JP2007335034A - Perpendicular magnetic recording disk and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording disk which can improve a reverse magnetic domain nucleus formation magnetic field (Hn) and may improve heat stability and recording density in the perpendicular magnetic recording disk equipped with a miniaturization acceleration layer between a foundation layer and a magnetic recording layer. <P>SOLUTION: A magnetic disk is equipped with at least a foundation layer 5, a miniaturization acceleration layer 6, and a magnetic recording layer 7 on the substrate 1 in this order and used for perpendicular magnetic recording. It is characterized that the miniaturization acceleration layer 6 is a non-magnetism layer of a granular structure which contains a non-magnetic material between crystal particles containing cobalt (Co), chrome (Cr) and at least one noble metal element, and the magnetic recording layer 7 is a ferromagnetic layer of a granular structure which contains a non-magnetic material between crystal particles which contain at least cobalt (Co). <P>COPYRIGHT: (C)2008,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.

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of an HDD (hard disk drive) using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 100 GB has been required for a 2.5-inch diameter magnetic disk used for HDDs and the like. In order to meet such a demand, per 1 inch. It is required to realize an information recording density exceeding 200 Gbits. In order to achieve a high recording density in a magnetic disk used for an HDD or the like, it is necessary to refine the magnetic crystal particles that achieve a magnetic recording layer that records information signals and to reduce the layer thickness. It was. 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 impaired, and the so-called thermal fluctuation phenomenon that the recording signal disappears has occurred, which has been an impediment to increasing the recording density of the magnetic disk.

  In order to solve this obstacle, a perpendicular magnetic recording type magnetic disk has recently been proposed. In the case of the perpendicular magnetic recording system, unlike the case of the in-plane magnetic recording system, the easy axis of magnetization of the magnetic recording layer is adjusted to be oriented in the direction perpendicular to the substrate surface. The perpendicular magnetic recording method can suppress the thermal fluctuation phenomenon as compared with the in-plane recording method, and is suitable for increasing the recording density.

The magnetic recording medium used for perpendicular magnetic recording system, because they exhibit a high thermal stability and excellent recording characteristics, CoCrPt-SiO ₂ perpendicular magnetic recording medium (refer to Non-Patent Document 1) and, CGC type vertical medium (Non-patent Document 2) has been proposed. Further, in order to improve the S / N ratio, a Ru—SiO ₂ underlayer (Patent Documents 1 and 2) and the like have been proposed together with these techniques. As a film forming process there, a high Ar gas pressure sputtering process is usually used for the purpose of miniaturization of magnetic particles.
T. Oikawa et.al., IEEE Trans. Magn, vol.38, 1976-1978 (2002) Y. Sonobe et al., IEEE Trans. Magn, vol. 37, 1667-1670 (2001) JP 2002-334424 A JP 2003-123245 A

In the perpendicular magnetic recording medium, as in the in-plane magnetic recording medium, the recording density of the magnetic disk is mainly improved by reducing the magnetization transition region noise of the magnetic recording layer. In order to reduce noise, it is necessary to improve the crystal orientation of the magnetic recording layer and to reduce the crystal grain size and the magnitude of the magnetic interaction. In the above-described CoCrPt—SiO ₂ type perpendicular magnetic recording medium, by using a high Ar gas pressure sputtering process, the magnetic particles are refined, and at the same time, SiO ₂ is segregated at the grain boundaries, and the magnetic grains between the grains of the magnetic recording layer are magnetized. Interaction is reduced.

The crystal grain size and the magnitude of the magnetic interaction are influenced by the horizontal thickness of SiO ₂ segregated at the grain boundaries. Increasing the amount of SiO ₂ improves the S / N ratio at high recording density. On the other hand, when the amount of SiO ₂ is increased, the perpendicular magnetic anisotropy deteriorates, and deterioration of thermal stability and increase of noise become problems. Further, since a high Ar gas pressure sputtering process is used, there is a problem that the orientation of the recording layer is deteriorated and the surface property of the medium is deteriorated.

