JPWO2010035810A1 - Perpendicular magnetic recording medium and method for manufacturing perpendicular magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the coercive force Hc and improve the reliability of a perpendicular magnetic recording medium by reducing the mixing of oxides into magnetic particles of a magnetic recording layer and improving the crystal orientation of the magnetic particles. An object of the present invention is to provide a possible perpendicular magnetic recording medium and a method for manufacturing the perpendicular magnetic recording medium. A perpendicular magnetic recording medium according to the present invention includes a perpendicular magnetic recording medium including a base layer 118 made of ruthenium and a magnetic recording layer 122 for recording signals in this order on a disk substrate. In FIG. 100, the underlayer 118 includes a first underlayer 118a and a second underlayer 118b. The oxygen content contained in the first underlayer is Amol%, and the oxygen content contained in the second underlayer. When the content of oxygen contained in the magnetic recording layer is Cmol%, the relationship between the contents is A <B <C. [Selection] Figure 1

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 and a method of manufacturing the perpendicular magnetic recording medium.

  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, an information recording capacity exceeding 200 GB has been required for a 2.5-inch diameter magnetic recording medium used for HDDs and the like. 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 order to achieve a high recording density in a magnetic recording medium used for an HDD or the like, a perpendicular magnetic recording medium of a perpendicular magnetic recording system has recently been proposed. 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).

  Furthermore, in order to realize a high recording density in the perpendicular magnetic recording medium, the crystal orientation of the underlayer, which is the lower layer of the magnetic recording layer, and the separability of the magnetic particles are important. Conventionally, in a perpendicular magnetic recording medium, two Ru layers (a lower first underlayer (Ru # 1) and an upper second underlayer (Ru # 2)), which have different film formation processes, are continuously formed. It is formed into a film. Ru # 1 is formed at a low gas pressure, and Ru # 2 is formed at a high gas pressure (see, for example, Patent Document 2). Ru # 1 mainly contributes to the vertical orientation of the upper magnetic recording layer, and Ru # 2 mainly contributes to the separation of the magnetic particles.

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

JP 2006-024346 A JP 2008-108415 A

  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 other electromagnetic conversion characteristics, and the track width is narrowed. Among them, the improvement in SNR is important in order to read and write 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 magnetic particles is promoted, the exchange interaction is cut off, so that the noise can be greatly reduced and the SNR can be remarkably improved.

In the CoCrPt—SiO ₂ perpendicular magnetic recording medium described above, by adding an oxide such as SiO ₂ , the oxide can be segregated at the grain boundary without hindering the epitaxial growth of CoPt. Thus, the SNR is improved by miniaturizing the magnetic particles and promoting isolation between the magnetic particles. However, when the amount of oxide is excessively increased, the coercive force Hc and the perpendicular magnetic anisotropy are deteriorated, which causes a problem of deterioration of thermal stability and increase of noise.

  It was also found that the addition of oxides would cause the oxides that would normally segregate at the grain boundaries to enter the columnar magnetic particle crystals. As a result, the crystal orientation of the magnetic particles is lowered, and crystal lattice defects are increased. As a result, the magnetocrystalline anisotropy energy was reduced, causing a significant decrease in the coercive force Hc.

  When the coercive force Hc decreases, the magnetization of the magnetic recording layer is reversed even by a weak magnetic field. Therefore, when a strong magnetic field is applied from the magnetic head to the magnetic recording layer during writing to the perpendicular magnetic recording medium, magnetization reversal occurs in the adjacent track due to the leakage magnetic field, that is, the weak magnetic field. As a result, a phenomenon in which recorded information is lost over several μm centering on the track to be written, that is, WATE (Wide Area Track Erasure) occurs, and the reliability of the perpendicular magnetic recording medium is lowered. .

  Further, the refinement and isolation of magnetic particles are affected by the thickness in the horizontal direction (in-plane direction) of the oxide segregated at the grain boundaries. Increasing the amount of oxide improves the SNR at high recording density. On the other hand, when the amount of oxide is excessively increased, the coercive force Hc and the perpendicular magnetic anisotropy deteriorate, and deterioration of thermal stability and increase of noise become problems. In other words, it is effective to contain an oxide at the grain boundary, but since an upper limit naturally occurs in the amount of the oxide that can be contained, there is a limit in improving miniaturization and isolation.

  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.

  Further, in the conventional perpendicular magnetic recording medium, two layers (Ru # 1, Ru # 2) having different film forming processes at low gas pressure and high gas pressure are laminated as the Ru-based underlayer in the perpendicular magnetic recording medium. However, in Ru # 2, it is necessary to set a high gas pressure in order to promote separability. However, when the gas pressure is high, there is a problem that the film becomes sparse and the reliability deteriorates.

  In view of such a problem, the present invention reduces the mixing of oxides into the magnetic particles of the magnetic recording layer and improves the crystal orientation of the magnetic particles, thereby increasing the coercive force Hc, and the perpendicular magnetic recording medium. It is an object of the present invention to provide a perpendicular magnetic recording medium and a method for manufacturing the perpendicular magnetic recording medium that can improve the reliability of the recording medium. Further, there is provided a perpendicular magnetic recording medium and a perpendicular magnetic recording medium manufacturing method capable of improving SNR and further increasing recording density by promoting miniaturization and isolation of magnetic particles in a magnetic recording layer. The purpose is to provide. It is another object of the present invention to provide a perpendicular magnetic recording medium capable of achieving both improvement in recording / reproducing characteristics by increasing the separation of magnetic particles and improvement in reliability by lowering gas pressure during Ru # 2 film formation, and a method for manufacturing the same. And

  As a result of extensive studies by the inventors in order to solve the above-described problems, the inventors have focused on the fact that the crystal orientation of the magnetic particles in the magnetic recording layer is greatly influenced by the state of the underlying layer that forms the basis of the growth. And by further research, the state of the magnetic recording layer and the underlayer changes depending on the oxygen content contained in each layer, and optimizing such content is effective in solving the above problems. The headline and the present invention have 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 includes at least a ruthenium underlayer on a disk substrate and a magnetic recording layer for recording a signal. In the perpendicular magnetic recording medium provided in this order, the underlayer is composed of the first underlayer and the second underlayer, the oxygen content contained in the first underlayer is Amol%, and the oxygen content contained in the second underlayer is When the content is B mol% and the content of oxygen contained in the magnetic recording layer is C mol%, the content relationship is A <B <C. It is preferable that A ≧ 0 and B> 0.

  In the above configuration, the first underlayer, the second underlayer, and the magnetic recording layer contain either one or both of oxygen atoms as a simple substance and oxygen atoms as an oxide. If the amount and the amount of oxygen atoms as oxides are combined to make the oxygen content, the oxygen content will increase stepwise from the first underlayer to the magnetic recording layer. That is, as the first underlayer moves from the magnetic recording layer, the content of substances other than the substances that become crystal grains in the underlayer or the magnetic recording layer increases stepwise. With such a configuration, separation of crystal grains can be promoted stepwise (substantially continuously) from the first underlayer to the magnetic recording layer.

  Further, when oxygen or oxide is contained in the underlayer as described above, oxygen or oxide (substance other than Ru crystal particles) is precipitated at the boundary of Ru crystal particles in the underlayer. Separation is promoted. As a result, in the magnetic recording layer formed on the underlayer, crystal grains (magnetic particles) of the magnetic recording layer are precipitated on Ru crystal grains of the underlayer, and oxygen (or oxide) of the underlayer is deposited. On the boundary, oxygen (or oxide) contained in the magnetic recording layer having a high affinity with oxygen (or oxide) forming the boundary is precipitated to form a grain boundary. Accordingly, precipitation of oxides in the magnetic recording layer at grain boundaries can be promoted, and mixing of oxides into columnar crystal grains is reduced. Thereby, the crystal orientation of crystal grains in the magnetic recording layer is improved, and the coercive force Hc can be increased.

  Furthermore, as described above, by containing oxygen in the underlayer, the separation and refinement of Ru crystal particles can be promoted more than the conventional underlayer that does not contain oxygen. The crystal grains are refined, and the magnetic grains of the magnetic recording layer grow in a columnar shape on the surface of the refined underlayer to form a granular structure. Therefore, the miniaturization and isolation of the magnetic particles in the magnetic recording layer can be promoted.

  Further, by configuring the underlayer with the two layers of the first underlayer and the second underlayer as described above, the advantages of the conventional underlayer having the two-layer structure can be obtained. That is, it is possible to improve the crystal orientation of the magnetic recording layer by the first underlayer and to reduce the particle size of the magnetic particles of the magnetic recording layer by the second underlayer.

  Note that, as indicated above as A ≧ 0 and B> 0, the first underlayer does not need to contain oxygen. This is because even if the first underlayer does not contain oxygen, the content relationship of A <B <C is established, and the above-described effect of the content relationship can be sufficiently obtained. It is. In addition, when the underlayer is composed of two layers of the first underlayer and the second underlayer, it is the second underlayer that exists immediately below the magnetic recording layer, so that at least the second underlayer contains oxygen. This is because the above-described effects can be sufficiently obtained.

  In the present application, the underlayer has a two-layer structure, but the present invention is not limited to this, and the underlayer can be formed by a single layer. In such a case, the oxygen content may be increased from the lower side (base side) to the upper side (magnetic recording layer side) of the underlayer.

  The magnetic recording layer preferably contains an oxide that segregates around crystal grains to form grain boundaries. Thereby, an oxide is segregated around the magnetic particles of a hard magnetic material made of a Co-based alloy to form a grain boundary, and the granular layer can have a columnar granular structure.

  The above content relationship is preferably 10 ≦ C / B ≦ 140. “C / B” means “C ÷ B”. Thereby, the content of oxygen contained in the magnetic recording layer and the second underlayer existing immediately below the magnetic recording layer can be optimized, and the above-described effects can be obtained most efficiently.

