JP2967070B2 - Perpendicular magnetic recording medium, method of manufacturing the same, and magnetic recording device - Google Patents

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 and a magnetic recording apparatus suitable for high-density magnetic recording with small reproduction noise and excellent recording magnetization stability.

[0002]

2. Description of the Related Art Currently, practically used magnetic recording systems include an N-pole and an N-pole, which are parallel to the surface of a magnetic recording medium and are magnetic poles.
This is an in-plane magnetic recording system in which magnetic recording is performed by magnetizing the poles, the S pole, and the S pole in a direction in which they face each other. In order to improve the linear recording density in the in-plane magnetic recording, the residual magnetization B
It is necessary to reduce the product of r and the magnetic film thickness t to increase the coercive force. In addition, in order to reduce medium noise generated from magnetization transition, it is necessary to orient the easy axis of the magnetic film parallel to the substrate surface and control the crystal grain size. In order to control the crystal orientation and grain size of the magnetic thin film, an underlayer for structure control is formed between the substrate and the magnetic film.

As a magnetic film of the longitudinal magnetic recording system, Co is used.
As the main components, and Cr, Ta, Pt, Rh, Pd,
A Co alloy thin film to which Ti, Ni, Nb, Hf or the like is added is used. As the Co alloy constituting the magnetic thin film, a material having a hexagonal close-packed lattice structure (hereinafter, referred to as an hcp structure) is mainly used. Co alloy thin film is c-axis of this crystal, <00.1>
Direction, and the easy axis is oriented in the in-plane direction. In order to control the crystal orientation and grain size of the magnetic thin film, an underlayer for structure control is formed between the substrate and the magnetic film. The underlayer is mainly composed of Cr, and Ti,
A material to which Mo, V, W, Pt, Pd, or the like is added is used. The magnetic thin film is formed by a vacuum evaporation method or a sputtering method.

As described above, in order to reduce medium noise and improve linear recording density in longitudinal magnetic recording, it is necessary to reduce the product of the residual magnetization Br of the magnetic film and the magnetic film thickness t. It has been studied to reduce the thickness of the magnetic film to 20 nm or less and to refine crystal grains. However, in such a medium in which the magnetic crystal grains are made fine, there is a very serious problem that the recording magnetization decreases due to thermal fluctuation, which is an obstacle to high-density recording.

On the other hand, the perpendicular magnetic recording system is a system in which magnetic domains are formed so that adjacent recording bits are perpendicular to the recording medium surface and are antiparallel to each other. There is an advantage that the magnetization becomes smaller and the magnetization is more stably maintained as the density becomes higher. This is one of the powerful means of the high density magnetic recording. For high-density recording by in-plane recording, as described above, the thickness of the magnetic film needs to be 20 nm or less, and in this case, there is a problem that the recording magnetization is lost due to thermal fluctuation. On the other hand, perpendicular recording has the advantage that the magnetic film thickness can be made thicker than in-plane recording, and the recording magnetization can be stably maintained. In order to improve the linear recording density by perpendicular recording, it is necessary to reduce the medium noise generated from inside the recording bit and from the magnetization transition, orient the easy axis of the magnetic film perpendicular to the substrate surface, and disperse the orientation of the easy axis. And the crystal grain size needs to be controlled.

As the magnetic film of the perpendicular magnetic recording system, Co
As the main components, and Cr, Ta, Pt, Rh, Pd,
A Co alloy thin film to which Ti, Ni, Nb, Hf or the like is added is used. As the Co alloy constituting the magnetic thin film, a material having an hcp structure is mainly used. The Co alloy thin film has an easy axis of magnetization in the c-axis <00.1> direction of the crystal, and orients the easy axis of magnetization in the vertical direction. The magnetic thin film is formed by a vacuum evaporation method or a sputtering method. In order to improve the linear recording density and reproducing output when magnetic recording is performed, to reduce reproducing noise and to improve magnetic recording characteristics, the Co alloy thin film is improved in c-axis vertical orientation and crystal grain size. Therefore, improvement measures such as forming an underlayer for structure control between the substrate and the magnetic film have been conventionally taken.

