JP2002329306A - Perpendicular magnetic recording medium and method of manufacturing for the same as well as magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium which quantitatively recognizes the ratio of a microcrystalline structure section occupied in a ferromagnetic material layer constituting a recording layer and is capable of realizing excellent static magnetic characteristics, a method of manufacturing for the same and a magnetic recording device. SOLUTION: The perpendicular magnetic recording medium 10 characterized in that the ferromagnetic material layer 12 positioned with a columnar structure section 14 on the microcrystalline structure section 13 consisting of microcrystals three- dimensionally randomly oriented with c-axes constitutes the recording layer, the thickness of the microcrystalline structure section 13 is defined as d<ini> , the thickness of the columnar structure section 14 as d<mag> , the perpendicular magnetic anisotropic energy of the ferromagnetic material layer 12 as Ku⊥ and the magnetic crystal gains of the columnar structure section 14 as Ku<grain> , and the d<ini> determined from Ku⊥ and d<ini> is <=5 nm and a method of manufacturing for the same as well as the magnetic recording device having this perpendicular magnetic recording medium and the ferromagnetic material layer 12 is disposed on a substrate across >=1 ground surface layer 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium, a method for manufacturing the same, and a magnetic recording apparatus, and more particularly, to a method for quantitatively determining the proportion of a microcrystalline structure in a ferromagnetic layer constituting a recording layer. The present invention relates to a perpendicular magnetic recording medium capable of stably realizing excellent magnetostatic characteristics, a manufacturing method thereof, and a magnetic recording device. The perpendicular magnetic recording medium according to the present invention is suitably used for hard disks, magnetic tapes and the like.

[0002]

2. Description of the Related Art In a magnetic recording medium mounted on a magnetic recording device such as a current hard disk device (HDD), a magnetization direction is fixed in an in-plane direction of a magnetic recording layer, and data is inverted by reversing the magnetization. A longitudinal recording method for recording is used. In this method, in order to increase the recording density per unit area, the length of the magnetization reversal direction is mainly reduced,
The development of magnetic recording media capable of improving the so-called linear recording density has been promoted.

Conventionally, a longitudinal recording method (longitudinal r
It is known that shortening the magnetization reversal length is effective in improving the linear recording density of an ecording medium (hereinafter referred to as an in-plane medium). It is required to increase the coercive force of the ferromagnetic layer as the magnetic recording layer and to reduce the residual magnetic flux density and thickness of the ferromagnetic layer.

However, when the thickness of the ferromagnetic layer is reduced in order to improve the linear recording density, the crystal grains constituting the ferromagnetic layer are reduced in size, and the volume V tends to decrease. When the product of the magnetic anisotropy energy Ku of the magnetic crystal grains and Ku · V, which is the product of the magnetic anisotropy energy, decreases to a certain extent or less, the thermomagnetic relaxation phenomenon that the magnetization direction of the magnetic crystal grains becomes unstable under the influence of heat. Generation, so-called thermal disturbance, is a concern.

Since this phenomenon becomes more apparent as the volume V of the crystal grains becomes smaller, development of a magnetic material having a large Ku is expected to maintain the thermal stability of recording magnetization. In order to respond to this, the present inventor has proposed a CoC having a predetermined ratio.
Japanese Patent Application No. 11-135038 discloses that an rGe-based ferromagnetic metal material can realize a large Ku. The present inventor has also found that thermal disturbance can be suppressed by reducing the particle size distribution of crystal grains, and as a specific measure, a magnetic recording medium provided with a seed layer made of W or WCr is promising. It was disclosed in Japanese Patent Application No. 11-150424.

On the other hand, a perpendicular recording method (perpen.
dicular recording) has the advantage that there is no abutting of magnetization as in an in-plane medium. In other words, even when the crystal grains of the ferromagnetic layer are made small, by maintaining an appropriate thickness, the volume V of the crystal grains can be maintained in the thickness direction. Easy to maintain stability.
For this reason, the perpendicular recording method has attracted attention as a technique capable of avoiding the problem of thermal disturbance which is a concern in the longitudinal recording method.

As a specific perpendicular magnetic recording medium, a CoCr alloy (Cr: 10 to 18 at) is used as a recording layer on a substrate.
%) Those provided with a film are widely known. (S.Iwasaki
andK.Ouchi: IEEE Trans. Magn. MAG-14 (1978) 849;
Literature 1) A recording layer composed of a CoCr film formed on a substrate by a sputter deposition method is a columnar fine particle composed of hcp crystal grown in a direction perpendicular to the film surface, and has an average particle diameter of 100 nm or less. It is reported that the c-axis of the hcp crystal substantially coincides with the direction of film growth.

Further, a soft magnetic film such as a NiFe alloy which is easily magnetized in the in-plane direction is provided between the base and the recording layer.
Layered media have also been proposed. (S.Iwasaki, Y.Nakamura
andK.Ouchi: IEEE Trans. Magn.MAG-15 (1979) 1456
Reference 2) As a result of analyzing the flow of magnetic flux at the time of recording and reproduction by the finite element method, the two-layer film medium including the soft magnetic film and the recording layer is more compared with the single layer medium including only the recording layer. The ability to write on the recording layer with a large coercive force, increase the reproduction voltage, and the presence of this soft magnetic film make it possible for the magnetic flux generated from the main pole of the magnetic head to converge with high density in the space at the tip of the main pole. Therefore, it is described that an increase in the magnetic field near the main magnetic pole is caused. (Shunichi Iwasaki, Shinji Tanabe: Transactions of the Institute of Electronics, Information and Communication Engineers, J66-C (1983) 740; Reference 3) In other words, the above-described perpendicular magnetic recording medium is less affected by demagnetization due to a demagnetizing field than the above-described in-plane medium. Therefore, since the thickness of the recording layer can be set to be large, the magnetic recording medium is considered promising as a magnetic recording medium that is resistant to thermal disturbance and suitable for high recording density.

However, in the perpendicular magnetic recording medium, there is a problem that a disordered structure called an “initial layer” is formed in an initial growth portion of a columnar structure which becomes a recording layer of the medium depending on a manufacturing method. . (Tsato Tanaka, Kazuhiro Ouchi, Shunichi Iwasaki: Journal of the Japan Society of Applied Magnetics vol.10, No.2 (1986) 65; Reference 4) In addition, the initial layer was analyzed by computer simulation,
There are also reports that compared the measured waveform with the measured waveform.
(Yoshihisa Nakamura, Ikuya Tagawa, Shunichi Iwasaki: Journal of the Japan Society of Applied Magnetics)
Vol.11, No.2 (1987) 119; Reference 5) According to these two reports, the initial layer has a two-dimensional random orientation of the easy axis of magnetization, that is, the c-axis, in the in-plane direction of the film surface. In the columnar structure grown above, a method of analyzing the c-axis as being oriented in the direction perpendicular to the film surface is introduced.

However, reports on the perpendicular magnetic recording media of the above-mentioned references 1 to 5 often discuss macroscopic changes in magnetic properties of the entire recording layer, and the intrinsic crystalline magnetic anisotropy of the columnar structure is often discussed. The properties and the anisotropic magnetic field equivalent thereto were not quantitatively evaluated excluding the influence of the initial layer. Therefore, a method of accurately grasping the initial layer existing in the medium has been desired.

On the other hand, as a method for accurately grasping the microcrystalline structure portion (initial layer) contained in the ferromagnetic layer of the perpendicular magnetic recording medium, the present inventors proposed that the microcrystalline structure portion be 3 As a microcrystal in which the c-axis is randomly oriented,
From the perpendicular magnetic anisotropy energy Ku ^⊥ of the ferromagnetic layer and the thickness d ^mag of the ferromagnetic layer, the crystal magnetic anisotropy energy Ku ^grain and / or the magnetic crystal grain of the columnar structure on the microcrystalline structure is obtained. Proposal of an evaluation method for perpendicular magnetic recording media to obtain the thickness d ⁱⁿⁱ of the microcrystalline structure (Shin Saito, Daiji Hasegawa, DD Jayaprawira, Ken Takahashi: Journal of the Japan Society of Applied Magnetics, 25, (200
1)), and the evaluation method is also disclosed in an application filed by the present applicant (Japanese Patent Application No. 2000-076021). According to the evaluation method described in the publication,
The thickness and magnetic properties of the microcrystalline structure and the columnar structure of the ferromagnetic layer, which could not be separated and analyzed by the conventional evaluation method, can be analyzed separately. It is possible to accurately grasp the magnetic anisotropic energy Ku ^grain and the thickness d ⁱⁿⁱ of the microcrystalline structure.