The magnetic recording layer may be made of CoCrPt—SiO ₂ —TiO ₂ . Thereby, SiO ₂ and TiO ₂ , which are nonmagnetic substances, are segregated around the magnetic particles of the hard magnetic material made of a Co-based alloy to form grain boundaries, and the magnetic recording layer has a columnar granular structure. it can. Therefore, the magnetic recording layer can have a hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ .

  The magnetic recording layer includes a first magnetic recording layer and a second magnetic recording layer, and the oxygen content Cmol% contained in the magnetic recording layer is the oxygen content contained in the first magnetic recording layer. Good.

  As described above, the magnetic recording layer has a two-layer configuration including the first magnetic recording layer and the second magnetic recording layer, so that the small crystal of the second magnetic recording layer continues from the crystal grains of the first magnetic recording layer. Particles grow. As a result, the second magnetic recording layer as the main recording layer can be miniaturized, and the SNR can be improved.

  In the above configuration, since the oxygen content contained in the magnetic recording layer is the oxygen content contained in the first magnetic recording layer, when the relationship of the contents is A <B <C, the first underlayer From the first magnetic recording layer to the first magnetic recording layer, the content of substances other than the substances that become crystal grains increases, and the separation of the crystal grains gradually (substantially continuously) from the first underlayer to the first magnetic recording layer. Can be promoted.

  In addition, since oxygen (or oxide) is precipitated at the boundaries of the Ru crystal grains in the underlayer existing immediately below the first magnetic recording layer, the magnetic properties of the first magnetic recording layer are formed on the Ru crystal grains of the underlayer. Oxygen (or oxide) contained in the first magnetic recording layer is deposited on the boundary of oxygen (or oxide) in the underlying layer. Therefore, it is possible to promote the precipitation of oxides contained in the first magnetic recording layer at the grain boundaries and reduce the mixing of oxides into the columnar magnetic particles. Thereby, the crystal orientation of the magnetic particles in the first magnetic recording layer can be improved and the coercive force Hc can be increased.

  Here, the oxygen content contained in the first magnetic recording layer was used as the oxygen content contained in the magnetic recording layer because the crystal grains (first magnetic layer) from the first underlayer to the first magnetic recording layer were used. If the separation of the magnetic particles in the recording layer is promoted stepwise, the crystal grains of the second magnetic recording layer formed on the first magnetic recording layer are affected by the crystal grains of the first magnetic recording layer. This is because separation is naturally promoted. In addition, if the mixing of oxide into the magnetic particles of the first magnetic recording layer is reduced, the influence of the oxide also reduces the mixing of oxide into the magnetic particles of the second magnetic recording layer.

The first magnetic recording layer may be made of CoCrPt—Cr ₂ O ₃ . As a result, a grain boundary is formed by segregating Cr ₂ O ₃ , which is a non-magnetic substance, around the magnetic particles of a hard magnetic material made of a Co-based alloy, and the first magnetic recording layer has a columnar granular structure. Can do. Therefore, the first magnetic recording layer can have a hcp crystal structure of CoCrPt—Cr ₂ O ₃ .

The second magnetic recording layer may be made of CoCrPt—SiO ₂ —TiO ₂ . Thereby, SiO ₂ and TiO ₂ , which are nonmagnetic substances, are segregated around the magnetic particles of the hard magnetic material made of the Co-based alloy to form grain boundaries, and the second magnetic recording layer has a columnar granular structure. be able to. Therefore, the second magnetic recording layer can have a hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ .

  In order to solve the above-described problems, a typical configuration of the perpendicular magnetic recording medium according to the present invention is that at least a ruthenium underlayer, a nonmagnetic granular layer, and a magnetic recording for recording a signal are formed on a disk substrate. In the perpendicular magnetic recording medium having the layers in this order, the underlayer is composed of the first underlayer and the second underlayer, and the oxygen content contained in the first underlayer is Amol% and the second underlayer is in the second underlayer. When the content of oxygen contained is B mol% and the content of oxygen contained in the nonmagnetic granular layer is D mol%, the content relationship is characterized by A <B <D.

  As described above, by providing the nonmagnetic granular layer on the underlayer, the granular layer of the magnetic recording layer is grown on the nonmagnetic granular layer, and the granular layer of the magnetic recording layer is separated from the initial growth stage. It becomes possible. Therefore, it is possible to promote isolation of the magnetic particles in the magnetic recording layer.

  In the above configuration, when the content relationship is A <B <D, the content of substances other than the substance that becomes crystal grains increases as the first underlayer moves from the non-magnetic granular layer. Therefore, the separation of crystal grains can be promoted stepwise (substantially continuously) from the first underlayer to the nonmagnetic granular layer, and finally the magnetic field is affected by the refinement of the crystal grains of the nonmagnetic granular layer. Separation of magnetic particles in the recording layer can be promoted. In addition, because of the influence of the separation of the underlayer, the mixing of oxides into the crystal grains of the non-magnetic granular layer can be reduced, so that the crystal orientation of the magnetic grains of the magnetic recording layer formed on the granular layer can be reduced. Thus, the coercive force Hc can be increased.

  The above content relationship is preferably 20 ≦ D / B ≦ 160. “D / B” means “D ÷ B”. Thereby, the content of oxygen contained in the nonmagnetic granular layer and the second underlayer existing immediately below the nonmagnetic granular layer can be optimized, and the above-described effects can be obtained most efficiently.

The nonmagnetic granular layer is preferably made of CoCr—SiO ₂ . Thereby, since non-magnetic substance SiO ₂ is segregated between non-magnetic crystal grains made of a Co-based alloy to form a grain boundary, the non-magnetic granular layer can have a granular structure.

  The nonmagnetic granular layer may be provided on the underlayer, that is, above the underlayer, and another layer may be provided between the nonmagnetic granular layer and the underlayer.

  In order to solve the above-described problems, a typical configuration of a method for manufacturing a perpendicular magnetic recording medium according to the present invention includes a base layer composed of at least a first base layer and a second base layer made of ruthenium on a disk substrate. And a magnetic recording layer for recording signals in this order, a first underlayer is formed by sputtering under an atmospheric gas at a predetermined pressure, and an atmosphere at a pressure higher than the predetermined pressure is formed. A second underlayer is formed by sputtering under a gas, and a target used for forming the second underlayer contains oxygen.

  The components based on the technical idea of the perpendicular magnetic recording medium and the description thereof can be applied to the method for manufacturing the perpendicular magnetic recording medium.

  Note that there is a reactive sputtering method as another method for containing oxygen in the base layer. 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 a mixed film of target atoms and active gas atoms. Therefore, oxygen can be contained in the underlayer by adding oxygen gas as an active gas during sputtering of the underlayer.

  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 underlayer 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 underlayer becomes nonuniform. Furthermore, since it is difficult to completely deaerate oxygen gas mixed in the layer when forming the underlayer, the oxygen gas remaining in the layer forms a layer after the underlayer. Get into the chamber. As a result, the magnetic recording layer is oxidized and the quality of the perpendicular magnetic recording medium is degraded.

  Therefore, by previously containing oxygen in the target used for sputtering as in the present application, a desired amount of oxygen can be uniformly contained in the underlayer without causing the above-described problems.

  In order to solve the above-mentioned problem, another typical configuration of the perpendicular magnetic recording medium according to the present invention includes a disk substrate on which at least a ruthenium base layer and a Co-based alloy crystal grain on the base layer. In a perpendicular magnetic recording medium comprising a granular layer having a granular structure grown in a columnar shape, the underlayer contains elements and oxygen contained in the granular layer. That is, the underlying layer contains an oxide of an element contained in the granular layer immediately above.

  As described above, by containing oxygen in the underlayer, crystal grains of ruthenium (hereinafter referred to as “Ru”) can be made finer than conventional underlayers that do not contain oxygen. Thereby, a fine columnar structure (column) is generated on the surface of the underlayer, and the crystal particles in the granular layer form a columnar granular structure on the column, so that the isolation of the crystal particles is promoted. Further, the crystal grains of the granular layer existing on the base layer are miniaturized by miniaturizing the Ru crystal grains of the base layer. Accordingly, it is possible to promote the miniaturization and isolation of the magnetic particles (crystal particles) of the magnetic recording layer having a granular structure, and to improve the SNR.

  Note that the element contained in the granular layer and contained in the granular layer in the above structure is a substance used as a carrier for containing oxygen in the underlying layer, and is an oxide in which the element and oxygen are combined. Can be included. The oxide is decomposed at the time of sputtering, and Ru, the contained metal, and oxygen are mixed to form an underlayer. The reason why the Ru crystal is refined by containing oxygen is considered to be because oxygen as an impurity prevents crystal growth or becomes the nucleus of crystal growth when the Ru crystal grows. .

  On the other hand, when the granular layer is formed on the underlayer by sputtering, interfacial diffusion occurs. Therefore, for example, when an element (substance) that is completely different from the element contained in the granular layer is used as the carrier, the crystal orientation of the crystal particles in the granular layer is deteriorated due to the mixing of the element into the granular layer. Therefore, by using an element contained in the granular layer as a carrier as in the present invention, oxygen is contained in the underlayer without causing a decrease in the crystal orientation of the granular layer, so that the crystal grains in the granular layer can be refined and isolated. Can be achieved.

  The underlayer is composed of a first underlayer and a second underlayer having different gas pressures during film formation by sputtering in this order, and at least the second underlayer preferably contains an element and oxygen.

  When the underlayer is composed of two layers, the second underlayer is present immediately below the granular layer. Therefore, according to the above configuration, by containing an element and oxygen in at least the second underlayer, the Ru crystal grains in the second underlayer existing immediately below the granular layer can be miniaturized. Can be obtained.

