JP2003242623A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium having a sufficiently high coercive force with low noise. <P>SOLUTION: The magnetic recording medium consists of the constitution in which a magnetic layer 4 has a granular structure composed of ferromagnetic crystal particles having a hexagonal closest packing structure and nonmagnetic grain boundaries of oxides, etc., interposed between the ferromagnetic crystal particles; a ground surface layer 2 has a nonmagnetic intermediate layer 3 having a body-centered cubic lattice structure and having the hexagonal closest packing structure essentially consisting of at least one element among Ru, Os and Re between the magnetic layer and the ground surface layer; the rate of mismatching (Δ=|d<SB>1</SB>-d<SB>2</SB>|/d<SB>1</SB>) between the inter-crystal plane spacing (d<SB>1</SB>) of the crystal particles constituting the magnetic layer and the inter-crystal spacing (d<SB>2</SB>) of the crystal particles constituting the nonmagnetic intermediate layer is kept within 10%; the crystal particles of a grain size ≥8 nm among the crystal particles constituting the nonmagnetic intermediate layer are ≤10%; and the standard deviation value of the grain sizes is ≤1.4 nm. These layers are deposited without prior heating of the substrate 1 before the deposition of the layers. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly, it has a low noise and sufficiently high coercive force to be mounted on various magnetic recording devices such as external storage devices such as personal computers. And a high-performance and highly-reliable magnetic recording medium.

[0002]

2. Description of the Related Art A magnetic storage device is one of the information recording devices that has been supporting the advanced information society in recent years, and the recording density of a magnetic recording medium used in the magnetic storage device has been improved as the amount of information has increased. And low noise is required. In order to realize a high recording density, it is necessary to reduce the unit in which the magnetization reversal occurs, and for that purpose, it is necessary to miniaturize the size of the magnetic particles. In order to reduce noise, it is important to reduce the size of magnetic particles and at the same time reduce the fluctuation of magnetization due to magnetic interaction between particles. In a conventional medium using a CoCrPt alloy for the magnetic layer, a large amount of Cr is added in order to segregate enough Cr to the grain boundary in order to reduce noise, but in such a case, the magnetic anisotropy of the magnetic particle itself is added. This leads to a decrease in the Ku value, which deteriorates the thermal stability of the medium. Further, if the amount of Pt added is increased in order to improve the magnetic anisotropy Ku value, conversely, segregation of Cr at the grain boundaries is inhibited, and as a result,
There is a trade-off relationship that the medium noise increases.

In order to solve these problems, various magnetic layer compositions and structures, and various non-magnetic underlayer and seed layer materials have been proposed, and in particular, an oxide called a granular magnetic layer is generally used. A medium having a magnetic crystal grain structure surrounded by a non-magnetic matrix such as a substance or a nitride has been proposed. In the granular medium, magnetic particles are almost completely magnetically insulated by the interposition of a non-magnetic substance, and each particle (about 4 to 10 nm) serves as a minimum magnetization unit, and a fine particle of at least this size is used. Not only high-density recording becomes possible, but also suppression of inter-particle exchange interaction by enclosing a non-magnetic matrix can be expected. Further, as a characteristic of this granular magnetic layer, unlike the conventional CoCrPt-based magnetic layer, since it is mainly the Si oxide that is responsible for segregation to the grain boundaries, it is not necessary to add a large amount of Cr. is there. This means that in the granular magnetic layer, Si oxide is forcibly deposited on the grain boundaries, so that segregation is promoted without causing a decrease in the magnetic anisotropy Ku value, and compatibility with low noise is achieved. It means that you are struck. Further, in the future, higher recording density will be required, but for that purpose, it is essential to reduce the thickness of the magnetic layer. This thinning of the magnetic layer causes a decrease in magnetic energy KuV (Ku: magnetic anisotropy, V: activation volume). Therefore, in order to suppress this decrease in magnetic energy, it is essential to increase the magnetic anisotropy Ku value. Therefore, it is necessary to add more Pt to the magnetic layer composition. However, in a conventional CoCrPt-based magnetic layer, addition of a large amount of Pt hinders segregation of Cr at grain boundaries and causes an increase in noise. However, in a granular magnetic layer, even if a large amount of Pt is added, Si oxide is added. Is easily segregated to the grain boundaries, which has the advantage that the Pt amount can be increased while maintaining the isolation of the grains.