[0012]

Incidentally, it has been reported that it is effective to improve the squareness ratio of a perpendicular magnetic recording medium in order to improve the recording / reproducing characteristics such as the resolution and overwrite characteristics of the medium (Shigeru Tadokoro). , Kazuhiro Ouchi, Yoshihisa Nakamura,
Shunichi Iwasaki: "M-H curve squareness ratio of Co-Cr layer and performance of two-layer film medium", IEICE technical report), and improvement to make the squareness ratio close to 1 to suppress thermal demagnetization of the medium (Yoshiyuki Hirayama, Kenya Ito, Yukio Honda, Masaaki Nihon: Journal of the Japan Society of Applied Magnetics vol.21, No.82 (1997), 98). Based on these ideas, in order to produce a perpendicular magnetic recording medium having excellent recording / reproduction characteristics and heat-resistant demagnetization characteristics, it is necessary to design a medium for improving the squareness ratio of the medium. The relationship between ratios has been unclear in the past.

The present invention has been made in view of the above circumstances, and it is possible to quantitatively grasp the proportion of the microcrystalline structure in the ferromagnetic layer forming the recording layer, thereby realizing excellent magnetostatic characteristics. A first object is to provide a perpendicular magnetic recording medium. A second object of the present invention is to provide a method for manufacturing a perpendicular magnetic recording medium capable of stably producing a perpendicular magnetic recording medium having excellent magnetostatic characteristics. Still another object of the present invention is to provide a magnetic recording device that can record and reproduce information at a higher density by providing a magnetic recording medium having the above-described characteristics.

[0014]

The present inventor has made the above evaluation
Research on the structure of perpendicular magnetic recording media
If the following configuration is adopted, the above purpose can be achieved.
I learned that That is, the perpendicular magnetic recording according to the present invention
The recording medium is composed of microcrystals whose c-axis is randomly oriented three-dimensionally.
Magnetism in which a columnar structure is located on a microcrystalline structure
The perpendicular magnetic recording medium wherein the physical layer forms a recording layer,
Let d be the thickness of the microcrystalline structureⁱⁿⁱ, The thickness of the columnar tissue portion
d^magThe perpendicular magnetic anisotropy energy of the ferromagnetic layer
Ku ^⊥The magnetocrystalline anisotropy of the magnetic crystal grains in the columnar structure
Ku energy^grainAnd the above Ku^⊥And the above d
^magAnd d obtained fromⁱⁿⁱIs less than 5 nm
Features.

Next, the perpendicular magnetic recording medium according to the present invention will be described.
The thickness d of the microcrystalline structure ⁱⁿⁱIs 2 nm or less
It is preferred that Next, the perpendicular magnetic recording according to the present invention is described.
In the recording medium, the thickness d of the microcrystalline structure ⁱⁿⁱBut,
It is preferably 0.5 nm or less.

Next, in the perpendicular magnetic recording medium according to the present invention, the ferromagnetic layer may be provided on the base via at least one or more underlayers.

Next, in the perpendicular magnetic recording medium according to the present invention, at least one of Ta or T
A structure having a metal base film made of a material containing i can also be employed.

Next, in the perpendicular magnetic recording medium according to the present invention, the underlayer may have an amorphous underlayer made of at least one amorphous material. Next, in the perpendicular magnetic recording medium according to the present invention,
Preferably, the amorphous material contains carbon. As the amorphous material, a material having high wettability capable of covering up the base is more preferable. Next, the perpendicular magnetic recording medium according to the present invention is characterized in that the thickness d ⁱⁿⁱ of the microcrystalline structure is 0.2 nm or less.

Next, in the perpendicular magnetic recording medium according to the present invention, the coating film may have at least one soft magnetic film.

In the perpendicular magnetic recording medium according to the present invention, the soft magnetic film is preferably made of a soft magnetic material having a composition of FeTaN.

Further, a configuration may be adopted in which a layer containing carbon is formed between the soft magnetic film and the ferromagnetic material layer. To
A structure in which a layer containing Ta or Ti is formed can also be employed.

Next, in the perpendicular magnetic recording medium according to the present invention, the ferromagnetic layer may be made of a material containing Co and Cr as main components.

Next, in the perpendicular magnetic recording medium according to the present invention, the thickness of the ferromagnetic layer can be set to 50 nm or less. In the perpendicular magnetic recording medium according to the present invention, the thickness of the ferromagnetic layer may be set to 20 nm or less.

Next, the method for manufacturing a perpendicular magnetic recording medium according to the present invention comprises a heating step for heating a non-magnetic substrate,
A film forming step of forming at least a ferromagnetic layer on the substrate by a film forming method, wherein the heating step heats the substrate to a surface temperature of 220 ° C. or more. It is characterized by doing.

Next, a magnetic recording apparatus according to the present invention comprises a perpendicular magnetic recording medium as described above, a drive unit for driving the magnetic recording medium, and a magnetic head for recording and reproducing magnetic information. Recording and reproducing magnetic information on the moving magnetic recording medium by the magnetic head.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. (Perpendicular Magnetic Recording Medium) FIG. 1 is a sectional view schematically showing an embodiment in which a perpendicular magnetic recording medium according to the present invention is applied to a hard disk of a computer. A perpendicular magnetic recording medium 10 shown in FIG. Substrate 1 made of a non-magnetic material
1, a ferromagnetic layer 12 containing Co and Cr as main components is provided via an underlayer 15. The ferromagnetic layer 12 functioning as a recording layer includes a microcrystalline structure portion 13 and a And the columnar tissue portion 14 located at And
A protective layer 16 is formed on the ferromagnetic layer 12.

(Base) As the base 11 according to the present invention,
For example, aluminum, titanium and its alloys, silicon, glass, carbon, ceramics, plastics,
A non-magnetic substrate 11a made of a resin and a composite thereof, and a non-magnetic coating film 11b made of a different material as necessary were subjected to surface coating by sputtering, vapor deposition, plating, or the like. Things can be mentioned.

The non-magnetic coating film 11b provided on the substrate 11a does not magnetize at high temperature, has conductivity, has good thermal conductivity, and is easy to machine, but has an appropriate surface hardness. Is preferred. As the nonmagnetic coating film 11b satisfying such conditions, a NiP film, a NiTa film, a NiAl film, or a NiTi film formed by a sputtering method or a plating method is particularly preferable.

In particular, in the case of a perpendicular magnetic recording medium, it is desirable to reduce the gap between the magnetic head and the medium in order for the magnetic head to read a signal written on the medium satisfactorily. That is, when recording and reproducing while the magnetic head flies above the medium, it is necessary to reduce the flying height.
Alternatively, it is more preferable that recording and reproduction can be performed by bringing the magnetic head into contact with the medium surface without flying. Therefore, as the substrate 11 for a perpendicular magnetic recording medium, a material having excellent surface smoothness is preferable. Furthermore, it is desirable that the parallelism of the front and back surfaces of the substrate, the waviness in the circumferential direction of the substrate, and the surface roughness are appropriately controlled. From such a viewpoint, a preferable substrate 11 is, for example, a glass substrate, a silicon substrate, an aluminum substrate, or NiP on these substrates.
A film provided with a coating film made of a film, a NiTa film, a NiAl film, or a NiTi film may be used. Among them, a glass substrate is more preferable because it also has rigidity that can cope with thinning of the base.

The base 11 is provided with irregularities on its surface layer for the purpose of improving the friction and wear when the surfaces of the perpendicular magnetic recording medium 10 and the magnetic head come into contact and slide during recording and reproduction. A buffer layer may be provided.

Further, the substrate 11 serves as a layer functioning as a nucleus for promoting crystal growth in the initial growth stage of crystal grains forming the ferromagnetic layer 12 and the like deposited thereon, and is a two-dimensional flat film. Instead, a seed layer in the form of an island-like film having a locally scattered shape may be provided. Such a seed layer is expected to promote the miniaturization of the crystal grains constituting the deposited film formed thereon and the reduction of the particle size distribution.