However, several Gb / in ² or more, particularly to achieve a 10Gb / in ² or more ultra-high density magnetic recording, noise contained in addition to the reproduction signal to improve the linear recording density, particularly medium of the microstructure It is important to reduce the medium noise caused by the above. For this purpose, it is necessary to control the thin film structure at a higher level in addition to the crystal orientation of the magnetic thin film. Conventionally, various improvements have been attempted to reduce medium noise. For example, (1) a method of segregating non-magnetic Cr in a CoCr-based alloy at a crystal grain boundary or in a grain in order to reduce a magnetic interaction between magnetic particles, and (2) a method of controlling a sputtering gas pressure to control a magnetic property. For example, a method of isolating particles morphologically.

[0008]

Although the improvement of the medium structure as described above has promoted the reduction of the medium noise, the medium is formed in the direction opposite to the magnetization direction, which is the origin of the medium noise in perpendicular magnetic recording. The effect of reducing the reverse magnetic domain and the accompanying irregular magnetic domain has not yet been sufficiently obtained.
An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to reduce the dispersion of magnetic anisotropy, in particular, by controlling the perpendicular magnetic anisotropy and crystal orientation of a perpendicular magnetization film formed on a substrate, To provide a perpendicular magnetic recording medium and a magnetic recording apparatus having excellent low noise characteristics and stability of recording magnetization by controlling a fine magnetic domain structure when magnetic recording is performed, and suitable for ultra-high density magnetic recording. It is in.

[0009]

According to the present invention, a magnetic film composed of crystal grains having a large magnetic anisotropy is formed on a substrate, and the easy axis of the magnetic crystal grains is highly oriented perpendicular to the substrate surface. In addition, the above object is achieved by providing a medium structure in which the dispersion of the easy axis is reduced. That is, in the perpendicular magnetic recording medium according to the present invention, the axis of easy magnetization of the magnetic film formed on the substrate is oriented in a direction substantially perpendicular to the substrate surface, and the magnetization-magnetic field curve in the direction of easy magnetization of the magnetic film,
The saturation magnetization Ms and the residual magnetization Mr without demagnetization correction are M
A perpendicular magnetic recording medium having a relationship of r / Ms ≧ 0.8, wherein the magnetic film represents Ku ₁ , Ku ₂ , and Ku ₃ as uniaxial anisotropy constants, and θ represents spontaneous magnetization and an easy axis of the magnetic film. , The crystal magnetic anisotropy energy E of the magnetic film is approximated by the following equation (Equation 1), and the magnetic torque L per unit volume measured under the condition that the magnetization of the magnetic film is almost saturated is obtained. It is a thin film having uniaxial magnetic anisotropy described by the following equation (Equation 2), where Ku ₁ and Ku ₂ are Ku ₂ / (Ku ₁ + Ku ₂ ) ≦ 0.3
Satisfies the following relationship:

[0010]

E ≒ Ku ₁ sin ² θ + Ku ₂ sin ⁴ θ + Ku ₃
sin ⁶ θ

L２− (Ku ₁ + Ku ₂ −2πMs ² ) sin 2θ
+ (Ku ₂ sin4θ) / 2 In the perpendicular magnetic recording medium, it is preferable that at least one underlayer for structure control is formed on a substrate, and a magnetic film is formed on the underlayer. At this time, the underlayer and the magnetic film are preferably films grown epitaxially.

The magnetic film contains Co as a main component,
r, Fe, Mo, V, Ta, Pt, Si, B, Ir,
It is made of a material containing an alloy or a compound composed of at least one element selected from W, Hf, Nb, Ru, Ni and rare earth elements, and has a hexagonal close-packed structure.
The perpendicular magnetic anisotropy constant Ku of the magnetic film (Ku = Ku ₁ + K
It is preferable that the relationship Ku> 2πMs ² holds between u ₂ ) and the saturation magnetization Ms.

The uniaxial anisotropy constants Ku ₁ and Ku ₂ are as follows:
A magnetic torque curve measured by changing the applied magnetic field H with respect to the magnetic film is subjected to Fourier analysis, and the relationship between Ku ₁ , Ku ₂ obtained by the Fourier analysis and the reciprocal (1 / H) of the applied magnetic field is 1 / H. It can be a value obtained by extrapolating to = 0. Further, the magnetic recording apparatus according to the present invention includes the above-described perpendicular magnetic recording medium, a holder for holding the perpendicular magnetic recording medium, a magnetic head for recording and reproducing information on the perpendicular magnetic recording medium, It includes moving means for moving the relative position between the head and the perpendicular magnetic recording medium, and control means for controlling these.

