JP2010086583A - 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 securing a high SNR while enhancing reliability by increasing strength of a coated film of a granular layer, and to provide a method for manufacturing the same. <P>SOLUTION: In the perpendicular magnetic recording medium 100 including at least a granular layer having a granular structure which is made of a Co-based alloy and where crystal grains are grown in a columnar shape on a disk base body 110, the granular layer (a non-magnetic granular layer 120, a first magnetic recording layer 122a, a second magnetic recording layer 122b) is film-deposited on the disk base body 110 by changing film-deposition speed from a low speed to a high speed or from the high speed to the low speed. <P>COPYRIGHT: (C)2010,JPO&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 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).
T. Oikawa et.al., IEEE Trans. Magn, vol.38, 1976-1978 (2002) JP 2006-024346 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, improvements in electromagnetic conversion characteristics such as overwrite characteristics (OW characteristics) and SNR, tracks There are various things such as narrowing the width. Among them, improvement of SNR (Signal to Noise Ratio) is important for reading and writing accurately and at high speed even in a recording bit having a small area.

  The SNR is improved mainly by reducing the magnetization transition region noise of the magnetic recording layer. Factors effective for noise reduction include improvement of the crystal orientation of the magnetic recording layer, refinement of the particle size of the magnetic particles, and isolation of the magnetic particles. Above all, when the isolation of 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.

  Therefore, in order to promote isolation of magnetic particles, a method of forming a magnetic recording layer in a state where the pressure of the atmospheric gas in the chamber is set to a predetermined pressure has been conventionally used. As a result, the film formation rate was reduced and the formation of fine pores in the film promoted the isolation of magnetic particles (crystal particles). However, the presence of pores in the film makes the film rough. As a result, the film strength is reduced, and damage and defects due to contact with the magnetic head are likely to occur, leading to a decrease in the reliability of the magnetic recording medium.

  However, if the coating density is increased in order to improve the reliability, the isolation of the magnetic particles is hindered and the SNR is lowered. Therefore, at present, the SNR and the reliability of the magnetic recording medium are in a trade-off relationship, and it has been difficult to improve both performances. For this reason, establishment of a method for improving reliability while ensuring a high SNR has been an issue.

  In view of such problems, the present invention provides a perpendicular magnetic recording medium and a method of manufacturing a perpendicular magnetic recording medium that can ensure high SNR while improving reliability by increasing the strength of the film of the granular layer. The purpose is to provide.

  As described above, when the film formation rate is adjusted, it is clear that the kinetic energy of the scattered particles due to sputtering changes and the state of the deposited film changes. That is, when the deposition rate of the granular layer is increased, migration in which atoms deposited on the disk substrate move irregularly is promoted, and the film is in a dense state (high density). However, the high density of the film inhibits the isolation of crystal particles. Conversely, when the film formation rate is slowed down, the film becomes rough and the isolation of crystal grains can be promoted, but the reliability of the magnetic recording medium is lowered.

  As a result of extensive studies by the inventors in order to solve the above-described problems, attention was paid to the film structure of a granular layer having a granular structure such as a magnetic recording layer. That is, it is possible to form one granular layer from two films having different states by forming a granular layer, which has conventionally been formed at a constant rate, while changing the deposition rate. I thought. And by further research, the state of the two films can be optimized by adjusting the film formation rate, which is effective in solving the problem of improving the reliability while ensuring a high SNR. As a result, the present invention has been completed.

  That is, in order to solve the above-described problems, a typical configuration of the perpendicular magnetic recording medium according to the present invention includes a granular layer having a granular structure in which crystal grains are grown in a columnar shape made of a Co-based alloy on a disk substrate. In the perpendicular magnetic recording medium provided, the granular layer is formed by changing the film formation speed on the disk substrate from a low speed to a high speed or from a high speed to a low speed.

  By reducing the film formation rate during the formation of the granular layer, the film (granular layer) after film formation is more than the film formed at the conventional film formation speed (hereinafter referred to as “medium speed”). The film has a low density (hereinafter referred to as “low density”), and a film in which the isolation of crystal grains is promoted more than the conventional film. Therefore, the SNR can be improved by providing such a low-density coating on the granular layer.