For example, by performing RF sputtering film formation by using a CoNiPt target to which an oxide such as SiO ₂ is added, a structure in which each magnetic crystal grain is surrounded by a non-magnetic oxide and individually separated is formed. It has been reported that a granular recording film can be formed and low noise can be realized (see Patent Document 1). In such a granular magnetic film, the non-magnetic non-metal grain boundary phase physically separates the magnetic particles, so that the magnetic interaction between the magnetic particles is reduced and the zigzag magnetic domain wall generated in the transition region of the recording bit is reduced. It is believed that low noise characteristics can be obtained by suppressing the formation. Further, it has been reported that an underlayer having a body-centered cubic structure is previously formed as an underlayer on which a magnetic layer having a hexagonal close-packed structure is formed (see Patent Documents 2 and 3). A magnetic recording medium having a structure in which an intermediate layer having a non-magnetic body-centered cubic structure is provided between a magnetic layer and an underlayer has also been reported (see Patent Document 4).

[0005]

[Patent Document 1] US Pat. No. 5,679,473

[Patent Document 2] JP-A-11-213371

[Patent Document 3] Japanese Patent Laid-Open No. 2000-123445

[Patent Document 4] Japanese Patent Laid-Open No. 2000-82210

[0006]

In order to realize a medium having excellent electromagnetic conversion characteristics by using a granular magnetic layer, an oxide such as SiO ₂ contained in a target and a Co-based alloy are formed into a film. Need to be separated well in
At the same time, it is important to make the size of the magnetic particles uniform and reduce noise. Further, when the amount of Pt in the granular magnetic layer is increased with further increase in recording density, the lattice constant of the CoCrPt alloy in the magnetic layer increases in proportion only to the amount of Pt. In the layer, it is expected that the lattice constant mismatch between the magnetic layers will increase and the lattice matching will deteriorate.

However, even if low noise can be realized by the structure in which the non-magnetic non-metal grain boundary phase physically separates magnetic particles, it has a hexagonal close-packed structure and a body-centered cubic structure.
In addition, when a non-magnetic intermediate layer is formed by using a material having a difference in crystal plane distance from the magnetic layer crystal of 15% or more, the lattice between the non-magnetic intermediate layer and the magnetic layer crystal is formed. Due to poor matching, there is a limit to easily controlling the particle size of the magnetic particles forming the magnetic layer by forming the magnetic layer on the non-magnetic intermediate layer. That is, in order to realize a magnetic recording medium having a further low noise, it is required to control the crystal size and the magnetic particle size to a higher degree.

The present invention has been made in view of the above problems, and an object of the present invention is to control the structure and particle size distribution of a nonmagnetic intermediate layer to thereby provide a magnetic layer thereon. By controlling the structure of and the grain size of the crystal grains to realize low noise, and controlling the distance between the crystal grains of the magnetic film, the interaction between the magnetic crystal grains is reduced and the magnetic crystal grains are Another object is to provide a magnetic recording medium having a sufficiently high coercive force even when it is made small. The present inventors have made a detailed study on noise reduction by controlling the grain size of the granular magnetic layer. As a result, when forming the magnetic layer, the hexagonal close-packed crystal structure has the same crystal structure as that of the ferromagnetic crystal grains of the magnetic layer. When a crystalline non-magnetic intermediate layer having a structure is provided, the Co particles in the magnetic layer grown on the crystalline non-magnetic intermediate layer grow corresponding to the crystalline material (crystal particles) of the non-magnetic intermediate layer, It was found that the oxide in the magnetic layer was deposited and grew corresponding to the crystalline grain boundary porous region or amorphous. That is, it was revealed that by controlling the crystal grain size of the non-magnetic intermediate layer, the crystal grain size of the magnetic layer grown thereon can be controlled, and excellent magnetic properties can be realized. In other words, the magnetic layer crystal grains are epitaxially grown on the crystal grains of the non-magnetic intermediate layer produced by the sputtering method, and as a result, the crystal orientation of the non-magnetic intermediate layer can be taken over by the magnetic layer. It is possible to control the crystal orientation of the magnetic layer and to form the crystal grain boundaries of the amorphous phase around the crystal grains forming the magnetic layer, thereby controlling the crystal state of the granular magnetic layer. Of.