Furthermore, as a measure against contact and sliding between the surfaces of the perpendicular magnetic recording medium 10 and the magnetic head (Contact Start Stop, CSS) when the substrate 11 rotates / stops, a conventional surface is used. Similar to the base for the internal magnetic recording medium, the surface of the base 11 may be provided with substantially concentric minor scratches (texture).

(Underlayer) In the perpendicular magnetic recording medium 10 of the present embodiment, the underlayer 15 is disposed between the base 11 and the ferromagnetic layer 12.
It has. The underlayer 15 may be made of any material that allows the ferromagnetic layer 12 formed thereon to be oriented in the c-plane.
Any material may be used. The configuration of the underlayer 15 is not limited to the single-layer structure shown in FIG. 1, but may be a two-layer or more multilayer structure. The base layer 15 can be configured to include a metal material made of a single element such as Ti, Ta, Ru, Cu, and Pt, or a layer made of an alloy material obtained by adding Cr or the like to these. If these materials are used as the underlayer 15, the coercive force and the squareness can be improved. Alternatively, N, Zr,
One or more elements selected from C, B and the like may be added. The addition of such an element promotes the miniaturization of the crystal grains of the underlayer 15 and is expected to have the effect of improving the recording / reproducing characteristics of the medium.

The underlayer 15 is made of CoCr (Cr
≧ 25 at%), NiFe, CoZr
Nb, NiNbFe, FeAlSi, NiCuMoF
e, FeBN, FeTaN, FeCN, FeCoN, F
A soft magnetic material such as eCoB or FeSiC, or a hard magnetic material such as SmCo provided below these soft magnetic materials may be used. Further, as the underlayer 15, carbon, S
An amorphous material such as iO ₂ , SiN, NiTa, NiNb, and NiZr may be used. If a non-magnetic material such as CoCr is used, the squareness ratio and coercive force can be improved, and if a soft magnetic material is used, particularly when a single pole head is used as a magnetic head for recording and reproduction, Since the closed magnetic path is formed between the layer made of the soft magnetic material and the single pole head, the efficiency of the magnetic flux acting on the perpendicular magnetic recording medium can be improved. Further, if the above-mentioned amorphous material is used, the crystallinity (information on crystal arrangement) of a base located under the amorphous material can be erased.
As a result of the epitaxial growth of the ferromagnetic layer 12 on the underlayer 15, it is possible to prevent the in-plane orientation of the c-axis. In addition, in the ferromagnetic layer 12 formed on the amorphous material, an effect of preventing the microcrystalline structure portion 13, which is a portion having a disordered crystal structure, from being formed thick can be expected. In particular, carbon is preferable because it has high wettability and can be formed so as to cover the entire surface even with a small film thickness, and the above effect can be exerted on the entire substrate surface.

The above-mentioned metal material, non-magnetic material, and soft magnetic material can constitute the underlayer 15 as a single layer, but can also have a multilayer structure in which layers composed of these materials are combined. For example, although not particularly limited, a CoZrNb layer may be formed from the substrate 11 side.
A configuration of a three-layer structure in which a Ti layer and a CoCr layer are sequentially laminated can be given. By forming the underlayer 15 in a multilayer structure as described above, there is an advantage that desired magnetic characteristics and recording / reproducing characteristics can be easily obtained. When the underlayer 15 has a multi-layer structure, the thickness of each layer constituting the underlayer 15 changes depending on the combination thereof, and thus may be appropriately set according to the target magnetic characteristics and recording / reproducing characteristics.

(Ferromagnetic layer) Ferromagnetic layer 1 according to the present invention
2 is a hexagonal close-packed structure (hexagona) in which Co and Cr are the main components and the easy axis of magnetization is oriented substantially perpendicular to the film surface.
It is preferable to use a magnetic film having a closest packed structure (hcp), and a magnetic film to which other elements are added as necessary may be used. Specific examples of the material constituting the ferromagnetic layer 12 include CoCr (Cr <25 at%),
CoCrNi, CoCrTa, CoCrPt, CoCr
Alloys such as PtTa, CoCrPtB and the like can be mentioned. Further, the grain size control of the crystal grains forming the ferromagnetic layer 12 and the segregation control between the grains, the crystal magnetic anisotropy energy K
For the purpose of controlling the u ^grain or controlling the corrosion resistance of the ferromagnetic layer 12, in addition to the elements constituting the alloy, Fe, Mo,
An element selected from V, Si, B, Ir, W, Hf, Nb, Ru, a rare earth element, or the like may be made of a material obtained by appropriately adding to the above alloy.

(Saturation magnetization: Ms, perpendicular magnetic anisotropy energy: ^Ku⊥ , recording layer thickness: d ^mag ) The “saturation magnetization: Ms” according to the present invention is obtained by using a vibrating sample magnetometer (VSM). Is the saturation magnetization of the entire recording layer obtained from the magnetization curve measured by the above method. The term “perpendicular magnetic anisotropy energy: Ku ^⊥ ” according to the present invention refers to a perpendicular magnetic thin film obtained by demagnetizing the saturation value of a sin2θ component of a perpendicular torque curve measured using a high-sensitivity torque magnetometer described later. Is the uniaxial magnetic anisotropy energy of the direction. In the evaluation method according to the present invention, the “film thickness of the recording layer: d ^mag ” refers to the film thickness of the recording layer defined by the product of the film formation rate and the film formation time, which is grasped in advance, in the film forming apparatus used. This is the designed film thickness. In this specification,
The ferromagnetic layer 12 in which the columnar structure portion 14 is located on the microcrystalline structure portion 13 corresponds to the recording layer.

(Evaluation Method of Perpendicular Magnetic Recording Medium)
FIG. 2 shows a method for evaluating a perpendicular magnetic recording medium according to the present invention.
This will be described with reference to FIG. FIG. 2 is a schematic sectional view showing an example of the perpendicular magnetic recording medium according to the present invention. Note that among the components shown in FIG. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The perpendicular magnetic recording medium 20 shown in FIG. 2 has a structure in which a ferromagnetic layer 12 and a protective layer 16 are sequentially provided on a substrate 11 composed of a substrate 11a and a coating film 11b provided thereon. The magnetic layer 12 includes a microcrystalline structure 13 and the microcrystalline structure 13.
And a columnar tissue portion 14 located above.

The present evaluation method, for example, was determined using a torque magnetometer, using perpendicular magnetic anisotropy energy Ku ^⊥ ferromagnetic layers constituting the medium, nanocrystalline structure section 13 forming the ferromagnetic layer In this method, the magnetic structure of the columnar tissue portion 14 is separately evaluated. Here, the case where a torque magnetometer is used will be described. However, the perpendicular magnetic anisotropy is obtained from the in-plane loop of the perpendicular magnetization film observed by a magnetization curve measuring device (Kerr Loop Tracer, KLT) using the magnetic Kerr effect or VSM. A method of analyzing the energy ^Ku⊥ may be used. The method as such methods of calculating the perpendicular magnetic anisotropy energy Ku ^⊥ than the anisotropic magnetic field Hk was determined from such as saturated magnetization Ms (Kazuhiro Ouchi: 1984 Tohoku Dissertation; Reference 6, C.Byun , JMSivertsen and JHJudy: J. Appl.
Phys., Vol.57 (1985) 3997; Reference 7) and Sucksmith-Th
ompson method (W. Sucksmith and JEThompson: "The magne
tic anisotropy of cobalt ", Proc. Roy. Sco., vol.A2
25 (1954) 362: Reference 8).

FIG. 3 shows a perpendicular magnetic recording medium 20 having the configuration shown in FIG. 2 using a self-made high-sensitivity torque magnetometer.
And the measurement of the vertical torque medium manufactured by changing the thickness of the ferromagnetic layer 12 is a graph showing an example of determining the perpendicular magnetic anisotropy energy Ku ^⊥ The results of this torque measurement. Incidentally, the perpendicular magnetic recording medium used for the above-described torque measurement was formed by coating CoNi ₁₃ Cr ₁₆ Ta on a substrate 11 made of glass.
_{4 The} ferromagnetic layer 12 is formed by sputtering using a target.
Is formed, and a protective layer 16 made of carbon is formed thereon. As shown in FIG. 3, s of the torque magnetic field lines
The saturation value L ^sat (2θ) of the in2θ component can be obtained from the result of plotting L (2θ) with respect to 1 / H and linearly extrapolating 1 / H to zero. (Hereinafter, referred to as extrapolation) and Ku ^⊥, considering demagnetizing field, Ku ^⊥ =
L ^sat (2θ) + 2πMs ² can be derived.