  In addition, by increasing the film formation rate during the formation of the granular layer, the density of the film after film formation is higher than that of the film formed at the conventional film formation rate (medium speed) (hereinafter “ This film is a film having a higher film strength than a film formed at a conventional film formation rate (medium speed) (hereinafter referred to as “medium density film”). Therefore, the reliability of the magnetic recording medium can be improved by providing a high-density coating on the granular layer.

  Therefore, according to the above configuration, when the deposition rate is changed from low to high during the formation of the granular layer, a low-density coating is formed on the disk substrate side, and a high-density coating is formed thereon. The Further, when the film forming speed is changed from a high speed to a low speed, a high-density film is formed on the disk substrate side, and a low-density film is formed thereon. Therefore, in any case, the granular layer is composed of a low-density film and a high-density film. Accordingly, a high SNR can be secured by providing a low-density coating on the granular layer, and the reliability of the perpendicular magnetic recording medium can be improved by providing a high-density coating, while ensuring a high SNR. Reliability can be improved.

  As described above, the upper and lower positional relationships of the low-density and high-density coatings in the granular layer are not limited. In order to solve the problem of the present invention that improves the reliability while securing a high SNR, it is important that the granular layer has a two-layer structure including a low-density film and a high-density film. This is because the upper and lower positional relationship, that is, the film formation order of the low-density film and the high-density film is not an element for solving the problems of the present invention.

  In addition, it is not preferable that the granular layer is composed of only one of the high-density film and the low-density film. For example, when the granular layer is composed of only a high-density film, the film strength is improved, and the reliability is remarkably increased. However, the isolation of crystal grains in the granular layer is hindered, and the SNR is significantly reduced. Further, when the granular layer is composed of only a low-density film, the isolation of the crystal particles in the granular layer is promoted, so that a high SNR is ensured. However, since the low density film is more profound than the conventional film, the reliability of the perpendicular magnetic recording medium cannot be improved. Therefore, in order to improve the reliability while ensuring a high SNR, the granular layer should be composed of two layers of a high-density film and a medium-density film as described above.

  In addition, as a method for changing the film formation speed at the time of forming the granular layer, adjustment of a bias voltage which is a voltage applied to the substrate at the time of film formation, film formation power which is a voltage applied to the target at the time of film formation And adjustment of the pressure of the atmospheric gas in the chamber during film formation can be exemplified. By selecting one or a plurality from these groups and adjusting them during the formation of the granular layer, it is possible to change the deposition rate to a desired rate.

  When the film formation rate is changed by the bias voltage, the film formation rate can be increased by increasing the bias voltage, and the film formation rate can be decreased by decreasing the bias voltage. Also, when changing the deposition rate depending on the deposition power, increase the deposition power to a higher power by setting the deposition power to a higher power, and lower the deposition rate by lowering the deposition power. Can do. When changing the deposition rate by the atmospheric gas pressure, the deposition rate is lowered by setting the atmospheric gas pressure to a high gas pressure, and the deposition rate is increased by lowering the atmospheric gas pressure. Can be speed. Therefore, a high-density film can be obtained by changing the film-forming speed by these techniques and the film-forming speed is set high, and a low-density film can be obtained by setting the film-forming speed low.

  The granular layer is preferably a nonmagnetic granular layer or a magnetic recording layer.

  The nonmagnetic granular layer and the magnetic recording layer are a layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape, that is, a granular layer. Therefore, when the non-magnetic granular layer or the magnetic recording layer is formed, the film formation rate is changed as described above, so that the layer is composed of two layers of a low-density film and a high-density film. Can be maintained in an isolated state and the film strength can be improved. Thereby, it is possible to improve the reliability while ensuring a high SNR.

  If the granular layer is a magnetic recording layer, the density of the film can be increased while directly promoting the isolation of crystal grains (magnetic particles) of the magnetic recording layer. Therefore, the film strength of the magnetic recording layer can be improved, the reliability of the magnetic recording medium can be improved, and a high SNR can be ensured. Further, if the granular layer is a non-magnetic granular layer, the isolation of crystal grains in the non-magnetic granular layer is promoted, and the crystal grains (magnetic particles) in the magnetic recording layer grow on the crystal grains. In addition, isolation of crystal grains in the magnetic recording layer can be promoted. And the intensity | strength as the whole perpendicular magnetic recording medium increases because the intensity | strength of a nonmagnetic granular layer improves. Therefore, in any case, it is possible to secure a high SNR of the magnetic recording medium and improve the reliability.

