JP2009277319A - Vertical magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical magnetic recording medium capable of providing a further improvement against RFPE in view of a coercive force Hc and a saturation magnetic field Hs. <P>SOLUTION: In the vertical magnetic recording medium 100 including a soft magnetic layer 114 and a vertical magnetic recording layer 122 on a substrate 110, a nucleation magnetic field Hn/the coercive force Hc is set to 0.35 or more, and the nucleation magnetic field Hn/the saturation magnetic field Hs is set to 0.23 or more. By setting the nucleation magnetic field Hn and the saturation magnetic field Hs with respect to the coercive force Hc to the ranges based on the RFPE dependency of Hn/Hc and Hn/Hs, a reverse magnetic domain is made difficult to be formed with respect to a return field. By setting the nucleation magnetic field Hn/the coercive force Hc to 0.40 or more and the nucleation magnetic field Hn/the saturation magnetic field Hs to 0.24 or more, an RFPE value can be caused to be substantially zero. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium widely used in computer storage devices and the like, and more specifically to a perpendicular magnetic recording medium such as a perpendicular magnetic recording disk mounted on a perpendicular magnetic recording HDD (hard disk drive) and the like. It relates to a manufacturing method.

  In recent years, the information society has continued to advance rapidly, and in a magnetic recording apparatus represented by an HDD (Hard Disk Drive), for example, a single disk is used for a 2.5-inch diameter magnetic disk as a magnetic recording medium. An information recording capacity exceeding 160 Gbytes has been demanded.

  In order to achieve a high recording density in a magnetic disk, it is necessary to refine the magnetic crystal grains forming a magnetic recording layer for recording information signals and to reduce the layer thickness. However, in the case of magnetic disks of the in-plane magnetic recording method (also called longitudinal magnetic recording method or horizontal magnetic recording method) that have been commercialized conventionally, as a result of the progress of miniaturization of magnetic crystal grains, superparamagnetic phenomenon The so-called thermal fluctuation phenomenon, in which the thermal stability is impaired and the recording signal disappears, has become an obstructive factor for increasing the recording density of the magnetic disk.

  In order to perform stable recording and reproduction at such a high recording density, it is preferable to adopt a perpendicular magnetic recording system as a magnetic recording and reproducing system. In the perpendicular magnetic recording system, unlike the in-plane magnetic recording system, the easy axis of magnetization of the magnetic recording layer is adjusted so that the magnetic crystal grains are 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 magnetic recording method, and is suitable for increasing the recording density.

  A perpendicular magnetic recording medium is a two-layer perpendicular magnetic recording medium in which a soft magnetic backing layer composed of a soft magnetic layer and a perpendicular magnetic recording layer composed of a hard magnetic layer are provided on a substrate. It is said that reproduction can be realized.

  FIG. 6 is a conceptual diagram of a perpendicular magnetic recording system using a double-layered perpendicular magnetic recording medium as a perpendicular magnetic recording medium. The two-layered perpendicular magnetic recording medium 10 includes a soft magnetic backing layer 11 made of a soft magnetic layer formed on a substrate and a perpendicular magnetic recording layer 12 made of a hard magnetic layer formed on the soft magnetic backing layer 11. Prepare. The perpendicular magnetic recording head includes a main pole 13 that is a source of a recording magnetic field, a coil 14 that excites the main pole 13, and a magnetic circuit that forms a magnetic circuit together with the soft magnetic underlayer 11 by guiding the magnetic flux from the main pole 13. It consists of yokes (trailing-side return yoke 15 and leading-side return yoke 16).

In the two-layered perpendicular magnetic recording medium 10, the soft magnetic backing layer 11 is a layer made of a magnetic material (soft magnetic material) exhibiting soft magnetic properties, and the hard magnetic layer is a magnetic material exhibiting hard magnetic properties. It is a layer made of a body (hard magnetic body). Usually, the hard magnetic layer becomes the perpendicular magnetic recording layer 12. On the other hand, the soft magnetic backing layer 11 serves to help the main pole 13 serving as a magnetic head attached to the two-layered perpendicular magnetic recording medium 10 to record a signal on the perpendicular magnetic recording layer 12 made of a hard magnetic layer. Yes. Magnetic flux enters the medium perpendicularly from the main pole 13 and recording is performed. The magnetic flux that has entered returns to the trailing return yoke 15 serving as the Retune Pole through the soft magnetic underlayer 11.
JP 2007-49850 A