  In addition, since the underlayer is composed of the first underlayer and the second underlayer as described above, as is conventionally known, the first underlayer has a Ru crystal orientation due to a low gas pressure. In the second underlayer, Ru crystals can be miniaturized by a high gas pressure. Therefore, it is possible to promote the refinement and isolation of the crystal grains in the granular layer by a synergistic effect.

  The element is preferably Co. Co is an element contained in a Co-based alloy constituting the granular layer. Therefore, according to such a configuration, as described above, the crystal grains of the granular layer can be miniaturized and isolated without reducing the crystal orientation of the granular layer. In addition, since Co has a hcp structure similar to Ru and is close to Ru having a lattice constant, it is possible to prevent a decrease in crystal orientation of the underlayer. For this reason, Co is most suitable as such an element.

  The Co-based alloy is a CoCr alloy, and the element may be either one or both of Co and Cr. Thereby, as described above, the crystal grains of the granular layer can be miniaturized and isolated without reducing the crystal orientation of the granular layer.

The granular layer includes an oxide that segregates around crystal grains to form a grain boundary, and the oxide is selected from the group consisting of SiO ₂ , TiO ₂ , and Cr ₂ O ₃ . Is SiO ₂ , the element is either Co or Si or both, and the oxide is TiO ₂ , the element is either Co or Ti or both, and the oxide is Cr ₂ O ₃ , The element may be either Co or Cr or both.

According to the above configuration, in the granular layer, around the crystal particles in which crystals of the hcp structure made of a Co-based alloy are continuously grown in a columnar shape, 1 or ₂ from the group consisting of SiO ₂ , TiO ₂ , Cr ₂ O ₃ A plurality of non-magnetic substances selected can be segregated to form a grain boundary to form a granular structure. Moreover, said element contained in the base layer is an element which comprises the oxide contained in a granular layer. Therefore, as described above, the crystal grains of the granular layer can be miniaturized and isolated without reducing the crystal orientation of the granular layer.

  Further, the above element may be an element in which the Gibbs free energy ΔG of the oxide of the element is larger than that of the ruthenium oxide.

  In general, in a reaction in which an element and oxygen are combined to form an oxide, when the oxide is a metal oxide, the larger the Gibbs free energy ΔG (hereinafter referred to as “ΔG”), Become unstable and easily reduced. Therefore, an oxide of an element having a larger ΔG than ruthenium is an oxide that is more easily reduced than a ruthenium oxide. In other words, ruthenium is an element that is more easily oxidized than an element having a larger ΔG than ruthenium. I can say that.

  Therefore, according to the above configuration, when the element contained in the underlayer is an oxygen carrier, that is, when the underlayer is sputtered using a target contained as an oxide, an oxide of an element having a larger ΔG than Ru. Oxygen atoms contained in the metal are desorbed from the oxide and bonded to Ru which is more easily oxidized than the element, thereby forming a Ru oxide. Therefore, oxygen can be efficiently contained in the underlayer.

  In order to solve the above problems, another typical configuration of the method for manufacturing a perpendicular magnetic recording medium according to the present invention includes a first underlayer film forming step of sputtering ruthenium under an atmospheric gas at a predetermined pressure, and ruthenium. A second underlayer film forming step of sputtering in an atmosphere gas higher than a predetermined pressure, and a granular layer for forming a granular layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape on the second underlayer And a target used for forming the second underlayer contains an oxide of an element constituting the granular layer.

  The components based on the technical idea of the perpendicular magnetic recording medium and the description thereof can be applied to the method for manufacturing the perpendicular magnetic recording medium. Further, the advantages of preliminarily containing oxygen in the target used for sputtering are as described above.

  In order to solve the above problems, another typical configuration of the perpendicular magnetic recording medium according to the present invention is a perpendicular magnetic recording in which at least a Ru-based underlayer and a magnetic recording layer are formed in this order on a disk substrate. The Ru-based underlayer, which is a medium, is composed of three layers of a first underlayer, a second underlayer, and a third underlayer from the disk substrate side. The first and third underlayers are Ru ( Ruthenium) or a Ru alloy material, and the second underlayer is made of a Ru or Ru alloy material containing an oxide.

  In the perpendicular magnetic recording medium according to the present invention, the first to third underlayers are continuously formed by different film formation processes, and at least the first underlayer of the first and second underlayers is formed. The base layer is formed at a low gas pressure of 0.3 Pa to 1.5 Pa, and at least the third base layer of the second and third base layers is formed at a high gas pressure of 3 Pa to 7 Pa. Features.

  According to the present invention, magnetic particles are separated by inserting a second underlayer made of Ru or Ru alloy material containing an oxide between the first and third underlayers constituting the Ru-based underlayer. The recording / reproduction characteristics are improved.

  In addition, by improving the separability by introducing the second underlayer made of Ru or Ru alloy material containing oxide, the gas pressure at the time of forming the third underlayer can be reduced, and the reliability is improved. be able to.

  In addition, since the Ru-based material is used in all of the first to third underlayers, the connection from the first underlayer to the third underlayer is improved, and deterioration of crystal orientation is prevented. You can also.

  In order to solve the above problems, another typical configuration of the method for manufacturing a perpendicular magnetic recording medium according to the present invention is such that at least a Ru-based underlayer and a magnetic recording layer are formed in this order on a disk substrate. A method of manufacturing a perpendicular magnetic recording medium, wherein a Ru-based underlayer includes a first underlayer made of Ru or Ru alloy material from a disk substrate side, and a second underlayer made of Ru or Ru alloy material containing an oxide. It is characterized in that three layers of a base layer, a third underlayer made of Ru or a Ru alloy material are sequentially formed.

  The components based on the technical idea of the perpendicular magnetic recording medium and the description thereof can be applied to the method for manufacturing the perpendicular magnetic recording medium.

  According to the present invention, it is possible to increase the coercive force Hc and improve the reliability of the perpendicular magnetic recording medium by reducing the mixing of oxides into the magnetic particles of the magnetic recording layer and improving the crystal orientation of the magnetic particles. It is possible to provide a perpendicular magnetic recording medium and a method for manufacturing the perpendicular magnetic recording medium. Also, a perpendicular magnetic recording medium and a perpendicular magnetic recording medium manufacturing method that can improve SNR and achieve higher recording density by promoting the miniaturization and isolation of magnetic particles in the magnetic recording layer Can be provided. Furthermore, it is possible to achieve both improvement in recording / reproduction characteristics by increasing the separation of magnetic particles and improvement in reliability by lowering the gas pressure during Ru # 2 film formation.

It is a figure explaining the structure of the perpendicular magnetic recording medium concerning this embodiment. It is a graph which shows the relationship between the content ratio C / B of oxygen of the 2nd underlayer and the 1st magnetic recording layer, and the coercive force Hc. It is a graph which shows the relationship between oxygen content ratio C / B of a 2nd base layer and a nonmagnetic granular layer, and coercive force Hc. It is a figure which shows the relationship between oxygen content of a 2nd base layer, and coercive force Hc. It is a figure explaining the performance evaluation of the perpendicular magnetic recording medium of an Example and a comparative example. It is a figure explaining the structure of the perpendicular magnetic recording medium concerning 3rd Embodiment. It is a block diagram of the base layer in the perpendicular magnetic recording medium shown in FIG. It is a figure which shows the relationship between the material of a base layer, and the film-forming gas pressure. It is a figure which shows the relationship between the material of the base layer in the perpendicular magnetic recording medium of a comparative example, and the film-forming gas pressure. It is a figure which shows the characteristic list of Examples 4-8 and the comparative example 4. FIG.

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 ... Auxiliary recording layer, 126 ... medium protective layer, 128 ... lubricating layer, 200 ... perpendicular magnetic recording medium, 218a ... first underlayer, 218b ... second underlayer, 218c ... third underlayer

  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.

(First embodiment)
In the first embodiment, first, embodiments of the perpendicular magnetic recording medium and the manufacturing method thereof according to the present invention are described, and then the oxygen contained in the underlayer, the nonmagnetic granular layer, and the magnetic recording layer, which is a feature of the present invention, is described. The content relationship will be described.

[Perpendicular magnetic recording medium and manufacturing method thereof]
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 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 auxiliary recording layer 124, the medium protective layer 126, and the lubricating layer 128 are included. 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 124 by a DC magnetron sputtering method, and the medium protective layer 126 can be formed by a CVD (Chemical Vapor Deposition) method. Thereafter, the lubricating layer 128 can be formed by dip coating. 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, 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 CrTi 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.

  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 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 compositions of the first soft magnetic layer 114a and the second soft magnetic layer 114c include a Co-based alloy such as CoTaZr, a Co-Fe based alloy such as CoCrFeB, and a Ni-Fe such as a [Ni-Fe / Sn] n multilayer structure. A system alloy or the like can be used.

  The pre-underlayer 116 is a non-magnetic alloy layer, and has an effect of protecting the soft magnetic layer 114 and an easy axis of hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon. A function of orienting in the direction perpendicular to the disk (an effect of promoting alignment of orientation of crystal grains in the underlayer 118) is provided. 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 the 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. Furthermore, by increasing the pressure, the size of the crystal lattice is reduced. Since the size of the Ru crystal lattice is larger than that of the Co crystal lattice, if the Ru crystal lattice is made smaller, it approaches that of Co, and the crystal orientation of the Co granular layer can be further improved.

  Furthermore, in this embodiment, a target containing oxygen is used for sputtering when forming the second underlayer 118b. As a result, it is possible to make the second underlayer 118b contain a desired amount of oxygen more easily and uniformly than when the reactive sputtering method is used. Further, the use of the reactive sputtering method does not cause problems such as oxidation of the magnetic recording layer 122.

  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 the 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 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 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 particles can be epitaxially grown continuously 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. Note that the configuration is not limited to this, and the magnetic recording layer 122 may be a single layer.

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 particles were epitaxially grown continuously from the granular structure of the nonmagnetic granular layer 120.