  The granular layer is a magnetic recording layer, and the magnetic recording layer is composed of a first magnetic recording layer and a second magnetic recording layer. At least the second magnetic recording layer has a film formation speed on a disk substrate from a low speed. The film formation may be performed at a high speed or at a high speed to a low speed.

  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.

  Further, by changing the film formation rate as described above when forming the second magnetic recording layer, the second magnetic recording layer can have a two-layer structure of a low-density film and a high-density film. Thereby, the crystal grains (magnetic grains) of the second magnetic recording layer can be isolated and the film strength can be improved. Therefore, it is possible to improve reliability while ensuring a high SNR.

  In the above configuration, the film formation speed is changed at least when the second magnetic recording layer is formed. When there are a plurality of granular layers in the magnetic recording medium, the magnetic property of the second magnetic recording layer as the main recording layer is determined. This is because maintaining the isolated state of the particles is most effective for securing a high SNR. Furthermore, when there are a plurality of granular layers, the second granular magnetic recording layer is the uppermost granular layer when viewed from the disk substrate side, so that by improving the film strength of the second magnetic recording layer, The layer formed on the disk substrate side with respect to the second magnetic recording layer can be protected from damage due to contact with the magnetic head. Therefore, even from the viewpoint of improving the reliability of the magnetic recording medium, it is most preferable to improve the film strength by changing the film forming speed when forming the second magnetic recording layer.

  The low speed range is preferably 0.5 to 1.5 nm / sec, and the high speed range is preferably 3.5 to 5.0 nm / sec. The effects described above can be most efficiently obtained by setting the low film deposition rate and high deposition rate values within such ranges.

  In order to solve the above-mentioned problems, a typical configuration of a method for manufacturing a perpendicular magnetic recording medium according to the present invention is to provide a granular layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape on a disk substrate. The film is formed on the disk substrate by changing the film formation speed from a low speed to a high speed or from a high speed to a low speed.

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

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the perpendicular magnetic recording medium which can ensure high SNR, improving a reliability by raising the intensity | strength of the film | membrane of a granular layer, and a perpendicular magnetic recording medium can be provided. .

  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 this embodiment, first, an embodiment of a perpendicular magnetic recording medium and a method for manufacturing the same according to the present invention will be described, and then a film configuration in a granular layer, which is a feature of the present invention, will be described in detail.

[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 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. 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.

  The nonmagnetic granular layer 120 is a nonmagnetic layer having a granular structure. A non-magnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and a granular layer of the first magnetic recording layer 122a (or magnetic recording layer 122) is grown thereon, whereby the magnetic granular layer is initially formed. It has the effect of separating from the growth stage (rise). Thereby, isolation of the magnetic particles of the magnetic recording layer 122 can be promoted. The composition of the nonmagnetic granular layer 120 can be a granular structure by forming a grain boundary by segregating a nonmagnetic substance between nonmagnetic crystal grains made of a Co-based alloy. Note that the pressure of the atmospheric gas in the chamber was set to 1 to 3 Pa when the nonmagnetic granular layer 120 was sputtered.

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 (CrO ₂ , 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. Note that the atmospheric gas pressure in the chamber was set to 2 to 4 Pa during sputtering of the first magnetic recording layer 122a and the second magnetic recording layer 122b.

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 grains (grains) made of CoCrPt to form grain boundaries, and the magnetic grains A granular structure grown in a columnar shape was formed.

  Further, in the present embodiment, when the second magnetic recording layer 122b is formed, the film formation rate is changed from either a low speed to a high speed or from a high speed to a low speed. The low speed range is 0.5 to 1.5 nm / sec, and the high speed range is 3.5 to 5.0 nm / sec. As a result, the second magnetic recording layer 122b can be composed of a two-layer coating consisting of a low-density coating and a high-density coating. Therefore, it is possible to maintain a high SNR with a low-density film, and to improve the reliability of the perpendicular magnetic recording medium 100 with a high-density film, and to improve the reliability while ensuring a high SNR. Become.

