JPH11306532A - Magnetic recording medium and magnetic storage device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic storage device which allows recording and reproducing of high-density information and has high reliability. SOLUTION: This magnetic storage device has the magnetic recording medium, a drive section for driving this medium in a recording direction, a magnetic head consisting of a recording part and a reproducing part, a means for moving this magnetic head relative to the magnetic recording medium and a recording and reproducing signal processing means for executing the signal input to the magnetic head and the reproduction of the output signal from the magnetic head. In such a case, the reproducing part of the magnetic head comprises a magneto-resistive magnetic head and the magnetic recording medium comprises a magnetic layer 23 formed via a single layer or plural ground surface layers 21, 22. At least one layer of these ground surface layers 21, 22 is formed of the layer consisting of an amorphous or microcrystalline material which consists essentially of Ni and contains at least one element of Nb and Ta.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic storage device, specifically a magnetic storage device having a recording density of 4 gigabits per square inch or more, and a low-noise and thermomagnetic relaxation device for realizing this. The present invention relates to a magnetic recording medium having high stability in which attenuation of reproduction output is suppressed.

[0002]

2. Description of the Related Art In recent years, with a rapid increase in recording density of a magnetic storage device, a magnetic head having high sensitivity and a magnetic recording medium having high coercive force and low noise have been demanded. Currently, a magneto-resistive head (MR head) is mainly used as a magnetic head, but the development of a giant magneto-resistive head (GMR head) that is two to three times more sensitive than this is also rapidly progressing. In.

In addition, with the spread of notebook personal computers, a glass substrate having high impact resistance that can withstand portable use is substituted for a conventional NiP-plated Al-Mg alloy substrate (hereinafter referred to as Al substrate) medium. Media development is progressing rapidly. However, in the case of a glass substrate medium, due to poor adhesion, intrusion of impurity gas from the substrate into the film, deterioration of orientation, enlargement of particle size, etc.,
Magnetic properties tend to deteriorate compared to Al substrate media. As a remedy for these, formation of new layers called an intermediate film, a seed layer, a barrier layer, etc. between the substrate and the underlying layer has been attempted. For example, Japanese Patent Application No. 62-293511
No., Japanese Patent Application No. 62-293512, Ti, Zr, Hf, V, Nb, Ta, C
It is shown that by forming an intermediate film made of an oxide of a metal containing at least one of r, Mo, W, and Mn, the adhesion is improved and good CSS characteristics can be obtained.
Also, JP-A-4-153910 discloses Y and Ti, Zr, Hf, V, Nb, T
It has been shown that by forming an amorphous or microcrystalline film made of one of a, Cr, Mo, and W, the grain size is reduced and noise is reduced. JP-A-5-135343 discloses that a coercive force is improved by forming an oxygen isolation layer containing a rare earth element and one element selected from Ta, Y, Nb, and Hf on a glass substrate. Have been. Furthermore, when an amorphous Cr alloy or V alloy is formed on the substrate, the Cr underlayer formed thereon is oriented (211), so that the Co alloy magnetic layer is epitaxially grown to move the easy axis of magnetization into the film plane. Toward
(10.0) orientation and high coercive force can be obtained.
It is shown in 7-73441. Note that the layers formed directly on the substrate for the purpose of controlling the particle size and preventing the intrusion of impurities are hereinafter referred to as first underlayers in the present specification, and the purpose is to control the orientation of the magnetic layer by epitaxial growth. Made
An underlayer having a bcc structure made of a Cr alloy or the like is referred to as a second underlayer.

In order to reduce the medium noise, it is necessary to reduce the size of the magnetic particles and to reduce the exchange interaction between the particles. However, since the finely divided magnetic crystal is strongly affected by thermal disturbance, the recording magnetization increases with time. Phenomenon occurs. This phenomenon is called thermomagnetic relaxation and is a phenomenon that becomes significant as the recording density increases. Therefore, in order to achieve a high recording density, it is necessary to achieve both suppression of the thermal magnetic relaxation and low noise.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to control the crystal orientation, the average grain size, and the grain size dispersion of a magnetic layer appropriately to achieve low noise and sufficient thermal magnetic relaxation. Providing a stable magnetic recording medium and providing a highly reliable magnetic storage device with a recording density of 4 gigabits per square inch or more by combining this magnetic recording medium with a highly sensitive magnetic head It is in.

