JP3222141B2 - Magnetic recording medium and magnetic storage device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic drum, a magnetic tape, a magnetic disk,
According to a magnetic recording medium such as a magnetic card and a magnetic storage device,
In particular, the present invention relates to a thin-film magnetic recording medium suitable for ultra-high density recording and a magnetic storage device using the same.

BACKGROUND ART In recent years, as a result of widespread use of computers in the general public, a highly information-oriented society has been developed, and the amount of information handled by individuals is steadily increasing. Accordingly, miniaturization and large capacity of external storage devices, high-speed access, and low bit cost have become indispensable issues. In particular, the magnetic disk device is capable of rewriting information, has high speed access to recorded information, and is suitable for a large capacity, and can be said to be the mainstream of external storage devices. Actually, the areal recording density has been increased by about ten times in ten years, and the magnetic disk device has been the mainstream of the external storage device. The magnetic recording medium used in the magnetic storage device includes a coating type magnetic recording medium in which powder of an oxide magnetic material is applied on a substrate, and a thin film magnetic recording medium in which a thin film of a metal magnetic material is deposited or sputtered on a substrate. Are known. This thin film magnetic recording medium has a higher density of the magnetic substance in the recording film than the coating type magnetic recording medium and is suitable for higher density recording. Therefore, for example, most of the magnetic disk devices use a thin-film magnetic recording medium.

The general structure of a thin film magnetic recording medium is disclosed in
A structure in which a base film, a magnetic film, and a protective film are sequentially laminated on a substrate as described in JP-A-226414 and JP-A-63-201911 is well known. Recently, as a medium having more excellent noise characteristics, Japanese Patent Application Laid-Open No. 63-241717,
Forming a base film on a substrate as described in 173313,
A multilayer magnetic recording medium in which a magnetic layer and a non-magnetic intermediate layer are alternately laminated thereon is known.

In order to increase the storage capacity of the magnetic disk drive, it is necessary to increase the coercive force of the thin-film magnetic recording medium. As a technique for increasing the coercive force, a bias sputtering method in which a negative bias voltage is applied to a substrate when a base film or a magnetic film is formed and a sputtering gas collides with a substrate surface simultaneously with the film formation has attracted attention. These are, for example, IEE Transactions on Magnetics, Volume 26,
1282 pages, 1990 issue, Journal of the Japan Society of Applied Magnetics, 16, 541
Page 1992.

To realize high-density recording of 1 gigabit or more per square inch in the future, the product of the residual magnetic flux density of the magnetic recording medium and the film thickness of the magnetic material (hereinafter referred to as residual Magnetic flux density Abbreviated as magnetic product film thickness)
Is an essential condition to be 150 G · μm or less. At this time, the coercive force must be at least 2000 Oe. Further, even if the coercive force can be increased, if the noise of the medium cannot be reduced, as a result, the recording / reproducing characteristics become insufficient,
Cannot be used as a magnetic recording medium. It is very difficult to satisfy the above condition only by the conventional method.

In order to solve this problem, in the present invention, the underlayer film for controlling the crystal growth of the magnetic film is improved, and further, the coherence of the crystal with the magnetic film is improved, thereby increasing the coercive force of the magnetic film.
Reduce media noise. The prior art does not mention any matching between the crystal lattices of the underlying film and the magnetic film. A magnetic recording medium having excellent recording / reproducing characteristics can be provided by improving the consistency.

When the product of the residual magnetic flux density and the film thickness of the magnetic recording medium is 150 G · μm or less, the sensitivity is not always sufficient in a conventional inductive magnetic head or a recording / reproducing separation type head for reproducing using the magnetoresistance effect. Therefore, it is desirable to use a head with higher reproduction sensitivity. In addition, it is more preferable that the signal modulation / demodulation circuit is compatible with high-density recording.

A first object of the present invention is to provide a magnetic recording medium having a high coercive force and low medium noise during high-density recording. A second object of the present invention is to provide a large-capacity magnetic storage device that makes full use of the characteristics of a magnetic recording medium.

DISCLOSURE OF THE INVENTION The first object is to provide a magnetic recording medium (in-plane recording medium) in which at least a cubic underlayer and a hexagonal magnetic layer are sequentially formed on a nonmagnetic substrate. Product is 10G ・ μm or more and 150G ・ μm or less, holding force is 2
000 Oe or more, the magnetic layer contains Co as a main component, the c-axis length of the magnetic layer is 4.105 angstroms or more, and the a-axis length of the underlayer is Is larger in the range of 0.1% to 1.5% than the c-axis length of the magnetic layer.

The thickness of the underlayer is preferably 50 nm or less, and more preferably 28 nm or less, in order to reduce the crystal grain size of the magnetic film. However, if the thickness of the underlayer is 1 nm or less, favorable crystal growth cannot be performed, which is not preferable.

The magnetic film of the magnetic recording medium preferably has uniaxial anisotropy. In Co having a dense hexagonal lattice crystal structure, the c-axis becomes the easy axis of magnetization, and has uniaxial anisotropy in the c-axis direction.
By controlling the direction of the c-axis by the base film, a magnetic recording medium having excellent recording / reproducing characteristics is manufactured.