Further, a method of manufacturing a perpendicular magnetic recording medium according to the present invention comprises a step of epitaxially growing a base layer on a substrate, and a step of forming a main component of Co on the base layer, which contains Cr, Fe, and Mo. , V, Ta, Pt, Si, B, Ir,
A magnetic film made of a material containing at least one element selected from the group consisting of W, Hf, Nb, Ru, Ni and a rare earth element, and having a hexagonal close-packed structure in which the axis of easy magnetization is oriented substantially perpendicular to the substrate surface. In the magnetic film, in the magnetization-magnetic field curve in the easy magnetization direction, the saturation magnetization Ms and the residual magnetization Mr without demagnetization correction have a relationship of Mr / Ms ≧ 0.8, and the magnetization of the magnetic film Is approximately saturated, the magnetic torque L per unit volume is L ≒ − (Ku ₁ + K
u ₂ −2πMs ² ) sin2θ + (Ku ₂ sin4θ) /
2 (Ku ₁ , Ku ₂ : uniaxial anisotropy constant defined by the above [Equation 1]; θ: angle between spontaneous magnetization and easy axis of the magnetic film) , The uniaxial anisotropy constants Ku ₁ and Ku ₂ , the perpendicular magnetic anisotropy constant Ku (Ku = Ku ₁
+ Ku ₂ ) and the saturation magnetization Ms are Ku ₂ / (Ku ₁ + K
u ₂ ) ≦ 0.3, and a step of epitaxially growing a magnetic film that satisfies Ku> 2πMs ² at the same time.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of an example of a magnetic recording device according to the present invention. The magnetic recording device includes a magnetic disk 1, a magnetic head 2 for recording and reproduction, a suspension 3 supporting the magnetic head, an actuator 4, a voice coil motor 5, a recording and reproduction circuit 6, a positioning circuit 7, an interface control circuit 8, and the like. You. Magnetic disk 1
Is an underlayer for controlling the structure such as crystal orientation of a magnetic film on a disk-shaped substrate such as a glass substrate, a Si substrate, a NiP-coated aluminum substrate, a carbon substrate, a magnetic film formed thereon, and a protective film. And a magnetic recording medium having a protective film covered with a lubricating film.

The magnetic film contains Co as a main component and Cr,
Fe, Mo, V, Ta, Pt, B, Ir, W, Hf, N
A hexagonal close-packed structure made of a material containing at least one element selected from b, Ru, Ni, and a rare earth element is used as a basic structure, and the easy axis of the magnetic film is oriented in a direction perpendicular to the substrate surface. In order to obtain a perpendicular recording medium in which the easy axis of magnetization of the magnetic film is oriented vertically to the substrate surface and the dispersion of perpendicular magnetic anisotropy is small, an underlayer for controlling the structure of the magnetic film is provided between the substrate and the magnetic film. Provide. Non-magnetic or paramagnetic CoCr alloy, Ti, Ti
Cr alloy or Pt, Ru, Ta, Mo, P
An hcp polycrystalline film, a microcrystalline film, an amorphous underlayer, or an amorphous underlayer such as Si or Ge to which d, V, Nb, Zr or the like is added is used.

The magnetic head 2 includes a slider, a magnetic pole of a magnetic recording ring-type head provided thereon, and a magnetoresistive, giant magnetoresistive, or spin-valve element or a magnetic tunnel type for reproducing recorded signals. It is composed of elements. In order to reduce the disturbance of the recording magnetic domain at the end of the track during magnetic recording, the trailing side of the recording head,
It is desirable that both ends of the track of the leading magnetic pole are aligned. It is preferable that the track width of the reproducing head is smaller than the track width of the recording head magnetic pole in order to reduce reproduction noise generated from both ends of the recording track. The magnetic head 2 is supported by the suspension 3 and has a function of correcting a yaw angle generated when the magnetic head 2 moves from the inner circumference to the outer circumference of the magnetic disk 1.