In order to solve this problem, the inventors insert a CoCr—SiO ₂ layer as a miniaturization promoting layer between the underlayer (crystal orientation control layer: Ru) and the magnetic recording layer (CoCrPt—SiO ₂ ). Thus, it has been found that the SN ratio can be improved by the refinement of magnetic particles and the segregation of SiO _{2 in} a low Ar gas process, and a patent application has already been filed (Japanese Patent Application No. 2005-086220).

  For example, when the magnetic recording layer is formed on the underlayer without using the miniaturization promoting layer, the magnetic crystal grains can grow from any position on the underlayer. In some cases, the particle distribution may be disturbed. However, even if the metal crystal particles are disturbed in the vicinity of the interface with the underlayer by forming a nonmagnetic miniaturization promoting layer, the distribution is almost uniform in the vicinity of the interface with the magnetic recording layer. Will be. Since the crystal grains of the magnetic recording layer grow on the basis of the crystal grains of the miniaturization promoting layer, the orientation of the magnetic crystal grains can be improved and the miniaturization can be promoted.

  However, new problems have arisen. That is, in the above configuration, the magnetic particles CoCrPt of the magnetic recording layer and the nonmagnetic particles CoCr of the miniaturization promoting layer are combined to function as magnetic particles. As a result, the average magnetization amount is reduced, and the perpendicular magnetic anisotropy (Ku) is deteriorated. As a result, the reverse domain nucleation magnetic field (Hn) decreases, and at the same time, the thermal stability of the recording / reproducing signal deteriorates (so-called thermal fluctuation problem).

  The present invention relates to a perpendicular magnetic recording disk having a miniaturization promoting layer between an underlayer and a magnetic recording layer, and can improve the reverse domain nucleation magnetic field (Hn) and improve the thermal stability and recording density. The object is to provide a magnetic recording disk.

  In order to solve the above problems, a typical configuration of a perpendicular magnetic recording disk according to the present invention is a magnetic disk used for perpendicular magnetic recording having at least an underlayer, a miniaturization promoting layer, and a magnetic recording layer in this order on a substrate. The miniaturization promoting layer is a non-magnetic layer having a granular structure including a non-magnetic substance between crystal grains containing cobalt (Co), chromium (Cr) and at least one noble metal element, and the magnetic recording layer is at least It is a ferromagnetic layer having a granular structure including a nonmagnetic substance between crystal grains containing cobalt (Co).

A non-magnetic substance is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and cobalt (Co) and Any nonmagnetic substance that does not dissolve in solution may be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

  By adding a noble metal to the nonmagnetic miniaturization promoting layer as described above, anisotropy with respect to the magnetic recording layer can be improved. For this reason, the crystal grains of the magnetic recording layer become highly oriented from the rising edge (initial layer: for example, between about 0.5 nm and 2 nm in thickness), and the reverse domain nucleation magnetic field (Hn) can be improved. The term “non-magnetic” includes not only completely non-magnetic but also weak magnetism that does not cause a problem in the function of the magnetic disk. The nonmagnetic granular layer may have, for example, weak magnetism that is negligible compared to the ferromagnetic layer.

As the noble metal element, one or more elements selected from platinum (Pt), palladium (Pd), and ruthenium (Ru) can be used. Therefore, for example, the miniaturization promoting layer can be made of CoCrRu—SiO ₂ or CoCrPt—SiO ₂ . Furthermore, rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), and gold (Au) can also be used as noble metal elements.

  The content of the nonmagnetic substance in the miniaturization promoting layer is preferably 5 mol% to 20 mol%, and more preferably 10 mol% to 14 mol%. This is because when the content is 5 mol% or less, a sufficient composition separation (segregation) structure cannot be formed, and thus miniaturization of the magnetic recording layer cannot be promoted. Moreover, it is because Co becomes difficult to form an hcp crystal when it is 20 mol% or more. The film thickness of the miniaturization promoting layer is preferably 0.25 nm to 5 nm, more preferably 0.5 to 2 nm.