In order to control the direction of the c-axis of Co, which is a magnetic film, the base film is preferably a crystal having a body-centered cubic lattice, but the base film may be a face-centered cubic lattice and a NaCl-type crystal. , Co can be controlled in principle in the direction of the c-axis. V, Cr, Zr, and underlayers with a body-centered cubic lattice structure
It is preferable that at least one selected from Nb, Mo, Hf, Ta, and W is a main component. When these are used as alloys, Cr-P, Cr-Ti, Cr-V, Cr-Zr,
Cr-Nb, Cr-Mo, Cr-Hf, Cr-Ta, Cr-W, Cr-Fe, Mo
-Nb, Mo-Pt, Mo-Ge, W-Ta, W-Si and the like are particularly preferable, but the composition is not limited as long as the crystal of the base film exhibits a body-centered cubic lattice.

The length of the a-axis length of the base film As a technique for increasing the c-axis length of the magnetic layer in the range of 0.1% or more and 1.5% or less, in addition to the alloying of adding another element to the underlayer as described above, Bias sputtering for applying a voltage can be employed. Of course, either DC bias or RF bias may be used as a bias application method. As a feature of the film manufactured by performing the bias sputtering, the concentration of the sputter gas detected from the film is higher than that of the film manufactured without performing the bias sputtering. The concentration of the sputtering gas detected from the film formed by performing the bias sputtering is about 100 ppm or more.

As an adjustment method for changing the a-axis length of the base film, in addition to the above, a film is formed by changing the sputtering gas to He, Ne, Ar, Kr, Xe, or Rn. There is also a method of changing film forming conditions such as input power during film formation and a film forming rate. When the film forming conditions are changed, the concentration of the sputter gas detected in the film changes, but is not captured as much as when the bias sputtering is performed.

The method for adjusting the a-axis length of the underlayer described above may be used as a method for setting the c-axis length of the magnetic layer to 4.105 angstroms or more.

The composition of the magnetic layer should be changed to CoCr to reduce the medium noise.
Ta, CoCrPt, CoSiTa, CoSiPt, CoCrPtTa, CoCrTaSi, Co
It is particularly preferable to use CrPtSi, CoCrTaB, and CoCrPtB.

The magnetic layer is a single layer or a multilayer. When the magnetic layer has a multilayer structure, it is preferable to provide a non-magnetic intermediate layer between the magnetic layers. The non-magnetic intermediate layer is formed by the same approach as the above-described underlayer. When the composition of the magnetic layer is different from the composition of the first layer and the composition of the second layer, it is necessary to determine the a-axis length of the nonmagnetic intermediate layer in relation to the magnetic layer formed thereon. Furthermore, even when the composition of the magnetic film is the same for the first layer and the second layer, the composition of the nonmagnetic intermediate layer and the underlayer or the film forming conditions may be changed.

An underlayer control film may be provided between the substrate and the underlayer. P, Ni, V, Cr, Zr, Nb, Mo, Hf,
It is preferable that at least one selected from Ta and W is a main component. When these elements are used as an alloy, Ni-P, Cr-P, Cr-Ti, Cr-V, Cr-Zr,
-Nb, Cr-Mo, Cr-Hf, Cr-Ta, Cr-W, Cr-Fe, Mo-
Nb, Mo-Pt, Mo-Ge, W-Ta, W-Si and the like are particularly preferable in controlling the crystal orientation of the underlayer.

The second object is to provide a recording-only inductive magnetic head using a medium of the present invention, a magnetic material having a saturation magnetic flux density of at least 1.2 T in at least a part of a magnetic pole, and a read-only magnetic disk having a giant magnetoresistive element. This is achieved by using a magnetic head in combination with the magnetoresistive head of the present invention. The recording / reproducing signal processing means for performing waveform processing on an input signal and an output signal with respect to the magnetic head includes a signal processing circuit using maximum likelihood codes, and a circuit for correcting asymmetry of the reproduced signal of the magnetic head using the giant magnetoresistance effect, The flying height of the slider on which the magnetic head is mounted is preferably set to 0.05 μm or less.

The underlayer is provided for controlling crystal growth of the magnetic film. For example, when Cr having a body-centered cubic structure is used for the underlayer and a Co-based alloy having a dense hexagonal structure is used for the magnetic film, the (1) Cr (100) plane is formed between the underlayer and the magnetic film. Growing parallel to the substrate, the Co (110) plane grows epitaxially,
(2) Cr (110) plane grows parallel to the substrate, and Co (100)
Surface, Co (001) surface, and Co (101) surface are epitaxially grown. This is because when the underlying film and the magnetic film are grown in the relationship of the above (1) and (2), the lattice constant of each surface becomes closest. By utilizing this relationship well, the crystal growth of the magnetic film can be controlled.

The magnetic film is not generally used only with pure Co, but is added with an element such as Cr, Ta, or Pt for the purpose of improving coercive force or reducing noise in recording / reproducing characteristics. Pure
The c-axis length of Co (plane spacing between (001) planes) is 4.046 angstroms, but the c-axis length increases when the above elements are added. That is, the lattice of the magnetic film is increased by the addition of the above elements. Therefore, the lattice matching with the underlayer described above does not match, and the crystal growth (orientation) of the magnetic film cannot be controlled. Therefore, it is necessary to adjust the size of the lattice of the base film in accordance with the size of the lattice of the magnetic film.

