JP2010086565A - Perpendicular magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium capable of enhancing OW characteristics while maintaining coercive force Hc and an SNR and achieving high recording density, and to provide a method of manufacturing the same. <P>SOLUTION: The perpendicular magnetic recording medium sequentially includes at least: a front underlayer 116 containing Ni, W and Pd on a disk base body 110; an underlayer 118 film-deposited on the front underlayer 116 and containing Ru; and a non-magnetic granular layer 120 film-deposited on the underlayer 118 and having a granular structure which is made of a Co-based alloy and whose crystal grains grow in a columnar shape. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like 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 perpendicular magnetic recording disk used for an HDD or the like, it is necessary to refine the magnetic crystal grains constituting the magnetic recording layer for recording information signals and reduce the layer thickness. was there. Specifically, it is necessary to improve coercive force and electromagnetic conversion characteristics such as SNR (Signal to Noise Ratio). However, in the case of a magnetic disk of the in-plane magnetic recording method (also called longitudinal magnetic recording method or horizontal magnetic recording method) that has been commercialized conventionally, as a result of the progress of miniaturization of magnetic crystal grains, superparamagnetic phenomenon The thermal stability of the recording signal is lost, and the so-called thermal fluctuation phenomenon that the recording signal disappears has occurred, which has been an obstacle to increasing the recording density of the in-plane magnetic disk. In order to solve this hindrance factor, a perpendicular magnetic recording disk 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.

  The problem of thermal stability has been solved, and in recent years, HDD drives have come to be used even in environments that are not conventionally used. For example, a stable operation under severe conditions has been demanded for HDDs, such as a car navigation system mounted on an automobile.

  In order to operate stably under severe conditions, it is necessary to improve the coercive force as well as the thermal stability. The coercive force is a force for magnetizing a magnetized magnetic body in the reverse direction. If the coercive force is weak, information stored in the HDD is easily lost. Currently, HDDs have been developed that have higher coercivity than conventional products. Several methods for increasing the coercive force are known. For example, methods such as increasing the thickness of the magnetic recording layer and improving the crystal orientation of the magnetic recording layer (increasing the perpendicular magnetic anisotropy) are known. ing.

Conventionally, a Ru underlayer is provided to increase the crystal orientation of the magnetic recording layer, and a pre-underlayer (seed layer) is provided to further improve the crystal orientation of the Ru underlayer. Yes. Patent Document 1 proposes a perpendicular magnetic recording medium using an alloy containing NiW as a seed layer (pre-underlayer). Patent Document 1 describes that a seed layer is formed using a sputtering target containing Ni, and that the grain size of an underlayer or a granular magnetic layer deposited subsequently to the seed layer is reduced to reduce lattice mismatch. ing. Patent Document 1 describes that as the amount of W increases, the crystal size decreases and the recording / reproduction characteristics improve, but if added too much, Δθ50 of the Ru underlayer deteriorates and the crystal orientation deteriorates. (Paragraph 0028).
JP 2007-179598 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 increasing the recording density include improvements in magnetostatic characteristics such as coercive force Hc and reverse domain nucleation magnetic field Hn, and electromagnetic properties such as overwriting characteristics (OW characteristics), SNR, and narrowing of track width. Improvement of conversion characteristics can be mentioned. When the coercive force Hc is increased, the magnetized magnetic field is not easily affected by the external magnetic field, and the force to keep the recorded signal is increased. Further, a high SNR is important for reading and writing accurately and at high speed even in a recording bit having a small area.

  Among the above, the OW characteristic is a characteristic indicating the ease of rewriting the signal of the magnetic disk. The OW characteristic and the coercive force Hc are basically in a trade-off relationship, and a strong coercive force means that the magnetization direction is difficult to reverse, so that it is difficult to rewrite intentionally. In order to perform rewriting while having a high coercive force, it is conceivable to improve the performance of the magnetic head or improve the OW characteristics by another means.

  However, although the performance of the magnetic head itself is gradually evolving, it cannot smoothly follow the rapid improvement in coercive force. On the magnetic head side, low power consumption is one of the major issues, and there is a demand for rewriting without applying a large output.