[0009]

In order to achieve such an object, the present invention provides a nonmagnetic underlayer, a magnetic layer, a protective layer, and a nonmagnetic underlayer on a substrate. In a magnetic recording medium having a structure in which a lubricant film is sequentially formed and laminated, the magnetic layer has ferromagnetic crystal grains having a hexagonal close-packed structure, and oxides interposed between the ferromagnetic crystal grains. And a non-magnetic grain boundary, and the underlayer has a body-centered cubic lattice structure. The invention according to claim 2 is the magnetic recording medium according to claim 1, characterized in that the composition of the magnetic layer contains Pt in an amount of 12 at% or more and 20 at% or less.

The inventions according to claims 3 to 4 are:
The magnetic recording medium according to claim 1, further comprising a nonmagnetic intermediate layer having a hexagonal close-packed structure between the magnetic layer and the underlayer, the nonmagnetic intermediate layer containing at least Ru, Os, and Re. It is a non-magnetic metal containing one element as a main component, and has a crystal plane spacing (d ₁ ) of the crystal grains forming the magnetic layer and a crystal plane spacing (d ₂ ) of the crystal grains forming the non-magnetic intermediate layer. Inconsistency (Δ = | d ₁ −d ₂ | /
It is characterized in that d ₁ ) is within 10%, more preferably, the degree of mismatch is 2.5% or more and 7.0% or less. According to a fifth aspect of the present invention, in the magnetic recording medium according to the fourth aspect, 10% or less of the crystal grains constituting the nonmagnetic intermediate layer have a grain size of 8 nm or more, and , The standard deviation of particle size is 1.
It is characterized by being 4 nm or less. However, the "standard deviation" in this specification is the square root of the unbiased variance.

The invention according to claim 6 is the same as claim 1.
The magnetic recording medium according to any one of items 1 to 5, wherein the substrate is not heated before film formation. Further, the invention according to claim 7 is the magnetic recording medium according to any one of claims 1 to 6, wherein the substrate is a resin substrate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a diagram for explaining a structural example of a magnetic recording medium of the present invention, in which an underlayer 2, a non-magnetic intermediate layer 3, a magnetic layer 4 and a protective layer are formed on a substrate 1. The layer 5 and the lubricant film 6 are sequentially laminated and configured. Here, as the substrate 1, a 3.5 ″ diameter polyolefin resin disk having a smooth surface was used, which was washed and then introduced into a sputtering apparatus to form an underlayer 2 by a DC sputtering method. The stratum 2 has a body-centered cubic lattice structure.

A nonmagnetic intermediate layer 3 was formed on the underlayer 2 by DC sputtering under the conditions of a film forming rate of 2.3 nm / sec and a discharge Ar gas pressure of 30 mTorr. Following this, CoCrP containing 10 mol% of SiO ₂ was added.
Using a t target, a granular magnetic layer 4 having a layer thickness of 10 nm was formed by an RF sputtering method under a discharge Ar gas pressure of 15 mTorr. Various composition ratios shown in Table 1 are used for the composition ratios of Co, Cr and Pt. Then, a carbon protective layer 5 was deposited to a thickness of 8 nm, taken out from the vacuum in the sputtering apparatus, and a liquid lubricant was applied to form a lubricant film 6 having a thickness of 1.5 nm. Here, the composition of the nonmagnetic intermediate layer 3 is as follows: Ti.30 at% Cr, Co.35 at% Cr, O
s, Re, or Ru. The substrate 1 was not heated prior to the formation of the nonmagnetic intermediate layer 3.