  In this embodiment, in order to change the deposition rate as described above, the deposition power, which is the voltage applied to the target when the second magnetic recording layer 122b is deposited, is adjusted. Since the range of the film forming power varies depending on the sputtering apparatus to be used, it is preferable to set the film forming speed within a range suitable for each sputtering apparatus so that the film forming speed is within the above range.

  In this embodiment, the film formation speed is changed by adjusting the film formation power as described above. However, the present invention is not limited to this, and adjustment of the bias voltage, which is a voltage applied to the substrate during film formation. The film formation speed can be changed to a desired speed also by adjusting the pressure of the atmospheric gas in the chamber during film formation.

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 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 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.

  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 (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 film configuration in the granular layer, which is a feature of the present invention, will be described.

[Membrane structure in granular layer]
In the above-described embodiment, the layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape includes the nonmagnetic granular layer 120 and the magnetic recording layer 122 (the first magnetic recording layer 122a and the second magnetic recording layer). Layer 122b). Therefore, the granular layer in this embodiment is the nonmagnetic granular layer 120 and the magnetic recording layer 122 (the first magnetic recording layer 122a and the second magnetic recording layer 122b).

  At the time of forming the granular layer, the film forming speed is changed from either a low speed to a high speed or from a high speed to a low speed. The low speed range is preferably 0.5 to 1.5 nm / sec, and the high speed range is preferably 3.5 to 5.0 nm / sec. The film forming step of changing the film forming speed, that is, changing the film forming power in this embodiment may be performed in the step of forming any one granular layer, or a plurality or all of the granular layers may be performed. You may perform in the process of forming a layer. Further, the film formation power may be switched between two stages or multiple stages, or the film formation power may be gradually changed.

  When a granular layer is formed at a low speed (slow film formation speed), that is, when a film is formed at a low film formation power (low power), the film after film formation is formed at a low density (conventional medium speed). The film has a density lower than that of the medium-density film, and the isolation of crystal grains is promoted. Therefore, it is possible to maintain a high SNR by providing a coating on the granular layer. In addition, when the granular layer is formed at a high speed (high film formation speed), that is, when the film is formed at a high film formation power (high power), the film after film formation has a high density (conventional medium speed). The film has a higher density than the medium-density film formed, and the film strength is remarkably improved. Therefore, the reliability of the perpendicular magnetic recording medium 100 can be improved by providing a film on the granular layer.

  Therefore, when the film forming speed is changed from a low speed to a high speed, the granular layer is composed of a two-layer film consisting of a low-density film on the disk substrate 110 side and a high-density film thereon. When the speed is changed from a high speed to a low speed, the granular layer is composed of a two-layer film consisting of a high-density film on the disk substrate 110 side and a low-density film thereon. That is, in any case, the granular layer is composed of a low-density film and a high-density film. As a result, it is possible to maintain a high SNR with a low-density coating on the granular layer and to improve the reliability of the perpendicular magnetic recording medium 100 with a high-density coating. Can be raised together.

  When the magnetic recording layer 122 is selected as the granular layer, the film strength of the magnetic recording layer 122 can be increased while maintaining isolation of crystal grains (magnetic particles) of the magnetic recording layer 122 directly. When the nonmagnetic granular layer 120 is selected as the granular layer, the isolation of the crystal grains of the magnetic recording layer 122 can be maintained indirectly by maintaining the isolation of the crystal grains of the nonmagnetic granular layer 120, By improving the film strength of the nonmagnetic granular layer 120, the reliability of the perpendicular magnetic recording medium 100 as a whole is increased. Therefore, in any case, it is possible to secure the high SNR of the perpendicular magnetic recording medium 100 and improve the reliability, but it is possible to efficiently isolate the crystal grains of the magnetic recording layer 122 and improve the film strength. Therefore, it is preferable to select the magnetic recording layer 122 as the granular layer.

  Furthermore, when the magnetic recording layer 122 is composed of the first magnetic recording layer 122a and the second magnetic recording layer 122b as in the present embodiment, at least the second magnetic recording layer 122b has a film formation rate of low to high. The film may be formed by changing the speed or either high speed or low speed. As a result, the second magnetic recording layer 122b has a two-layer structure of a low-density film and a high-density film, crystal grains (magnetic particles) of the second magnetic recording layer 122b are isolated, and the film strength is improved. can do. Therefore, it is possible to improve reliability while ensuring a high SNR.