[0006]

An object of the present invention is to provide a magnetic recording medium having a magnetic layer formed on a substrate with a single-layer or multi-layer underlayer interposed therebetween, wherein at least one of the underlayers contains Ni as a main component. A magnetic recording medium comprising an amorphous or microcrystalline material containing at least one element of Nb and Ta, a drive unit for driving the magnetic recording medium in a recording direction, a recording unit, and a reproduction unit. A magnetic head comprising:
The magnetic storage device includes a magnetic storage device having means for moving the magnetic head relative to the magnetic recording medium, and recording and reproduction signal processing means for performing signal input to the magnetic head and reproduction of an output signal from the magnetic head. This is achieved by a magnetic storage device in which the reproducing section of the head is constituted by a magnetoresistive head.

Here, in the case of amorphous, a clear peak due to X-ray diffraction is not observed, or a clear diffraction spot or diffraction ring due to electron beam diffraction is not observed, but a halo-shaped diffraction ring is observed. Say that. Further, the term “microcrystal” means that the crystal grain has a crystal grain size smaller than the crystal grain size of the magnetic layer, and preferably has an average grain size of 8 nm or less. N
The amount of b added is preferably in the range of 20 to 70 at%, and the amount of Ta added is preferably in the range of 30 to 60 at%. Outside the above composition range, crystallization of the base alloy or enlargement of crystal grains occurs, which is not preferable. By using the above-mentioned amorphous or microcrystalline structure alloy as the first underlayer, crystal grains of the magnetic layer can be made finer and uniform, low noise, and attenuation of reproduction output due to thermomagnetic relaxation. Is obtained. Here, the first underlayer is a general term for layers directly formed on the substrate for the purpose of controlling the particle size, preventing intrusion of impurities, and the like as described above. Al ₂ O ₃ , SiO ₂ , Ti
When at least one oxide selected from O ₂ , ZrO ₂ and Ta ₂ O ₅ is added, the crystal grains of the magnetic layer become finer and more uniform, and a low-noise medium can be obtained. This is because the added oxide phase is uniformly precipitated in the Ni alloy of the parent phase, so that these become nucleation sites and fine and uniform crystal grains are formed thereon. The second underlayer of Cr or a body-centered cubic structure (bcc structure) containing Cr as a main component formed on the first underlayer has a (100) orientation.
Therefore, the magnetic layer having a hexagonal close-packed structure (hcp structure) formed thereon has an axis of easy magnetization c by epitaxial growth.
The orientation is (11.0) with the axis oriented substantially in the film plane. For this reason,
A high coercive force and a coercive force squareness ratio S * are obtained, and a recording density of 4 gigabits per square inch or more can be achieved. The first underlayer according to the present invention is characterized in that it has better adhesion to a glass substrate, and it is not particularly necessary to provide a layer for improving the adhesion. However, a continuous film for improving the CSS characteristics by forming an uneven shape on the surface of the medium or a discontinuous film grown in an island shape can be formed between the substrate and the first underlayer. In addition, Ni-P was plated as a substrate
In the case of using an Al alloy substrate or an amorphous carbon substrate, as in the case of using a glass substrate, it was confirmed that the crystal grains of the magnetic layer were fine and uniform, and that the medium noise was reduced and the thermomagnetism was reduced. The effect of suppressing the relaxation was confirmed.

The second underlayer formed on the first underlayer and for controlling the orientation of the magnetic layer by epitaxial growth or the like has a bcc containing Cr or Cr as a main component and containing Ti, V, Mo or the like. Structured alloys can be used. Also, bcc
It can be composed of two or more layers having a structure.

For the magnetic layer, an alloy containing Co as a main component having an hcp structure can be used, but in order to obtain a high coercive force, it is particularly preferable to use a Co alloy containing Pt. Further, a magnetic alloy containing a rare earth element having high crystal magnetic anisotropy such as SmCo and FeSmN can be used. Furthermore, the magnetic layer may be composed of a single layer or a plurality of layers with a non-magnetic intermediate layer interposed therebetween.In this case, the thickness t of the magnetic layer in Br × t of claim 6 is the thickness of each magnetic layer. Shall represent the sum of As magnetic properties of the magnetic layer, the coercive force measured by applying a magnetic field in the recording direction is 2 kOe or more, and the product Br × t of the residual magnetic flux density Br and the film thickness t is 40 gauss.
It is preferable that the thickness be not less than 120 microns and not more than 120 gauss because good recording / reproducing characteristics can be obtained in a recording density region of not less than 4 gigabits per square inch. If the coercive force is smaller than 2400 Oe, the output at a high recording density (200 kFCI or more) becomes undesirably small.
Also, when Br × t is larger than 120 Gauss / micron, the resolution is reduced, and when it is smaller than 40 Gauss / micron, the reproduction output is undesirably reduced.