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 particles (grains) made of CoCrPt to form grain boundaries, and the magnetic particles 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 22a and the second magnetic recording layer 22b are different materials (targets), but the present invention is not limited to this, and the same composition and type may be used. Examples of nonmagnetic substances for forming the nonmagnetic region include silicon oxide (SiO _x ), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ ). Examples thereof include oxides such as O ₅ ), cobalt oxide (CoO or Co ₃ O ₄ ), 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 auxiliary recording layer 124 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 124 needs to be adjacent or close to the magnetic recording layer 122 so as to have a magnetic interaction. As a material of the auxiliary recording layer 124, for example, CoCrPt, CoCrPtB, or a small amount of oxides can be contained in these. The purpose of the auxiliary recording layer 124 is to adjust the reverse magnetic domain nucleation magnetic field Hn and the coercive force Hc, thereby improving the heat resistance fluctuation characteristic, the OW characteristic, and the SNR. In order to achieve this object, it is desirable that the auxiliary recording layer 124 has high perpendicular magnetic anisotropy Ku and saturation magnetization Ms. In the present embodiment, the auxiliary recording layer 124 is provided above the magnetic recording layer 122, but may be provided below.

  The auxiliary recording layer 124 may be a CGC structure (Coupled Granular Continuous) that forms a thin film (continuous layer) exhibiting high perpendicular magnetic anisotropy and high saturation magnetization MS instead of a single layer. The CGC structure is an exchange energy control layer comprising a magnetic recording layer having a granular structure, a thin film coupling control layer made of a nonmagnetic material such as Pd or Pt, and an alternating laminated film in which thin films of CoB and Pd are laminated. It can consist of.

  Further, “magnetically continuous” means that magnetism is continuous. “Substantially continuous” means that the magnetism may be discontinuous not by a single magnet but by grain boundaries of crystal grains when observed in the entire auxiliary recording layer 124. 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 124, 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). The function and action of the auxiliary recording layer 124 are not necessarily clear, but Hn and Hc can be adjusted by having magnetic interaction (perform exchange coupling) with the granular magnetic grains of the magnetic recording layer 122, 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 a 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 126 can be formed by forming a carbon film by a CVD method while maintaining a vacuum. The medium protective layer 126 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 128 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 126. Due to the action of the lubricating layer 128, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 100, damage or loss of the medium protective layer 126 can be prevented.

  Through the above manufacturing process, the perpendicular magnetic recording medium 100 was obtained. Next, the relationship among the oxygen contents contained in the underlayer 118, the nonmagnetic granular layer 120, and the magnetic recording layer 122, which is a feature of the present invention, will be described.

[Relationship between contents of oxygen contained in underlayer, nonmagnetic granular layer, and magnetic recording layer]
In the present embodiment, as described above, at least the base layer 118 (the first base layer 118a and the second base layer 118b) made of ruthenium, the nonmagnetic granular layer 120, and the signal are recorded on the disk substrate 110. The perpendicular magnetic recording medium includes the magnetic recording layer 122 (the first magnetic recording layer 122a and the second magnetic recording layer 122b) in this order.

  The content of oxygen contained in the first underlayer 118a is Amol%, the content of oxygen contained in the second underlayer 118b is Bmol%, and the content of oxygen contained in the first magnetic recording layer 122a is Cmol%. Then, the relationship of content is good to be A <B <C. Note that A ≧ 0 and B> 0. In addition, the above oxygen indicates oxygen atoms as simple substances and oxygen atoms as oxides contained in each layer, and the oxygen content refers to the amount of oxygen atoms as simple substances and the oxides as oxides. This is the combined amount of oxygen atoms.

  By satisfying the above relational expression, the oxygen content including the oxygen atoms as simple substances and the oxygen atoms as oxides contained in each layer satisfies the above relational expression, so that it goes from the first underlayer 118a to the first magnetic recording layer 122a. In addition, the content of oxygen, that is, the content of substances other than substances that become crystal particles in each layer, increases stepwise. Thereby, the crystal grains can be refined stepwise (substantially continuously) from the first underlayer 118a to the first magnetic recording layer 122a.

  In addition, when oxygen or an oxide is contained in the underlayer 118, oxygen or oxide (substance other than Ru crystal particles) is precipitated at the boundaries of the Ru crystal particles in the underlayer 118, so that the Ru crystal particles are separated. Is promoted. Thereby, in the first magnetic recording layer 122a formed on the underlayer 118, the crystal grains of the first magnetic recording layer 122a are precipitated on the Ru crystal particles of the underlayer 118, and oxygen ( Alternatively, oxygen (or oxide) contained in the first magnetic recording layer 122a having high affinity with oxygen (or oxide) forming the boundary is deposited on the boundary of the oxide) to form a grain boundary. To do. Accordingly, precipitation of oxides in the first magnetic recording layer 122a at the grain boundaries can be promoted, and mixing of the oxides into the columnar crystal grains can be reduced, and crystal grains (magnetic particles) in the first magnetic recording layer 122a can be reduced. ) Is improved, and the coercive force Hc can be increased.

  Furthermore, as described above, by adding oxygen to the underlayer 118, it is possible to promote further isolation (separation) and refinement of the Ru crystal particles of the underlayer 118. Thereby, the crystal grains of the underlayer 118 having a columnar structure are refined, and the magnetic particles of the magnetic recording layer 122 grow in a columnar shape on the surface of the refined underlayer 118 to form a granular structure. Miniaturization and isolation of the magnetic particles of the layer 122 can be promoted.

  Note that, as described above, A ≧ 0 and B> 0, the first base layer 118a may not contain oxygen. This is because even if the first underlayer 118a does not contain oxygen, the content relationship of A <B <C is established, and the above-described content relationship can be sufficiently obtained. Because.

  As described above, the base layer 118 is made to contain oxygen, and the oxygen content of the base layer 118 and the first magnetic recording layer 122a is set so as to satisfy the above relational expression. The separation of the particles can be promoted, and the influence can promote the separation of the crystal particles of the first magnetic recording layer 122a and the substance forming the grain boundary. Thereby, the mixing of oxides into the columnar crystal particles can be reduced, and the crystal orientation of the crystal particles in the first magnetic recording layer 122a can be improved, and consequently the coercive force Hc can be improved.

  It should be noted that if the first underlayer 118a to the first magnetic recording layer 122a are miniaturized in steps, and the mixing of oxides into the magnetic particles of the first magnetic recording layer 122a can be reduced, the second The crystal grains in the magnetic recording layer 122b are naturally refined by the influence of the crystal grains in the first magnetic recording layer 122a, and the mixing of oxides into the magnetic grains is reduced. Therefore, it is sufficient that the content relationship is the above inequality, and the content of oxygen contained in the second magnetic recording layer 122b is not included as an element in the inequality.

  Unlike this embodiment, when the magnetic recording layer 122 in the perpendicular magnetic recording medium 100 is composed of only one layer, the underlayer 118 (the first underlayer 118a and the second underlayer 118b) and a single layer are formed. The oxygen content contained in the magnetic recording layer 122 may be set so as to satisfy the above relational expression. Thereby, the same advantage as this embodiment can be acquired.

  The relationship between the oxygen content of the second underlayer 118b and the first magnetic recording layer 122a (or the single magnetic recording layer 122) is preferably 10 ≦ C / B ≦ 140. “C / B” means “C ÷ B”. This optimizes the oxygen content contained in the first magnetic recording layer 122a (or the single magnetic recording layer 122) and the second underlayer 118b located immediately below the first magnetic recording layer 122a, so that the above-described effects can be achieved most efficiently. Obtainable.

  Further, when the nonmagnetic granular layer 120 is provided between the base layer 118 (first base layer 118a) and the magnetic recording layer 122 (first magnetic recording layer 122a) as in this embodiment, the nonmagnetic granular layer is provided. The oxygen content in the layer 120 is Dmol%, and the oxygen content in the underlayer 118 (the first underlayer 118a and the second underlayer 118b) and the nonmagnetic granular layer 120 is A <B <D. You may set so that a relational expression may be satisfy | filled. As a result, oxygen (content of a substance other than the substance that becomes crystal grains) increases from the first underlayer 118a to the nonmagnetic granular layer 120, and the first underlayer 118a extends from the first underlayer 118a to the nonmagnetic granular layer 120. Particle separation can be promoted stepwise (substantially continuously).

  Further, since the separation of the crystal grains of the nonmagnetic granular layer 120 can be promoted and the mixing of oxides into the crystal grains can be reduced by the influence of the separation of the underlayer 118, the magnetic recording layer is affected by the influence of the nonmagnetic granular layer 120. The separation of the magnetic particles 122 can be promoted, and the mixing of oxides into the magnetic particles can be reduced. Therefore, the crystal orientation of the magnetic particles of the magnetic recording layer 122 formed on the nonmagnetic granular layer 120 can be improved, and the coercive force Hc can be increased.

  The relationship between the oxygen content of the second underlayer 118b and the nonmagnetic granular layer 120 is preferably 20 ≦ D / B ≦ 160. “D / B” means “D ÷ B”. Thereby, the content of oxygen contained in the nonmagnetic granular layer 120 and the second underlayer 118b existing immediately below can be optimized, and the above-described effects can be obtained most efficiently.

  As described above, in the present embodiment, the underlayer 118 has a two-layer structure, but the present invention is not limited to this, and the underlayer 118 can also be formed by a single layer. In such a case, the oxygen content may be increased from the lower side (substrate side) to the upper side (granular layer side) of the base layer 118.