  Although paradoxically, if high OW characteristics can be obtained, rewriting can be performed even if the coercive force Hc is increased. Therefore, it is allowed to increase the coercive force without changing the performance of the magnetic head. The If a film having a high coercive force is used, the thickness of the magnetic recording layer can be reduced. As a result, the spacing loss from the magnetic head to the soft magnetic layer can be reduced (narrowed), so that the diffusion of magnetic flux can be prevented and the density thereof can be increased, and the recording bits can be miniaturized. Recording density can be increased. Therefore, in order to achieve high recording density, improvement of OW characteristics has become a very important issue as well as development of a film having a high coercive force Hc and improvement of SNR.

  In view of these problems, the present invention improves the OW characteristics while maintaining the coercive force Hc and SNR, and manufactures a perpendicular magnetic recording medium and a perpendicular magnetic recording medium that can achieve higher recording density. It aims to provide a method.

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

  That is, in order to solve the above problems, a typical configuration of the perpendicular magnetic recording medium according to the present invention is formed on a disk substrate on a front base layer containing at least Ni, W, and Pd, and on the front base layer. And a granular layer having a granular structure in which crystal grains are grown in a columnar shape made of a Co-based alloy formed on the underlying layer.

  As described above, by including Pd in the pre-underlayer, it is possible to improve the OW characteristics as compared with the conventional pre-underlayer containing no Pd.

  The pre-underlayer may have a Pd content of 3 at% to 15 at%. This is because if it is 3 at% or less, the desired effect of improving the OW characteristics cannot be obtained. On the other hand, if it is 15 at% or more, the Ni content decreases and the crystal orientation deteriorates.

  The pre-underlayer may have a total content of W and Pd of 5 at% to 25 at%. If it is 5 at% or less, Ni becomes magnetized (soft magnetism) and becomes a noise source. On the other hand, if it is 25 at% or more, Ni becomes amorphous and the crystal orientation of the layer above it cannot be improved.

  Δθ50 between the underlayer and the granular layer may be 4 degrees or less. By keeping the orientation dispersion angle Δθ50 within a desired range, the SNR of the perpendicular magnetic recording medium is improved and the recording density can be improved.

  In order to solve the above problems, a method for manufacturing a perpendicular magnetic recording medium comprising at least a front underlayer, a Ru underlayer, and a magnetic recording layer on a substrate in order, Sputtering may be performed using a target containing Ni, W, and Pd while applying a DC bias to the substrate.

  With this configuration, it is possible to obtain a magnetic recording medium that can improve the OW characteristics while maintaining the coercive force Hc and SNR, and contribute to a higher recording density.

  The DC bias voltage may be within a range of (-300V to -500V). With this configuration, the soft magnetic layer, the pre-underlayer, and the magnetic recording layer can be formed more smoothly.

  According to the configuration of the present invention, by setting the ratio of Ni, W, and P, which are metals contained in the previous underlayer, within a predetermined range, the OW characteristics can be promoted while maintaining the coercive force Hc and SNR. It is possible to provide a perpendicular magnetic recording medium and a method of manufacturing the perpendicular magnetic recording medium that can achieve the higher recording density.

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

(Embodiment)
In the present embodiment, first, after describing an embodiment of the perpendicular magnetic recording medium according to the present invention and the manufacturing method thereof, a pre-underlayer containing at least Ni, W, and Pd, which is a feature of the present invention, an underlayer containing Ru, The relationship between the content of oxygen contained in the granular layer and the magnetic recording layer will be described.

  FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 according to the present embodiment. The perpendicular magnetic recording medium 100 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.

  By forming the adhesion layer 112 in contact with the disk substrate 110, the adhesion between the soft magnetic layer 114 formed thereon and the disk substrate 110 and the soft magnetic layer 114 can be improved. Peeling of the layer 114 can be prevented. The crystal grain of each layer formed on this is provided with the function to make it fine and uniform. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous (amorphous) alloy film so as to correspond to the amorphous glass surface.