The coercive force Hc of the magnetic recording medium thus manufactured was measured by a vibrating sample magnetometer VSM, and the recording / reproducing characteristics were measured by a spin stand tester using a GMR head. The signal-to-noise ratio SNR at a linear recording density of 270 kFCI was evaluated. Table 1 with some measurement results
Shown in.

[0015]

【table 1】 When the intermediate layer is TiCr, the degree of mismatch is as large as 12% or more, which hinders the epitaxial growth between the magnetic layer and the intermediate layer, and the grain size and its variation are large. Therefore, the characteristics of Hc and SNR are Ru. And Re are inferior to the case of the intermediate layer. In the case of the CoCr alloy, the degree of mismatch is smaller than that of the Ru and Re intermediate layers, but it is difficult to reduce the grain size by the film forming process. As a result, the magnetic crystal grains are large, and as a result, the SNR is Ru. And the Re intermediate layer is significantly inferior. Mismatch degree (Δ = | d ₁ ) between the crystal plane spacing (d ₂ ) of the crystal grains forming the non-magnetic intermediate layer 3 and the crystal plane spacing (d ₁ ) of the crystal grains forming the magnetic layer 4
-D ₂ | / d ₁ ) is 10% or less, more preferably 2.5% or more and 7.0% or less, in the non-magnetic intermediate layer having a hexagonal close-packed structure composed of Re, Os, and Ru,
It was confirmed that Hc and SNR were greatly improved. (Example 2) In this example, an underlayer for controlling the crystal grain size of the non-magnetic intermediate layer shown in FIG. 1 was formed by sputtering.
A non-magnetic intermediate layer was formed thereon. The intermediate layer material was limited to Ru. Deposition rate is 2.3 nm / sec and 1.1 nm
/ Sec was implemented. Other film forming conditions and the like are the same as the conditions described in the first embodiment.

Ru is used as the material of the non-magnetic intermediate layer,
As a result of TEM observation of the cross section of the non-magnetic intermediate layer formed by the DC sputtering method under the conditions of the film forming rate of 2.3 nm / sec and the discharge Ar gas pressure of 70 mTorr, the cross section of the nonmagnetic intermediate layer was columnar and was porous in the direction perpendicular to the substrate. A high quality structure was observed, and it was confirmed that the columnar crystals were grown without abnormal growth such as crystal grains becoming large during the growth. Furthermore, no so-called "initial growth layer" was observed near the interface between the underlayer and the nonmagnetic intermediate layer. Further, when the crystal grain size was obtained by performing plane observation with a TEM, the average grain size was about 6 nm, the crystal grain size distribution had a normal distribution, and the standard deviation was 1.
It was 8 nm.

Further, for the purpose of refining the crystal grains constituting the non-magnetic intermediate layer, the film forming rate is set to 1.1 nm / sec and the layer thickness 20 is set under the condition of the discharge Ar gas pressure of 70 mTorr.
It was formed to have a thickness of nm. As a result of observing the non-magnetic intermediate layer thus obtained with a cross-section TEM, a columnar crystal and porous structure was observed in the direction perpendicular to the substrate.
It was confirmed that the columnar crystals grew without abnormal growth such as crystal grains becoming large during the crystal growth. Furthermore, in the vicinity of the interface between the underlayer and the non-magnetic intermediate layer,
No initial growth layer was observed either. Further, when the crystal grain size was obtained by performing a plane observation with a TEM, the average grain size was about 5 nm, the crystal grain size distribution was a normal distribution, and the standard deviation was 1.4 nm.