  Note that the reason why the deposition rate is changed at least during the deposition of the second magnetic recording layer 122b is to maintain the isolated state of the magnetic particles of the second magnetic recording layer 122b as the main recording layer. The film strength of the second magnetic recording layer 122b, which is the most effective granular layer as viewed from the disk substrate 110 side, is improved as compared with the second magnetic recording layer 122b. This is because the layer formed on the 110 side can be protected from damage due to contact with the magnetic head.

  Therefore, when the magnetic recording layer 122 is composed of the first magnetic recording layer 122a and the second magnetic recording layer 122b, the film formation speed is changed at least when the second magnetic recording layer 122b is formed, so that the second magnetic recording It is preferable to improve the film strength while maintaining the magnetic particles of the layer 122b isolated. However, the present invention is not limited to this, and the film formation speed may be changed at the time of forming both the first magnetic recording layer 122a and the second magnetic recording layer 122b.

  As described above, the order of forming the low-density film and the high-density film in the granular layer, that is, the vertical positional relationship is not limited. This is because if the granular layer has a two-layer structure composed of a low-density coating and a high-density coating, the problem of improving the reliability while ensuring a high SNR can be solved.

  In addition, it is not preferable that the granular layer is composed of only one of the high-density film and the low-density film. When the granular layer is composed of only a high-density coating, the reliability is remarkably increased due to the improvement of the coating strength, but the SNR is remarkably lowered due to the inhibition of the isolation of the crystal particles in the granular layer. When the granular layer is composed only of a low-density coating, high SNR is ensured by promoting the isolation of crystal grains in the granular layer, but reliability is not ensured due to insufficient coating strength. Therefore, in order to improve the reliability while ensuring a high SNR, the granular layer should have a two-layer structure composed of a high-density film and a low-density film as described above.

  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)
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 a NiW alloy having an fcc structure. As the first underlayer 118a, a Ru film was formed in an Ar atmosphere at a predetermined pressure (low pressure: for example, 0.6 to 0.7 Pa). As the second underlayer 118b, a Ru film was formed in an Ar atmosphere at a pressure higher than a predetermined pressure (high pressure: for example, 4.5 to 7 Pa). The nonmagnetic granular layer 120 was formed in an Ar atmosphere at a pressure of 1 to 3 Pa, and the composition 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 under an Ar atmosphere at a pressure of 2 to 4 Pa, and formed an hcp crystal structure of CoCrPt—Cr ₂ O ₃ . The second magnetic recording layer 122b is formed by changing the film formation power, which is a voltage applied to the target, from low power to high power or from high power to low power in an Ar atmosphere at a pressure of 2 to 4 Pa. The film formation rate is changed from either a low speed to a high speed or from a high speed to a low speed, and the film is formed as an example of a composite oxide (a plurality of types of oxides) at the grain boundary portion. SiO ₂ and TiO ₂ And an hcp crystal structure of CoCrPt—SiO ₂ —TiO ₂ was formed. The low speed range is 0.5 to 1.5 nm / sec, and the high speed range is 3.5 to 5.0 nm / sec. 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 invention will be evaluated using the perpendicular magnetic recording medium 100 obtained by the above manufacturing method. FIG. 2 is a diagram for explaining the performance evaluation of the perpendicular magnetic recording medium 100 of the example and the comparative example. Example 1 is a perpendicular magnetic recording medium 100 in which the second magnetic recording layer 122b is formed by changing the film formation rate from a low speed to a high speed. Example 2 is a case where the film formation speed is increased from a high speed. The perpendicular magnetic recording medium 100 has the second magnetic recording layer 122b formed at a low speed. The comparative example is a perpendicular magnetic recording medium in which the second magnetic recording layer 122b is formed at a constant medium speed as before without changing the film forming speed. Here, the high film forming speed is 3.5 to 5.0 nm / sec, the medium speed is 1.5 to 3.5 nm / sec, and the low speed is 0.5 to 1.5 nm / sec. It is.

  Further, the reliability shown in FIG. 2 was evaluated by a corrosion test (corrosion test) which is one of reliability tests. In such a corrosive test, the perpendicular magnetic recording media of Examples and Comparative Examples after three days in an environment of a temperature of 90 ° C. and a humidity of 95% were subjected to an optical surface defect analyzer (OSA: Optical Surface Analyzer). Observed and counted the number of defects on the surface.