Further, by forming carbon as a protective layer of a magnetic layer with a thickness of 5 nm to 30 nm and further providing a lubricating layer of an adsorbent perfluoroalkyl polyether or the like with a thickness of 2 nm to 20 nm, high reliability and high density can be achieved. A recordable magnetic recording medium is obtained. Further, a carbon film to which hydrogen or nitrogen is added as a protective layer, or a film made of a compound such as silicon carbide, tungsten carbide, (W-Mo) -C, (Zr-Nb) -N, or a compound of these compounds The use of a mixed film of carbon and carbon is preferred because the sliding resistance and corrosion resistance can be improved.

Further, the magneto-resistance effect type magnetic head used in the magnetic recording apparatus of the present invention sandwiches the magneto-resistance sensor section.
The interval between the shield layers (shield interval) is preferably 0.30 μm or less. This is because when the shield interval is 0.30 μm or more, the resolution is reduced, and the phase jitter of the signal is increased. Further, the magneto-resistance effect type magnetic head is composed of a plurality of conductive magnetic layers that generate a large resistance change due to a relative change in their magnetization directions due to an external magnetic field, and a conductive layer disposed between the conductive magnetic layers. By using a magnetoresistive sensor including a conductive nonmagnetic layer and utilizing the giant magnetoresistance effect or the spin valve effect, the signal intensity can be further increased.
A highly reliable magnetic storage device having a recording density of 5 gigabits per square inch or more can be realized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> FIG.
This will be described with reference to FIG. 1, FIG. 2 and FIG. FIGS. 1 (a) and 1 (b) show a schematic plan view and a schematic sectional view of the magnetic storage device of this embodiment. This device is a magnetic storage device having a well-known structure including a magnetic head 1, a drive unit 2 for the magnetic head, a recording / reproducing signal processing means 3 for the magnetic head, a magnetic recording medium 4, and a drive unit 5 for rotating the magnetic recording medium. .

FIG. 2 shows the structure of the magnetic head. This magnetic head is a composite type head having both an electromagnetic induction type magnetic head for recording and a magnetoresistive magnetic head for reproduction formed on the base 6. The recording head is a coil 7
Upper write pole 8 and lower write pole and upper shield layer 9 sandwiching
And the thickness of the gap layer between the recording magnetic poles was 0.3 μm.
Cu having a thickness of 3 μm was used for the coil. The reproducing head comprises a magnetoresistive sensor 10 and electrode patterns 11 on both ends thereof.The magnetoresistive sensor is sandwiched between a lower recording magnetic pole / upper shield layer and a lower shield layer 12 each having a thickness of 1 μm, and the distance between the shield layers is 0.25 μm. It is. In FIG. 2, the gap layer between the recording magnetic poles and the gap layer between the shield layer and the magnetoresistive sensor are omitted.

FIG. 3 shows a sectional structure of the magnetoresistive sensor.
The signal detection area 13 of the magnetic sensor is a gap layer 14 of Al oxide.
The horizontal bias layer 15, the separation layer 16, and the magnetoresistive ferromagnetic layer 17 are sequentially formed thereon. The magnetoresistive ferromagnetic layer has
A 20 nm NiFe alloy was used. 25nm NiFe for lateral bias layer
Although Nb was used, any ferromagnetic alloy such as NiFeRh having relatively high electric resistance and good soft magnetic properties may be used. The lateral bias layer is magnetized in an in-plane direction (lateral direction) perpendicular to the current by a magnetic field generated by a sense current flowing through the magnetoresistive ferromagnetic layer, and applies a lateral bias magnetic field to the magnetoresistive ferromagnetic layer. As a result, a magnetic sensor showing a linear reproduction output with respect to the leakage magnetic field from the medium can be obtained. For the separation layer for preventing the shunt of the sense current from the magnetoresistive ferromagnetic layer, Ta having relatively high electric resistance was used, and the film thickness was 5 nm. At both ends of the signal detection region, there are tapered portions 18 processed into a tapered shape. The tapered portion includes a permanent magnet layer 19 for converting the magnetoresistive ferromagnetic layer into a single magnetic domain, and a pair of electrodes 11 formed thereon for extracting a signal. The permanent magnet layer needs to have a large coercive force and the magnetization direction does not easily change, and CoCr, CoCrPt alloy, or the like is used.