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

  The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to 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 composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c includes a Co-based alloy such as CoTaZr, a Co—Fe based alloy such as CoCrFeB and CoFeTaZr, and a Ni like a [Ni—Fe / Sn] n multilayer structure. A Fe 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 the easy axis of the hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon. It has a function of orienting the disk in the vertical direction. 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.

  As the material of the pre-underlayer 116, an alloy made of Ni, W, Pd is used. By including Pd in the pre-underlayer 116 as described above, it is possible to improve the OW characteristics as compared with the conventional pre-underlayer 116 that does not contain Pd.

  In the front ground layer 116, the coercive force Hc is improved by increasing the Ni content of the NiW alloy. This is because the (111) face of the Ni fcc structure (face-centered cubic lattice structure) corresponds to the (0001) of the hcp structure of the Ru underlayer, thereby improving the crystal orientation of the film above it. It is considered that the coercive force Hc is improved. On the other hand, when the ratio of Ni decreases, when the predetermined ratio is exceeded, the crystal structure of the alloy containing Ni becomes amorphous.

  That is, the more Ni in the pre-underlayer 116, the better the crystal orientation of the layer above it, and the addition of W promotes the refinement of crystals. If Pd is further added, the OW characteristics are improved. This is presumably because the saturation magnetic field Hs is reduced by adding Pd. In addition, since Pd itself has an fcc structure, crystal orientation can be maintained, and Pd is considered to promote the refinement of Ni similarly to W.

  The pre-underlayer 116 may have a Pd content of 3 at% to 15 at%. As described above, OW characteristics can be improved by adding Pd to NiW. This is because if it is 3 at% or less, the desired effect of improving the OW characteristics cannot be obtained. On the other hand, if it is 15 at% or more, the Ni content decreases and the crystal orientation deteriorates.

  The ratio of W and Pd combined in Ni is preferably between 5 at% and 25 at%, which is the peak of OW characteristics. With this configuration, the required performance can be realized. If it is 5 at% or less, Ni becomes magnetic (soft magnetism), and the front ground layer 116 becomes a noise source. On the other hand, if it is 25 at% or more, Ni becomes amorphous, and the crystal orientation of the layer above it cannot be improved.

  Δθ50 between the underlayer and the granular layer may be 4 degrees or less. Δθ50 represents the degree of variation in crystal orientation, and the smaller the value, the better the orientation. By improving the crystal orientation control within a desired range of Δθ50, the film quality of the previous underlayer is improved. The pre-underlayer 116 having an improved Δθ50 has an ordered crystal structure, and as a result, the crystal orientation is improved. As a measuring method of Δθ50, the magnetic anisotropy is increased and the magnetic interaction is increased. Therefore, the coercive force Hc is also improved. As a result, the SNR of the perpendicular magnetic recording medium 100 becomes good, and the recording density can be improved.

  For the formation of the pre-underlayer, it is desirable to apply a DC bias. The DC bias voltage may be within a range of (−300V to −500V). With this configuration, the pre-underlayer 116 can be formed more smoothly.

  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.

  Furthermore, in this embodiment, a target containing an oxide of an element constituting a granular layer described later 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. 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 (Cr), chromium oxide (Cr ₂ O ₃ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  In this embodiment, the nonmagnetic granular layer 120 is provided on the underlayer 188 (second underlayer 188b). However, the present invention is not limited to this, 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.

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.

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

The materials used for the first magnetic recording layer 122a and the second magnetic recording layer 122b described above are merely examples, and the present invention is not limited thereto. In the present embodiment, the first magnetic recording layer 122a and the second magnetic recording layer 122b are made of different materials (targets). However, the present invention is not limited to this, and materials having the same composition and type may be used. Examples of the nonmagnetic substance for forming the nonmagnetic region include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (Cr _X O _Y ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), Examples thereof include oxides such as tantalum oxide (Ta ₂ O ₅ ), iron oxide (Fe ₂ O ₃ ), and boron oxide (B ₂ O ₃ ). Further, nitrides such as _BN, a carbide such as B 4 _{C 3} can also be suitably used.