The crystal structure of the non-magnetic intermediate layer formed under the constant film forming conditions other than the film forming rate was analyzed by the in-plane X-ray diffraction method to examine the film forming rate dependence of the crystal orientation. As a result, in addition to the strong Ru (002) peak that appears near 2θ = 18 °, Ru (10) appears near 2θ = 17 ° and 19 °.
0) and Ru (101) weak peaks were observed. By analyzing this result together with the result of the above-mentioned TEM observation, it was confirmed that the C axis of Ru was preferentially oriented in the plane, and the crystal orientation was controlled by controlling the film formation rate. It was confirmed that it is possible to control the particle size and its distribution while maintaining it. (Embodiment 3) In this embodiment, an underlayer for controlling the crystal grain size of the non-magnetic intermediate layer shown in FIG. 1 is formed by sputtering.
A non-magnetic intermediate layer was formed thereon. Ru was used as the material for the non-magnetic intermediate layer, and the film formation rate was 2.3 by the DC sputtering method.
Nonmagnetic intermediate layers having different layer thicknesses were formed under the conditions of nm / sec and discharge Ar gas pressure of 70 mTorr. Other film forming conditions and the like are the same as the conditions described in the first embodiment.

A non-magnetic intermediate layer with a relatively thin film thickness of 10 nm and a non-magnetic intermediate layer with a relatively thick film thickness of 50 nm are used as a planar TEM.
Observation and determination of crystal grain size by image analysis based on the results showed that the average grain sizes were 6 nm and 8 nm, respectively. The particle size distribution has a normal distribution with standard deviations of 1.4 nm and 2.2 nm, respectively. Cross-sectional TEM observation of these nonmagnetic intermediate layers confirmed that all films had a columnar structure, and an initial growth layer was observed near the interface between the underlayer and the nonmagnetic intermediate layer. There wasn't. In this example, an underlayer for controlling the crystal grain size of the nonmagnetic intermediate layer shown in FIG. 1 was further formed by the sputtering method, and the nonmagnetic intermediate layer was formed thereon. Other film forming conditions and the like are the same as the conditions described in the first embodiment. Ru was used as the material of the non-magnetic intermediate layer, and the film formation rate was fixed to 2.3 nm / sec and the film thickness was fixed to 20 nm by the DC sputtering method.
Ar gas pressure is 0.7 times 70 mTorr (49 m
Torr) and 1.2 times (84 mTorr).

The nonmagnetic intermediate layer thus formed was observed by a plane TEM, and the crystal grain size was determined by image analysis based on the results. The average grain sizes were 8 nm and 5 n, respectively.
It was m. The particle size distribution was a normal distribution with standard deviations of 2.4 nm and 1.9 nm, respectively.
Incidentally, cross-sectional TEM observation of these non-magnetic intermediate layers confirmed that all films had a columnar structure,
No initial growth layer or the like was observed near the interface between the underlayer and the non-magnetic intermediate layer. As a result of analyzing the crystal orientation of these non-magnetic intermediate layers by in-plane X-ray diffraction method and TEM observation,
It was confirmed that the C axis of Ru was preferentially oriented in the plane. Although there is no significant difference in the crystal orientation depending on the film forming conditions, when the layer thickness of the non-magnetic intermediate layer is increased, the variation in crystal grain size is increased due to crystal defects and crystal growth. It was also confirmed that when the Ar gas pressure was reduced, the crystal grain size increased, and the film became dense, so that the crystal grain boundary region between the crystal grains became narrow.