FIG. 4 shows the layer configuration of the magnetic recording medium used in this embodiment. The substrate 20 is made of soda lime glass that is chemically strengthened, and the first underlayer 21 is made of Ni-35at% Ta having a thickness of 50 nm,
The second underlayer 22 has a thickness of 10 nm of Cr-15at% Ti, and the magnetic layer 23 has a thickness of 22 nm.
A Co-20at% Cr-10at% Pt alloy was used. Further, a carbon film was formed to a thickness of 10 nm as the protective film 24, and a lubricating layer made of an adsorbent perfluoroalkyl polyether or the like was provided to a thickness of 2 to 20 nm as a medium for evaluating the recording and reproducing characteristics. The method of manufacturing the medium is as follows. First, the alkali-cleaned substrate was heated to 300 ° C. by a lamp heater to form a first underlayer, and then heated again to 200 ° C. Then, a second underlayer, a magnetic layer, and a protective film were sequentially formed thereon.
Film formation from the first underlayer to the protective film was performed continuously in a vacuum, and all film formation was performed in a 10 mTorr Ar gas atmosphere by DC sputtering.

In order to examine the film structure of the first underlayer, first, only the Ni-35at% Ta alloy was formed on the substrate by the above-mentioned manufacturing method.
50 nm was formed. Figure 5 shows the X-ray diffraction profile of this single-layer film.
Shown in There is only a halo-like broad peak around 2θ = 41.5 °, but no clear diffraction peak. This indicates that the Ni-30at% Ta alloy has an amorphous or microcrystalline structure. When the single-layer film was observed with an electron microscope, extremely fine crystal grains were found, but all of the particle diameters were 4 nm or less. Next, FIG. 6 shows the X-ray diffraction profile of the medium on which the carbon protective film was formed by the above-described manufacturing method. The figure also shows the X-ray diffraction profile of a medium using Cr for the first underlayer formed as a comparative example. In the example medium, (2)
Only the (00) diffraction peak and the (11.0) diffraction peak from the magnetic layer are observed. Thus, the second underlayer has an orientation with the (100) plane oriented parallel to the substrate, and the magnetic layer has its c-axis, which is the axis of easy magnetization, oriented in-plane by epitaxial growth.
It turns out that (11.0) orientation is taken. On the other hand, in the comparative example medium, (00.
2) and (10.1) diffraction peaks are observed, indicating that there is a component whose c-axis is raised from within the film plane. Next, the average particle size and the particle size distribution of the magnetic layer were determined by electron microscopy by the following methods. First, after the medium is polished to several tens of microns, the thickness of the magnetic layer is reduced to about 10 nm by ion thinning. Next, a lattice image is observed in a high-resolution mode of a transmission electron microscope to obtain a lattice image of about 2,000,000 times printed on photographic paper. The lattice image is taken into a scanner, the lattice image is displayed on a personal computer screen, and a line where the lattice fringe changes (intersects) is drawn along the grain boundary with a portion where the lattice fringes change (intersect) to form a grain boundary network. Figure 1 shows an example of the grain boundary network obtained in this way.
See Figure 7. Using commercially available particle analysis software, the area of each crystal grain surrounded by the grain boundary network was determined, and the diameter of a perfect circle having the same area as the area was defined as the particle diameter of each crystal grain. The crystal grain size was calculated for 100 to 300 crystal grains by the above method. FIG. 8 (a) is a histogram of the particle size frequency of the medium of the present example, and FIG. 8 (b) is normalized by the crystal grain size and the area of all the crystal grains obtained by observing the area of the crystal grain having the crystal grain size smaller than that. A curve (hereinafter, referred to as an integrated area ratio curve) representing the relationship between the calculated values (hereinafter, referred to as an integrated area ratio curve) is shown. In this integrated area ratio curve, the crystal grain size at which the integrated area ratio is 0.5 is defined as the average particle size, and the difference between the crystal particle size at which the integrated area ratio is 0.75 and the crystal particle size at which the integrated area ratio is 0.25 is the particle size. Defined as variance. The average particle size and the particle size dispersion of the medium of this example were 13.8 nm and 5.4 nm, respectively. On the other hand, in the comparative example medium, the average particle size and the particle size dispersion were 17.1 nm and 7.8 nm, respectively.
It can be seen that in the medium of this example using a Ta alloy, the average particle size was reduced by about 20%, and the particle size dispersion was also reduced. Table 1 shows the magnetic characteristics and normalized medium noise of both media.