  As shown in FIG. 2, the magnetic recording layer 122 in Example 1 has a low-density coating on the first magnetic recording layer 122a side (disk substrate 110 side) of the second magnetic recording layer 122b, and a high density thereon. It becomes the composition of film. In addition, the magnetic recording layer 122 in Example 2 has a configuration of a high density coating on the first magnetic recording layer 122a side (the disk substrate 110 side) of the second magnetic recording layer 122b, and a low density coating thereon. . And a comparative example is comprised only from the film | membrane of medium density similarly to the past.

  Referring to the evaluation of the SNR of the example and the comparative example, the evaluation of the SNR increases in the order of the example 1, the example 2, and the comparative example. Further, referring to the evaluation of reliability of the example and the comparative example, the evaluation becomes higher in the order of the comparative example, the example 2, and the example 1.

  FIG. 3 is a diagram for explaining the details of the evaluation of FIG. 3A shows the SNR and the track width in Examples and Comparative Examples, and FIG. 3B shows the results of the corrosive test in Examples and Comparative Examples. The track width described above is not the actual track width of the perpendicular magnetic recording medium 100 but the track width at which the track profile obtained in the storable width test shows a predetermined ratio.

  As shown in FIG. 3 (a), although the SNR is slightly lower in the first and second embodiments than in the comparative example as a whole, the recording density of the perpendicular magnetic recording medium 100 is increased in all the series of the examples. Sufficient SNR is obtained. Further, in Example 2, since the upper layer has a low-density coating, that is, a layer in which the isolation of the magnetic particles is promoted more than the high-density coating, it is considered that the SNR higher than that in Example 1 could be secured. It is done.

  Further, from FIG. 3A, the difference between the example (Example 1 and Example 2) and the comparative example is about 1.5 nm at the maximum in the track width. There is no difference that hinders recording density.

  As shown in FIG. 3B, the number of corrosion spots increases in the order of Example 1, Example 2, and Comparative Example. From this, it is possible to increase the film strength of the second magnetic recording layer 122b by forming the second magnetic recording layer 122b by changing the film forming speed as in the embodiment, thereby causing the occurrence of corrosion. It can be understood that the reliability of the perpendicular magnetic recording medium 100 can be improved. Further, in Example 1, since a high-density film, that is, a film having higher strength than that of the low-density film is in the upper layer, it is considered that higher reliability than that in Example 2 could be obtained.

  As described above, according to the present invention, the granular layer is formed by changing the film formation rate from either a low speed to a high speed or from a high speed to a low speed. And two coatings of high density. Thereby, it becomes possible to maintain the high SNR of the granular layer by the low-density coating and to improve the reliability by the high-density coating. Therefore, it is possible to further improve the quality of the perpendicular magnetic recording medium 100 while increasing the recording density.

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

  The present invention can be used as a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD or the like 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 performance evaluation of the perpendicular magnetic recording medium of an Example and a comparative example. It is a figure explaining the detail of evaluation of FIG.

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 (5)

In a perpendicular magnetic recording medium comprising a granular layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape on a disk substrate,
The perpendicular magnetic recording medium according to claim 1, wherein the granular layer is formed on the disk substrate by changing a film formation speed from a low speed to a high speed or from a high speed to a low speed.   The perpendicular magnetic recording medium according to claim 1, wherein the granular layer is a nonmagnetic granular layer or a magnetic recording layer. The granular layer is a magnetic recording layer;
The magnetic recording layer is composed of a first magnetic recording layer and a second magnetic recording layer,
2. The film formation method according to claim 1, wherein at least the second magnetic recording layer is formed on the disk substrate by changing a film formation speed from a low speed to a high speed or from a high speed to a low speed. Perpendicular magnetic recording medium. The low speed range is 0.5 to 1.5 nm / sec,
2. The perpendicular magnetic recording medium according to claim 1, wherein the range of the high speed is 3.5 to 5.0 nm / sec.   A granular layer having a granular structure made of a Co-based alloy and having crystal grains grown in a columnar shape on a disk substrate is changed from a low speed to a high speed or from a high speed to a low speed on the disk base. Forming a perpendicular magnetic recording medium.

Images