Also, rather than making the size of the underlying film lattice equal to the size of the magnetic film lattice, the size of the underlying film lattice is reduced by 0.1%.
The larger the value is in the range of 1.5% or more, the higher the coercive force and the smaller the noise. If the grating is made larger than this range, the coercive force will be degraded and noise will increase.
The reason for this is not clear, but it is considered that magnetostriction was favorably induced by applying strain to the lattice. If the size of the lattice of the underlayer is further increased to further increase the lattice distortion, the above-described consistency between the underlayer and the magnetic film is deteriorated, the epitaxial relationship is broken, and the control of crystal growth (orientation) is prevented. become unable. Therefore, it is preferable to increase the size of the lattice of the underlayer in the range of 0.1% or more and 1.5% or less.

As a method of controlling the lattice size of the underlayer film and the magnetic film, (1) alloying by adding another element, (2) bias sputtering is performed (a sputtering gas is taken into the magnetic film, and With a significant increase in substrate temperature),
(3) A film is formed by changing the sputtering gas to He, Ne, Ar, Kr, Xe, and Rn. (Each gas is not used as 100% pure gas, but may be a mixed gas. The atomic radius depends on the type of gas. (4) Optimization of film formation conditions such as gas pressure during sputtering, substrate temperature, input power during film formation, film formation rate, etc. Yes, there are. Various other methods are conceivable. Basically, the underlayer is composed of crystal grains having a substantially cubic lattice crystal structure, and the magnetic film is substantially composed of crystal grains having a dense hexagonal lattice crystal structure. Any method may be used as long as the condition is satisfied. Further, the underlayer preferably has a body-centered cubic crystal structure,
In principle, a face-centered cubic lattice and a NaCl-type crystal structure may be used.

The orientation of the c-axis of the magnetic film need not be laid in the plane, that is, the c-axis does not need to be oriented parallel to the substrate, and some may be vertically standing. The present invention focuses on the point that the Cr (100) plane parallel to the substrate grows epitaxially with the Co (110) plane as one measure of the relationship between the size of the crystal lattice of the base film and the magnetic film, and defines this. It is. That is,
It is considered that not only a specific axis of the crystal has increased, but the entire crystal has increased.If the crystal lattice of the underlying film and the magnetic film in this relationship increases, the crystal lattice of the other surface also increases. We believe that the consistency of that aspect has also improved. However, it is unknown whether all axes of the crystal are growing at the same rate.

Since it is difficult to measure the a-axis length of the base film in a plane parallel to the substrate by the usual evaluation method of X-rays or the like, the a-axis length perpendicular to the plane parallel to the substrate is measured and substituted for the above-described reason. be able to. From the Diffraction pattern of a planar TEM (transmission electron microscope) image, it is possible to measure the a-axis length of the base film on a plane parallel to the substrate which is originally desired to be known.

In the magnetic recording medium of the present invention, the product of the residual magnetic flux density and the film thickness can be reduced to 150 G · μm or less while the coercive force is maintained at 2000 Oe or more, and a high S / N (signal to noise ratio) can be secured. But,
When the residual magnetic flux density film thickness product is smaller than 10 G · μm, the influence of thermal fluctuation increases and the coercive force is significantly deteriorated. In addition, if the residual magnetic flux density film thickness is set to 10 G · μm or less,
The reproduction output becomes too small, which is not preferable.

The crystal grain size of the underlayer substantially determines the crystal grain size of the magnetic film. To reduce noise, it is better to reduce the crystal grain size of the underlayer. In order to control the crystal grain size of the base film, the film thickness is one of the major factors depending on the composition and the film formation conditions. If the film thickness is too large, the crystal grains are enlarged, so that the thickness of the base film is preferably 1 nm or more and 50 nm or less. Further, the thickness is more preferably 1 nm or more and 28 nm or less.

The composition of the magnetic layer is CoCr to reduce the medium noise.
Ta, CoCrPt, CoSiTa, CoSiPt, CoCrPtTa, CoCrTaSi, Co
It is particularly preferable to use CrPtSi, CoCrTaB, and CoCrPtB.

The structure of a medium manufactured using this method is not limited to a structure in which the magnetic layer such as an underlayer, a magnetic layer, and a protective layer is a single layer, but also includes an underlayer, a magnetic layer, a nonmagnetic intermediate layer, a magnetic layer, and a nonmagnetic intermediate layer. It may have a multilayer structure of layers,..., Protective layers. In a multilayer magnetic structure, the thickness of each magnetic layer is reduced, and the thickness between the magnetic layers is reduced.
With a nonmagnetic intermediate layer of 0.1 nm or more interposed, the magnetic layers can be laminated while the crystal grains are refined, and the exchange interaction can be reduced until each layer can be regarded as substantially independent. In this case, the magnetic interaction between the magnetic layers can be weakened, the noise can be reduced according to the statistical sum, and the noise can be further reduced as compared with the single-layer medium. Regarding the output, the reproduction output can be increased by laminating the magnetic layers in multiple layers.