FIG. 2 is a sectional view schematically showing the structure of a perpendicular magnetic recording medium. FIG. 2A uses two underlayers. A first underlayer 12 and a second underlayer 12 are formed on a substrate 11.
It has a structure in which an underlayer 13, a magnetic film 14, and a protective film 15 are sequentially laminated. FIG. 2B shows a case in which one underlayer is used. An underlayer 12 and a magnetic film 1 are formed on a substrate 11.
4. It has a structure in which a protective film 15 is laminated.

As the substrate 11, a Si substrate, a glass substrate, a NiP-coated Al substrate, a carbon substrate, a polymer substrate, or the like can be used. Here, a disk-shaped Si disk having a thermally oxidized Si film formed on its surface is used. This will be described with an example using. In the example described here, the medium was produced by an ultra-high vacuum DC magnetron sputtering apparatus.
The cleaned substrate 11 was set in a sputtering apparatus, and subsequently, the substrate 11 was heated to about 230 ° C. to form an underlayer for controlling the crystal grain size and magnetic anisotropy of the magnetic film. The underlayer can be arbitrarily selected depending on the type of the magnetic film formed thereon, and the underlayer can be formed by laminating at least one layer made of the same material or different materials. As the magnetic film, a material having a hexagonal close-packed structure, a body-centered cubic lattice structure, a face-centered hexagonal lattice structure, or an orthorhombic structure can be used. For example, when using a material having an hcp (hexagonal close-packed structure) structure containing Co as a main component as the magnetic film, the underlayer is most commonly made of Ti, Ta, Ru, H
Polycrystalline film, microcrystalline film, amorphous film, Si, Ge, etc., which are mainly composed of a material having an hcp structure such as f, Co, and the like, to which Cr, V, W, etc. are added. It is possible to select an amorphous film to be formed. On this underlayer, a magnetic film 1 to be a recording film in the same vacuum.
4. The protective film 15 was formed sequentially.

The medium A according to one embodiment of the present invention is shown in FIG.
A first underlayer 12 made of a 30-nm-thick amorphous Ge film is formed on a substrate 11 and a 20-nm-thick hcp structure Co-35 at% Cr non- A second underlayer 13 made of a magnetic alloy was formed, and subsequently, a Co-19 at% Cr-10 at% Pt alloy magnetic film 14 having a thickness of 30 nm and a carbon protective film 15 having a thickness of 5 nm were formed. The medium A was produced by a DC magnetron sputtering method under an Ar gas pressure of 2 mTorr.

The Ge film used as the first underlayer 12 is made of X
Although the macroscopic structure by the line diffraction was amorphous, according to the backscattered electron diffraction of the thin film surface, a partly crystalline structure was observed in the amorphous diffraction line, and the amorphous structure was observed. It was determined that the film had a regular arrangement on a part of the film surface. As a result of observing the surface of the second underlayer and the surface of the magnetic film with an atomic force microscope (AFM), both the amplitude of the surface undulations and the period of the undulations were flat thin films of 10 nm or less.

The medium B according to another embodiment of the present invention is shown in FIG.
3A, the underlayers 12 and 13 are made of the same material as the medium A, and the magnetic film 14 is made of Co-15a.
A t% Cr-4at% Ta alloy was used. A medium C according to another embodiment of the present invention has a cross-sectional structure schematically shown in FIG.
Polycrystalline first underlayer 12 made of 0 at% Cr alloy film
Is formed thereon, and a 20 nm-thick hcp structure Co-
A second underlayer 13 made of a 35 at% Cr nonmagnetic alloy is formed, followed by a 30 nm thick Co-19 at% Cr-1.
A 0 at% Pt alloy magnetic film 14 and a carbon protective film 15 having a thickness of 5 nm were formed. Each of the thin films was formed by a DC magnetron sputtering method under an Ar gas pressure of 2 mTorr. As a result of observing the surface of the second underlayer and the surface of the magnetic film with an atomic force microscope (AFM), both the amplitude of the surface undulations and the period of the undulations were flat thin films of 10 nm or less.