As described above, the thickness of the non-magnetic intermediate layer and the time of film formation
Crystal grains that form the non-magnetic intermediate layer due to the Ar gas pressure of
It was confirmed that it is possible to control the particle size and structure of. Na
If the thickness of the non-magnetic intermediate layer is 5 nm or less, film formation
It is difficult to form a stable film because of the device configuration.
If the thickness is 100 nm or more, it takes a long time to form the film.
Therefore, there are manufacturing restrictions. (Example 4) In this example, the conditions described in Example 2 were used.
Co-based alloy magnetic layer on the non-magnetic intermediate layer
A film was formed to produce a magnetic recording medium. That is, in non-magnetic
Ru of the interlayer is deposited at a film-forming rate of 2.3 nm / sec and discharge Ar gas
20nm is formed under the condition of pressure 70mTorr.
On top, SiO_TwoCo added with 10 mol%₇₆Cr
₁₂Pt₁₂RF sputtering method using a target
The granular magnetic layer was formed under a discharge Ar gas pressure of 15 mTorr.
A 10 nm film was formed. Next to this, a carbon protective film
After stacking 8 nm, take out from the vacuum and then liquid
Apply 1.5 nm of lubricant to form a lubricant film.
A magnetic recording medium having the structure shown was produced. Note that these
The substrate was not heated prior to film formation.

FIG. 2 shows the result of a plane TEM observation of the structure of the magnetic layer of the magnetic recording medium thus obtained. The magnetic crystal grains forming the magnetic layer are granular grains surrounded by a nonmagnetic phase region. It was confirmed that it had a structure. Also,
From the result of the lattice image observation in the vicinity of the grain boundary under the high resolution observation condition, it was found that the Co alloy crystal grain was crystalline and the grain boundary was amorphous. The average distance between crystal grains is
It was 1.1 nm and its standard deviation was 2.0 nm. Furthermore, when the crystal grain size was determined, the average grain size was 4.9 nm. FIG. 3 is a diagram for explaining the crystal grain size distribution constituting the Ru nonmagnetic intermediate layer and the magnetic layer of the magnetic recording medium of the present embodiment. The crystal grain size distribution constituting the magnetic layer has a grain size of about 4 nm. There is a peak at around 8 nm, and when the variation is determined, the standard deviation divided by the average particle diameter is 0.4.

FIG. 4 is a cross-sectional TEM observation result of this magnetic film. A crystal lattice connection is seen between the non-magnetic intermediate layer and the magnetic layer, and the crystal grains forming the magnetic layer are non-magnetic intermediate layers. It can be seen that epitaxial growth occurs from the interface with. It was also found that the crystalline phase of the Co alloy and the amorphous phase of the grain boundaries have different growth mechanisms of the magnetic film and have different metal structures. From the result of in-plane X-ray diffraction, 2θ = 1
A strong peak of Co (002) was observed near 9 °, and θ
Considering together the X-ray diffraction result by the −2θ method and the TEM observation result, it can be seen that Co (100) is preferentially oriented. As a result of measuring the magnetic characteristics of this magnetic layer with a vibrating sample magnetometer (VSM), the coercive force is 2.9 kO.
e, the squareness ratio S, which is an index of the squareness of the hysteresis in the MH loop, was 0.8, and the coercive force squareness ratio S ^* was 0.8, and had good magnetic properties. As described above, the reason why the hysteresis is close to the square shape is that the growth mechanism of the magnetic layer is different from that of the past due to the formation of the grain boundary region of the non-magnetic phase. This is the result of the reduced interaction between particles. (Embodiment 5) In this embodiment, an underlayer for controlling the crystal grain size of the non-magnetic intermediate layer shown in FIG. 1 is formed by sputtering.
A non-magnetic intermediate layer was formed thereon. Ru was used as the material of the non-magnetic intermediate layer, and the film formation rate was 1.1 by the DC sputtering method.
Non-magnetic intermediate layers having different layer thicknesses were formed under the conditions of nm / sec and discharge Ar gas pressure of 70 mTorr. Other film forming conditions and the like are the same as those described in Example 1, and the magnetic recording medium is manufactured. The substrate was not heated prior to film formation.