The non-magnetic intermediate layer may be manufactured by the same approach as the underlayer described above. When the compositions of the first and second magnetic layers are different, it is necessary to determine the a-axis length of the non-magnetic intermediate layer in relation to the magnetic layer formed thereon. Further, even when the composition of the magnetic film is the same for the first layer and the second layer, the composition or the film forming conditions of the nonmagnetic intermediate layer and the underlayer may be changed for the purpose of noise reduction or the like.

An underlayer control film may be provided between the substrate and the underlayer.
For example, even when the composition and the film forming conditions of the underlayer are the same, the crystal orientation and the like may be changed by changing the substrate. Conversely, even when the substrates are the same, the crystal orientation and the like may be changed by changing the composition of the base film or the film forming conditions. In order to minimize such a phenomenon, it is effective to provide a base control film.

Combination of the medium of the present invention, an inductive magnetic head dedicated to recording using a magnetic material having a saturation magnetic flux density of 1.2 T or more in at least a part of a magnetic pole, and a read-only magnetoresistive head including a giant magnetoresistive element By using the magnetic head, a high-quality reproduction output can be obtained, and a large-capacity magnetic storage device more than twice as large as the conventional one can be realized.

This is because a recording-only induction magnetic head using a magnetic material having a saturation magnetic flux density of at least 1.2 T in at least a part of the magnetic pole has a higher recording magnetic field than a conventional magnetic head having a saturation magnetic flux density of about 1.0 T. As a result, sufficient recording becomes possible even with a medium having a high coercive force, and the overwrite characteristics are significantly improved. This is because the recording magnetic field becomes steep and the medium noise is suppressed low. Furthermore, one of the major factors is that a read-only magnetic head utilizing the giant magnetoresistance effect can obtain a reproduction output five times or more as compared with a conventional inductive magnetic head. A signal processing circuit using the maximum likelihood code is further added to the combination of the magnetic recording medium and the magnetic head,
And a circuit that corrects the asymmetry of the reproduction signal of the magnetic head using the giant magnetoresistance effect, and the flying height of the slider on which the magnetic head is mounted is set to 0.05 μm or less, so that it is three times or more as compared with the conventional case. Large-capacity magnetic storage device can be realized.

The magnetic recording medium of the present invention uses a magnetic film containing Co as a main component, has a c-axis length of 4.105 angstroms or more of the magnetic film exhibiting the hcp structure, and has an a-axis length of a cubic underlayer film. Is larger than the c-axis length of the magnetic film by 0.1% or more and 1.5% or less, so that the residual magnetic flux density film thickness product is 150 G · μm.
Even if it becomes less than the above, it has a high coercive force of 2000 Oe or more and can realize recording / reproducing characteristics corresponding to high-density recording.

Furthermore, the magnetic recording medium and at least a part of the magnetic pole
A recording-only magnetic head using a magnetic material having a saturation magnetic flux density of 1.2 T or more, a reproduction-only magnetic head using the giant magnetoresistance effect, a signal processing circuit using maximum likelihood decoding, and a magnetism using the giant magnetoresistance effect By combining a circuit that corrects the asymmetry of the read signal of the head and by setting the flying height of the slider of the magnetic head to 0.05 μm or less, a high-quality read output and an extremely low error rate can be obtained. A large-capacity, high-density magnetic storage device can be obtained as compared with the device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing a cross section of one embodiment of a magnetic recording medium according to the present invention, and FIG. 2 is an X-ray of a magnetic film in the magnetic recording medium of the first embodiment. FIG. 3 is a diffraction diagram. FIG. FIG. 4 is a diagram showing the relationship between
Element concentration added to Cr and FIG. 5 is a diagram showing the relationship between the c-axis length of the magnetic film of the magnetic recording medium of Example 2 and the coercive force;
FIG. 6 shows the X-axis of the underlying film of the magnetic recording medium according to the present invention in which the a-axis length of the underlying film was changed by changing the sputtering gas.
FIG. 7 is an X-ray diffraction diagram showing a difference in crystal orientation depending on the presence or absence of a base control film of the magnetic recording medium according to the present invention. FIGS. 8 and 9 are recording diagrams of the present invention, respectively. FIG. 10 is a diagram schematically illustrating the structure of a read / separation type magnetic head, FIG. 10 is a diagram schematically illustrating the structure of a magnetic storage device of the present invention, and FIG. FIG. 4 is a block diagram showing an example of the above.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the accompanying drawings. Incidentally, the residual magnetic flux density film thickness product of the magnetic recording medium shown in this embodiment is all 150G · μm or less,
The residual magnetic flux density film thickness product is 100 G
From 120 G · μm. (Embodiment 1) A cross-sectional view of an embodiment of a magnetic recording medium according to the present invention is shown in FIG.
Shown in the figure. Hereinafter, a method for manufacturing the magnetic recording medium of this embodiment will be described. Substrate made of Ni-P plated Al alloy with outer diameter 95mmφ
11, after etching under RF30W for 10 seconds under the conditions of a substrate temperature of 300 ° C., an Ar gas pressure of 2.5 mTorr, and an input power density of 5 W / cm ² , by DC magnetron sputtering. Cr-xat% Ti as underlayers 12 and 12 '
(X = 0, 5, 10, 15, 20) was deposited to a thickness of 50 nm. Then
Under the same film forming conditions, as the magnetic layers 13 and 13 ', Co-19 at%
After forming a film of Cr-8 at% Pt to a thickness of 25 nm, and finally forming a film of C to a thickness of 10 nm as the protective layers 14 and 14 ', lubricating layers 15 and 15' of 3 nm perfluoroalkylpolyether were formed by dipping.