A medium D according to another embodiment of the present invention is shown in FIG.
(A) has the cross-sectional structure schematically shown, the underlayers 12 and 13 are made of the same material as the medium C, and the magnetic film 14 is made of Co-1
A 5 at% Cr-4 at% Ta alloy was used. The magnetic films in the media A, B, C and D have an hcp structure, and the growth direction is a <002> direction perpendicular to the substrate surface, and all are epitaxially grown thin films from the interface of the underlayer. It was confirmed by X-ray diffraction and electron microscope observation.

By adding non-magnetic Cr or Ta to the magnetic film, the non-magnetic layer or the weak magnetic layer can be locally segregated at the grain boundaries or within the magnetic crystal grains, and the magnetic isolation of the magnetic grains can be improved. Has been confirmed by composition analysis using an electron microscope. Further, the magnetic anisotropy of the magnetic film can be improved by adding Pt. In each of the above embodiments, the protective film 15 on the medium surface is used.
In each case, a carbon film having a thickness of 5 nm was used, but B, Si carbide, Si nitride, diamond-like carbon, or the like may be used.

Next, a medium for comparison was prepared as follows. The medium E for comparison has a cross-sectional structure schematically shown in FIG. 2A, and has a polycrystalline first underlayer made of a 30 nm thick hcp structure Ti-10 at% Cr alloy film on a substrate 11. A second underlayer 13 made of a nonmagnetic alloy made of a Co-35 at% Cr alloy having a thickness of 20 nm and having a hcp structure was formed thereon. This underlayer was formed by DC magnetron sputtering with an Ar gas pressure for sputtering at a high gas pressure of 15 mTorr. On the underlayer, subsequently, Co-19a having a thickness of 30 nm is formed.
A t% Cr-10at% Pt alloy magnetic film 14 and a carbon protective film 15 having a thickness of 5 nm were formed. Magnetic film 14
Was manufactured by a DC magnetron sputtering method with an Ar gas pressure of 2 mTorr. As a result of observing the surface of the second underlayer and the surface of the magnetic film of the medium E with an atomic force microscope (AFM), the amplitude of the surface undulation and the period of the undulation were all in the range of 10 to 50 nm.

The medium F for comparison has a cross-sectional structure schematically shown in FIG. 2 (b), and is formed on a substrate 11 of a polycrystalline Ti-10 at% Cr alloy film of a 30 nm thick hcp structure. 1 underlayer 12 is formed, and a 30 nm-thick Co-
A 19 at% Cr-10 at% Pt alloy magnetic film 14 and a carbon protective film 15 having a thickness of 5 nm were formed. Both the underlayer 12 and the magnetic film 14 have an Ar gas pressure of 2 mTo.
It was produced by rr DC magnetron sputtering. As a result of observing the surface of the underlayer and the surface of the magnetic film in the medium F with an atomic force microscope (AFM), the amplitude of the surface undulation and the period of the undulation were 10 nm or less on the surface of the underlayer.
The thickness was 10 to 25 nm on the surface of the magnetic film.

Each of the magnetic films 14 of the comparative media E and F has an hcp structure, and the <002> direction is oriented almost perpendicular to the substrate surface. The grown thin film was confirmed by X-ray diffraction and electron microscope observation. The magnetic properties of each of the above media were measured with a vibrating sample magnetometer (VSM). The perpendicular magnetic anisotropy Ku of the magnetic film is obtained by measuring a magnetic torque curve for each sample, performing a Fourier analysis on the magnetic torque curve per unit volume, and calculating the above [Equation 1] and The uniaxial magnetic anisotropy constants Ku ₁ and Ku ₂ in the direction perpendicular to the film surface of the magnetic film were determined from the relationship of the above [Equation 2] with respect to the magnetic torque L per unit volume.

In order to more accurately determine the values of Ku ₁ and Ku ₂ , the magnitude of the external magnetic field H applied to the magnetic film in the measurement of the magnetic torque curve is measured in a range of 15 to 5 kOe. The values of the uniaxial magnetic anisotropy constants Ku ₁ and Ku ₂ measured under each applied magnetic field H and the reciprocal of the applied magnetic field (1/1)
H) was determined. That is, the value of Ku ₁ , Ku ₂ versus 1
In the plot showing the relationship of / H, the value obtained by extrapolating to 1 / H = 0 was defined as the value of Ku ₁ and Ku ₂ of each magnetic film.