Furthermore, in this embodiment, one type of nonmagnetic material (oxide) is used in the first magnetic recording layer 122a and two types of nonmagnetic substances (oxides) in the second magnetic recording layer 122b. However, the present invention is not limited to this. It is also possible to use a composite of two or more kinds of nonmagnetic substances in either or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b. Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to contain SiO ₂ and TiO ₂ as in this embodiment. Therefore, unlike the present embodiment, when the magnetic recording layer 122 is composed of only one layer, the magnetic recording layer 122 is preferably made of CoCrPt—SiO ₂ —TiO ₂ .

  The 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 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.

  Note that “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 with the granular magnetic grains of the magnetic recording layer 122 (with exchange coupling), and heat resistance. It is thought that fluctuation characteristics and SNR are improved. In addition, since the crystal grains connected to the granular magnetic grains (crystal grains having magnetic interaction) have a larger area than the cross section of the granular magnetic grains, the magnetization is easily reversed by receiving a large amount of magnetic flux from the magnetic head. It is thought to improve the characteristics.

  The medium protective layer 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. Other methods for manufacturing the lubricating layer 128 include a spray method, and the film may be formed by a method other than the dip coating method.

(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. The adhesion layer 112 was made of CrTi. In the soft magnetic layer 114, the composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c was CoFeTaZr, and the composition of the spacer layer 114b was Ru. The composition of the pre-underlayer 116 was an alloy using Ni, W, and Pd. As the first underlayer 118a, a Ru film was formed in an Ar atmosphere at a predetermined pressure (low pressure: for example, 0.6 to 0.7 Pa). 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. The composition of the nonmagnetic granular layer 120 was nonmagnetic CoCr—SiO ₂ . The first magnetic recording layer 122a contained Cr ₂ O ₃ as an example of an oxide at the grain boundary part, and formed a hcp crystal structure of CoCrPt—Cr ₂ O ₃ . The second magnetic recording layer 122b contains SiO ₂ and TiO ₂ as examples of complex oxides (plural types of oxides) at the grain boundary part, and has a CoCrPt—SiO ₂ —TiO ₂ hcp crystal structure. The composition of the auxiliary recording layer 124 was CoCrPtB. The medium protective layer 126 was formed using C ₂ H ₄ and CN by the CVD method, and the lubricating layer 128 was formed using PFPE by the dip coating method.

Hereinafter, the effectiveness of the present embodiment will be evaluated using the perpendicular magnetic recording medium 100 obtained by the above manufacturing method. In Example 1, the pre-underlayer 116 was Ni ₉₂ W ₅ Pd ₃ , Comparative Example 1 was Ni ₉₅ W ₅ , and Comparative Example 2 was Pd. The configuration described above is used except for the pre-underlayer 116.

  FIG. 2 shows the relationship between the film thickness and the OW characteristics when the pre-underlayer 116 is formed. According to FIG. 2, the OW characteristics tend to decrease as the thickness of the front ground layer 116 increases as a whole. This is because the coercive force Hc is improved by increasing the thickness of the front ground layer 116, and the OW specification is lowered instead. However, it can be seen that the OW characteristics of Example 1 are higher than those of Comparative Example 1 and Comparative Example 2 even when the film thickness is the same, indicating good results.

  FIG. 3 shows the relationship between the film thickness and SNR characteristics when the pre-underlayer 116 is formed. Although Example 1 has some differences in characteristics depending on the film thickness, it can be seen that the results are almost the same or better than Comparative Example 1. Note that Comparative Example 2 shows a significantly lower value than that of Example 1 and Comparative Example 1.

  FIG. 4 shows the relationship between the film thickness and the coercive force when the pre-underlayer 116 is formed. According to FIG. 4, the coercive force Hc tends to be improved as the thickness of the pre-underlayer 116 increases as a whole. Among them, the comparative example 2 shows the most excellent characteristics with respect to the coercive force, followed by the comparative example 1 and finally the example 1. Thus, the coercive force of Example 1 shows characteristics that cannot be said to be good compared to Comparative Example 1 and Comparative Example 2, respectively. However, it has a coercive force to be established as a perpendicular magnetic recording medium, and cannot be said to be a significant deterioration in characteristics.

  FIG. 5 is a diagram illustrating the value of Δθ50 with respect to the coercive force. As shown in FIG. 5, Δθ50 is generally stable with respect to the coercive force, and there is no tendency to consistently go up and down. Referring to FIG. 5, it can be seen that Example 1 shows a better value than Comparative Example 1 and Comparative Example 2 regardless of the film thickness. From this, Example 1 shows that it is close to the ideal value of Δθ50, and it is presumed that a crystal with high orientation and high magnetic anisotropy is formed.

  FIG. 6 is a diagram illustrating a hysteresis curve. It can be read that Example 1 has a lower saturation magnetic field Hs than Comparative Example 1. This means that the saturation magnetization Ms can be reached even with a weak external magnetic field, which supports the improvement of the OW characteristics.

  FIG. 7 is a diagram for explaining an evaluation summarizing the above-described experimental results. The OW characteristics of Example 1 are remarkably improved as compared with Comparative Example 1 and Comparative Example 2. As for the SNR characteristics, Example 1 is almost equivalent to Comparative Example 1, and shows better characteristics than Comparative Example 2. The coercive force is slightly lower in Example 1 than in Comparative Example 1 and Comparative Example 2, but is in a range that does not cause a problem as a magnetic recording medium. Δθ50 is significantly improved in Example 1 compared to Comparative Example 1 and Comparative Example 2.

From these facts, it can be seen that the OW characteristics are improved even though the magnetic interaction is improved and the coercive force Hc is maintained. This is because the addition of Pd reduces the lattice constant mismatch between Ni ₉₂ W ₅ Pd ₃ constituting the pre-underlayer 116 and Ru constituting the first underlayer 118a. It is considered that the OW characteristics are improved by improving the crystal orientation of the nonmagnetic granular layer 120 and the magnetic recording layer 122.

  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 in 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.

It is a figure explaining the structure of the magnetic recording medium which concerns on this embodiment. It is a figure explaining the OW characteristic at the time of changing the film thickness of Example 1, the comparative example 1, and the comparative example 2. FIG. It is a figure explaining the characteristic of SNR at the time of changing the film thickness of Example 1, the comparative example 1, and the comparative example 2. FIG. It is a figure explaining the characteristic of Hc at the time of changing the film thickness of Example 1, the comparative example 1, and the comparative example 2. FIG. It is a figure explaining the value of (DELTA) (theta) 50 with respect to a coercive force. It is a figure explaining a hysteresis curve. It is a figure explaining the evaluation which summarized each experimental result.

Explanation of symbols

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

Claims (6)

A pre-underlayer comprising at least Ni, W, Pd on the disk substrate;
An underlayer containing Ru formed on the previous underlayer;
A perpendicular magnetic recording medium comprising: a granular layer made of a Co-based alloy formed on the underlayer and having a granular structure in which crystal grains are grown in a columnar shape in this order.   The perpendicular magnetic recording medium according to claim 1, wherein the pre-underlayer has a Pd content of 3 at% to 15 at%.   2. The perpendicular magnetic recording medium according to claim 1, wherein the pre-underlayer has a total content of W and Pd of 5 at% to 25 at%.   2. The perpendicular magnetic recording medium according to claim 1, wherein [Delta] [theta] 50 of the underlayer and the granular layer is 4 degrees or less. A method for manufacturing a perpendicular magnetic recording medium comprising at least a front underlayer, a Ru underlayer, and a magnetic recording layer in this order on a substrate,
A method of manufacturing a perpendicular magnetic recording medium, wherein sputtering is performed while applying a direct current bias to a substrate using a target containing Ni, W, and Pd when forming the pre-underlayer.   7. The method of manufacturing a perpendicular magnetic recording medium according to claim 6, wherein the DC bias voltage is in the range of -300V to -500V.

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