[0017]

[Table 1]

Here, the normalized medium noise has a linear recording density of 26.
This is a value defined as a value obtained by standardizing the medium noise measured under the condition of 0 kFCI by the isolated reproduction wave output and the square root of the track width, and thereafter, the medium noise is evaluated using this value. The medium of this embodiment has large coercive force and S *, and has low normalized medium noise.

As described above, by using the Ni-35 at% Ta alloy for the first underlayer, the crystal grains of the magnetic layer are oriented (11.0) and fine and uniform at the same time, and high Hc, high S * and low noise are obtained. It has become clear that a suitable medium can be obtained. When this medium was incorporated in the above-mentioned magnetic storage device and the recording and reproducing characteristics were evaluated under the condition of 4 gigabits per square inch, a high device S / N of 1.8 was obtained. When a CSS test (contact start / stop test) was performed, 30,000 times of C
Even when SS was performed, the friction coefficient was 0.3 or less. Furthermore, the number of bit errors after 50,000 head seek tests from the inner circumference to the outer circumference of the medium is 10 bits / surface or less, and the average failure interval is 30
More than 10,000 hours were achieved.

<Embodiment 2> In a medium having the same film configuration as in Embodiment 1, a 30 nm-thick Ni-Ta alloy or Ni-
An Nb alloy was used, a 30 nm Cr-20at% Mo alloy was used for the second underlayer, and a 18 nm Co-18at% Cr-8at% Pt-2at% Ta alloy was used for the magnetic layer. The relationship between the Ta and Nb concentrations in the first underlayer and the coercive force, and the normalized medium noise defined in Example 1, respectively.
9 and shown in FIG.

In a medium using a Ni-Ta alloy for the first underlayer, a high coercive force of 2400 Oe or more and a low normalized medium noise of 0.018 or less are obtained at a Ta concentration of 30 to 60 at%. As a result of X-ray diffraction measurement, within this composition, the Ni-Ta alloy had an amorphous or microcrystalline structure similar thereto, and the magnetic layer showed a strong (11.0) orientation. At a Ta concentration of 30 at% or less or 60 at% or more, the Ni-Ta alloy was crystallized, and the orientation of the magnetic layer became a mixed phase of (10.1) and (10.1) and (00.2) oriented crystal grains. . Within the above composition range, the saturation magnetic flux density of the Ni—Ta alloy is as low as 100 G or less, so that there is no particular problem in practical use. To obtain a lower noise medium, the Ta concentration should be 35
~ 55at% is particularly preferred.

In a medium using a Ni--Nb alloy for the first underlayer, a high coercive force of 2400 Oe or more and a low normalized medium noise of 0.018 or less are obtained at an Nb concentration of 20 to 70 at%. As a result of X-ray diffraction measurement, Ni-Nb alloy
Like the -Ta alloy, it had an amorphous or near-crystalline structure. The saturation magnetic flux density was 100 G or less, which was not a problem in practical use. In addition, especially when the Nb concentration is 30 to 60 at
% Medium, the (11.0) peak strength of the magnetic layer is about 30 to 50% stronger than the medium using the Ni-Ta alloy, and the coercive force is also 200 to 300%.
Oersted is big. Therefore, in order to obtain a medium having a particularly high coercive force, it is desirable to set the Nb concentration to 30 to 60 at%. N
At a b concentration of 20 at% or less or 70 at% or more, the Ni-Nb alloy was crystallized, and diffraction peaks from the magnetic layer also appeared at (10.1) and (00.2) peaks in addition to the (11.0) peak.

<Embodiment 3> In a medium having the same film configuration as in Embodiment 1, a 30 nm-thick Ni-40at% Nb alloy was used for a first underlayer, a 20 nm-thickness Cr-20at% V alloy was used for a second underlayer, 14 nm Co-22 for magnetic layer
An at% Cr-6at% Pt alloy was used. As a comparative example, a medium using a V-20at% Ta alloy for the first underlayer was formed.