The magnetic layer thus obtained is treated with a planar TE.
As a result of M observation, it was confirmed that the crystal grains forming the magnetic layer had a granular structure surrounded by a region of the non-magnetic phase. Further, from the result of the lattice image observation under the high resolution condition, it was found that the Co alloy crystal grains were crystalline and the grain boundaries were amorphous. The average distance between the crystal grains was 1.5 nm, and the standard deviation was 1.4 nm. Furthermore, when the crystal grain size was determined, the average grain size was 4.0 nm. FIG. 5 is a diagram for explaining the crystal grain size distribution constituting the Ru non-magnetic intermediate layer and the magnetic layer of the magnetic recording medium of the present embodiment. The crystal grain size distribution constituting the magnetic layer has a grain size of 6n.
There was a peak in the vicinity of m, and the variation was found to be standard deviation / average particle size of 0.2.

When the cross-sectional structure of this film was observed by TEM, a lattice connection was found between the non-magnetic intermediate layer and the magnetic layer, and the crystal grains constituting the magnetic layer had an interface with the non-magnetic intermediate layer. It was found that the film was epitaxially grown. It was also found that the crystal phase and the grain boundary phase in the magnetic layer have different metal structures due to the difference in their growth mechanism. From the in-plane X-ray diffraction result, a strong peak of Co (002) was observed near 2θ = 19 °, and θ−2θ
Considering together the X-ray diffraction result by the method and the TEM observation result, it can be seen that Co (100) is preferentially oriented. As a result of measuring the magnetic characteristics of this magnetic layer by VSM, the coercive force was 3.5 kOe, the squareness ratio S, which is an index of the squareness of hysteresis in the MH loop, was 0.9, and the coercive force squareness ratio S ^* was 0. It was 0.8 and had good magnetic properties. As described above, the hysteresis that is close to the square shape is caused by the fact that the grain size distribution becomes a normal distribution and that the growth mechanism of the magnetic layer is different from before because of the existence of grain boundaries in the non-magnetic intermediate layer. As a result, the interaction between the magnetic crystal grains is reduced. (Example 6) Table 2 is a summary of the recording / reproducing characteristic evaluation results of the magnetic disks using the magnetic films having the magnetic characteristics shown in Examples 4 and 5. Here, the recording / reproducing characteristic is the linear recording density of 160 kFC when the reproducing output of the isolated reproducing waveform measured by the spin stand tester using the GMR head is used.
It is evaluated by I.

[0026]

[Table 2] The magnetic recording medium of Example 5 had noise reduced by 35% and SNR improved by 16% as compared with the magnetic recording medium of Example 4. This is due to the results of particle size analysis of the magnetic layer,
By controlling the crystal grain size of 8 nm or more of the non-magnetic intermediate layer from 40% (data of Example 4 shown in FIG. 3) to 10% (data of Example 5 shown in FIG. 5), the magnetic layer Particles with a crystal grain size of 4 nm or less can be reduced from 15% to 5%, and the variation in the grain size (standard deviation / average grain size) can be suppressed to 0.2. Done S
It was found that the NR value was also greatly improved. Example 5 in which the magnetic layer was laminated on the intermediate layer having a standard deviation of the particle diameter of 1.4 nm showed excellent noise characteristics, and it was shown that the standard deviation of the particle diameter of the intermediate layer is preferably 1.4 nm or less. Was done.

This is because the particles having a crystal grain size of 8 nm or more existing in the non-magnetic intermediate layer have a characteristic of separating the magnetic grains growing thereon, and the crystal grain size of the magnetic layer, the variation, and
Since it has the effect of making it difficult to control the grain boundary segregation of the metal element, if the ratio of the crystal grains in the non-magnetic intermediate layer having a grain size of 8 nm or more is reduced to 10% or less, the crystal grains in the non-magnetic intermediate layer have a
This is because the ratio of the magnetic layer crystal grains corresponding to the pair 1 increases. Furthermore, in this crystal growth, more precise lattice matching is promoted, the lattice matching between the upper and lower interfaces of the magnetic layer and the nonmagnetic intermediate layer is improved, and the columnar porous structure of the nonmagnetic intermediate layer causes the segregation structure. Is promoted, so that good electromagnetic conversion characteristics can be obtained.