Table 1 below shows the characteristics of the medium of the present invention and the medium for comparison. In Table 1, Δθ ₅₀ is one of the indices for evaluating the orientation of the crystal axis. Here, the rocking curve of the <002> diffraction X-ray peak of the CoCr alloy crystal was measured and indicated by its half-value width.
In addition, the magnetic recording sample (MFM: Magnetic Force Microscop)
e) Observation was performed to evaluate the size of the structure of the irregular magnetic domain that causes noise in the medium. The diameter of the irregular magnetic domain was determined by observing the magnetization state of the medium surface with a magnetic force microscope, and indicated by the diameter of a circle having the same area as the magnetic domain of the irregular structure formed on the surface. The observation of the magnetization state may be performed using a spin-polarized scanning microscope, a bitter observation method, a Lorentz-type electron microscope, or the like, in addition to the magnetic force microscope.

For magnetic recording, a ring-type magnetic head (track width 2 μm, gap length 0.2 μm) is used, and for reproduction, a magnetoresistive head (MR head) is used. The recording / reproducing characteristics of the medium were measured with the distance between the surface of the film and the magnetic pole of the magnetic head being 30 nm). The medium noise N / S ₀ is a linear recording density of 250
The noise measured by kFCI was reduced to low linear recording density (5 kFC
The value is standardized by the reproduced signal output in I).

[0030]

[Table 1]

As is clear from Table 1, the squareness ratio Mr / Ms of the magnetic film in the direction perpendicular to the film surface is large (especially 0.8 or more), and the uniaxial anisotropy in the direction perpendicular to the film surface of the magnetic film. By reducing the sex constant ratio Ku ₂ / (Ku ₁ + Ku ₂ ),
This has the effect of reducing the dispersion of the magnetic anisotropy of the magnetic film. As a result, the diameter and distribution width of the irregular magnetic domains that cause medium noise can be reduced, which is suitable for reducing medium noise.

Further, by setting the ratio Mr / Ms of the saturation magnetization Ms and the residual magnetization Mr without demagnetization correction to be 0.8 or more, the magnetically recorded magnetization can be stably held for a long time. Particularly in perpendicular magnetic recording, even under the most severe conditions where the demagnetizing effect is high and the remanent magnetization state (or DC erasure state), it was possible to suppress the attenuation to a small attenuation rate of 20% or less.

FIG. 3 shows the relationship between the medium noise and the diameter of the irregular magnetic domain with respect to the ratio of the uniaxial anisotropy constant Ku ₂ / (Ku ₁ + Ku ₂ ) among the characteristics of the media A to F shown in Table 1. It is shown. As is clear from this figure, Ku ₂ / (Ku ₁ +
By making Ku ₂ ) smaller, in particular, Ku ₂ / (Ku ₁₎
In the medium satisfying the condition of + Ku ₂ ) ≦ 0.3, it can be seen that the diameter and distribution width of the irregular magnetic domain can be reduced, and the effect of reducing the medium noise is large. Ku ₂ / (Ku ₁ + Ku ₂ ) ≦
When the condition of 0.25 is satisfied, ultra high density magnetic recording of 10 Gb / in ² or more is possible.

FIG. 4 shows the results of comparing the recorded magnetization states of the media A to F shown in Table 1 with a magnetic force microscope.
Perpendicular magnetic recording was performed using a ring-type magnetic head after DC erasing the entire surface of the medium. The figure shows a state where the recording magnetic domains 32 are recorded in the DC erasure area 31. In the figure, the contrast between light and dark indicates that the average direction of magnetization is the same. The smaller the fluctuation of the magnetization transition 33 shown in the figure, the smaller the diameter, the distribution width, and the density of the irregular magnetic domain 34 formed inside the recording magnetic domain 32, the smaller the medium noise. The irregular magnetic domains 34 are called reverse magnetic domains formed in the direction opposite to the direction of magnetization mainly due to the influence of the demagnetizing field.
This causes medium noise during recording and reproduction, and also hinders high-density recording.