X-ray diffraction measurement was performed on a single-layer film having only a first underlayer formed on a glass substrate. As a result, only a halo-shaped peak was observed in both the Ni-Ta alloy film and the V-Ta alloy film.
All were found to have an amorphous or microcrystalline structure. In addition, for the medium formed up to the carbon protective film, X
When a line diffraction measurement was performed, a strong bcc (200) peak and hcp (1
1.0) A peak was observed. However, a strong bcc (211) peak and hcp
(10.0) peak was observed. Table 2 shows the average particle size, particle size dispersion, and normalized medium noise of both magnetic layers obtained by the method described in Example 1.

[0025]

[Table 2]

The average particle size of the example medium is small. In the lattice image of the example medium, some portions in which lattice fringes of adjacent crystals were orthogonal were observed. This is because a plurality of (11.0) -oriented magnetic crystal grains are formed on one (100) -oriented second base crystal grain.
This indicates that the crystal has a bicrystal structure grown epitaxially with the axis perpendicular to the axis. On the other hand, such a bicrystal structure was not observed in the medium of the comparative example. This is because the surface of the second base crystal of the medium of the comparative example is a two-fold symmetric (211) plane, and thus all (10.0) -oriented magnetic crystal grains can grow only with the c-axis aligned in the same direction. Therefore, it is considered that the reason why the medium of the example has low noise is that the magnetic crystal grains are further refined than the base crystal grains by the bicrystal structure.

A composite head using the sensor shown in FIG. 11 as a medium and a reproducing magnetic head in this embodiment was incorporated in the magnetic storage device described in the first embodiment. This sensor has a 5 nm Ta buffer layer 26, a 7 nm first magnetic layer 27,
m Cu intermediate layer 28, 3 nm second magnetic layer 29, 10 nm Fe-50at%
It has a structure in which Mn antiferromagnetic alloy layers 30 are sequentially formed. For the first magnetic layer, a Ni-20at% Fe alloy was used, and for the second magnetic layer, Co was used. The magnetization of the second magnetic layer is fixed in one direction by the exchange magnetic field from the antiferromagnetic layer. On the other hand, the direction of magnetization of the first magnetic layer, which is in contact with the second magnetic layer via the non-magnetic layer, changes due to the leakage magnetic field from the magnetic recording medium, so that a resistance change occurs. Such a change in resistance due to a change in the relative direction of magnetization of the two magnetic layers is called a spin valve effect. In this embodiment, a spin valve magnetic head utilizing this effect is used as a reproducing head. The tapered portion has the same configuration as the magnetic sensor of the first embodiment. When the recording and reproducing characteristics were evaluated under the condition of 5 gigabits per square inch, a high device S / N of 2.0 was obtained.

Example 4 After heating a NiP-plated Al-Mg alloy substrate (hereinafter referred to as Al substrate) to 280 ° C., a 30 nm-thick Ni-50at% Nb alloy as a first underlayer, a second 10 nm Cr-20at% V alloy as underlayer, 14 nm Co-22at% C as magnetic layer
r-6at% Pt alloy, 10 carbon films with hydrogen added to the protective film
nm formed. The first underlayer is formed in a mixed gas atmosphere containing 3% nitrogen added to Ar.
% Hydrogen was used. All other layers were performed in a pure Ar atmosphere. A DC bias of -300 V was applied to the substrate only during the formation of the magnetic layer. As a comparative example, a medium using a Mo-12at% Y alloy for the first underlayer was formed under the same conditions as described above. Only the first underlayer was formed under the same conditions as described above, and TEM observation revealed that both the Ni—Nb alloy and the Mo—Y alloy had a microcrystalline structure with a grain size of 5 nm or less.

Further, in order to examine the thermomagnetic relaxation characteristics, a change with time of the reproduction output was measured. FIG. 12 shows a temporal change in a value obtained by normalizing a reproduction output Et of a signal recorded at a linear recording density of 260 kFCI with a reproduction output E0 immediately after recording. In the present example medium, the decay rate of the reproduction output after 96 hours (E96h-E0) / E0 is 2
%, But about 15% lower in the comparative example medium. The particle size distribution of the medium of this example determined by TEM observation was about 20% lower than that of the medium of the comparative example. Therefore, it is considered that the reason why the attenuation of the reproduction output was suppressed in the example medium is that the ultrafine magnetic crystal grains were eliminated by the uniform particle diameter.
The medium of this embodiment and the spin-valve magnetic head described in Embodiment 3 were incorporated in the magnetic storage device described in Embodiment 1, and the recording and reproduction characteristics were evaluated under the condition of 5 gigabits per square inch. S / N was obtained. In addition, a CSS test showed that the coefficient of friction was less than 0.2 even after 30,000 cycles of CSS.