[0028]

As described above, according to the present invention,
At least Ru, Os, and Re are provided between the magnetic layer and the underlayer.
Also has a hexagonal close-packed structure with one element as the main component
Crystals of crystalline particles that have a non-magnetic intermediate layer and that make up the magnetic layer
Surface spacing (d₁) And the crystal grains forming the non-magnetic intermediate layer
Crystal face spacing (d_Two) Inconsistency (Δ = | d₁-D_Two｜ / d
₁) Is configured to be within 10%, so noise
Can be realized and has excellent magnetic characteristics and electromagnetic conversion characteristics.
It is possible to provide a magnetic recording medium that performs Furthermore
By controlling the distance between the crystal grains of the magnetic layer,
It is possible to reduce the interaction between magnetic crystalline particles,
Even if the crystal grain size is reduced
And has a sufficiently high coercive force, so the effect of thermal disturbance is small.
In addition, it is possible to realize stable and high density recording.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a magnetic recording medium of the present invention.

2 is a plane TEM image showing the magnetic layer structure of the magnetic recording medium of Example 4. FIG.

FIG. 3 is a diagram for explaining a crystal grain size distribution of a non-magnetic intermediate layer and a magnetic layer of a magnetic recording medium of Example 4.

FIG. 4 is a sectional TEM image of a non-magnetic intermediate layer and a magnetic layer region of a magnetic recording medium of Example 4.

FIG. 5 is a diagram for explaining a crystal grain size distribution of a non-magnetic intermediate layer and a magnetic layer of a magnetic recording medium of Example 5.

[Explanation of symbols]

1 substrate 2 Underlayer 3 Non-magnetic intermediate layer 4 Magnetic layer 5 protective layer 6 Lubricant film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Uesumi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Naoki Takizawa             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Tadaaki Oikawa             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 5D006 BB01 BB02 BB07 BB09 CA01                       CA05 CA06 CB01                 5D112 AA03 FA04 GA02

Claims (7)

[Claims] 1. A magnetic recording medium having a structure in which a non-magnetic underlayer, a magnetic layer, a protective layer, and a lubricant film are sequentially laminated on a substrate, wherein the magnetic layer is hexagonal. Having a granular structure composed of a ferromagnetic crystal grain having a closest packing structure and a non-magnetic grain boundary mainly composed of an oxide interposed between the ferromagnetic crystal grains,
A magnetic recording medium, wherein the underlayer has a body-centered cubic lattice structure. 2. The magnetic recording medium according to claim 1, wherein the Pt content in the composition of the magnetic layer is 12 at% or more and 20 at% or less. 3. A nonmagnetic intermediate layer having a hexagonal close-packed structure is provided between the magnetic layer and the underlayer, and the nonmagnetic intermediate layer contains at least one element of Ru, Os, and Re as a main component. And the crystal plane spacing (d ₁ ) of the crystal grains constituting the magnetic layer and the crystal plane spacing (d) of the crystal grains constituting the nonmagnetic intermediate layer.
₂ ) the degree of mismatch (Δ = | d ₁ −d ₂ | / d ₁ ) is 10
The magnetic recording medium according to claim 1, wherein the content is within%. 4. The degree of inconsistency is 2.5% or more and 7.0%.
The magnetic recording medium according to claim 3, wherein: 5. Of the crystal grains forming the non-magnetic intermediate layer, 10% or less of the crystal grains having a grain size of 8 nm or more,
The magnetic recording medium according to claim 4, wherein the standard deviation of the particle diameter is 1.4 nm or less. 6. The magnetic recording medium according to claim 1, wherein the substrate is not heated before film formation. 7. The magnetic recording medium according to claim 1, wherein the substrate is a resin substrate.