First, the c-axis length of the Co-19 at% Cr-8 at% Pt magnetic film used in this example was measured. Normally, when a base film and a magnetic film are sequentially formed on a Ni-P plated Al alloy at a substrate temperature of 300 ° C.,
The magnetic film has a dense hexagonal lattice (hcp) crystal structure, and its orientation is (110) in a plane parallel to the substrate. That is, the c-axis is in the plane (parallel to the substrate). In general, the distance between planes is measured by an x-ray θ-2θ scanning method. However, in this measurement method, the length of the c-axis cannot be measured because the distance between planes parallel to the substrate is measured. Moreover, Ni-P plated Al
When an alloy is used, the peak of Ni-P just overlaps the 2θ position of the (002) plane. Therefore, the substrate temperature was set to 300 ° C., a sample in which only a magnetic film was formed directly on a glass substrate was prepared, and the c-axis length of this sample was measured. FIG. 2 shows the measurement results.

From FIG. 2, it can be seen that the spacing between the (002) planes is 2.054 angstroms. Therefore, the length of the c-axis is 2
Doubled to 4.108 angstroms.

When the coercive force of the medium manufactured by using this magnetic film and changing the additive concentration of Ti to Cr in the underlayer was examined, the results shown in FIG. 3 were obtained. The coercive force shows the maximum value when the concentration of Ti added is 10 at%. This is the base film Investigating the relationship between Is 4.138 angstroms. It is about 0.73% larger than the c-axis length of the magnetic film. In addition, As the value of Becomes 1.5% or more larger than the c-axis length of the magnetic film, the coercive force becomes lower than 2000 (Oe).

From the above results, at least the length of the a-axis of the underlying film (cubic) perpendicular to the plane parallel to the substrate It was found that the coercive force increased when the size was 0.1% or more and 1.5% or less than the c-axis length of the magnetic film (hexagonal).

In the above-described embodiment, Ti was added to Cr of the base film to increase the a-axis length perpendicular to the plane parallel to the substrate. However, as shown in FIG. It can be seen that similar results are obtained when W and V are used. Also, besides this
Similar results were obtained for Zr, Hf, Nb, and Ta. Cr as a main component has a bcc crystal structure, and any element may be used to increase the a-axis length as long as other elements are added to such an extent that this crystal structure is not broken. Furthermore, it is not necessary to limit the main component to Cr, for example, the same as Cr
V, Zr, Nb, Mo, Hf, Ta, and W exhibiting a bcc structure may be used as a main component. When an alloy underlayer is used, Cr-P,
Cr-Ti, Cr-V, Cr-Zr, Cr-Nb, Cr-Mo, Cr-Hf, Cr
-Ta, Cr-Ta, Cr-W, Cr-Fe, Mo-Nb, Mo-Pt, Mo-
Ge, W—Ta, W—Si, etc. are particularly preferred for controlling the crystal.

In controlling the crystal orientation of the magnetic layer, not only the bcc structure is effective but also, for example, a face-centered cubic lattice (fc
It may have a crystal structure of c) or NaCl type.

Example 2 As a medium of Example 2, a medium similar to that shown in FIG. Hereinafter, a method for producing the medium of this example will be described in detail. A substrate temperature of 300 ° C. and Ar gas pressure were applied to a substrate 11 made of Ni-P plated Al alloy having an outer diameter of 65 mmφ.
DC deposition under the conditions of 2.0 mTorr and input power density of 6 W / cm ²
Underlayers 12 and 12 'are formed by magnetron sputtering.
25 nm, then the magnetic layers 13 and 13 'are 20nm, the protective layer 14,
14 'is sequentially formed to a thickness of 5 nm.
5, 15 'were formed. At this time, magnetic layers 13 and 13 'having various compositions were used to change the c-axis length. For example, Co-16at% Cr-4at% Ta, Co-16at% Cr-6
at% Ta, Co-16at% Cr-8at% Ta, Co-19at% Cr-8at%
Pt, Co-15at% Cr-12at% Pt, Co-19at% Cr-12at% Pt
Were used. When these magnetic films were used, as shown in Example 1, the length of the a-axis of the cubic base film was reduced. 0.1% or more 1.5% longer than c-axis length of magnetic film showing hcp structure
The composition of the underlayer was adjusted to have the following sizes.