Example 5 A medium having the same film configuration as that of Example 1 was formed to have a thickness of 30 nm using a material in which four types of oxides shown in Table 3 were added to the first underlayer.

[0031]

[Table 3]

Film formation was performed by RF sputtering in an Ar gas atmosphere of 10 mTorr, and a crystallized glass substrate was used as a substrate. Co-20at% Cr-7at% Pt-2 with a two-layer structure sandwiching a 2nm Cr layer using a 50nm Cr-20at% Ti alloy for the second underlayer
An at% Ta alloy was used, and the film thicknesses were both 9 nm. Everything after the second underlayer was performed in a pure Ar atmosphere of 5 mTorr by DC sputtering. The substrate was heated by a lamp heater to 220 ° C. only after the formation of the first underlayer.

As a result of TEM observation, each of the first underlayers was amorphous or had a microcrystalline structure with an average particle size of 4 nm or less. As shown in Table 3, all media exhibit high coercivity of 2400 Oe or more and low normalized media noise of 0.015 or less, which is sufficient to achieve a recording density of 4 gigabits per square inch or more. I understood. Extremely good CSS especially for media with Al2O3 added to the first underlayer
Characteristics were obtained. The medium to which SiO2 is added has a high coercive force, and the medium to which ZrO2 is added has low noise. In the medium to which Ta2O5 was added, S * was large, but as a result of X-ray diffraction measurement, the hcp (11.0) diffraction peak of the magnetic layer of the medium was about 30 to 50% higher than that of the other medium. Therefore, it is considered that S * is large because the c-axis, which is the easy axis of magnetization, is strongly oriented in the film plane. Further, Table 3 also shows the decay rate of the reproduction output after 96 hours described in Example 4, but the first underlayer
Medium with TiO2 added is particularly low.

As the first underlayer, no oxygen is added (Ni-40at% Nb) -16at% Al, (Ni-40at% Nb) -10at% Si, (Ni-
40at% Nb) -16at% Ta, (Ni-40at% Nb) -20at% Ti, (Ni-40at% N
b) A medium in which -12 at% Zr was formed into a film in a mixed gas atmosphere containing 10% oxygen added to Ar was formed. In addition, the underlayer has a gas pressure of 20.
DC sputtering was performed at mTorr. These media also showed high coercivity of 2400 Oe or more and low normalized media noise of 0.015 or less, similar to the above media, and were found to be sufficient to achieve a recording density of 4 gigabits per square inch or more. .

[0035]

The magnetic recording medium of the present invention has the effect of reducing medium noise and suppressing the reproduction output attenuation due to thermomagnetic relaxation. By using the magnetic recording medium of the present invention in combination with a magnetoresistive head, a magnetic storage device having a recording density of 4 gigabits per square inch or more and an average number of failures of 300,000 hours or more can be realized. Becomes

[Brief description of the drawings]

FIGS. 1A and 1B are a schematic plan view and a sectional view taken along the line AA ′ of a magnetic storage device according to an embodiment of the present invention, respectively.

FIG. 2 is a perspective view showing an example of a sectional structure of a magnetic head in the magnetic storage device of the present invention.

FIG. 3 is a schematic diagram illustrating an example of a cross-sectional structure of a magnetoresistive sensor section of a magnetic head in the magnetic storage device of the present invention.

FIG. 4 is a schematic diagram showing an example of a cross-sectional structure of a magnetic recording medium according to one embodiment of the present invention.

FIG. 5 shows the first underlayer single layer used in one embodiment of the present invention.
It is a figure showing an X-ray diffraction profile.

FIG. 6 is a diagram showing X-ray diffraction profiles of magnetic recording media of one example of the present invention and a comparative example.

FIG. 7 is a diagram illustrating a grain boundary network obtained by observing a magnetic recording medium according to an embodiment of the present invention with a transmission electron microscope.

FIGS. 8A and 8B are diagrams showing an area ratio distribution of magnetic crystal grains in a magnetic recording medium according to one embodiment of the present invention, and a product curve thereof.

FIG. 9 is a diagram showing the relationship between the Ta concentration in the first underlayer of the medium of one embodiment of the present invention, the coercive force, and the normalized medium noise.

FIG. 10 shows Nb in a first underlayer of a medium according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a relationship among a density, a coercive force, and a normalized medium noise.

FIG. 11 is a schematic diagram showing an example of a cross-sectional structure of a magnetoresistive sensor section of a magnetic head in the magnetic storage device of the present invention.

FIG. 12 is a diagram showing a change over time in a reproduction output of a medium according to an embodiment of the present invention.

[Explanation of symbols]

1 ... magnetic head, 2 ... magnetic head drive unit, 3 ... recording / reproduction signal processing system, 4 ... air recording medium, 5 ... magnetic recording medium drive unit, 6 ... substrate, 7 ... coil, 8 ... upper recording magnetic pole, 9 ... lower recording magnetic pole and upper shield layer, 10 ... magnetic resistance sensor, 1
1 ... conductor layer, 12 ... lower shield layer, 13 ... signal detection area, 14 ... gap layer between shield layer and magnetoresistive sensor, 15 ... lateral bias layer, 16. Separation layer, 17 ... Magnetoresistance ferromagnetic layer, 18 ... Tapered section, 19 ... Permanent magnet layer, 20 ... Substrate, 21 ... First underlayer, 22 ... Second layer Underlayer, 23 ... Magnetic layer, 24 ... Protective film, 25 ... Buffer layer, 26 ... First magnetic layer, 27 ... Intermediate layer, 28 ... Second magnetism Layer, 29 ... antiferromagnetic layer.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshio Takahashi 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. Inside the Central Research Laboratory (72) Inventor Kaoru Tanahashi 1-280 Higashi Koikekubo, Kokubunji City, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. 72) Inventor Yoshitsugu Koiso 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] In a magnetic recording medium having a magnetic layer formed on a substrate with a single layer or a plurality of underlayers interposed therebetween, at least one of the underlayers contains Ni as a main component and at least one of Nb and Ta. A magnetic recording medium comprising an amorphous or microcrystalline material containing one kind of element. 2. The amorphous or microcrystalline material containing Ni as a main component further comprises Al ₂ O ₃ , SiO ₂ , Ta ₂ O ₅ , TiO ₂ and ZrO _2.
2. The magnetic recording medium according to claim 1, comprising at least one oxide selected from the group consisting of: 3. The magnetic recording medium according to claim 1, wherein an average crystal grain size of the underlayer containing Ni as a main component is 8 nm or less. 4. An underlayer having substantially a body-centered cubic lattice structure is formed between the underlayer containing Ni as a main component and a magnetic layer, and the magnetic layer is substantially close-packed hexagonally. 4. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is an alloy mainly containing Co having a lattice structure. 5. A magnetic recording medium, a driving unit for driving the magnetic recording medium in a recording direction, a magnetic head comprising a recording unit and a reproducing unit, means for moving the magnetic head relative to the magnetic recording medium, In a magnetic storage device having recording / reproduction signal processing means for performing signal input to a magnetic head and reproduction of an output signal from the magnetic head, a reproduction unit of the magnetic head is constituted by a magnetoresistive magnetic head, and 5. A magnetic storage device comprising the magnetic recording medium according to claim 1, 2, 3, or 4. 6. A magnetoresistive sensor of the magnetoresistive effect type magnetic head is formed between two shield layers made of a soft magnetic material separated from each other by a distance of 0.30 μm or less, and The product Br × t of the thickness t of the magnetic film and the residual magnetic flux density Br measured by applying a magnetic field in the direction of travel of the magnetic head relative to the magnetic recording medium during recording is 4
0 gauss micron or more, 120 gauss micron or less, and the coercive force of the magnetic recording medium measured by applying a magnetic field in the same direction as the above magnetic field application direction is 2400 Oe or more. The magnetic storage device according to claim 5. 7. A magneto-resistance effect type magnetic head comprising: a plurality of conductive magnetic layers which generate a large resistance change when their magnetization directions are relatively changed by an external magnetic field; 7. The magnetic storage device according to claim 5, wherein the magnetic storage device is configured by a magnetoresistive sensor including a conductive nonmagnetic layer disposed.