FIG. 4A shows, as shown in Table 1 and FIG.
The graph shows typical magnetization states found in the media A and C in which the ratio of the uniaxial anisotropy constant Ku ₂ / (Ku ₁ + Ku ₂ ) is the smallest. As is clear from the figure, a clear recording magnetic domain 32 is formed, and a magnetization transition 3 formed at the boundary of the recording bit.
3 also has a small fluctuation, the amplitude of the fluctuation is as fine as about 30 nm, and the diameter and distribution of the irregular magnetic domains 34 are small. FIG.
(B) shows the magnetization states of the media B and D. In this case, clear recording magnetic domains 32 are formed, but the diameter and distribution of the irregular magnetic domains 34 are slightly larger than those of the media A and C. This is due to the ratio of Mr / Ms in the media B and D and Ku ₂ / (Ku ₁ +
This is because the value of Ku ₂ ) is inferior to those of the media A and C.

FIG. 4C shows the magnetization state of the medium E.
In this case, the fluctuation of the magnetization transition 33 is large, and a large number of large irregular magnetic domains are formed inside the recording magnetic domain. This is because the unevenness of the surface of the underlayer is large, and the magnetic anisotropy of the magnetic film formed thereon, that is, Ku ₂ / (Ku ₁ + Ku ₂ ), is large. FIG. 4D shows the magnetization state of the medium F. In this case, although the fluctuation of the magnetization transition 33 and the diameter of the irregular magnetic domain were smaller than those of the medium E, countless irregular magnetic domains were observed. This is because the magnetic film was formed directly on the thin single-layer underlayer, and the crystal orientation and grain size of the magnetic film were not sufficiently controlled, resulting in a large dispersion of the magnetic anisotropy of the magnetic film. .

[0037]

According to the present invention, the fluctuation structure of the magnetization transition of the recording magnetic domain which causes the medium noise is small, and the formation of the irregular magnetic domain due to the demagnetizing field acting on the magnetic film can be greatly reduced. It is possible to reduce the medium noise and ensure the stability of the recording magnetization, and to realize a perpendicular magnetic recording medium suitable for high-density magnetic recording and a magnetic recording apparatus using the same.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a magnetic recording device.

FIGS. 2A and 2B are schematic cross-sectional views of a perpendicular magnetic recording medium, wherein FIG.
FIG. 1 is a schematic cross-sectional view of magnetic recording media A, B, C, D according to the present invention and a comparative medium E, and FIG.

FIG. 3 is a comparison diagram of noise and irregular magnetic domains of a magnetic recording medium according to the present invention and a comparative medium.

4A and 4B are comparison diagrams of recording magnetization states of a magnetic recording medium according to the present invention and a comparative medium, wherein FIG. 4A is an explanatory diagram of recording magnetization states of a magnetic recording medium A and a medium C according to the present invention, and FIG.
FIG. 3 is an explanatory view of the recording magnetization state of the magnetic recording media B and D according to the present invention, FIG. 3C is an explanatory view of the recording magnetization state of the comparative medium E, and FIG. .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Magnetic head, 3 ... Suspension, 4 ... Actuator, 5 ... Voice coil motor, 6
... Recording / reproducing circuit, 7 ... Positioning circuit, 8 ... Interface control circuit, 11 ... Substrate, 12 ... First underlayer, 13 ...
Second underlayer, 14: magnetic film, 15: protective film, 31: DC erase area, 32: recording magnetic domain, 33: magnetization transition, 34: irregular magnetic domain

Continuing from the front page (72) Inventor Kenya Ito 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi Central Research Laboratory, Inc. (56) References JP-A-7-176027 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/66 G11B 5/85

Claims (8)