  By the way, as shown in FIG. 6, in a two-layered perpendicular magnetic recording medium 10 having a soft magnetic underlayer 11, a trailing edge shielded pole head (SPH) having a trading shield (TS) may generate a steep magnetic field. it can. On the other hand, as shown in FIGS. 7A to 7C, a magnetic field opposite to the magnetic field from the main pole 13 is generated immediately below the edge of the trading shield. Although the area of the trading shield 17 is sufficiently larger than the area of the main pole 13 as viewed from the ABS surface, the magnetic field at the edge of the trading shield 17 on the main pole 13 side becomes stronger because the gap is narrow. As a result, as shown in FIG. 7C, immediately after writing by the main pole 13, a reverse magnetic domain is formed by the return field, which causes noise. This phenomenon is RFPE (Return Field-induced Partial Erasure). This phenomenon appears more prominently as the write current is larger, and is characterized by being more susceptible to the demagnetizing field of the medium and the bit and more likely to occur at the center of the bit where the demagnetizing field is strong and at a low frequency signal.

  Conventionally, RFPE has been reduced by adjusting the thickness of the soft magnetic underlayer and the reverse domain nucleation magnetic field Hn as an improvement measure from the medium for this problem.

  However, there is a limit to the improvement to RFPE only by adjusting the film thickness and Hn of the soft magnetic backing layer, and further improvement to RFPE is desired.

  The present invention has been made in view of such points, and an object thereof is to provide a perpendicular magnetic recording medium capable of further improving RFPE and a method of manufacturing the same, by taking into consideration the coercive force Hc and the saturation magnetic field Hs. And

  The present inventor discovered the dependence of Hn / Hc and Hn / Hs on RFPE, and made the nucleation magnetic field Hn and the saturation magnetic field Hs in a certain range with respect to the coercive force Hc, thereby reversing the return field. The inventors have found that it is difficult to form a magnetic domain and completed the present invention.

  In the perpendicular magnetic recording medium having a soft magnetic layer and a perpendicular magnetic recording layer on a substrate, the present invention provides a nucleation magnetic field Hn / coercive force Hc of 0.35 or more and a nucleation magnetic field Hn / saturation magnetic field Hs of 0. It is characterized by being 23 or more.

  By setting the nucleation magnetic field Hn / coercive force Hc to 0.40 or more and the nucleation magnetic field Hn / saturation magnetic field Hs to 0.24 or more, the RFPE value can be made substantially zero.

  Further, from the RFPE dependency of Hn / Hc and Hn / Hs, it is possible to determine a magnetostatic characteristic that can reduce the RFPE value to a desired value.

  The coercive force Hc is 4000 to 4600 Oe, the nucleation magnetic field Hn is 1820 to 1890 Oe, and the saturation magnetic field Hs is 7550 to 7890 Oe. The coercive force Hc is 4600 to 4800 Oe, the nucleation magnetic field Hn is 1890 to 1980 Oe, and the saturation magnetic field Hs is 7890 to 8230 Oe. The coercive force Hc is 4800 to 5000 Oe, the nucleation magnetic field Hn is 1980 to 2060 Oe, and the saturation magnetic field Hs is 8230 to 8580 Oe. Further, the coercive force Hc is 5000 to 5400 Oe, the nucleation magnetic field Hn is 2060 to 2220 Oe, and the saturation magnetic field Hs is 8580 to 9280 Oe.

  According to the present invention, in a perpendicular magnetic recording medium having a soft magnetic layer and a perpendicular magnetic recording layer on a substrate, Hn and Hs are set within a certain range with respect to Hc, so that a reverse magnetic domain with respect to a return field is obtained. Can be made difficult to form, and RFPE can be improved.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. Note that dimensions, materials, and other specific numerical values shown in the following examples are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified.

  FIG. 1 is a cross-sectional view showing the structure of the perpendicular magnetic recording disk 100 according to the present embodiment. The perpendicular magnetic recording disk 100 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, an orientation control layer 116, a first underlayer 118a, and a second underlayer 118b. , A miniaturization promoting layer 120, a first magnetic recording layer 122a, a second magnetic recording layer 122b, a continuous layer 124, a medium protective layer 126, and a lubricating layer 128. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c function together as the soft magnetic layer 114, and the first base layer 118a and the second base layer 118b function together as the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together function as the magnetic recording layer 122.