  The content of the nonmagnetic substance in the magnetic recording layer is preferably 8 mol% to 16 mol%, more preferably 10 mol% to 14 mol%. This is because a sufficient S / N ratio cannot be obtained because a sufficient composition separation (segregation) structure cannot be formed at 8 mol% or less. Further, if it is 16 mol% or more, Co becomes difficult to form an hcp crystal, so that sufficient perpendicular magnetic anisotropy cannot be obtained and high Hn cannot be obtained. The film thickness of the magnetic recording layer is preferably 20 nm or less, more preferably 9 nm to 15 nm.

  Further, when the content of the nonmagnetic substance in the miniaturization promoting layer is Amol% and the content of the nonmagnetic substance in the magnetic recording layer is Bmol%, 0.3 ≦ A / B ≦ 2.5. Is preferred. This is because, by setting the contents of the nonmagnetic substance in both layers to the same level, the crystal grains in the magnetic recording layer can easily grow based on the crystal grains in the miniaturization promoting layer.

  It is preferable to provide an orientation control layer having an amorphous or fcc structure between the base and the underlayer. Note that the orientation control layer is a layer having an action of controlling the orientation of crystal grains of the underlayer. The orientation control layer is made of, for example, a Ni-based alloy such as Ta, Nb, or NiP, a Co-based alloy such as CoCr, a nonmagnetic layer containing Ta or Ti, and a material such as Pd or Pt. be able to.

  It is preferable to provide an amorphous soft magnetic layer between the base and the underlayer. In the present invention, the soft magnetic layer is not particularly limited as long as it is formed of a magnetic material exhibiting soft magnetic properties. For example, an FcTaC alloy, FeTaN alloy, FeNi alloy, FeCoB alloy, FeCo alloy, etc. An Fe-based soft magnetic material, a Co-based soft magnetic material such as a CoTaZr-based alloy, a CoNbZr-based alloy, or an FeCo-based alloy soft magnetic material can be used.

  The soft magnetic layer preferably has a magnetic property of 0.01 to 80 Oersted (Oe), preferably 0.01 to 50 Oersted, in coercive force (Hc). The saturation magnetic flux density (Bs) preferably has a magnetic characteristic of 500 emu / cc to 1920 emu / cc. The thickness of the soft magnetic layer is 10 nm to 1000 nm, desirably 20 nm to 150 nm. If it is less than 10 nm, it may be difficult to form a suitable magnetic circuit between the magnetic head, the perpendicular magnetic recording layer, and the soft magnetic layer, and if it exceeds 1000 nm, the surface roughness may increase. Moreover, when it exceeds 1000 nm, sputtering film formation may become difficult.

  The substrate is preferably amorphous glass. When annealing in a magnetic field is required for controlling the magnetic domain of the soft magnetic layer, the substrate is preferably made of glass because of excellent heat resistance. As the glass for the substrate, amorphous glass and crystallized glass can be used, and examples thereof include aluminosilicate glass, aluminoborosilicate glass, soda lime glass, and the like. Among these, aluminosilicate glass is preferable. Further, when the soft magnetic layer is made amorphous, it is preferable that the substrate is made of amorphous glass. Use of chemically strengthened glass is preferable because of its high rigidity.

  A typical configuration of a method for manufacturing a perpendicular magnetic recording disk according to the present invention is a method for manufacturing a magnetic disk used for perpendicular magnetic recording, in which at least an underlayer, a miniaturization promoting layer, and a magnetic recording layer are provided in this order on a substrate. And forming a granular non-magnetic layer containing a non-magnetic substance between crystal grains containing cobalt (Co), chromium (Cr) and at least one noble metal element as a miniaturization promoting layer, and at least as a magnetic recording layer A ferromagnetic layer having a granular structure including a nonmagnetic substance is formed between crystal grains containing cobalt (Co). In forming the magnetic recording layer, sputtering, particularly DC magnetron sputtering, can be preferably used.

  According to the present invention, in a perpendicular magnetic recording disk having a miniaturization promoting layer between an underlayer and a magnetic recording layer, the reverse domain nucleation magnetic field (Hn) is improved, and the thermal stability and the recording density are improved. A perpendicular magnetic recording disk can be provided.

  Embodiments of the perpendicular magnetic recording medium according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium according to the present embodiment, FIG. 2 is a schematic diagram for explaining the vicinity of a magnetic recording layer, and FIG. It is a figure which shows the change of (Hn). The numerical values shown in the following examples are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

  The perpendicular magnetic recording medium shown in FIG. 1 includes a disk substrate 1, an adhesion layer 2, a soft magnetic layer 3, an orientation control layer 4, an underlayer 5a, an underlayer 5b, a miniaturization promoting layer 6, a magnetic recording layer 7, and coupling control. A layer 8, an exchange energy control layer 9 (continuous layer), a medium protective layer 10, and a lubricating layer 11 are configured.

  First, an amorphous aluminosilicate glass was formed into a disk shape by direct pressing to produce a glass disk. The glass disk was ground, polished, and chemically strengthened in order to obtain a smooth nonmagnetic disk substrate 1 made of a chemically strengthened glass disk. The disc diameter is 65 mm. When the surface roughness of the main surface of the disk substrate 1 was measured with an AFM (atomic force microscope), it was a smooth surface shape with Rmax of 4.8 nm and Ra of 0.42 nm. Rmax and Ra are in accordance with Japanese Industrial Standard (JIS).

  On the obtained disk substrate 1, a film was formed from the adhesion layer 2 to the exchange energy control layer 9 in order by DC magnetron sputtering in an Ar atmosphere using a vacuum-deposited film forming apparatus to protect the medium. Layer 10 was deposited by CVD. Thereafter, the lubricating layer 11 was formed by dip coating. Hereinafter, the configuration and manufacturing method of each layer will be described.

  The adhesion layer 2 was formed using a Ti alloy target so as to be a 10 nm Ti alloy layer. By forming the adhesion layer 2, the adhesion between the disk substrate 1 and the soft magnetic layer 3 can be improved, so that the soft magnetic layer 3 can be prevented from peeling off. As a material of the adhesion layer 2, for example, a Ti-containing material can be used. From the practical viewpoint, the thickness of the adhesion layer is preferably 1 nm to 50 nm.

  The soft magnetic layer 3 was formed using a CoTaZr target so as to be an amorphous CoTaZr layer of 50 nm.

  The orientation control layer 4 has an action of protecting the soft magnetic layer 3 and an action of promoting the refinement of crystal grains of the underlayer 5a. The orientation control layer 4 was formed using a Ta target so that an amorphous Ta layer was formed to a thickness of 3 nm.

  The underlayers 5a and 5b have a two-layer structure made of Ru. When forming Ru on the upper layer side, the crystal orientation can be improved by increasing the Ar gas pressure as compared to forming Ru on the lower layer side.

The miniaturization promoting layer 6 has a 1.5-nm hcp crystal structure by using a hard magnetic target made of CoCrRu containing ruthenium (Ru) as an example of a noble metal and SiO ₂ as an example of a nonmagnetic substance. Formed. The composition of the target for forming the miniaturization promoting layer 6 is CoCr ₄₀ Ru of 88 (mol%) and SiO ₂ of 12 (mol%) (the attached numbers are atomic%). Note that CoCrPt—SiO ₂ may be used instead of Ru, for example, using Pt.

The magnetic recording layer 7 has an 11 nm hcp crystal structure using a hard magnetic target made of CoCrPt containing SiO ₂ as an example of a non-magnetic substance. The composition of the target for forming the magnetic recording layer 7 is 90 (mol%) for CoCr ₁₀ Pt and ₁₀ (mol%) for SiO ₂ (the attached numbers are atomic%).

  That is, when the content of the nonmagnetic substance in the miniaturization promoting layer 6 is Amol% and the content of the nonmagnetic substance in the magnetic recording layer 7 is Bmol%, 0.3 ≦ A / B ≦ 2.5. It has become. Thus, by setting the content of the nonmagnetic substance in both layers to the same level, the crystal grains in the magnetic recording layer can easily grow based on the crystal grains in the miniaturization promoting layer.

Note that the noble metal contained in the magnetic recording layer 7 and the noble metal contained in the miniaturization promoting layer 6 are preferably the same. For example, when the magnetic recording layer 7 is CoCrPt, the miniaturization promoting layer 6 is preferably CoCrPt—SiO ₂ , and when the magnetic recording layer 7 is CoCrRu, the miniaturization promoting layer 6 is CoCrRu—SiO _2. Is preferred. Thereby, the orientation during crystal growth of the magnetic recording layer can be improved.

  The coupling control layer 8 was formed of a Pd (palladium) layer. The coupling control layer 8 can be formed of a Pt layer in addition to the Pd layer. The thickness of the coupling control layer 8 is preferably 2 nm or less, and more preferably 0.5 to 1.5 nm.

  The exchange energy control layer 9 is made of an alternating laminated film of CoB and Pd, and is formed of a low Ar gas. The film thickness of the exchange energy control layer 9 is preferably 1 to 8 nm, and desirably 3 to 6 nm.

  As the medium protective layer 10, the medium protective layer 10 made of hydrogenated carbon having a film thickness of 3.5 nm was formed by a plasma CVD method in a mixed gas containing 30% hydrogen in Ar. Since the film hardness is improved by using hydrogenated carbon, the perpendicular magnetic recording layer can be more effectively protected against an impact from the magnetic head.

  The lubricating layer 11 was formed by dip coating using PFPE (perfluoropolyether). The film thickness of the lubricating layer 11 is about 1 nm.

  Through the above manufacturing process, a perpendicular magnetic recording medium was obtained. When the miniaturization promoting layer 6 and the magnetic recording layer 7 in the obtained perpendicular magnetic recording disk were analyzed in detail using a transmission electron microscope (TEM), they had a granular structure. Specifically, it was confirmed that a grain boundary portion made of a nonmagnetic substance was formed between crystal grains having an hcp crystal structure containing Co.

  Here, as shown in FIG. 2, Ru of the underlayer 5b, crystal grains 6a (Co-based alloy) of the miniaturization promoting layer 6, and magnetic grains 7a (Co-based alloy) of the magnetic recording layer 7 are crystallographic. Connected to. This is because the crystal grain 6a, the magnetic grain 7a, and the silicon oxides 6b and 7b of the miniaturization promoting layer 6 and the magnetic recording layer 7 are continuously grown.

  For comparison, when the miniaturization promoting layer 6 does not contain a noble metal, when Ru is included as a noble metal, and when Pt is included as a noble metal, the thickness of the magnetic recording layer 7 is varied from 9 nm to 11 nm and perpendicular. A magnetic recording medium was manufactured. FIG. 3 shows an evaluation of the magnetostatic characteristics of the obtained perpendicular magnetic recording disk by measuring the reverse domain nucleation magnetic field (Hn) using the Kerr effect.

  As shown in FIG. 3, by adding the noble metal to the miniaturization promoting layer 6, the reverse magnetic domain nucleation magnetic field (Hn) is improved by about 100 [Oe]. This is presumably because the orientation is higher than the initial layer where the magnetic recording layer 7 is formed. Further, when the precious metal is Ru, Hn is improved as the magnetic recording layer 7 is thickened, and is improved by about 200 [Oe] at a position where the thickness is 11 nm. This is considered to be due to the fact that the crystal orientation provided by Ru acts. Further, when the thermal stability characteristics of these media were examined, improvement in output deterioration was observed in a form following the change in Hn.

  From these facts, the inclusion of a noble metal in the miniaturization promoting layer 6 can improve the reverse domain nucleation magnetic field (Hn) and at the same time improve the thermal stability. Therefore, the magnetic particles can be further miniaturized and the recording density can be improved.

  Although not shown, when the magnetic recording layer is thicker than 15 nm, the reverse domain nucleation magnetic field (Hn) is lowered. This is because the magnetization rotation mode becomes non-simultaneous rotation because the crystal grains become coarse. Therefore, the thickness of the magnetic recording layer is preferably 15 nm or less.

In the above embodiments, the nonmagnetic substance is described as silicon oxide (SiO ₂ ), but the grain boundary around the magnetic grains is so controlled that the exchange interaction between the magnetic grains (magnetic grains) is suppressed or blocked. Any nonmagnetic substance that can form a part and does not dissolve in cobalt (Co) may be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), and zircon oxide (ZrO ₂ ).

  INDUSTRIAL APPLICABILITY The present invention can be used as a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like and a manufacturing method thereof.

It is a figure explaining the structure of the perpendicular magnetic recording medium based on an Example. It is a schematic diagram explaining the magnetic recording layer vicinity. It is a figure which shows the change of a reverse domain nucleation magnetic field (Hn) at the time of changing the thickness of a magnetic-recording layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Disk base | substrate 10 ... Medium protective layer 11 ... Lubrication layer 2 ... Adhesion layer 3 ... Soft magnetic layer 4 ... Orientation control layer 5a, 5b ... Underlayer 6 ... Refinement | miniaturization promotion layer 6a ... Crystal grain 6b ... Silicon oxide 7 ... Magnetic Recording layer 7a ... Magnetic grain 7b ... Silicon oxide 8 ... Coupling control layer 9 ... Exchange energy control layer

Claims (10)

A magnetic disk used for perpendicular magnetic recording comprising at least an underlayer, a miniaturization promoting layer, and a magnetic recording layer in this order on a substrate,
The miniaturization promoting layer is a non-magnetic layer having a granular structure including a non-magnetic substance between crystal grains containing cobalt (Co), chromium (Cr) and at least one noble metal element,
2. The perpendicular magnetic recording disk according to claim 1, wherein the magnetic recording layer is a ferromagnetic layer having a granular structure including a nonmagnetic substance between crystal grains containing at least cobalt (Co).   2. The perpendicular magnetic recording disk according to claim 1, wherein the noble metal element is one or more elements selected from platinum (Pt), palladium (Pd), and ruthenium (Ru).   2. The perpendicular magnetic recording disk according to claim 1, wherein the thickness of the magnetic recording layer is 15 nm or less.   2. The perpendicular magnetic recording disk according to claim 1, wherein the content of the nonmagnetic material in the miniaturization promoting layer is 5 mol% to 20 mol%.   2. The perpendicular magnetic recording disk according to claim 1, wherein the content of the nonmagnetic material in the magnetic recording layer is 8 mol% to 16 mol%.   When the content of the nonmagnetic substance in the miniaturization promoting layer is Amol% and the content of the nonmagnetic substance in the magnetic recording layer is Bmol%, 0.3 ≦ A / B ≦ 2.5. The perpendicular magnetic recording disk according to claim 1.   2. The perpendicular magnetic recording disk according to claim 1, further comprising an orientation control layer having an amorphous or fcc structure between the base and the underlayer.   2. The perpendicular magnetic recording disk according to claim 1, further comprising an amorphous soft magnetic layer between the base and the underlayer.   2. The perpendicular magnetic recording disk according to claim 1, wherein the substrate is made of amorphous glass. A method of manufacturing a magnetic disk used for perpendicular magnetic recording comprising at least an underlayer, a miniaturization promoting layer, and a magnetic recording layer in this order on a substrate,
Forming a nonmagnetic layer having a granular structure including a nonmagnetic material between crystal grains containing cobalt (Co), chromium (Cr) and at least one noble metal element as the miniaturization promoting layer;
A method of manufacturing a perpendicular magnetic recording disk, comprising forming a ferromagnetic layer having a granular structure including a nonmagnetic substance between crystal grains containing at least cobalt (Co) as the magnetic recording layer.

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