(57) [Claims] 1. An easy axis of magnetization of a magnetic film formed on a substrate is oriented in a direction substantially perpendicular to the surface of the substrate, and a magnetization-magnetic field curve of the magnetic film in the easy direction of magnetization is subjected to saturation magnetization Ms and demagnetizing field correction. The perpendicular magnetic recording medium wherein the residual magnetization Mr has a relationship of Mr / Ms ≧ 0.8, wherein the magnetic film has a crystal magnetic anisotropy energy E of E ≒ Ku ₁ si.
n ² θ + Ku ₂ sin ⁴ θ + Ku ₃ sin ⁶ θ (Ku ₁ , Ku
₂ , Ku ₃ : uniaxial anisotropy constant, θ: angle between spontaneous magnetization and the easy axis of the magnetic film), and the magnetic torque per unit volume measured under the condition that the magnetization of the magnetic film is almost saturated. Is L ≒ − (Ku ₁ + Ku ₂ −2πMs ² ) sin 2θ + (K
u ₂ sin 4θ) / 2, which is a thin film having uniaxial magnetic anisotropy, wherein Ku ₁ and Ku ₂ are Ku ₂ / (Ku ₁ +
A perpendicular magnetic recording medium satisfying the relationship: Ku ₂ ) ≦ 0.3. 2. The perpendicular magnetic recording medium according to claim 1, wherein at least one underlayer for structure control is formed on the substrate, and a magnetic film is formed on the underlayer. Characteristic perpendicular magnetic recording medium. 3. The perpendicular magnetic recording medium according to claim 2, wherein the underlayer and the magnetic film formed on the substrate are films grown epitaxially. 4. The perpendicular magnetic recording medium according to claim 1, wherein the magnetic film contains Co as a main component, and further contains Cr, Fe, Mo, V, Ta, Pt, Si,
A perpendicular magnetic recording medium comprising a material containing at least one element selected from the group consisting of B, Ir, W, Hf, Nb, Ru, Ni and a rare earth element, and having a hexagonal close-packed structure. 5. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic anisotropy constant Ku (K
Ku = 2πM between u = Ku ₁ + Ku ₂ ) and the saturation magnetization Ms.
A perpendicular magnetic recording medium, wherein the relationship of s ² is satisfied. 6. The perpendicular magnetic recording medium according to claim 1, wherein the uniaxial anisotropy constants Ku ₁ and Ku ₂ are measured by changing a magnetic field H applied to the magnetic film. This is a value obtained by performing a Fourier analysis on the magnetic torque curve and extrapolating 1 / H = 0 to the relationship between Ku ₁ and Ku ₂ obtained by the Fourier analysis and the reciprocal (1 / H) of the applied magnetic field. A perpendicular magnetic recording medium characterized by the above-mentioned. 7. The perpendicular magnetic recording medium according to claim 1, a holder for holding the perpendicular magnetic recording medium, and recording / reproducing information on / from the perpendicular magnetic recording medium. A magnetic recording apparatus comprising: a magnetic head for moving the magnetic head, a moving unit for moving a relative position between the magnetic head and the perpendicular magnetic recording medium, and a control unit for controlling these. 8. A step of epitaxially growing a base layer on a substrate; and forming a main component of Co on the base layer by adding Cr, Fe, Mo, V, Ta, Pt, Si,
A hexagonal close-packed structure made of a material containing at least one element selected from the group consisting of B, Ir, W, Hf, Nb, Ru, Ni, and a rare earth element, wherein an easy axis of magnetization is oriented substantially perpendicular to the substrate surface. The magnetic film has a saturation magnetization Ms and a residual magnetization Mr without demagnetization correction of Mr / Ms in a magnetization-magnetic field curve in an easy magnetization direction.
≧ 0.8, and the crystal magnetic anisotropy energy E of the magnetic film is E ≒ Ku ₁ sin ² θ + Ku ₂ sin ⁴ θ + Ku
₃ sin ⁶ θ (Ku ₁ , Ku ₂ , Ku ₃ : uniaxial anisotropy constant,
θ: the angle between the spontaneous magnetization and the easy axis of the magnetic film), and the magnetic torque L per unit volume measured under the condition that the magnetization of the magnetic film is almost saturated is L ≒ − (Ku ₁ + Ku ₂ −2).
πMs ² ) sin2θ + (Ku ₂ sin4θ) / 2, and has the uniaxial anisotropy constant Ku.
₁ , Ku ₂ , the perpendicular magnetic anisotropy constant Ku (Ku = Ku ₁ + K
u ₂ ) and the saturation magnetization Ms are Ku ₂ / (Ku ₁ + Ku ₂ )
Epitaxial growth of a magnetic film that satisfies ≦ 0.3 and Ku> 2πMs ² at the same time.