  The disk substrate 110 is preferably non-magnetic glass. Specific examples include aluminosilicate glass, aluminoborosilicate glass, soda lime glass, and aluminosilicate glass is particularly preferable. Since the aluminosilicate glass is smooth and has high rigidity, the magnetic spacing, particularly the flying height of the magnetic head, can be more stably reduced. Aluminosilicate glass can obtain high rigidity and strength by chemical strengthening. When the soft magnetic layer 114 is amorphous, the disk substrate 110 is also preferably made of amorphous glass. When an aluminosilicate glass is used for the disk substrate 110, an amorphous aluminosilicate glass is formed into a disk shape by direct pressing to produce a glass disk. 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.

Subsequently, on the obtained disk substrate 110, a DC magnetron sputtering apparatus is used as the sputtering apparatus 200 as a vacuum film forming apparatus, and the deposition from the adhesion layer 112 to the continuous layer 124 is sequentially performed. CVD (Chemical as a film deposition system)
A film was formed using a Vapor Deposition apparatus. Thereafter, the lubricating layer 128 was formed by dip coating. Note that it is also preferable to use an in-line film forming method in terms of high mass productivity. Hereinafter, the configuration of each layer will be described.

Below, the structure and manufacturing method of each layer are explained in full detail.
The adhesion layer 112 is a layer for improving the adhesion with the disk substrate 110 and can prevent the soft magnetic layer 114 from peeling off. As a material of the adhesion layer 112, for example, a CrTi alloy can be used. The thickness of the adhesion layer 112 is preferably 1 nm to 50 nm. For example, the adhesion layer 112 is formed by using a Ti alloy target to form a 10 nm Ti alloy layer.

  The soft magnetic layer 114 includes 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. It was configured as follows. Thereby, the magnetization direction of the soft magnetic layer 114 can be aligned along the magnetic path (magnetic circuit) with high accuracy. Thus, since the perpendicular component of the magnetization direction is extremely reduced, noise generated from the soft magnetic layer 114 can be reduced.

  FeCoTaZr can be used as the composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c. As the composition of the spacer layer 114b, ruthenium (Ru) can be used. Note that the first soft magnetic layer 114a and the second soft magnetic layer 114c are not limited to the above-described composition. Co-based alloys (CoTaZr, CoZrNb, CoB, etc.) can be used. The total thickness of the soft magnetic layer 114 is 40 nm to 120 nm, preferably 40 nm to 100 nm.

  The orientation control layer 116 has a function of protecting the soft magnetic layer 114 and a function of promoting alignment of crystal grains of the underlayer 118. The material of the orientation control layer 116 can be selected from Ni, Cu, Pt, Pd, Zr, Hf, and Nb. Furthermore, it is good also as an alloy which contains these metals as a main component and contains any one or more additional elements of Ti, V, Ta, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected.

  The underlayer 118 has an hcp structure, and the crystal of the hcp structure of the magnetic recording layer 122 can be grown as a granular structure. Therefore, the higher the crystal orientation of the underlayer 118, the more the orientation of the magnetic recording layer 122 can be improved. As the material of the underlayer 118, Ru can be used, but in addition, it can be selected from RuCr and RuCo. Ru has an hcp structure and can satisfactorily orient a magnetic recording layer containing Co as a main component.

  In the present embodiment, the base layer 118 has a two-layer structure made of Ru. When forming the second base layer 118b on the upper layer side, the Ar gas pressure is set higher than when forming the first base layer 118a on the lower layer side. When the gas pressure is increased, the free movement distance of the plasma ions to be sputtered is shortened, so that the film formation rate is reduced and the crystal orientation can be improved. Further, by increasing the pressure, the size of the crystal lattice is reduced. Since the size of the Ru crystal lattice is larger than that of the Co crystal lattice, if the Ru crystal lattice is made smaller, it approaches that of Co, and the crystal orientation of the Co granular layer can be further improved.

The miniaturization promoting layer 120 is composed of a nonmagnetic granular layer. A nonmagnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and the granular layer of the first magnetic recording layer 122a is grown thereon, so that the magnetic granular layer can be grown from the initial growth stage (rise). Has the effect of separating. The composition of the miniaturization promoting layer 120 was nonmagnetic CoCr—SiO ₂ .