(Example)
On the disk substrate 110, a film was formed in order from the adhesion layer 112 to the auxiliary recording layer 124 in an Ar atmosphere by a DC magnetron sputtering method using a film forming apparatus that was evacuated. Unless otherwise noted, the Ar gas pressure during film formation is 0.6 Pa. For the adhesion layer 112, CrTi ₅₀ was deposited to a thickness of 10 nm. The soft magnetic layer 114 has a first soft magnetic layer 114a and the second soft magnetic layer 114c each has a (Co ₆₀ Fe ₄₀ ) 92-Ta3-Zr5 film thickness of 20 nm, and the spacer layer 114b has a Ru film thickness of 0.5 nm. . The pre-underlayer 116 was formed of NiW ₅ with a thickness of 7 nm. As the first underlayer 118a, 10 nm of Ru containing oxygen was deposited. The second underlayer 118b was formed by depositing 10 nm of Ru containing oxygen at 5 Pa. The nonmagnetic granular layer 120 was formed by depositing nonmagnetic (CoCr ₄₀ ) 88-(SiO ₂ ) 12 with a thickness of 1 nm at 3 Pa. The first magnetic recording layer 122a was formed by depositing (CoCr ₁₂ Pt ₁₈ ) 93- (Cr ₂ O ₃ ) 7 at 2 Pa at 2 nm. The second magnetic recording layer 122b was 10nm deposited at 3Pa a _{(Co 71 Cr 13 Pt 16)} 90- (SiO 2) 5- (TiO 2) 5. The auxiliary recording layer 126 was formed of 7 nm of Co ₆₂ Cr ₁₈ Pt ₁₅ B ₅ . The protective layer 128 was formed to a thickness of 5 nm using C ₂ H ₄ and N ₂ by the CVD method, and the lubricating layer 130 was formed to 1.3 nm using PFPE by the dip coating method.

  Hereinafter, the effectiveness of the present invention will be evaluated using the perpendicular magnetic recording medium 100 obtained by the above manufacturing method. For easy understanding, in the perpendicular magnetic recording medium 100 described below, the oxygen content A contained in the first underlayer 118a is set to 0 mol%, and the oxygen content B contained in the second underlayer 118b. And the oxygen content C contained in the first magnetic recording layer 122a or the oxygen content D contained in the nonmagnetic granular layer 120 will be described. Even in such a case, it goes without saying that A <B <C.

  FIG. 2 is a graph showing the relationship between the oxygen content ratio C / B and the coercive force Hc of the second underlayer 118b and the first magnetic recording layer 122a. As shown in FIG. 2, the coercive force Hc increases remarkably when the oxygen content ratio C / B increases, reaches a peak when C / B reaches around 30, and further increases C / B. Slowly descends. Since the reference value of the coercive force Hc necessary for enabling data retention even when the track width is narrowed as the recording density is increased is 5250 Oe or more, referring to FIG. 2, C / B is 10 to 140. It can be seen that the range is preferred. Therefore, the relationship between the oxygen content in the second underlayer 118b and the first magnetic recording layer 122a is preferably 10 ≦ C / B ≦ 140.

  In FIG. 2, since the C / B is remarkably lowered from near 30 to 0, the relationship between the C / B is less than 1 and the oxygen content of the second underlayer 118b and the first magnetic recording layer. Needless to say, it is not preferable that the relation of the oxygen content of 122a satisfies B> C.

  FIG. 3 is a graph showing the relationship between the oxygen content ratio D / B and the coercive force Hc of the second underlayer 118b and the nonmagnetic granular layer 120. As shown in FIG. 3, the coercive force Hc increases remarkably when the oxygen content ratio D / B increases, reaches a peak when it reaches around D / B 60, and gradually increases as D / B increases. Descend. As described above, since the reference value of the coercive force Hc is 5250 Oe or more, referring to FIG. 3, it can be understood that D / B is preferably in the range of 20 ≦ D / B ≦ 160. Therefore, the relationship between the oxygen content in the second underlayer 118b and the nonmagnetic granular layer 120 is preferably 20 ≦ D / B ≦ 160.

  In FIG. 3, since D / B is remarkably lowered as it approaches 0 from around 60, the relationship between the D / B is less than 1 and the oxygen content of the second underlayer 118b and the nonmagnetic granular layer 120. Needless to say, it is not preferable that the relationship of the oxygen content of B is such that B> D.

  FIG. 4 is a diagram showing the relationship between the oxygen content of the second underlayer 118b and the coercive force Hc. As shown in FIG. 4, the coercive force Hc increases when the oxygen content of the second underlayer 118b increases, and decreases when the oxygen content exceeds about 0.2 mol%. This is because when the second underlayer 118b contains oxygen or an oxide, the separation of Ru crystal grains in the second underlayer 118b is promoted, whereby the oxide of the magnetic recording layer 122 is precipitated at the grain boundaries. Therefore, it is presumed that the mixing of oxides into the columnar crystal particles can be reduced, the crystal orientation is improved, and the coercive force Hc is increased. Note that when the oxygen content is increased beyond 0.2 mol%, the Ru crystal becomes too fine, and as a result, the crystallinity of the Ru crystal is gradually lost and exists on the Ru crystal. It is presumed that the crystal grains of the layer can no longer contribute to the improvement of crystal orientation.

  As described above, according to the perpendicular magnetic recording medium according to the first embodiment, by optimizing the oxygen content of each layer from the underlayer 118 to the magnetic recording layer 122, the magnetic particles of the magnetic recording layer 122 are converted into magnetic particles. Thus, it is possible to improve the crystal orientation of the magnetic particles, increase the coercive force Hc, and improve the reliability of the perpendicular magnetic recording medium.

(Second Embodiment)
As described above, in order to achieve high recording density of the perpendicular magnetic recording medium, improvement of SNR is indispensable, and in order to improve SNR, miniaturization and isolation of magnetic particles in the magnetic recording layer are required. Need to promote. As a result of intensive studies by the inventors, the refinement and isolation of the magnetic particles (crystal grains) in the magnetic recording layer exist on the base layer side that is the basis of the growth, that is, on the disk substrate side with respect to the magnetic recording layer. It was found that the layer was greatly affected. As described in the first embodiment, such a layer changes its state by containing oxygen.

  In the first embodiment, the oxygen content is gradually increased from the underlayer to the magnetic recording layer to improve the crystal orientation of the magnetic particles, whereas in the second embodiment, By making the base layer contain oxygen and an element contained in the granular layer interposed between the magnetic recording layer and the underlayer, crystal grains in the granular layer are made finer and isolated.

  The perpendicular magnetic recording medium according to the second embodiment and the method for manufacturing the perpendicular magnetic recording medium will be described first, and then the elements in the foundation layer 118 and the granular layer, which are features of the second embodiment, will be described. For the perpendicular magnetic recording medium and the method for manufacturing the same according to the second embodiment, only differences from the first embodiment will be described in order to avoid duplication.

  In the second embodiment, a target containing an oxide of an element constituting a granular layer is used for sputtering when forming the second underlayer 118b. Thereby, oxygen can be contained in the second underlayer 118b and the refinement of the Ru crystal particles can be promoted. As a result, fine irregularities are generated on the surface of the base layer 118, and the isolation and miniaturization of crystal grains in the granular layer are promoted, and the SNR can be improved.

  Further, an element contained in the oxide, that is, an element serving as a carrier for allowing the second base layer 118b to contain oxygen is an element constituting the granular layer. Thereby, the fall of the crystal orientation of a granular layer can be prevented. Furthermore, by using a target containing an oxide of an element constituting the granular layer as described above, a desired amount of oxygen can be more easily and uniformly applied to the second underlayer 118b than when the reactive sputtering method is used. It becomes possible to make it contain.

[Configuration of Elements in Underlayer 118 and Granular Layer]
Similar to the first embodiment, also in the second embodiment, the underlayer 118 is composed of two layers, a first underlayer 118a and a second underlayer 118b. The layers made of a Co-based alloy and having a granular structure in which crystal grains are grown in a columnar shape are a nonmagnetic granular layer 120 and a magnetic recording layer 122 (first magnetic recording layer 122a and second magnetic recording layer 122b). Among the layers having such a granular structure, the layer provided on the base layer 118 (second base layer 118b) is the nonmagnetic granular layer 120. Therefore, the granular layer shown in this application is the nonmagnetic granular layer 120. . Therefore, hereinafter, the nonmagnetic granular layer 120 will be described as an example of the granular layer in the present embodiment.

  In the second embodiment, the second underlayer 118b contains an element and oxygen contained in the granular layer, that is, the nonmagnetic granular layer 120.

  By containing oxygen in the second underlayer 118b, the refinement of the Ru crystal particles in the second underlayer 118b is promoted, and thus the crystal grains in the layer formed on the second underlayer 118b are also refined. Is done. In addition, since finer irregularities are generated on the surface of the second underlayer 118b due to the refinement of the Ru crystal grains, the crystal grains of the nonmagnetic granular layer 120 form a columnar granular structure on the irregularities, and the crystal Particle isolation is promoted. As a result, the isolation of the magnetic particles of the magnetic recording layer 122 formed on the nonmagnetic granular layer 120 can be promoted, and the SNR can be improved.

  The element contained in the second underlayer 118b is an element contained in the oxide contained in the target used for forming the second underlayer 118b, and the second underlayer 118b contains oxygen. It is a substance used as a carrier for making it. Since such oxide is decomposed during sputtering, the second base layer 118b is formed from a mixture of Ru, an element contained in the oxide, and oxygen. Therefore, by making the element contained in the second underlayer 118b an element that constitutes the nonmagnetic granular layer 120, the second underlayer 118b is formed without causing a decrease in the crystal orientation of the nonmagnetic granular layer 120. It becomes possible to contain oxygen.

Similar to the first embodiment, also in the second embodiment, the nonmagnetic granular layer 120 is made of CoCr—SiO ₂ . Since such CoCr—SiO ₂ is a CoCr alloy (Co-based alloy), the element contained in the second underlayer 118b includes first one or both of Co and Cr. Next, since CoCr—SiO ₂ contains SiO ₂ as an oxide that segregates around the crystal grains of Co to form a grain boundary, Si is an example of such an element. Therefore, one or a plurality of elements contained in the second underlayer 118b can be selected from the group consisting of Co, Cr, and Si.