FIG. 5 shows the coercive force of the medium manufactured according to this example. From FIG. 5, it can be seen that a c-axis length of 4.105 Å or more is necessary to secure a coercive force of 2000 Oe or more. The composition of the magnetic film is not limited to the composition shown in this embodiment, but may be any composition as long as the c-axis length is equal to or greater than 4.105 angstroms. However, in order to reduce the medium noise, the composition of the magnetic film should be CoCrTa or CoCrTa.
CrPt, CoSiTa, CoSiPt, CoCrPtTa, CoCrTaSi, CoCrPtS
i, CoCrTaB, and CoCrPtB are more preferable.

As a method of increasing the a-axis length of the underlying film exhibiting a cubic lattice, a method by adding an element has been described, but another method is also possible. One example is shown in FIG. Sixth
The figure shows Cr-15 as a base film on a Ni-P plated Al alloy substrate.
The X-ray diffraction measurement result of the medium on which at% Ti is formed is shown. In order from the bottom of the diffraction chart shown in FIG. 6, 1) a medium using Ar as a sputtering gas (Comparative Example), 2) a medium manufactured by applying a negative DC bias of 200 V to the substrate side when forming an underlayer film, The results of 3) a medium using Kr as a sputtering gas and 4) a medium using Xe as a sputtering gas are shown, respectively.
In each of the above three media, the 2θ angle of CrTi (200) is shifted to a lower angle side than in the media made of simple Ar. The results are shown numerically in Table 1 (in Table 1, A represents the unit of Angstroms).

Of media made with Ar Is 4.146 angstroms, 4.178 angstroms for a medium made of Ar, and 4.163 angstroms for a medium made of Kr, and 4.116 angstroms for a medium made of Xe.
97 angstroms. From the above, it is understood that the application of the substrate bias and the change of the sputtering gas are also effective in adjusting the a-axis length of the base film. Needless to say, the same effect can be obtained even if He, Ne, or Rn is used as the sputtering gas.

Of these, He and Ne have the effect of making the a-axis length smaller than Ar. In addition, various methods can be used to adjust the a-axis length of the base film, such as the gas pressure during sputtering, the substrate temperature, the input power during film formation, and the film formation rate. Needless to say, these methods can also be used as a method for changing the c-axis length of the magnetic film. However, the c-axis length of the hcp-structured magnetic film is set to 4.105 angstroms or more, and the length of the a-axis of the underlying film (cubic crystal) is It is necessary to adjust the length of the magnetic film to be larger than the c-axis length in the range of 0.1% to 1.5%.

The medium of the present invention can be sufficiently applied to a multilayer magnetic recording medium provided with a non-magnetic intermediate layer. In this case, the non-magnetic intermediate layer may be manufactured by the same approach as the above-described underlayer. When the compositions of the first and second magnetic films are different, it is necessary to determine the a-axis length in relation to the magnetic layer formed thereon as the non-magnetic intermediate layer. Furthermore, even if the composition of the magnetic film is the same for the first layer and the second layer,
In order to improve the noise characteristics and the like of the medium, a method may be used in which the composition or film forming conditions of the non-magnetic intermediate layer are intentionally changed from those of the base film, and as a result, the a-axis lengths are made uniform.

Third Embodiment As a third embodiment, the effect of the underlayer control film will be described. Hereinafter, a method of manufacturing a medium (the structure of the medium is the same as that of FIG. 1) manufactured as the present example will be described. On a substrate 11 made of tempered glass having an outer diameter of 65 mmφ, under the film forming conditions of a substrate temperature of room temperature, an Ar gas pressure of 1.7 mTorr, and an input power density of 6 W / cm ² ,
An underlayer control film was formed by slightly oxidizing the surface of Cr formed by DC magnetron sputtering, and this was used as a new substrate 11. The substrate temperature is set to 300 ° C and Ar
Under the condition that the gas pressure is 1.7 mTorr and the input power density is 6 W / cm ² , the underlayer is formed by DC magnetron sputtering.
After sequentially forming 12, 12 ', magnetic layers 13, 13' and protective layers 14, 14 ', lubricating layers 15, 15' were formed by dipping.
At this time, Cr was used for the underlayers 12 and 12 ′, and the magnetic layers 13 and 12 ′ were used.
As 13 ', Co-16at% Cr-4at% Ta was used.

FIG. 7 shows the difference in crystal orientation depending on the presence or absence of the underlayer control film. FIG. 7 shows that there is a great difference in the crystal orientation depending on the presence or absence of the underlayer control film. The medium without the underlayer control film has a low X-ray intensity of Cr (200), and the medium with the underlayer control film has a high X-ray intensity of Cr (200). Thus, by providing the underlayer control film, the crystal orientation can be controlled regardless of the material of the substrate. It should be noted that it is not clear which crystal orientation of these media is better, and it is necessary to optimize the crystal orientation based on the design concept of the device including the recording density (recording bit length) and the signal processing circuit.

The material of the underlayer control film does not necessarily need to be adjusted to the same composition as that of the underlayer film. P, Ni, V, Cr, Zr,
It is preferable that Nr, Nb, Mo, Hf, Ta, and W are the main components. When these elements are used as an alloy, Ni
-P, Cr-P, Cr-Ti, Cr-V, Cr-Zr, Cr-Nb, Cr-
Mo, Cr-Hf, Cr-Ta, Cr-Ta, Cr-W, Cr-Fe, Mo-N
b, Mo-Pt, Mo-Ge, W-Ta, W-Si and the like are particularly preferable in controlling the crystal orientation of the underlayer.