The magnetic recording layer 122 includes a thin first magnetic recording layer 122a and a thick second magnetic recording layer 122b. The first magnetic recording layer 122a is a 2 nm CoCrPt—Cr ₂ O ₃ hcp crystal structure using a hard magnetic target made of CoCrPt containing chromium oxide (Cr ₂ O ₃ ) as an example of a nonmagnetic material. Formed. Nonmagnetic substances segregated around the magnetic substance to form grain boundaries, and the magnetic grains (magnetic grains) formed columnar granular structures. The magnetic grains were epitaxially grown continuously from the granular structure of the miniaturization promoting layer 120. For the second magnetic recording layer 122b, a 10-nm CoCrPt—TiO ₂ hcp crystal structure was formed using a hard magnetic target made of CoCrPt containing titanium oxide (TiO ₂ ) as an example of a non-magnetic substance. Also in the second magnetic recording layer 122b, the magnetic grains formed a granular structure.

  Here, the atmospheric gas pressure of the first magnetic recording layer 122a was set to a high pressure of 3 Pa to 10 Pa. Thus, high Hc and Hn could be obtained by forming a film using a high-pressure atmospheric gas. The atmospheric gas pressure of the second magnetic recording layer 122b was set to a low pressure of 0.6 Pa to 3 Pa. Thus, high impact resistance was able to be obtained by forming into a film using low pressure atmospheric gas.

In the present embodiment, different materials (targets) are used for the first magnetic recording layer 122a and the second magnetic recording layer 122b. However, there is no need to use different materials, and the materials are the same in composition and type. Also good. Examples of nonmagnetic substances for forming the nonmagnetic region include silicon oxide (SiO _x ), chromium (Cr), chromium oxide (CrO _x ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), An example is tantalum oxide (Ta ₂ O ₅ ).

  The continuous layer 124 is a CGC structure (Coupled Granular Continuous) by forming a thin film (auxiliary recording layer) exhibiting high perpendicular magnetic anisotropy on a magnetic layer having a granular structure. Thereby, in addition to the high density recording property and low noise property of the granular layer, the high heat resistance of the continuous film can be added. The composition of the continuous layer 124 was CoCrPtB.

The medium protective layer 126 is formed by depositing carbon by CVD while maintaining a vacuum and including diamond-like carbon. The medium protective layer 126 is a protective layer for protecting the perpendicular magnetic recording layer 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 layer can be protected more effectively against the impact from the magnetic head. For the medium protective layer 126, for example, a material such as C, SiO ₂ or ZrO ₂ can be used. From the viewpoint of increasing the recording density, the thickness of the medium protective layer is preferably 1 nm or more and 5 nm or less.

  The lubricating layer 128 was formed of PFPE (perfluoropolyether) by dip coating. For example, a material such as fluorinated alcohol or fluorinated carboxylic acid can be used for the lubricating layer 128. The film thickness of the lubricating layer 128 is about 1 nm.

(Evaluation methods)
Below, the evaluation method of RFPE is demonstrated.
A medium having the same structure as that of the perpendicular magnetic recording disk 100 having the structure shown in FIG. 1 was used as an evaluation target. An R / W analyzer and a magnetic head for perpendicular magnetic recording system having a trailing edge shielded pole head (SPH) on the recording side and a TMR element on the reproducing side were used.

The coercive force Hc, the nucleation magnetic field Hn, and the saturation magnetic field Hs were varied for each medium to be evaluated. The coercive force Hc of the media was 4600-5400 Oe (× 10 ³ / 4π A / m). Further, the nucleation magnetic field Hn of the media has a value in the range of 1820 to 2220 Oe, and the saturation magnetic field Hs has a value in the range of 7550 to 9280 Oe.

  FIG. 2 is a diagram showing RFPE dependence of Hn / Hc and Hn / Hs. The correlation between Hn / Hc and Hn / Hs was found to be RFPE-dependent. By increasing both Hn / Hc and Hn / Hs, it was confirmed that the RFPE value tends to decrease. In order to make the RFPE value smaller than 0.2, the magnetostatic characteristics (Hc, Hn, Hs) are set so that Hn / Hc is larger than 0.35 and Hn / Hs is larger than 0.23. ) Is effective. Further, in order to bring the RFPE value close to 0, the magnetostatic characteristics (Hc, Hn, Hs) of the media so that Hn / Hc is greater than 0.40 and Hn / Hs is greater than 0.24. It is desirable to control.