  Among the above, Co has an hcp structure similar to Ru and has a lattice constant close to Ru. Therefore, even if Co is contained in the second underlayer 118b, the crystal orientation of the second underlayer 118b is reduced. There is no invitation. Further, Co has a Gibbs free energy ΔG larger than Ru, so that its oxide is more easily reduced than Ru oxide. For this reason, when the second underlayer 118b is formed, oxygen atoms contained in the Co oxide are desorbed from the oxide and combined with Ru to form a Ru oxide. It becomes possible to contain oxygen efficiently. Therefore, Co is optimal as an element constituting the oxide contained in the second underlayer 118b, that is, included in the target used for forming the second underlayer 118b.

As the oxide forming the grain boundary, TiO ₂ and Cr ₂ O ₃ can be suitably used in addition to SiO ₂ . When the oxide is TiO ₂ , the element contained in the second underlayer 118b is either Co or Ti or both, and when the oxide is Cr ₂ O ₃ , the second underlayer 118b is contained. The element to perform is either Co or Cr or both. Further, as the oxide, the material shown in this embodiment can be used. In that case, it goes without saying that the element constituting the material is an element contained in the second underlayer 118b.

In addition, since the granular layer in this embodiment, that is, the nonmagnetic granular layer 120 is made of CoCr—SiO ₂ , there is one kind of oxide that forms the grain boundary, but the present invention is not limited to this, and the grain boundary is not limited to this. A plurality of oxides may be formed. In such a case, the elements constituting the plurality of oxides are elements contained in the second base layer 118b. For example, when the granular layer is made of CoCr—SiO ₂ —TiO ₂ , one or a plurality of elements contained in the second underlayer 118b can be selected from the group consisting of Co, Cr, Si, and Ti.

  In the present embodiment, the element and oxygen contained in the granular layer (nonmagnetic granular layer 120) are contained only in the second underlayer 118b. However, the present invention is not limited to this, and at least the second underlayer is included. What is necessary is just to contain the element and oxygen concerning 118b. Accordingly, elements and oxygen in both the first base layer 118a and the second base layer 118b may be contained.

  The element contained in the base layer 118 is preferably an element whose Gibbs free energy ΔG of the oxide of the element is larger than that of the Ru oxide. This is because, as described above, an oxide whose Gibbs free energy ΔG is larger than Ru is easier to reduce than an oxide of Ru. Therefore, when the base layer 118 is formed, oxygen atoms contained in the oxide of an element having a larger ΔG than Ru are desorbed from the oxide and combined with Ru to form a Ru oxide. This is because the formation 118 can efficiently contain oxygen.

  In the present embodiment, the nonmagnetic granular layer 120 is provided on the second underlayer 118b, but the present invention is not limited to this. For example, when the nonmagnetic granular layer 120 is not provided, the granular layer shown in the present application is the first magnetic recording layer 122a, and the element contained in the second underlayer 118b is an element constituting the first magnetic recording layer 122a. .

  In this embodiment, the underlayer 118 has a two-layer structure including the first underlayer 118a and the second underlayer 118b. However, the present invention is not limited to this, and the underlayer 118 may be a single layer. . Further, in the present embodiment, the magnetic recording layer 122 also has a two-layer structure including the first magnetic recording layer 122a and the second magnetic recording layer 122b. However, the present invention is not limited to this. It may be a single layer.

(Example)
Except for the second underlayer 118b, the auxiliary recording from the adhesion layer 112 is performed in the Ar atmosphere by the DC magnetron sputtering method using the film forming apparatus that is evacuated on the disk substrate 110 as in the first embodiment. The layers were sequentially formed up to the layer 124. The second underlayer 118b is formed of oxygen 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 an oxide of an element constituting the nonmagnetic granular layer 120. And Ru film | membrane containing the element which comprises the nonmagnetic granular layer 120 was formed into a film.

  Hereinafter, the effectiveness of the present invention will be evaluated using the perpendicular magnetic recording medium 100 according to the second embodiment obtained by the above manufacturing method. FIG. 5 is a diagram for explaining the performance evaluation of the perpendicular magnetic recording media 100 of the example and the comparative example. Here, the value of SNR required to achieve further higher recording density of the perpendicular magnetic recording medium 100 is 18.1 or more, and the thermal fluctuation phenomenon of the perpendicular magnetic recording medium 100 is suppressed, and its reliability. The value of the coercive force Hc required for ensuring the above is 4500 Oe or more. Example 1 uses a target containing Co oxide, Example 2 uses a target containing Cr oxide, and Example 3 uses a target containing Si oxide. The perpendicular magnetic recording medium 100 has a second underlayer formed thereon. Comparative Example 1 is a Ru-only target containing no oxide, Comparative Example 2 is a target containing a Ti oxide, and Comparative Example 3 is a target containing a Ta oxide. Each of the perpendicular magnetic recording media 100 is formed using a second underlayer. Note that any type of oxide was contained so that oxygen was 5000 wtppm.

  In the performance evaluation in FIG. 5, evaluation was made in the order of “◎” when the SNR was high, and in the order of “◯” and “Δ” from the high coercive force Hc when the SNR was a similar value. In addition, the evaluation was made x if the required SNR value or coercive force Hc value could not be satisfied.

  As shown in FIG. 5, in all the examples, the SNR and the coercive force Hc are higher than those of the perpendicular magnetic recording medium 100 in which the second underlayer 118b does not contain oxygen, that is, Comparative Example 1, and excellent evaluation is obtained. Obtained. From this, the second underlayer 118b is formed by using the nonmagnetic granular layer 120, that is, the target containing the oxide of the element constituting the layer immediately above the second underlayer 118b. It can be seen that oxygen was contained in the second underlayer 118b, which promoted the refinement of the Ru crystal grains in the second underlayer 118b. As a result, it can be understood that the isolation and refinement of the crystal grains of the nonmagnetic granular layer 120 and hence the magnetic recording layer 122 are promoted, and the SNR is improved. Therefore, it can be seen that containing oxygen in the second underlayer 118b is effective in improving the performance of the perpendicular magnetic recording medium 100.

  Further, when Examples 1, 2 and 3 are compared, although these Examples contain an element constituting the nonmagnetic granular layer 120, evaluation differs depending on the type of the element. This is because Co included in Example 1 has an hcp structure similar to Ru in crystal structure and a lattice constant close to Ru. Therefore, even if Co is included in the second underlayer 118b, the second underlayer is included. This is probably because the crystal orientation of 118b can be maintained and the crystal orientation of the nonmagnetic granular layer 120 and the magnetic recording layer 122 formed thereon is not affected. In addition, since Co has a Gibbs free energy ΔG larger than that of Ru, oxygen atoms of Co oxide combine with Ru to form a Ru oxide, and oxygen is efficiently contained in the second underlayer 118b. Thus, it is considered that the refinement of the crystal grains of the second underlayer 118b was further promoted.

  In Example 2, since the contained element is Cr and is also an element contained in the crystal particles of the granular layer, the ratio is slightly changed, but the influence is considered to be extremely small. In Example 3, the evaluation is lower than that in Example 1 and Example 2. This is because the element contained in the second underlayer 118b is Si constituting the oxide forming the grain boundary, and therefore it is considered that the influence is extremely small when it diffuses into the grain boundary. It is possible that the crystal orientation is disturbed by diffusion. From the above results, it can be understood that Co is optimal as an element contained in the second underlayer 118b.

  In Comparative Examples 2 and 3, an element that is not an element constituting the nonmagnetic granular layer 120 is contained in the second underlayer 118b, and the performance evaluation of the comparative example is lower than that of the example. This is presumably because an element that is not an element constituting the nonmagnetic granular layer 120 is mixed into the second underlayer 118b, and the effect of improving the crystal orientation of the granular layer by the underlayer 118 is hindered.

Here, in this embodiment, the granular layer immediately above the second underlayer 118b is the nonmagnetic granular layer 120, and the material constituting the nonmagnetic granular layer 120 is CoCr—SiO _2. Comparative Example 3 has a low evaluation. However, for example, when the nonmagnetic granular layer 120 is made of CoCr—SiO _2, or the perpendicular magnetic recording medium is not provided with a nonmagnetic granular layer, and the granular layer immediately above the second underlayer 118b is CoCr—SiO _2. In the case of a magnetic recording layer made of —TiO ₂ or the like, it can be easily estimated that high SNR and coercive force Hc can be obtained also in Comparative Example 2, and that high performance evaluation will be achieved. The same applies to Comparative Example 3.

  As described above, according to the perpendicular magnetic recording medium according to the second embodiment, a target containing an oxide of an element contained in a granular layer having a granular structure and formed immediately above the underlayer 118 is used. By forming the underlayer, oxygen can be contained in the underlayer 118 using such an element as a carrier. As a result, the refinement of the Ru crystal grains in the underlayer 118 can be promoted, and further refinement and isolation of the crystal grains of the granular layer, and hence the magnetic recording layer 122, can be achieved, thereby improving the SNR. it can. Therefore, the recording density of the perpendicular magnetic recording medium 100 can be further increased.

(Third embodiment)
The inventors have intensively studied to achieve a high recording density of the perpendicular magnetic recording medium. As a result, the underlayer is not only formed of a Ru2 layer having a different gas pressure, but also contains Ru containing oxide (oxygen). It has been found that by forming three layers with a material sandwiched between them, it is possible to achieve both improvement in recording / reproduction characteristics by promoting separation and improvement in reliability by reducing Ru # 2 gas pressure.

  Therefore, in the third embodiment, the underlying layer made of Ru is not only two layers of Ru layers formed by the film formation process having different gas pressures as in the first embodiment, but also an oxide (oxygen) between them. A perpendicular magnetic recording medium consisting of three layers sandwiching a Ru layer made of a Ru material containing) will be described. For the perpendicular magnetic recording medium and the method for manufacturing the same according to the third embodiment, only differences from the first embodiment will be described in order to avoid duplication.

  FIG. 6 is a diagram for explaining the configuration of a perpendicular magnetic recording medium according to the third embodiment. As shown in FIG. 6, the perpendicular magnetic recording medium 200 includes a disk substrate 110, an adhesion layer 112, a soft magnetic layer 114, a pre-underlayer 116, an underlayer 218, a magnetic recording layer 122, an auxiliary recording layer 124, and a medium protective layer 126. The lubricating layer 128 is used.

  FIG. 7 is a configuration diagram of the underlayer 218 in the perpendicular magnetic recording medium 200 shown in FIG. In the third embodiment, the base layer 218 (also referred to as a Ru-based base layer or an intermediate layer) has a three-layer structure made of Ru shown in FIG. That is, the base layer 218 includes a first base layer 218a on the lower layer side (Ru # 1 layer that is the first base layer), and a third base layer 218c on the upper layer side (Ru # 2 layer that is the third base layer). The second underlayer 218b (the second underlayer is oxygen-containing) sandwiched between the first underlayer 218a (Ru # 1 layer) and the third underlayer 218c (Ru # 2 layer). Ru layer).

The material of the Ru layer not containing oxide (oxygen), that is, the first underlayer 218a and the third underlayer 218c can be selected from RuCr and RuCo in addition to Ru. Ru has an hcp structure and can satisfactorily orient a magnetic recording layer containing Co as a main component. As a material of the Ru layer containing oxide (oxygen), that is, the second underlayer 218b, Ru—SiO ₂ , Ru—TiO ₂ , Ru—Cr ₂ O ₃ , Ru—CoO, Ru—CuO, RuO, Ru can be selected from _{-SiO 2 + TiO 2, Ru-} TiO 2 + Cr 2 O 3, Ru-SiO 2 + Cr2O 3, Ru-SiO 2 + TiO 2 + Cr 2 O 3. Ru + oxide can be expected to improve characteristics, such as _{Ru-SiO 2} + TiO 2 such composite oxide.

  FIG. 8 is a diagram showing the relationship between the material of the underlayer 218 and the film forming gas pressure. As shown in FIG. 8, the gas pressure condition in the film formation process of the underlayer 218 is such that when forming the upper third base layer 218 c, Ar gas is formed more than when forming the lower first base layer 218 a. The gas pressure is increased. Further, the gas pressure when forming the second underlayer 218b may be either a low gas pressure similar to that when forming the first underlayer 218a, or a higher gas pressure higher than that. However, when the gas pressure is high, it is necessary to suppress the film to a sparse state so that reliability is not deteriorated.

  Here, as described in the first embodiment, the crystal orientation can be improved by increasing the gas pressure when forming the base layer (the third base layer 218c on the upper layer side in this embodiment). On the other hand, the film becomes sparse and the reliability decreases. Therefore, in the third embodiment, a structure in which the second underlayer 218b (oxygen-containing Ru layer) is sandwiched between the first underlayer 218a (Ru # 1 layer) and the third underlayer 218c (Ru # 2 layer). It was. Therefore, the effect of improving the separability of the magnetic particles can be obtained, and the reliability can be maintained even if the Ar gas pressure in forming the third underlayer 218c is lowered. Even when the pressure was reduced from 6 Pa to 4 Pa at a high gas pressure, the recording / reproduction characteristics were not deteriorated.

  Note that at least the first base layer 218a of the first base layer 218a and the second base layer 218b is formed at a low gas pressure of 0.3 Pa to 1.5 Pa, and the second base layer 218b and the third base layer 218c Of these, at least the third underlayer 218c is preferably formed at a high gas pressure of 3 Pa to 7 Pa.

  Through the above manufacturing process, the perpendicular magnetic recording medium 200 can be obtained. The perpendicular magnetic recording medium 200 is not provided with the nonmagnetic granular layer 120 provided in the first embodiment (see FIG. 6). This is because the nonmagnetic granular layer 120 is not necessarily required, but the configuration is not limited to this, and the auxiliary recording layer 124 may be provided also in the perpendicular magnetic recording medium 200.

(Example)
The effectiveness of the present invention will be described below using examples and comparative examples. In the following description, the configurations of the perpendicular magnetic recording media of the examples and comparative examples will be described in detail, and then the evaluation thereof will be described in detail.

[Example 4]
Amorphous aluminosilicate glass was molded into a disk shape with a direct press to create a glass disk. The glass disk was then ground, polished, and chemically strengthened in order to obtain a smooth nonmagnetic disk substrate 110 made of a chemically strengthened glass disk. The disk substrate 110 has a diameter of 65 mm, an inner diameter of 20 mm, and a disk thickness of 0.635 mm. When the surface roughness of the obtained disk substrate 110 was observed with an AFM (atomic force microscope), it was confirmed that the surface was smooth with Rmax of 2.18 nm and Ra of 0.18 nm. Rmax and Ra conform to Japanese Industrial Standard (JIS).

On the disk substrate 110, the adhesion layer 112, the soft magnetic layer 114, the pre-underlayer 116, the underlayer 218, the magnetic recording layer 122, and the auxiliary recording layer 124 were sequentially formed by DC magnetron sputtering. Unless otherwise noted, the Ar gas pressure during film formation is 0.6 Pa. As the adhesion layer 112, a 10 nm CrTi ₅₀ layer was formed using a Ti alloy target. As the soft magnetic layer 114, a laminated film of two layers of soft magnetic materials that are antiferromagnetic exchange coupled across a nonmagnetic layer was formed. In the formation of the soft magnetic layer 114, first, as the first soft magnetic material layer (first soft magnetic layer 114a), 24 nm of (Co ₆₀ Fe ₄₀ ) 92-Ta3-Zr5 (amorphous layer) is formed. A film was formed. Next, a 2 nm Ru layer was formed as a nonmagnetic layer (spacer layer 114b). Then, as the second soft magnetic material layer (second soft magnetic layer 114c), an amorphous layer of 22.5 nm was formed in the same manner as the first soft magnetic material layer. Subsequently, a 6 nm NiW ₅ layer was formed as the pre-underlayer 116 on the soft magnetic layer 114.

  Next, three Ru layers were formed as the base layer 218. As the first underlayer 218a (Ru # 1 layer) on the lower layer side, a layer having a film thickness of 10 nm was formed by setting the gas pressure of the sputtering gas at the time of film formation to 0.7 Pa. The second underlayer 218b (oxygen-containing Ru layer) was formed using a Ru target (Ru—O) containing oxygen so as to have a concentration of 5000 wtppm at a sputtering gas pressure of 4 Pa. The film thickness of the second underlayer 218b was 2 nm. As the third base layer 218c (Ru # 2 layer) on the upper layer side, a gas pressure of sputtering gas at the time of film formation was 4.0 Pa, and a layer having a film thickness of 8 nm was formed. The gas pressure at the time of forming the third base layer 218c on the upper layer side is lowered from the conventional gas pressure (6 Pa) to 4 Pa.

Then, a hard magnetic target made of (Co ₇₁ Cr ₁₃ Pt ₁₆ ) 90- (SiO ₂ ) 5- (TiO ₂ ) 4- (Cr ₂ O ₃ ) 1 is used as the magnetic recording layer 122. A 5 nm film was formed. Next, a 7 nm thick Co ₆₂ Cr ₁₈ Pt ₁₅ B ₅ film was formed as the auxiliary recording layer 124 with the nonmagnetic layer interposed therebetween. Subsequent to the formation of the auxiliary recording layer 124, a medium protective layer 126 made of hydrocarbon (hydrogenated carbon) was formed by CVD. The film thickness of the medium protective layer 126 was 5 nm. Thereafter, a lubricating layer 128 made of PFPE (perfluoropolyether) was formed to 1.3 nm by dip coating. The film thickness of the lubricating layer 128 was 1 nm. As described above, the perpendicular magnetic recording medium according to Example 4 was produced.

[Example 5]
Since Example 5 was made the same conditions as Example 4 except for the underlayer 218, only the underlayer 218 will be described. As the first underlayer 218a (Ru # 1 layer) on the lower layer side, a layer having a film thickness of 10 nm was formed by setting the gas pressure of the sputtering gas at the time of film formation to 0.5 Pa. The second underlayer 218b was formed using a Ru target (Ru—SiO ₂ ) containing SiO ₂ so that oxygen was 5000 wtppm, at a sputtering gas pressure of 4.5 Pa. The film thickness of the second underlayer 218b was 4 nm. As the third base layer 218c (Ru # 2 layer) on the upper layer side, a gas pressure of sputtering gas at the time of film formation was set to 4.5 Pa, and a layer having a film thickness of 6 nm was formed. A perpendicular magnetic recording medium according to Example 5 was produced under the same conditions as in Example 4 except for the underlayer 218.

[Example 6]
Since Example 6 was made the same conditions as Example 4 except for the underlayer 218, only the underlayer 218 will be described. As the first underlayer 218a (Ru # 1 layer) on the lower layer side, a layer having a film thickness of 12 nm was formed by setting the gas pressure of the sputtering gas at the time of film formation to 0.7 Pa. The second underlayer 218b was formed at a sputtering gas pressure of 4.2 Pa using a Ru target (Ru—TiO ₂ ) containing TiO ₂ so that oxygen was 5000 wtppm. The film thickness of the second underlayer 218b was 3 nm. As the third base layer 218c (Ru # 2 layer) on the upper layer side, a gas pressure of sputtering gas during film formation was 4.2 Pa, and a layer having a thickness of 7 nm was formed. A perpendicular magnetic recording medium according to Example 6 was produced under the same conditions as in Example 4 except for the underlayer 218.