Example 4 The recording / reproducing characteristics of the magnetic recording media described in Example 1 and Example 2 were measured using a recording / reproducing separation type magnetic head schematically shown in FIG. The recording magnetic head is an inductive type thin-film magnetic head including a pair of recording magnetic poles 81 and 82 and a coil 83 interlinking with the recording magnetic poles.In order to avoid saturation of the magnetic poles, a part of the magnetic poles 81 and 82 has 1.2T. Has the above saturation magnetic flux density
Magnetic materials 84 and 85 such as CoNiFe are used. The magnetic material having a saturation magnetic flux density of 1.2 T or more may be provided on only one magnetic pole, or the entire magnetic pole may be made of a magnetic material having a saturation magnetic flux density of 1.2 T or more. The read-only magnetic head is a giant magnetoresistive element 86 composed of NiFe laminated with NiO, etc.
And a magnetoresistive effect head including a conductor layer 87 serving as an electrode, which is sandwiched between a pair of magnetic shield layers 88 and 89. This magnetic head is provided on a magnetic head slider base 810.

The linear recording density is 200k
The FCI, the track width was 2 μm, the gap length of the recording head was 0.4 μm, the shield interval of the reproducing head was 0.3 μm, and the flying height of the slider of the magnetic head was 0.04 μm.

In the medium of Example 1, the S / N (signal-to-noise ratio) measured under such recording / reproducing conditions was the most excellent for the Cr-10at% Ti underlayer, and 26 dB could be secured. In contrast,
Only about 20 dB was obtained with the medium under Cr. Also,
In the medium of Example 2, the medium having the largest c-axis is excellent,
dB was secured. The c-axis length of the magnetic film is set to 4.105 angstroms or more, and the a-axis length of the cubic underlayer is smaller than the c-axis length of the magnetic film having the hcp structure. It was found that the medium increased in the range of 0.1% to 1.5% had excellent recording / reproducing characteristics.

As a recording / reproducing separation type magnetic head, as shown in FIG. 9, even a head having a structure in which a lower magnetic pole for recording and a layer 92 serving as one side of a magnetic shield sandwiching a magnetoresistive head for reproduction is provided. Similar results were obtained. In FIG. 9, reference numeral 91 denotes a recording magnetic pole, 93 denotes a coil, 94 denotes a magnetic material having a large saturation magnetic flux density, 95 denotes a giant magnetoresistive element, 96 denotes a conductor layer, 97 denotes a magnetic shield layer, and 98 denotes a slider base.
Fifth Embodiment FIG. 10A is a top view of an example of a magnetic storage device.
A sectional view taken along the line AA 'is schematically shown in FIG. Magnetic recording media
The magnetic head 101 is held by a holder connected to the magnetic recording medium drive unit 102, and a magnetic head 103 schematically shown in FIG. 8 or FIG. 9 is arranged to face each surface of the magnetic recording medium 101. The magnetic head 103 is stably low-flying with a flying height of 0.05 μm or less, and is driven by the magnetic head drive unit 105 to a desired track with a head positioning accuracy of 0.4 μm or less.

The signal reproduced by the magnetic head 103 is subjected to waveform processing by a recording / reproducing signal processing system 104. The recording / reproducing signal processing system includes an amplifier 1, an analog equalizer 2, an AD converter 3, a digital equalizer 4, and a maximum likelihood decoder 5 as shown in FIG. The reproduced waveform of the head using the giant magnetoresistive effect differs from the recorded signal because the positive and negative magnitudes are asymmetrical due to the characteristics of the head and are affected by the frequency characteristics of the recording / reproducing system. It may be misread as a signal. The analog equalizer 2 has a function of adjusting a reproduced waveform and restoring the reproduced waveform. The restored waveform is converted into a digital signal through the AD converter 3, and the waveform is further adjusted by the digital equalizer 4.
Finally, the restored signal is demodulated by the maximum likelihood decoder 5 into the most likely data. With the reproduction signal processing system having the above configuration, recording and reproduction of signals are performed at an extremely low error rate. Note that existing ones may be used for the equalizer and the maximum likelihood decoder.

With the above-described device configuration, three times as compared with the conventional magnetic storage device,
A high-density magnetic storage device having more than twice the storage capacity was realized. Further, even when the maximum likelihood decoder is removed from the recording / reproducing signal processing system and replaced with a conventional waveform discrimination circuit, a magnetic storage device having a storage capacity twice or more as compared with the conventional one can be realized.

In the above embodiments, examples of a disk-shaped magnetic recording medium and a magnetic storage device using the same have been described. However, the present invention provides a tape-shaped or card-shaped magnetic recording medium having a magnetic layer on only one side, and It goes without saying that the present invention can be applied to a magnetic storage device using a magnetic recording medium.

Further, the method of manufacturing the magnetic recording medium is not limited to the DC magnetron sputtering method, and any method such as an ECR sputtering method, an ion beam sputtering method, a vacuum evaporation method, a plasma CVD method, a coating method, and a plating method may be used. ECR sputtering is particularly preferable because crystal growth of a metal material can be easily controlled.