The operation for determining Ku ^⊥ is performed for each medium having the ferromagnetic layers 12 having different thicknesses, and the result is summarized in the perpendicular magnetic anisotropy energy Ku ^{⊥ の of} FIG.
5 is a graph showing a relationship between the thickness and the thickness d ^mag of the ferromagnetic layer 12.

FIG. 4 shows that the perpendicular magnetic anisotropy energy Ku
The value of ^⊥ is increased gradually as the film thickness d ^{ma g} ferromagnetic layer 12 is increased, it can be seen that the saturation tendency thickness d ^mag is more 35 nm. However, from the graph of FIG. 4, it can be seen from the graph that the thickness d ⁱⁿⁱ of the microcrystalline structure constituting the medium and the crystal magnetic anisotropy energy Ku of the magnetic crystal grains of the columnar structure are different.
You can't read ^{g rain} .

[0043] Therefore, taking into account the presence of nanocrystalline structure portion 13 in the ferromagnetic layers 12, Ku ^⊥ is explained phenomenon showing a tendency of saturation with respect to the film thickness of the ferromagnetic layer 12. As described above, the perpendicular magnetic recording medium according to the present invention has the microcrystalline structure 1
3 is a ferromagnetic layer 12 in which a columnar structure portion 14 is located
Constitutes a recording layer, so that it is necessary to separate and evaluate the magnetic structures of the microcrystalline structure 13 and the columnar structure 14 in order to discuss the effect of the microcrystalline structure 13 on the magnetic properties of the medium. There is. In addition, observation of the cross-sectional structure using a TEM revealed that the microcrystalline structure 13 was three-dimensionally randomly oriented along the c-axis, whereas the columnar structure 14 was c-plane oriented. ing.

[0044] Therefore, because the perpendicular magnetic anisotropy energy Ku ^⊥ of medium obtained from the torque measurements is observed with columnar structure portion 14 as the sum of contributions from nanocrystalline structure part 13, vertical columnar structure portion 14 Magnetic anisotropy energy Ku
Using ^⊥column and perpendicular magnetic anisotropy energy Ku ^⊥Ini the nanocrystalline structure part 13, it is expressed by the following equation. (Equation ^{1) Ku ⊥ = Ku ⊥column ×} (V mag -V ini) /
However ^{V mag + Ku ini × V in} i / V mag, V mag overall volume ferromagnetic layer 12, V ⁱⁿⁱ is the total volume of the nanocrystalline structure part 13. Assuming that the film area is S,
When microcrystalline thickness of the tissue section 13 in the case of nanocrystalline structure part 13 is assumed to be flat and d ^ini, since a ^{V mag = S × d mag V} ini = S × d ini, the (formula 1 ) Can be replaced by: (Equation ^{2) Ku ⊥ = Ku ⊥column ×} (d mag -d ini) /
V ^mag + K ⁱⁿⁱ × d ^{in i} / d ^mag

Since the microcrystalline structure 13 is composed of microcrystals whose c-axis is randomly oriented in space,
The overall perpendicular magnetic anisotropy of the individual crystallites ^cancels each other out and can be approximated as Ku ^ｕini = 0. On the other hand, since the perpendicular magnetic anisotropy of the columnar structure portion 14 is equal to the crystal magnetic anisotropy of the single crystal grain forming each columnar structure, ^Ku⊥column = Ku ^grain . Therefore, the above (Equation 2) If d ⁱⁿⁱ is not zero, expressed as (Equation ^{3) Ku ⊥ × d mag =} 0 ( Equation ^{4) Ku ⊥ × d mag =} Ku grain × (d mag -d ini) .

The above (Equation 3) is a case where the ferromagnetic layer 12 is entirely composed of the microcrystalline structure 13 without having the columnar structure 14, and is determined by substituting the relationship of d ^mag = d ^ini. Can be. On the other hand, when the ferromagnetic layer 12 is composed of the microcrystalline structure 13 and the columnar structure 14, that is, when the thickness d ⁱⁿⁱ of the microcrystalline structure 13 satisfies 0 <d ⁱⁿⁱ <d ^mag , the above ( Equation 4) holds. The above (Equation 4) is Ku
^{When ⊥} × d ^mag is plotted on the ordinate and d ^mag is plotted on the abscissa, a linear approximation can be obtained. From the inclination of the linear approximation, the crystal magnetic anisotropy Ku ^grain of the magnetic crystal grains of the columnar structure portion 14 can be obtained.
This means that the linear approximation is extended, and the thickness d ⁱⁿⁱ of the microcrystalline structure 13 is determined from the intersection with the horizontal axis.

FIG. 5 is a diagram created based on the results of FIG.
5 is a graph in which ( ^Ku⊥ × d ^mag ) is the vertical axis and the thickness d ^mag of the ferromagnetic layer is the horizontal axis. The result of FIG. 5 is an example corresponding to the above (Equation 4). From the inclination of the linear approximation, Ku ^grain =
1.8 [× 10 ⁶ erg / cm ³ ] and d ⁱⁿⁱ from the intercept with the horizontal axis
= 7.5 [nm] can be read. As is apparent from the above (Equation 4), when the thickness of the microcrystalline structure 13 is infinitely close to 0, it is needless to say that d ⁱⁿⁱ = 0 can be analyzed according to the following equation. (Equation 5) ^Ku⊥ × d ^mag = K ^grain × d ^{mag The} above (Equation 5) indicates that the magnetic crystal of the columnar structure 14 is obtained from the inclination of the linear approximation even under the condition that the thickness of the microcrystalline structure 13 can be approximated to zero. suggesting that the crystal magnetic anisotropy energy ^Ku grai ⁿ of grain is obtained.

Although the above has been described in detail based on the expression expansion focusing on the film thicknesses d ^mag and d ⁱⁿⁱ , the expression expansion is performed by taking the area and the volume instead of the film thickness, and a graph is created by this. Needless to say, Ku ^grain and d ⁱⁿⁱ can be obtained. However, d ⁱⁿⁱ cannot be read directly from such a graph, and the trouble of recalculating the read numerical value occurs. On the other hand, the above-mentioned method uses the film thickness d
adopted expression expansion focusing on ^mag and d ^ini, since the graph, the horizontal axis intercept and slope of the linear approximation unit, Ku ^{GRAi n} and d
^It has the advantage that you can read ⁱⁿⁱ directly.

That is, according to the above-described evaluation method: A perpendicular magnetic recording medium in which a ferromagnetic layer in which a columnar texture portion is positioned on a microcrystal texture portion forms a recording layer is a microcrystal in which the microcrystal texture portion is three-dimensionally randomly oriented with a c-axis. From the perpendicular magnetic anisotropy energy ^Ku⊥ of the ferromagnetic layer and the thickness d ^mag of the ferromagnetic layer, the crystal magnetic anisotropy energy Ku ^grain of the magnetic crystal grains in the columnar structure portion and / or the thickness of the microcrystalline structure portion are obtained. By obtaining d ⁱⁿⁱ , it is possible to classify and analyze the thickness and magnetic properties of the microcrystalline structure that could not be analyzed separately by the conventional evaluation method.

2. If the thickness d ⁱⁿⁱ of the microcrystalline structure is greater than zero, the formula ^Ku⊥ × d ^mag = Ku ^grain × (d
By using ^mag -d ^ini), the perpendicular magnetic anisotropy energy Ku ^⊥ recording layer, the thickness d ^mag ferromagnetic layers, the thickness of the Ku ^grain and / or nanocrystalline structure of the recording layer d ⁱⁿⁱ is found. That is, when a microcrystalline structure exists, the crystal magnetic anisotropy energy Ku ^{grain of the} recording layer can be quantitatively grasped together with the thickness d ⁱⁿⁱ .