[Example 7]
Since Example 7 was made the same conditions as Example 4 except for the underlayer 218, only the underlayer 218 will be described. For the first underlayer 218a (Ru # 1 layer) on the lower layer side, a layer having a film thickness of 10 nm was formed with the gas pressure of the sputtering gas at the time of film formation being 0.6 Pa. The second underlayer 218b was formed using a Ru target (Ru—Cr ₂ O ₃ ) containing Cr ₂ O ₃ so that the oxygen was 5000 wtppm and a sputtering gas gas pressure of 4.0 Pa. The film thickness of the second underlayer 218b was 3 nm. For the third base layer 218c (Ru # 2 layer) on the upper layer side, a gas pressure of sputtering gas during film formation was 4.0 Pa, and a layer having a thickness of 7 nm was formed. A perpendicular magnetic recording medium according to Example 7 was produced under the same conditions as in Example 4 except for the underlayer 218.

[Example 8]
Since Example 8 was the same as Example 4 except for the underlayer 218, only the underlayer 218 will be described. As the first underlayer 218a (Ru # 1 layer) on the lower layer side, a layer having a thickness of 8 nm was formed by setting the gas pressure of the sputtering gas at the time of film formation to 0.7 Pa. The second underlayer 218b was formed using a Ru target (Ru—CoO) containing CoO so that oxygen becomes 5000 wtppm and a sputtering gas gas pressure of 4.0 Pa. The film thickness of the second underlayer 218b was 2 nm. As the third base layer 218c (Ru # 2 layer) on the upper layer side, a gas pressure of sputtering gas at the time of film formation was 4.0 Pa, and a layer having a film thickness of 8 nm was formed. A perpendicular magnetic recording medium according to Example 8 was produced under the same conditions as in Example 4 except for the underlayer 218.

[Comparative Example 4]
In Comparative Example 4, the base layer was a Ru2 layer not containing an oxide, and the same procedure as in Example 4 was performed except for the base layer. FIG. 9 is a diagram showing the relationship between the material of the underlayer and the deposition gas pressure in the perpendicular magnetic recording medium of the comparative example. In Comparative Example 4, as shown in FIG. 9, two Ru layers (Ru # 1 layer as the first underlayer + Ru # 2 layer as the second underlayer) were formed as the underlayer. In the Ru # 1 layer on the lower layer side, the gas pressure of the sputtering gas at the time of film formation was 0.7 Pa (low gas pressure), and the film thickness was 10 nm. In the upper Ru # 2 layer, the gas pressure of the sputtering gas during film formation was 4.0 Pa (high gas pressure), and the film thickness was 10 nm.

(Evaluation)
FIG. 10 is a diagram illustrating a list of characteristics of Examples 4 to 8 and Comparative Example 4. In the characteristic list shown in the figure, Δθ50 (Ru) and Δθ50 (Co) related to Examples 4 to 8 are perpendicular magnetic including first base layer 218a + second base layer 218b + third base layer 218c (three layers). The degree of orientation of the recording medium 200 (the entire magnetic disk), and Δθ50 (Ru) and Δθ50 (Co) in Comparative Example 4 are magnetic fields including an underlayer (two layers) composed of Ru # 1 layer + Ru # 2 layer. This is the degree of orientation of the entire disk. In each of Examples 4 to 8 and Comparative Example 4, regarding Co, the degree of orientation of Co in the magnetic recording layer 122 above it is shown. Compared to Comparative Example 4, in Examples 4 to 8, it was confirmed that the degree of orientation of the second underlayer 218b did not deteriorate.

  Further, from the evaluation items bER, MWw, Squash, and SNm of Examples 4 to 8, in the formation of the underlayer of the perpendicular magnetic recording medium, as in the third embodiment, between the Ru2 layers (the first underlayer 218a and By introducing a layer (second base layer 218b) formed with an oxide (oxygen) -containing Ru target between the third base layer 218c), the separation layer is promoted, that is, the RW characteristic ( bER, MWw, Squash, SNm) can be confirmed to be improved. Further, from the evaluation item Pin-on [pass count] regarding impact property, the gas pressure at the time of film formation of the third underlayer 218c (Ru # 2) is set to a low gas pressure, so that the film becomes dense and impact property is improved. The increase in reliability (Pin-on [pass count]) was confirmed.

  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 and a method of manufacturing the perpendicular magnetic recording medium.

Claims (21)

In a perpendicular magnetic recording medium comprising at least a base layer made of ruthenium and a magnetic recording layer for recording signals in this order on a disk substrate,
The underlayer is composed of a first underlayer and a second underlayer,
The content of oxygen contained in the first underlayer is Amol%,
The content of oxygen contained in the second underlayer is Bmol%,
When the content of oxygen contained in the magnetic recording layer is Cmol%,
The perpendicular magnetic recording medium according to claim 1, wherein the content relationship is A <B <C.   The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer contains an oxide that segregates around the crystal grains to form a grain boundary.   2. The perpendicular magnetic recording medium according to claim 1, wherein the content relationship further satisfies 10 ≦ C / B ≦ 140. The perpendicular magnetic recording medium according to claim 1, wherein the magnetic recording layer is made of CoCrPt—SiO ₂ —TiO ₂ . The magnetic recording layer is composed of a first magnetic recording layer and a second magnetic recording layer,
2. The perpendicular magnetic recording medium according to claim 1, wherein the content Cmol% of oxygen contained in the magnetic recording layer is a content of oxygen contained in the first magnetic recording layer. The perpendicular magnetic recording medium according to claim 5, wherein the first magnetic recording layer is made of CoCrPt—Cr ₂ O ₃ . The perpendicular magnetic recording medium according to claim 5, wherein the second magnetic recording layer is made of CoCrPt—SiO ₂ —TiO ₂ . In a perpendicular magnetic recording medium comprising at least an underlayer made of ruthenium, a nonmagnetic granular layer, and a magnetic recording layer for recording signals in this order on a disk substrate,
The underlayer is composed of a first underlayer and a second underlayer,
The content of oxygen contained in the first underlayer is Amol%,
The content of oxygen contained in the second underlayer is Bmol%,
When the content of oxygen contained in the nonmagnetic granular layer is Dmol%,
The perpendicular magnetic recording medium according to claim 1, wherein the content relationship is A <B <D.   The perpendicular magnetic recording medium according to claim 8, wherein the content relationship further satisfies 20 ≦ D / B ≦ 160. The perpendicular magnetic recording medium according to claim 8, wherein the nonmagnetic granular layer is made of CoCr—SiO ₂ . In a method of manufacturing a perpendicular magnetic recording medium comprising, on a disk substrate, an underlayer composed of at least a first underlayer made of ruthenium and a second underlayer, and a magnetic recording layer for recording a signal in this order.
Forming the first underlayer by sputtering under an atmospheric gas at a predetermined pressure;
Forming the second underlayer by sputtering under an atmosphere gas higher than the predetermined pressure;
A method for manufacturing a perpendicular magnetic recording medium, wherein the target used for forming the second underlayer contains oxygen. In a perpendicular magnetic recording medium comprising at least a ruthenium underlayer on a disk substrate and a granular layer having a granular structure in which crystal grains are grown in a columnar shape from a Co-based alloy on the underlayer,
The perpendicular magnetic recording medium, wherein the underlayer contains an element and oxygen contained in the granular layer. The underlayer is composed of a first underlayer and a second underlayer that have different gas pressures during film formation by sputtering in this order,
The perpendicular magnetic recording medium according to claim 12, wherein at least the second underlayer contains the element and oxygen.   The perpendicular magnetic recording medium according to claim 12, wherein the element is Co. The Co-based alloy is a CoCr alloy,
The perpendicular magnetic recording medium according to claim 12, wherein the element is one or both of Co and Cr. The granular layer includes an oxide that segregates around the crystal grains to form grain boundaries,
The oxide is one or more selected from the group consisting of SiO ₂ , TiO ₂ , Cr ₂ O ₃ ,
When the oxide is SiO ₂ , the element is either Co or Si or both,
When the oxide is TiO ₂ , the element is either Co or Ti or both,
The perpendicular magnetic recording medium according to claim 12, wherein when the oxide is Cr ₂ O ₃ , the element is one or both of Co and Cr.   The perpendicular magnetic recording medium according to claim 12, wherein the element is an element whose Gibbs free energy ΔG of the oxide of the element is larger than that of the ruthenium oxide. A first underlayer film forming step of sputtering ruthenium under an atmospheric gas at a predetermined pressure;
A second underlayer film forming step of sputtering ruthenium under an atmospheric gas higher than the predetermined pressure;
A granular layer forming step of forming a granular layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape on the second underlayer,
A method for manufacturing a perpendicular magnetic recording medium, wherein a target used for forming the second underlayer includes an oxide of an element constituting the granular layer. A perpendicular magnetic recording medium in which at least a Ru-based underlayer and a magnetic recording layer are formed in this order on a disk substrate,
The Ru-based underlayer is composed of three layers of a first underlayer, a second underlayer, and a third underlayer from the disk substrate side,
The first and third underlayers are made of Ru (ruthenium) or a Ru alloy material, and the second underlayer is made of a Ru or Ru alloy material containing an oxide. Medium. The first to third underlayers are continuously formed by different film formation processes,
At least the first underlayer of the first and second underlayers is formed at a low gas pressure of 0.3 Pa to 1.5 Pa, and at least the third underlayer of the second and third underlayers is formed. 2. The perpendicular magnetic recording medium according to claim 1, wherein the base layer is formed at a high gas pressure of 3 Pa to 7 Pa. A method of manufacturing a perpendicular magnetic recording medium in which at least a Ru-based underlayer and a magnetic recording layer are formed in this order on a disk substrate,
The Ru-based underlayer is made of a first underlayer made of Ru or Ru alloy material from the disk substrate side, a second underlayer made of Ru or Ru alloy material containing an oxide, and Ru or Ru alloy material. 3. A method of manufacturing a perpendicular magnetic recording medium, wherein three layers of a third underlayer are sequentially formed.

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