  By utilizing the RFPE dependency of Hn / Hc and Hn / Hs as described above, it is possible to determine the magnetostatic characteristics of a medium that can reduce the RFPE value. FIG. 3 is a correspondence table in which the nucleation magnetic field Hn and the saturation magnetic field Hs are determined with respect to the coercive force Hc of the media based on the RFPE dependency of Hn / Hc and Hn / Hs. Here, the coercive force Hc is divided into four classes. For a coercive force Hc of 4000 to 4600 Oe, the nucleation magnetic field Hn is 1820 to 1890 Oe, and the saturation magnetic field Hs is 7550 to 7890 Oe. Similarly, a nucleation magnetic field Hn and a saturation magnetic field Hs are defined for coercive forces Hc of 4600 to 4800, 4800 to 5000, and 5000 to 5400, respectively. As apparent from the calculation of Hn / Hc and Hn / Hs from the magnetostatic characteristics shown in FIG. 3, Hn / Hc is greater than 0.40 and Hn / Hs is greater than 0.24, and the RFPE value is It becomes possible to make it almost zero.

FIG. 4 shows the SNR characteristic before RFPE improvement (RFPE = 1.5 dB), and FIG. 5 shows the SNR characteristic after RFPE improvement (RFPE = 0.1 dB). In order to evaluate this phenomenon (RFPE) as a value, the SNR at the time of low Iw (write current) and low OVS (overshoot: the waveform temporarily exceeds the specified level) is referred to as reference, and high Iw and When the SNR at the time of high OVS was set to Stressed, the difference between the SNR of Reference and Stressed was evaluated. The reason for high Iw and high OVS is to clearly confirm the difference between each medium because RFPE appears remarkably.
As this difference increases, the RFPE value changes depending on the writing performance of the recording head, but it is confirmed that a correlation between the heads is obtained.

  Before the RFPE improvement shown in FIG. 4, the SN decreases as the write current Iw increases. On the other hand, it can be seen that after the RFPE improvement shown in FIG. 5, a high SN is maintained even when the write current Iw increases. It can also be seen that there is almost no difference between the SN of Reference and Stressed.

  The layer configuration, the material, the number, the size, the processing procedure, and the like in the above embodiment are merely examples, and various modifications can be made within the range where the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

Sectional drawing which showed the structure of the perpendicular magnetic recording disk by this embodiment The figure which shows RFPE dependence of Hn / Hc and Hn / Hs The figure which shows the correspondence table which defined the nucleation magnetic field Hn and the saturation magnetic field Hs with respect to the coercive force Hc of media The figure which shows the SNR characteristic before RFPE improvement The figure which shows the SNR characteristic after RFPE improvement Conceptual diagram of perpendicular magnetic recording system using double-layered perpendicular magnetic recording medium Diagram for explaining RFPE

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Perpendicular magnetic recording disk 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 ... Orientation control layer 118a ... 1st base layer 118b ... Second underlayer 120 ... miniaturization promoting layer 122a ... first magnetic recording layer 122b ... second magnetic recording layer 124 ... continuous layer 126 ... medium protective layer 128 ... lubricating layer

Claims (6)

  In a perpendicular magnetic recording medium having a soft magnetic layer and a perpendicular magnetic recording layer on a substrate, the nucleation magnetic field Hn / coercive force Hc is 0.35 or more, and the nucleation magnetic field Hn / saturation magnetic field Hs is 0.23 or more. A perpendicular magnetic recording medium.   The perpendicular magnetic recording medium according to claim 1, wherein the coercive force Hc is 4000 to 4600 Oe, the nucleation magnetic field Hn is 1820 to 1890 Oe, and the saturation magnetic field Hs is 7550 to 7890 Oe.   The perpendicular magnetic recording medium according to claim 1, wherein the coercive force Hc is 4600 to 4800 Oe, the nucleation magnetic field Hn is 1890 to 1980 Oe, and the saturation magnetic field Hs is 7890 to 8230 Oe.   The perpendicular magnetic recording medium according to claim 1, wherein the coercive force Hc is 4800 to 5000 Oe, the nucleation magnetic field Hn is 1980 to 2060 Oe, and the saturation magnetic field Hs is 8230 to 8580 Oe.   The perpendicular magnetic recording medium according to claim 1, wherein the coercive force Hc is 5000 to 5400 Oe, the nucleation magnetic field Hn is 2060 to 2220 Oe, and the saturation magnetic field Hs is 8580 to 9280 Oe. In a method of manufacturing a perpendicular magnetic recording medium in which a soft magnetic layer and a perpendicular magnetic recording layer are formed on a substrate, the nucleation magnetic field Hn / coercive force Hc is 0.35 or more, and the nucleation magnetic field Hn / saturation magnetic field Hs is set to 0. A method for manufacturing a perpendicular magnetic recording medium, wherein the number is 23 or more.

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