3. In the above 2, the abscissa represents the d ^mag and the K represents
Ku ^grain and / or d ⁱⁿⁱ can be visually ^grasped by using a linear approximation part of a graph in which the product of ^uｕ and the d ^mag is plotted on the vertical axis. Also, if the reference line of the linear approximation part is predetermined in the standard sample,
It is possible to estimate the cause of the deviation based on how much the prepared sample having the predetermined thickness deviates from the reference line in the upper or lower direction. This is an effective means for accurately controlling the film forming conditions of the medium and mass-producing a magnetic recording medium having desired magnetic characteristics.

4. The crystal magnetic anisotropy energy Ku ^grain of the magnetic crystal grain in the columnar structure is obtained from the inclination of the linear approximation in the above graph 3.

5. The thickness d ⁱⁿⁱ of the microcrystalline structure can be determined from the intersection with the horizontal axis in which the linear approximation in the above graph 3 is extended. That is, by accurately obtaining the inclination and the intersection, it is possible to strictly control the magnetic characteristics of the manufactured medium.

6. Further, when there is a tail part deviating from the linear approximation on the side where d ^mag of the linear approximation is small in the above graph 3, the distribution of the microcrystalline structure in the thickness direction is obtained from the tail. By grasping this distribution, the interface state between the microcrystalline structure and the columnar structure can be grasped. Therefore, based on the information on the interface state, the film forming conditions of the medium are accurately controlled, and this is an effective means when mass-producing a medium having desired magnetic characteristics.

7. If the thickness d ⁱⁿⁱ of the microcrystalline structure is zero, the perpendicular magnetic anisotropy energy Ku ^{強 磁性} of the ferromagnetic layer and the ferromagnetic layer can be calculated by using the following formula: Ku ^⊥ × d ^mag = Ku ^grain × d ^mag. From the thickness d ^mag of the body layer, the crystal magnetic anisotropy energy Ku ^grain of the magnetic crystal grains in the columnar structure is obtained. That is, even when the microcrystalline structure does not exist,
Crystal magnetic anisotropy energy K of magnetic crystal grains in columnar structure
u ^grain can be grasped quantitatively.

In the above description, the medium having the structure shown in FIG. 2, that is, the medium in which the microcrystalline structure 13 is provided in contact with the substrate 11 has been described as an example. Needless to say, a medium having the configuration shown in FIG.

Next, a method for manufacturing a perpendicular magnetic recording medium according to the present invention will be described. (Sputtering Method) As a sputtering method as an example of a method of manufacturing the perpendicular magnetic recording medium 10 according to the present invention, for example, a transport type sputtering method in which a thin film is formed while a substrate 11 moves in front of a target; Is fixed in front of the target to form a thin film. The former transport type sputtering method is advantageous in the production of a low-cost magnetic recording medium because of its high mass productivity, and the latter static type sputtering method has the advantage that the incident angle of the sputtered particles to the substrate 11 is stable, so that the recording is difficult. It is possible to manufacture a magnetic recording medium having excellent reproduction characteristics. When manufacturing the perpendicular magnetic recording medium 10 according to the present invention, it is not limited to either the transport type or the stationary type.

In the manufacturing method according to the present invention, impurities of Ar gas used for film formation include, for example, H ₂ O, O ₂ ,
CO ₂ , H ₂ , N ₂ , C _x H _y , H, C, O, CO and the like can be mentioned. In particular, impurities that affect the amount of oxygen taken into the film are estimated to be H ₂ O, O ₂ , CO ₂ , O, and CO.
Therefore, the impurity concentration of the present invention is represented by the sum of H ₂ O, O ₂ , CO ₂ , O, and CO contained in Ar gas used for film formation.

When producing the magnetic recording medium according to the present invention, the ultimate degree of vacuum of the film forming chamber for forming the underlayer 15 and the ferromagnetic metal layer 12 shown in FIG. 1 is set to the order of 10 ⁻⁷ Torr (10 ^−5).
It is possible to use a film forming chamber with a degree of vacuum used in current mass production machines (Pa units). However, needless to say, an ultra-clean process in which the ultimate degree of vacuum of the film formation chamber is set to 10 ⁻⁹ Torr (10 ⁻⁷ Pa) and the impurity concentration of the film formation gas is 1 ppb or less may be used. If this ultra-clean process is adopted, a magnetic recording medium having excellent recording / reproducing characteristics can be easily formed since the segregation structure of Cr is improved and the initial layer is reduced, so that the squareness and coercive force of the medium can be improved. It can be made.

(Surface Temperature of Heated Substrate) In the present invention, the “surface temperature of the heated substrate” does not depend on the material constituting the ferromagnetic layer, but is a factor of a film formation factor which affects the value of coercive force. One. In the method for manufacturing a perpendicular magnetic recording medium according to the present invention, the surface temperature of the substrate after heating is set to 220 ° C. or higher. This is because a film formed at a high surface temperature can achieve a higher coercive force, and a surface temperature of less than 220 ° C. tends to have a low squareness ratio, thereby exhibiting the original recording / reproducing characteristics. This is because it becomes difficult. On the other hand, if the surface temperature of the substrate is too high, the crystal grains of the ferromagnetic layer 12 are enlarged and the S / N ratio is reduced, and the surface roughness of the film-forming surface is increased to hinder low flying. Problems are more likely to occur. Further, if the substrate is heated to an excessively high temperature, the substrate tends to be easily damaged. Therefore, the surface temperature of the substrate in the method for producing a perpendicular magnetic recording medium of the present invention may be practically 350 ° C. or lower. preferable. Here, the damage of the base means an external change such as warpage, blistering, cracking, or the like, or an internal change such as an increase in magnetization of a non-magnetic constituent material or an increase in degas.

[0061]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 3) On a substrate made of a disk-shaped glass substrate, using a sputtering film forming apparatus,
An underlayer, a ferromagnetic layer, and a protective layer were sequentially formed to manufacture a perpendicular magnetic recording medium. Table 1 shows the manufacturing conditions of the perpendicular magnetic recording media of Examples 1 to 3, and Table 2 shows the configurations of the underlayer and the ferromagnetic layer.

[0063]

[Table 1]

[0064]

[Table 2]

The magnetic recording medium was formed using a sputtering film forming apparatus having a back pressure condition of 10 ⁻⁷ Torr (10 ⁻⁵ Pa) used in current mass production machines. At that time, the substrate temperature was set to 2 using a radiant heater.
50 ° C., Ar gas was used as a process gas, and the gas pressure during film formation was 2 to 4 mTorr (= 0.26 to 0.53).
Pa). Then, by changing the film formation time, perpendicular magnetic recording media having different thicknesses of the ferromagnetic layers in the range of 10 to 50 nm were produced. In addition, a disk-shaped glass substrate was used as a substrate, and the manufactured disk-shaped medium was formed into a circular sample having a diameter of 8 mm using an ultrasonic processing machine (M100 manufactured by Ultrasonic Industry Co., Ltd.).

The crystal structure of the thin film formed on the substrate was analyzed by an X-ray diffraction method (XRD: ATX-G manufactured by Rigaku Corporation). The saturation magnetization Ms of the sample was measured using a vibrating sample magnetometer (VSM: BHV-35 manufactured by Riken Denshi Co., Ltd.).

The perpendicular magnetic torque was measured by the above-mentioned extrapolation method using a self-made high-sensitivity torque magnetometer. At that time, the effective sensitivity is 3 × 10 ^{2 to} 3 × 10 ^-2 dyn / cm,
The maximum applied magnetic field was 20 kOe, and the magnetic field rotation speed was 2 degrees / second.

The perpendicular magnetic recording media of Examples 1 to 3
And based on the above evaluation method, d ⁱⁿⁱWas derived. So
The graph used for the calculation is shown in FIG. 6, and the graph shown in FIG.
FIG. 7 is an enlarged view of the vicinity of the intersection between the horizontal axis of FIG.
Shown in The vertical axes of the graphs shown in FIG. 6 and FIG.
(Ku^⊥× d^mag), And the horizontal axis indicates the ferromagnetic layer
Thickness d^magIs shown. Reference numerals 30 to 32 are
Approximate straight lines corresponding to Examples 1 to 3 are shown.
As shown in these graphs, the perpendicular magnetic properties of Examples 1 to 3
Film thickness d of microcrystalline structure of recording mediumⁱⁿⁱFigure 6 and Figure
7 corresponding to the intercept between the approximate straight lines 30 to 32 and the horizontal axis.
Thus, the thickness of each of Examples 1 to 3 is 5 nm or less.
This is slight in the perpendicular magnetic recording medium of this example.
Magnetostatic properties and recording / reproducing characteristics
Adversely affects performance compared to conventional perpendicular magnetic recording media
Suggest small. Further, as shown in FIG.
In the perpendicular magnetic recording medium of the second embodiment, dⁱⁿⁱIs 0.
Since it is 5 nm or less, the thickness of the microcrystalline structure is extremely small.
You can see that it is thin. That is, the perpendicular magnetism of the second embodiment
Almost all the ferromagnetic layer of the recording medium is composed of columnar textures.
With particularly excellent magnetic and recording / reproducing characteristics
This indicates that the medium is a perpendicular magnetic recording medium.

Comparative Example Next, for comparison, a disk-shaped glass substrate was used as a substrate, a ferromagnetic layer was directly formed on this glass substrate, and a protective layer made of carbon was formed on the ferromagnetic layer. And a perpendicular magnetic recording medium was produced by changing the target used for forming the ferromagnetic layer. The targets used for forming the ferromagnetic layer are shown below.

(Target Composition (at%)) Alloy 1: CoNi ₁₃ Cr ₁₆ Ta ₄ Alloy 2: CoCr ₁₀ Alloy 3: CoNi ₂₀ Cr ₁₀ Alloy 4: CoCr ₁₀ Ta ₂ Alloy 5: CoCr ₁₂ Pt ₆

For the above perpendicular magnetic recording medium, d ⁱⁿⁱ was derived in the same manner as in the first embodiment. FIG. 8 shows a graph created to derive this d ⁱⁿⁱ . In FIG. 8, approximate straight lines denoted by reference numerals 41 to 45 correspond to the above alloys 1 to 5, respectively. As shown in this figure, in the perpendicular magnetic recording medium in which a ferromagnetic layer is formed directly on a substrate, d ⁱⁿⁱ is larger than 5 nm. This is because the perpendicular magnetic recording medium of this comparative example is different from the above-described embodiments 1 to
3 shows that the magnetic recording medium is greatly affected by the microcrystalline structure as compared with the perpendicular magnetic recording medium of No. 3, suggesting that the magnetic properties are inferior to those of Examples 1 to 3 above.

(Examples 4 to 7) Next, the surface temperature of the substrate was changed from room temperature to 350 ° C.
It was made by changing to. FIG. 9 shows the results of measuring the magnetic characteristics of these perpendicular magnetic recording media by VSM. FIG. 9 is a graph showing the substrate surface temperature dependence of the squareness ratio of the perpendicular magnetic recording media of Examples 4 to 6, wherein the vertical axis represents the squareness ratio and the horizontal axis represents the substrate surface temperature (° C.). As shown in FIG. 9, if the substrate surface temperature is set to 220 ° C. or higher during the production of each perpendicular magnetic recording medium having a different underlayer configuration,
It was confirmed that a squareness ratio of 0.6 or more could be obtained. In particular, in the perpendicular magnetic recording medium of Example 6 using a three-layer structure in which Ti, C, and CoCr ₄₀ were sequentially laminated as the underlayer, the substrate surface temperature during the production was set to 220 ° C. or higher to achieve 0%. It was confirmed that a high squareness ratio of 0.8 or more was obtained.

Further, as shown in FIG. 9, in the perpendicular magnetic recording medium of Example 7 in which the thickness of the ferromagnetic layer was 30 nm, a high squareness ratio of 0.9 was obtained even at a substrate surface temperature of 200 ° C. Thus, it was confirmed that when the thickness of the ferromagnetic layer is small, a perpendicular magnetic recording medium having a high coercive force and a high squareness ratio can be manufactured even at a slightly lower substrate surface temperature.

[0074]

[Table 3]

(Embodiment 8) Next, a perpendicular magnetic recording medium having a structure similar to that of the above-mentioned Embodiment 6 and having a thickness of the ferromagnetic layer changed from 5 nm to 60 nm was manufactured. FIG. 10 shows the results of measuring the magnetic properties of these perpendicular magnetic recording media using the VSM. FIG. 10A is a graph showing the dependence of the squareness ratio of the perpendicular magnetic recording medium on the thickness of the ferromagnetic layer, where the vertical axis represents the squareness ratio and the horizontal axis represents the thickness (nm) of the ferromagnetic layer. Is shown. FIG. 10B is a graph showing the dependence of the coercive force of the perpendicular magnetic recording medium of this example on the thickness of the ferromagnetic material. The ordinate represents the coercive force (kOe), and the abscissa represents the ferromagnetic layer. The thickness (nm) is shown. As shown in FIG. 10, in the configuration of this example, the thickness of the ferromagnetic layer is set to 20 nm or more and 50 n or more.
m or less, a high coercive force of 3 kOe or more,
It was confirmed that a perpendicular magnetic recording medium having a high squareness ratio of 0.8 or more could be obtained. Further, the inventors of the present invention have studied the perpendicular magnetic recording medium having the underlayer having the configuration according to the present invention, and have found that the composition of the cobalt alloy constituting the ferromagnetic layer is appropriately changed to increase the strength. The thickness of the magnetic layer is 20 nm
In the following, it has been confirmed that a high coercive force of 3000 (Oe) or more can be obtained and a high squareness ratio of 0.8 or more can be obtained. More specifically, by increasing the Pt content of the cobalt alloy and using a cobalt alloy having a composition with a reduced B content for the ferromagnetic layer,
It has been confirmed that the above excellent magnetic properties can be obtained.

Among the perpendicular magnetic recording media of the above Examples and Comparative Examples, the media containing no carbon layer (the media of Example 5 and Comparative Example) had a microcrystalline structure thickness d ⁱⁿⁱ of 0.3 or more. In the medium according to the present invention, which has an underlayer including a carbon layer (Examples 6, 7, and 8), the production temperature is set to room temperature. To 350 ° C., the d ⁱⁿⁱ is 0 to
A perpendicular magnetic recording medium in the range of 0.2 nm, in which the microcrystalline structure is significantly reduced as compared with the conventional perpendicular magnetic recording medium, can be realized. Further, when the film formation temperature is 200 to
If the temperature is in the range of 350 ° C., d ⁱⁿⁱ is 0 to 0.1 nm.
And it is more preferable.

(Examples 9 and 10) Next, in order to clarify the effect of laminating a layer made of carbon in an underlayer,
As Examples 9 and 10, perpendicular magnetic recording media having the configuration shown in Table 4 were produced by changing the thickness of the ferromagnetic layer in the range of 0 to 50 nm. For these perpendicular magnetic recording media, In
plane XRD (Inplane X-ray Diffractometer)
FIGS. 11 and 12 show in-plane X-ray diffraction profiles obtained by performing the measurement. The in-plane X-ray diffraction profile reflects information on a crystal plane in a direction perpendicular to the thin film surface, which is about 20 nm in the surface layer of the thin film. FIG.
Is a graph showing an in-plane X-ray diffraction profile of the perpendicular magnetic recording medium of Example 9, where the vertical axis indicates intensity (arbitrary scale) and the horizontal axis indicates angle. FIG. 12 shows the first embodiment.
5 is a graph showing an in-plane X-ray diffraction profile of a perpendicular magnetic recording medium of 0, wherein the vertical axis indicates intensity (arbitrary scale) and the horizontal axis indicates angle.

First, focusing on the X-ray profile of the sample without the ferromagnetic layer shown in FIGS. 11 and 12, the ninth embodiment in which the carbon layer was formed between the Ti layer and the CoCr layer was used. In the perpendicular magnetic recording medium of No. 2, as shown by d ^mag = 0 nm in FIG.
A diffraction line from the 0) plane was observed, indicating that the CoCr layer of this perpendicular magnetic recording medium was c-plane oriented.
On the other hand, in the perpendicular magnetic recording medium of Example 10 in which the carbon layer was not formed, diffraction lines from the σ phase (330) plane of the CoCr layer were also observed as shown in ^dmag = 0 nm in FIG. It was confirmed that a phase different from that of the perpendicular magnetic recording medium of Example 9 was formed in the CoCr layer. Since the carbon layer has good wettability, only 1 n
Even if it is an extremely thin layer having a thickness of m or less, it has an effect of stably forming a nonmagnetic layer segregation type hcp phase without forming a σ phase in the CoCr layer.

Next, when comparing the samples on which the ferromagnetic layers were formed, diffraction lines from the (100) plane were observed, but the intensity was higher than that of the carbon layer formed below the CoCr layer. The perpendicular magnetic recording medium according to the ninth embodiment was larger than the perpendicular magnetic recording medium according to the tenth embodiment, indicating that the initial layer was significantly reduced. From the above, if the carbon layer is provided below the CoCr layer, the c of the CoCr layer on the carbon layer
In addition to improving the plane orientation, CoCr
It can be said that the ferromagnetic layer on the layer can be grown c-plane epitaxially without forming an initial layer.

From the above examples, it has been confirmed that according to the present invention, the microcrystalline structure of the ferromagnetic layer is extremely thin, and as a result, a perpendicular magnetic recording medium having a high coercive force and a high squareness ratio can be obtained. . However, the technical scope of the present invention is not limited to the above-described embodiment. For example, a soft magnetic layer may be further provided between the underlayer and the substrate having the structures described in the first to third embodiments. Also in this case, a perpendicular magnetic recording medium having an extremely thin microcrystalline structure can be obtained due to the effect of the underlayer.

(Examples 11 to 15) Next, as Examples 11 to 15 of the present invention, perpendicular magnetic recording media having the layer structure shown in Table 4 were produced. These perpendicular magnetic recording media include a layer made of FeTaN as a base layer as shown in Table 4,
Various layers are provided between the FeTaN layer and the ferromagnetic layer (CoCrPtB layer). Next, for the perpendicular magnetic recording media of Examples 11 to 15 produced above,
The recording / reproducing characteristics were evaluated. The measurement conditions are shown below. The method for producing these media is in accordance with Example 1 described above, and the present inventors used the FeTaN backing layer material used in the prior application (Japanese Patent Application No. 2001-2).
No. 88835) discloses that it is a backing layer material having low noise characteristics. The following describes that excellent recording and reproduction characteristics can be obtained by applying the low-noise backing layer to the underlayer of the present invention that can reduce d ⁱⁿⁱ and improve perpendicular magnetic characteristics. Verifying.

[Measurement device] Spin stand: LS90S (trade name) manufactured by Kyodo Electronics Co., Ltd. Media tester: RWA2550 ++ manufactured by GUZIK
(Product name) Recording head (inductive head): Track width (Tw) 0.38 μm Gap width (Gw) 0.25 μm Read head (GMR head): Track width (Tw) 0.25 μm Measurement circumference on disk: 22. 55 mm Disk rotation speed: 4200 rpm [SNR (Signal to Noise Ratio) measurement condition] Signal frequency: 15.7 MHz Noise measurement band: 1 MHz to 100 MHz Resolution bandwidth (RBW): 300 kHz Overwrite (O / W) measurement: 62.86 MHz / 1
5.7MHz

In the measurement using the measuring device and the measuring conditions, first, 40 mA was used for initializing the perpendicular magnetic recording medium.
Scanning was performed while moving the ring head to which the exciting current was applied in the radial direction of the medium with a swing width of about 1.5 tracks to erase the medium by dc. Next, 15.7 MH is added to a predetermined track.
A signal was written with z, and the recording and reproduction characteristics were evaluated using a GMR head. The measurement results are also shown in Table 4.

As shown in Table 4, FeTa was used as the underlayer.
In the perpendicular magnetic recording medium of Example 11 using only the N layer, 2
While an SNR of about 0 dB is obtained, FeTa
Example 1 in which a Ti layer was formed between an N layer and a ferromagnetic layer
In the perpendicular magnetic recording media 2 and 13, the SNR is improved by 2 dB or more. Example 1 in which a carbon layer and a CoCr layer were sequentially provided between the FeTaN layer and the ferromagnetic layer
In the perpendicular magnetic recording medium of No. 5, a significant improvement of 4 dB or more as compared with the medium of Example 11 was confirmed. However, FeT
When only a CoCr layer is provided on the aN layer, CoCr
The result was almost the same as that of the medium of Example 11 not including the layer. In the perpendicular magnetic recording medium of Example 15 in which an excellent SNR was obtained, the overwrite characteristics and the NLTS, which is the shift of the recording transition line, were also good, and the values of both were −45 dB and 20 dB, which are practically sufficient. It has become.
Further, in the perpendicular magnetic recording medium of Example 15, the T _{50, which} is an index of the fluctuation of the recording transition line, is also reduced as compared with the medium of the other examples, and according to the configuration of the present invention, it is extremely excellent. It has been confirmed that a perpendicular magnetic recording medium having improved recording / reproducing characteristics can be provided.

[0085]

[Table 4]

(Magnetic Recording Apparatus) Next, a magnetic recording apparatus according to the present invention will be described below with reference to the drawings. FIG.
FIG. 14 is a side sectional view showing an example of a hard disk device which is a magnetic recording device according to the present invention, and FIG. 14 is a plan sectional view of the magnetic recording layer shown in FIG. 13 and 14, 50 is a magnetic head, 70 is a hard disk drive, 7
1 is a housing, 72 is a magnetic recording medium, 73 is a spacer, 79
Is a swing arm and 78 is a suspension. The hard disk device 70 according to the present embodiment mounts the magnetic recording medium of the present invention described above.

The external shape of the hard disk drive 70 is a rectangular parallelepiped housing 71 having an internal space for accommodating a disk-shaped magnetic recording medium 72 and a magnetic head 50 and the like.
Inside the housing 71, a plurality of magnetic recording media 72 are alternately inserted into the spindle 74 with the spacers 73 and provided. The housing 71 is provided with a bearing (not shown) for a spindle 74, and a motor 75 for rotating the spindle 74 is provided outside the housing 71. With this configuration, all of the magnetic recording media 72 are rotatable around the spindle 74 in a state where a plurality of the magnetic recording media 72 are stacked with an interval for the magnetic head 50 to enter by the spacer 73.

The magnetic recording medium 72 inside the casing 71
A rotary shaft 77 called a rotary actuator supported by a bearing 76 in parallel with the spindle 74 is disposed at a side position of the rotary shaft 77. A plurality of swing arms 79 are attached to the rotating shaft 77 so as to extend into the space between the magnetic recording media 72. The magnetic head 5 is connected to the tip of each swing arm 79 via an elongated triangular plate-shaped suspension 78 fixed in a direction inclining toward the surface of each magnetic recording medium 72 at the upper and lower positions.
0 is attached. Although not shown, the magnetic head 50 includes a recording element for writing information to the magnetic recording medium 72 and a reproducing element for reading information from the magnetic recording medium 72.

The magnetic recording medium 72 is a perpendicular magnetic recording medium according to the present invention, in which the thickness of the microcrystalline structure included in the ferromagnetic layer is 5 nm or less.
Therefore, as described above, such a perpendicular magnetic recording medium is hardly affected by the microcrystalline structure and has excellent magnetic properties.

According to the above configuration, the magnetic recording medium 72 is rotated, and the magnetic head 50 can be moved in the radial direction of the magnetic recording medium 72 by the movement of the swing arm 79. It can be moved to any position above. In the hard disk device 70 having the above-described configuration, the magnetic recording medium 72 is rotated and the swing arm 79 is moved to move the magnetic head 50 to the magnetic field generated by the magnetic head 50 on the ferromagnetic metal layer forming the magnetic recording medium 72. , Desired magnetic information can be written on the magnetic recording medium 72. Further, by moving the swing arm 79 to move the magnetic head 50 to an arbitrary position on the magnetic recording medium 72,
The magnetic information can be read by detecting the leakage magnetic field from the ferromagnetic metal layer constituting the magnetic recording medium 72 with the reproducing element of the magnetic head.

When reading and writing magnetic information as described above, if the magnetic recording medium 72 has a high coercive force and excellent recording / reproducing characteristics as described above, it is possible to achieve a high recording density. It is possible to provide the hard disk device 70 that can perform stable recording and reproduction of magnetic information.

Since the hard disk device 70 described above with reference to FIGS. 13 and 14 is an example of the magnetic recording device according to the present invention, the number of magnetic recording media mounted on the magnetic recording device is as follows. Any number of one or more magnetic heads may be used, and any number of magnetic heads may be provided as long as the number is one or more. Further, the shape and the driving method of the swing arm 79 are not limited to those shown in the drawings, but may be a linear driving method or other methods.

[0093]

As described in detail above, in the perpendicular magnetic recording medium of the present invention, the columnar texture portion is located on the microcrystal texture portion composed of microcrystals whose c-axis is randomly oriented three-dimensionally. In a perpendicular magnetic recording medium in which the ferromagnetic layer forms a recording layer, the thickness of the microcrystalline structure is set to 5 nm or less, so that the influence of the microcrystalline structure can be almost eliminated, and a high coercive force and high A perpendicular magnetic recording medium having a squareness ratio can be provided.

Next, a method for manufacturing a perpendicular magnetic recording medium according to the present invention includes a step of heating a nonmagnetic substrate and a step of forming at least a ferromagnetic layer on the substrate by a film forming method. In the method for manufacturing a recording medium, in the step of heating the substrate, the substrate is heated to a surface temperature of 220 ° C. or more, so that a perpendicular magnetic recording medium having a high coercive force and a high squareness ratio is stably manufactured. be able to.

Next, the perpendicular magnetic recording medium of the present invention, a drive unit for driving the magnetic recording medium, and a magnetic head for recording and reproducing magnetic information are provided. On the other hand, if magnetic information is recorded and reproduced by the magnetic head, a magnetic recording medium having a high coercive force and a high squareness ratio is provided, so that a magnetic recording device capable of recording and reproducing information at a higher density is provided. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a perpendicular magnetic recording medium according to an embodiment of the present invention.

3 is a graph showing perpendicular magnetic anisotropy energy Ku of perpendicular magnetic recording media having the configuration shown in FIG. 2 and measuring perpendicular magnetic anisotropy energy of various media manufactured by changing the thickness of a ferromagnetic layer. It is a graph which shows the example which determined ^⊥ .

FIG. 4 is a graph showing the relationship between ^Ku⊥ and d ^mag of the perpendicular magnetic recording medium having the configuration shown in FIG.

FIG. 5 is a graph showing the relationship between ( ^Ku⊥ × d ^mag ) and d ^mag of the perpendicular magnetic recording medium having the configuration shown in FIG.

FIG. 6 is a graph showing the relationship between ( ^Ku⊥ × d ^mag ) and d ^mag of the perpendicular magnetic recording media of Examples 1 to 3 of the present invention.

FIG. 7 is a graph showing the vicinity of the origin of the graph shown in FIG. 6 in an enlarged manner.

Figure 8 is a perpendicular magnetic recording medium having the structure shown in FIG. 2, the various media manufactured by changing the material constituting the ferromagnetic layer and the relationship between the ^{d mag (Ku ⊥ × d mag} ) It is a graph shown.

FIG. 9A is a graph showing the relationship between the squareness ratio of the perpendicular magnetic recording media of Examples 4 to 7 of the present invention and the substrate surface temperature at the time of production, and FIG. 4 is a graph showing a relationship between a magnetic force and a substrate surface temperature during fabrication.

FIG. 10A is a graph showing the relationship between the squareness ratio and the thickness of a ferromagnetic layer of a perpendicular magnetic recording medium according to Example 8 of the present invention, and FIG. 5 is a graph showing a relationship between a magnetic force and a film thickness of a ferromagnetic layer.

FIG. 11 is a graph showing in-plane XRD measurement results of a perpendicular magnetic recording medium according to Example 9 of the present invention.

FIG. 12 is a graph showing an in-plane XRD measurement result of the perpendicular magnetic recording medium of Example 10 of the present invention.

FIG. 13 is a side sectional view showing an example of a magnetic recording apparatus according to the present invention.

FIG. 14 is a plan sectional view of the magnetic recording apparatus shown in FIG.

[Explanation of symbols]

 10, 20 Perpendicular magnetic recording medium 11 Base 12 Ferromagnetic layer 13 Microcrystalline structure 14 Columnar structure 15 Base layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) G11B 5/851 G11B 5/851 (72) Inventor Shin Saito 05 Aoba Aramaki Aoba-ku, Aoba-ku, Sendai, Miyagi Tohoku Univ. Graduate School of Engineering, Department of Electronics (72) Inventor David Jayapuraira 05 Aoba Aramaki, Aoba-ku, Aoba-ku, Sendai, Miyagi Prefecture Tohoku University Graduate School of Engineering, Department of Electronics (72) Inventor Ken Takahashi Taishiro, Sendai City, Miyagi Prefecture 2-20-2 Kuda Ward F-term (reference) 5D006 BB02 BB07 BB08 BB09 CA01 CA03 CA05 CA06 5D112 AA05 BB05 BB06 FA04 GB01

Claims (17)

[Claims] 1. A perpendicular magnetic recording medium in which a ferromagnetic layer in which a columnar texture portion is located on a microcrystal texture portion composed of microcrystals in which a c-axis is randomly oriented three-dimensionally forms a recording layer, The thickness of the microcrystalline structure is d ⁱⁿⁱ , the thickness of the columnar structure is d ^mag , the perpendicular magnetic anisotropy energy of the ferromagnetic layer is Ku ^⊥ , and the crystal magnetism of the magnetic crystal grains of the columnar structure is The anisotropic energy is defined as Ku ^grain, and the d ⁱⁿⁱ obtained from the Ku ^⊥ and the d ^mag is 5n
m or less. 2. The thickness d ⁱⁿⁱ of the microcrystalline structure is 2n.
2. The perpendicular magnetic recording medium according to claim 1, wherein m is equal to or less than m. 3. The method according to claim 1, wherein the thickness d ⁱⁿⁱ of the microcrystalline structure is ^equal to 0.
3. The magnetic recording medium according to claim 2, wherein the thickness is 5 nm or less. 4. The perpendicular magnetic recording according to claim 1, wherein the ferromagnetic layer is provided on the base via at least one or more underlayers. Medium. 5. The method according to claim 1, wherein the underlayer is made of at least one Ta.
5. The perpendicular magnetic recording medium according to claim 4, further comprising a layer made of a material containing Ti. 6. The perpendicular magnetic recording medium according to claim 4, wherein the underlayer has at least one layer made of an amorphous material. 7. The perpendicular magnetic recording medium according to claim 6, wherein the amorphous material contains carbon. 8. A film having a thickness d ⁱⁿⁱ of the microcrystalline structure of 0.
The perpendicular magnetic recording medium according to claim 7, wherein the thickness is 2 nm or less. 9. The perpendicular magnetic recording medium according to claim 4, wherein the underlayer has at least one layer made of a soft magnetic film. 10. The soft magnetic film is made of a soft magnetic material having a composition of FeTaN.
2. The perpendicular magnetic recording medium according to 1. 11. The perpendicular magnetic recording medium according to claim 9, wherein a layer containing carbon is formed between the soft magnetic film and the ferromagnetic layer. 12. The perpendicular magnetic recording medium according to claim 9, wherein a layer containing Ta or Ti is formed between the soft magnetic film and the ferromagnetic layer. 13. The method according to claim 1, wherein the ferromagnetic layer is made of a material containing Co and Cr as main components.
3. The perpendicular magnetic recording medium according to any one of 2. 14. The perpendicular magnetic recording medium according to claim 1, wherein the thickness of the ferromagnetic layer is 50 nm or less. 15. The perpendicular magnetic recording medium according to claim 1, wherein the thickness of the ferromagnetic layer is 20 nm or less. 16. A method for manufacturing a perpendicular magnetic recording medium, comprising: a heating step of heating a nonmagnetic substrate; and a film forming step of forming at least a ferromagnetic layer on the substrate. In the heating step, a surface temperature of a substrate on which the ferromagnetic layer is provided is heated to 220 ° C. or more, a method for manufacturing a perpendicular magnetic recording medium. 17. The perpendicular magnetic recording medium according to claim 1, a driving unit for driving the magnetic recording medium, and a magnetic head for recording and reproducing magnetic information. A magnetic recording apparatus for recording and reproducing magnetic information on the moving magnetic recording medium by the magnetic head.