape was formed.

The second main recording layer 222d is continuous with the first main recording layer 222c, but has a different composition and film thickness. The second main recording layer 222d is made of CoCrPt—SiO ₂ —TiO ₂ —CoO. Thereby, also in the second main recording layer 222d, nonmagnetic substances such as SiO ₂ , TiO ₂ , and CoO (composite oxide) are segregated around the magnetic particles (grains) made of CoCrPt to form grain boundaries, A granular structure in which magnetic particles were grown in a columnar shape was formed.

  As described above, in the present embodiment, the second main recording layer 222d contains CoO (Co oxide), and the second main recording layer 222d includes more oxide than the first main recording layer 222c. Yes. Thereby, separation of crystal grains can be promoted stepwise from the first main recording layer 222c to the second main recording layer 222d.

Further, by containing Co oxide in the second main recording layer 222d as described above, it is possible to prevent the crystallinity and crystal orientation of the magnetic particles from being deteriorated due to oxygen deficiency. Specifically, there is a fact that when an oxide such as SiO ₂ or TiO ₂ is mixed into the magnetic recording layer 222, oxygen deficiency occurs, and Si ions or Ti ions are mixed into the magnetic particles, thereby disturbing the crystal orientation and coercive force. Hc will fall. Therefore, by containing Co oxide, it can function as an oxygen carrier for compensating for this oxygen deficiency. As the Co oxide, CoO is exemplified, but Co ₃ O ₄ 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 can be compensated to complete Si and Ti ions as oxides, which can be precipitated at the 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 entire magnetic recording layer 222, there is a problem that the SNR is lowered. Therefore, by providing the first main recording layer 222c not mixed with Co oxide as described above, a high SNR is secured in the first main recording layer 222c, while a high coercive force Hc and an overshoot are obtained in the second main recording layer 222d. Light characteristics can be obtained. Note that the second main recording layer 222d is preferably thicker than the first main recording layer 222c. As a suitable example, the first main recording layer 222c is 2 nm and the second main recording layer 222d is 8 nm. be able to.

The materials used for the first main recording layer 222c and the second main recording layer 222d 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 ), zirconium 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.

  In the present embodiment, the second magnetic recording layer 222a is composed of the first main recording layer 222c and the second main recording layer 222d, that is, the magnetic recording layer 222 is composed of the first magnetic recording layer 122a and the first main recording layer 222c. The second main recording layer 222d (second magnetic recording layer 222a) is composed of three layers, and the second main recording layer 222c contains Co oxide. However, the present invention is not limited to this. For example, as in the perpendicular magnetic recording medium 100 according to the first embodiment, the magnetic recording layer is composed of two layers of the first magnetic recording layer and the second magnetic recording layer, and any one layer contains Co oxide. Is also possible.

(Example)
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 composition of the pre-underlayer 116 was a NiW alloy having an fcc structure. 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 film containing oxygen was 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. The composition of the nonmagnetic granular layer 120 was nonmagnetic CoCr—SiO ₂ . The first magnetic recording layer 122a contained Cr ₂ O ₃ as an example of an oxide at the grain boundary part, and formed a hcp crystal structure of CoCrPt—Cr ₂ O ₃ . The first main recording layer 222c contained SiO ₂ and TiO ₂ as examples of complex oxides (plural types of oxides) at the grain boundary part, and formed an hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ . The second main recording layer 222d contains SiO ₂ , TiO _2, and CoO as examples of complex oxides (plural types of oxides) at the grain boundary, and has an hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ —CoO. Formed. Dividing layers 124 were formed by 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.

  FIG. 6 is a diagram for explaining the SNR in the perpendicular magnetic recording medium 200 in which the second magnetic recording layer is composed of a plurality of layers. In FIG. 6, Example 5 is a perpendicular magnetic recording medium 200 in which the second magnetic recording layer is composed of two layers as described above. Example 6 is the perpendicular magnetic recording medium 100 having the same configuration as that of Example 5 except for the second magnetic recording layer, and the second magnetic recording layer is a single layer as in the first embodiment. It is a comparison object.

  Referring to FIG. 6, it can be seen that higher SNR can be secured in the fifth embodiment than in the sixth embodiment. From this, the second magnetic recording layer 222a is composed of two layers, a first main recording layer 222c and a second main recording layer 222d, and the second main recording layer 222d contains CoO (Co oxide). It can be understood that it is possible to increase the SNR of the perpendicular magnetic recording medium and contribute to achieving higher recording density.

  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 as a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD or the like.

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording medium, 110 ... Disk base | substrate, 112 ... Adhesion layer, 114 ... Soft magnetic layer, 114a ... 1st soft magnetic layer, 114b ... Spacer layer, 114c ... 2nd soft magnetic layer, 116 ... Pre-underlayer, 118 ... Underlayer, 118a ... First underlayer, 118b ... Second underlayer, 120 ... Non-magnetic granular layer, 122 ... Magnetic recording layer, 122a ... First magnetic recording layer, 122b ... Second magnetic recording layer, 124 ... Split layer, 126 ... auxiliary recording layer, 128 ... medium protective layer, 130 ... lubricating layer, 200 ... perpendicular magnetic recording medium, 222 ... magnetic recording layer, 222a ... second magnetic recording layer, 222c ... first main recording layer, 222d ... Second main recording layer

Claims (9)

At least on the substrate,
A magnetic recording layer having a granular structure in which a nonmagnetic grain boundary portion is formed between columnar crystal grains;
A nonmagnetic dividing layer containing Ru and oxygen provided on the magnetic recording layer;
A perpendicular magnetic recording medium comprising an auxiliary recording layer provided on the dividing layer and magnetically substantially continuous in an in-plane direction of the main surface of the substrate.   The perpendicular magnetic recording medium according to claim 1, wherein the dividing layer includes Ru and an oxide. The perpendicular magnetic recording medium according to claim ₂ , wherein the oxide is WO ₃ , TiO ₂ , or RuO.   The perpendicular magnetic recording medium according to claim 1, wherein the dividing layer has a thickness of 2 mm to 10 mm.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer includes two or more kinds of oxides. The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer includes SiO ₂ and TiO ₂ as oxides.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer contains 5 mol% or more of an oxide constituting the grain boundary part.   The magnetic recording layer includes a first main recording layer that does not include a Co oxide, and a second main recording layer that is provided on the first main recording layer and includes at least a Co oxide. Item 2. The perpendicular magnetic recording medium according to Item 1. The perpendicular magnetic recording medium further includes an underlayer provided below the magnetic recording layer and made of Ru or a Ru compound,
The perpendicular magnetic recording medium according to claim 1, wherein the dividing layer is a layer made of Ru formed at a gas pressure lower than a gas pressure at the time of forming the underlayer.