Continued on the front page (72) Inventor Masaaki Nihon 4-18-2 Harajuku, Shiroyama-cho, Tsukui-gun, Kanagawa (72) Inventor Joe Hosoe 6-45-10, Hirayama, Hino-shi, Tokyo (56) References JP-A-7 JP-A-29144 (JP, A) JP-A-7-14143 (JP, A) JP-A-7-37237 (JP, A) JP-A-7-176027 (JP, A) JP-A-2-113419 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/64-5/65 G11B 5/31 G11B 5/738

Claims (19)

(57) [Claims] In a magnetic recording medium in which a cubic underlayer and a hexagonal magnetic layer are sequentially formed on an amorphous substrate, the residual magnetic flux density of the magnetic recording medium and the magnetic layer The product of the film thickness is 10 Gm or more and 150 Gm or less, the coercive force is 2000 Oe or more, and the magnetic layer contains Co as a main component and c
The axis length is 4.105 angstroms or more, and the a-axis length of the underlayer is A magnetic recording medium characterized by being larger than the c-axis length of the magnetic layer by 0.1% or more and 1.5% or less. 2. The magnetic recording medium according to claim 1, wherein said underlayer has a thickness of 1 nm or more and 50 nm or less. 3. The magnetic recording medium according to claim 1, wherein said underlayer has a thickness of 1 nm or more and 28 nm or less. 4. The magnetic recording medium according to claim 1, wherein said magnetic layer comprises crystal grains having a crystal structure of a dense hexagonal lattice. 5. The magnetic recording medium according to claim 1, wherein said underlayer is made of crystal grains having a body-centered cubic structure. 6. A magnetic device according to claim 1, wherein said underlayer mainly comprises at least one selected from V, Cr, Zr, Nb, Mo, Hf, Ta and W. recoding media. 7. The underlayer according to claim 1, wherein the underlayer is Cr-P, Cr-Ti, Cr-V, kCr-
Zr, Cr-Nb, Cr-Mo, Cr-Hf, Cr-Ta, Cr-W, Cr-Fe,
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is Mo-Nb, Mo-Pt, Mo-Ge, W-Ta, or W-Si. 8. The magnetic recording medium according to claim 1, wherein said underlayer comprises crystal grains having a face-centered cubic crystal structure. 9. The magnetic recording medium according to claim 1, wherein said underlayer is made of crystal grains having a NaCl-type crystal structure. 10. The structure of said magnetic layer is CoCrTa, CoCrPt, CoCrPt.
SiTa, CoSiPt, CoCrTaPt, CoCrTaSi, CoCrPtSi, CoCrYT
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is aB, CoCrPtB. 11. The magnetic layer, wherein at least one of the underlayers contains at least one element selected from the group consisting of He, Ne, Xe, and Rn. 2. The magnetic recording medium according to claim 1. 12. The magnetic layer, wherein at least one of the underlayers contains 100 ppm or more of at least one element selected from the group consisting of He, Ne, Xe, and Rn. 2. The magnetic recording medium according to claim 1, wherein: 13. The magnetic recording medium according to claim 1, wherein said magnetic layer has a structure in which a plurality of magnetic films are formed via a non-magnetic intermediate layer. 14. The magnetic recording medium according to claim 1, further comprising a base control film between said substrate and said base layer. 15. A base control film between the substrate and the base layer, wherein the base control film is P, Ni, V, Cr, Zr, Nb, Mo, Hf, Ta, W,
Ni-P, Cr-P, Cr-Ti, Cr-V, Cr-Zr, Cr-Nb, Cr-Mo, C
r-Hf, Cr-Ta, Cr-W, Cr-Fe, Mo-Nb, Mo-Pt, Mo-Ge, W-
2. The magnetic recording medium according to claim 1, comprising Ta, W-Si. 16. A magnetic recording medium according to claim 1, a driving unit for driving said magnetic recording medium in a recording direction, and a magnetic head arranged to face each surface of said magnetic recording medium. A magnetic storage device comprising: means for moving the magnetic head relative to the magnetic recording medium; and recording / reproducing signal means for waveform-processing an input signal and an output signal to the magnetic head. 17. An inductive magnetic head, wherein:
17. The magnetic storage device according to claim 16, wherein the magnetic storage device is a read / write separated magnetic head including a head using a magnetoresistance effect. 18. The recording / reproducing separation type magnetic head comprising an induction type magnetic head and a head utilizing a magnetoresistive effect, wherein the induction type magnetic head has at least a part of 1.2T or more. 17. The magnetic storage device according to claim 16, further comprising a magnetic pole including a magnetic material having a saturation magnetic flux density, wherein the head using the magnetoresistance effect includes a giant magnetoresistance effect element. 19. The recording / reproducing signal processing means includes a signal processing circuit using a maximum likelihood signal and a circuit for correcting asymmetry of a reproduced signal of a magnetic head utilizing a giant magnetoresistance effect.
Flying height of slider on which magnetic head is mounted is 0.05 μm
17. The magnetic storage device according to claim 16, wherein: