JP2001243612A - Medium and device for magnetic recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vertical magnetic recording medium for high density magnetic recording, which realizes recording in a low magnetic field and a high reproduction output and is excellent in the preservation durability of recorded information, and a recording and reproducing device. SOLUTION: A magnetic recording medium 100 is provided with an auxiliary layer 2 between a substrate 1 and a recording layer 4. The layer 2 is made of magnetic material showing vertical magnetization in a room temperature area and intrasurface magnetization in a high temperature area, or is made of an intrasurface magnetization film in which magnetization is small in the room temperature area and large in the high temperature area. In recording/ reproduction mode, the magnetic recording medium 100 is effectively made into a vertical magnetic recording medium of a two-layer structure by the heating due to photo irradiation. Thus, information can reliably by recorded in a low magnetic field and a reproduction output is increased. In an information preservation mode, the medium 100 is effectively made to be a vertical magnetic recording medium of a single layer structure. Thus, the stability of a recording state is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium suitable for high-density magnetic recording and a magnetic recording apparatus having the same, and more particularly, to a magnetic recording medium which is heated by light irradiation or radiant heat to record and reproduce information. The present invention relates to a recording medium and a magnetic recording / reproducing apparatus including the same.

[0002]

2. Description of the Related Art With the development of information networks and the spread of multimedia, it has become an important issue to reduce the size, cost and capacity of magnetic disk devices, which are the main information recording devices that support them. I have.

[0003] Magnetic disk devices currently in practical use employ an in-plane magnetic recording system. That is, a magnetic disk having a magnetic film which is easily magnetized in a direction parallel to the disk surface as a recording film (hereinafter referred to as an in-plane magnetic disk) is used, and magnetic domains having in-plane magnetization are formed on the recording film. This is a recording method for performing recording. However, in such an in-plane magnetic recording system, when the thickness of the recording film of the magnetic disk is increased, a magnetic field (a so-called demagnetizing field) generated from a boundary between magnetic domains having different magnetization directions hinders formation of minute magnetic domains. Density recording became difficult, and it was necessary to reduce the thickness of the recording film in order to improve the recording density. However, when the recording film becomes very thin, thermal fluctuation of the recording magnetic domain occurs even at room temperature, and the magnetization of the recording magnetic domain decreases with time. as a result,
When such a recorded magnetic domain is reproduced, there arises a problem that a reproduced output is reduced.

[0004]

As a technique for solving such a problem in the longitudinal magnetic recording system, a perpendicular magnetic recording system has attracted attention. In the perpendicular magnetic recording system, a magnetic disk having a magnetic film whose easy magnetization direction is perpendicular to the disk surface is used as a recording film. Then, information is recorded by forming magnetic domains having magnetization perpendicular to the disk surface on the recording film. In such perpendicular magnetic recording, there is no problem in the above-described in-plane magnetic recording that a magnetic field generated from the boundary between magnetic domains having different magnetization directions inhibits formation of minute magnetic domains. Therefore, the thickness of the magnetic film of the magnetic disk is increased. be able to. For this reason, a magnetic disk according to the perpendicular magnetic recording method (hereinafter referred to as a perpendicular magnetic disk) is more resistant to thermal fluctuations than an in-plane magnetic disk, and forms minute recording magnetic domains in a magnetic film for high-density recording. can do.

Currently, two types of perpendicular magnetic disks are being studied. One is a magnetic disk provided with a magnetic layer having perpendicular magnetic anisotropy as a recording layer (hereinafter, such a magnetic disk is referred to as a single-layer perpendicular magnetic disk, and the recording layer used for the single-layer vertical recording Referred to as membrane). The other is a magnetic disk provided with a magnetic layer having in-plane magnetic anisotropy, a so-called in-plane magnetic layer, between a recording layer and a substrate in addition to a recording layer having perpendicular magnetic anisotropy (hereinafter, referred to as a magnetic layer). Such a magnetic disk is called a perpendicular magnetic disk having a two-layer structure, and a two-layer structure composed of a recording layer and an in-plane magnetic layer is called a two-layer perpendicular recording film.)

According to the findings of the present inventors, a perpendicular magnetic disk having a single-layer structure has a simple structure and is resistant to thermal fluctuation, but is compared with an in-plane magnetic disk having the same remanent magnetization and the same thickness. In this case, there is a problem that the obtained reproduction output is small. Further, in order to obtain a sufficient overwrite characteristic, the magnetic field generated from the recording head must be increased, and there is a problem that it is difficult to overwrite information.

On the other hand, in a perpendicular magnetic disk having a two-layer structure, as shown in FIG. 10, since a magnetic path is formed between the in-plane magnetization layer and the recording layer, the leakage magnetic field from the recording layer is reduced. Increase. Therefore, when the leakage magnetic field from the recording layer is detected using the reproducing head, the reproduction output increases. When a recording magnetic field is applied using a recording head, the magnetic path is closed by the recording layer, the in-plane magnetization layer, and the magnetic head as shown in FIG. Information can be recorded. Therefore, the above-described problem in the single-layer structure perpendicular magnetic disk is solved.

However, in a perpendicular magnetic disk having a two-layer structure, as shown in FIG. 11, a magnetic circuit is formed by a recording head and an in-plane magnetization layer. In this case, there is a possibility that an unintended magnetic field from outside is amplified by the magnetic circuit. As a result, depending on the medium structure and the type of recording head, the state of the recording magnetic domains formed in the recording layer may change even with a magnetic field of a few Oersteds, such as a leakage magnetic field generated from the motor of the magnetic disk drive. As described above, the perpendicular magnetic disk having the two-layer structure has a problem that the stability of the recording state is low. In a two-layer perpendicular magnetic disk, a domain wall is formed in the in-plane magnetic layer based on the recording magnetic domain of the recording layer. The domain wall is formed by using an in-plane magnetic layer using a soft magnetic material. It is also known that noise is liable to be generated at the time of information reproduction because the position of the magnetic domain wall is uncertain according to the size of the recording magnetic domain, and thus it is easy to move.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a first object of the present invention is to make it less susceptible to an unintended external magnetic field from the surroundings and to reduce the influence of a low magnetic field. An object of the present invention is to provide a perpendicular magnetic recording medium capable of reliably recording and overwriting information.

A second object of the present invention is to provide a perpendicular magnetic recording medium having a small output noise when the information is reproduced and the reproduction output is equal to or larger than that of the in-plane recording.

A third object of the present invention is to provide excellent heat stability,
40 gigabit / square inch (about 6.20 gigabit /
An object of the present invention is to provide a magnetic recording / reproducing apparatus capable of performing high-density magnetic recording of a square centimeter or more.

[0012]

As described above, the characteristics of a perpendicular magnetic disk having a single-layer structure and a perpendicular magnetic disk having a two-layer structure are complementary. That is, a perpendicular magnetic disk having a two-layer structure having an in-plane magnetic layer is superior in recording and reproducing information, and a perpendicular magnetic disk having a single-layer structure is superior in storing information. Therefore, when recording and reproducing information, a magnetic disk that effectively functions as a perpendicular magnetic disk having a two-layer structure and effectively functions as a perpendicular magnetic disk having a single-layer structure in an information holding state. If realized, the above problem would be solved.

According to a first aspect of the present invention, on a substrate:
In a magnetic recording medium comprising a recording layer having perpendicular magnetic anisotropy and heated at the time of recording and reproducing information, an auxiliary layer is provided between the recording layer and the substrate, and the auxiliary layer is easily magnetized at room temperature. A magnetic recording medium is provided which has magnetic characteristics such that the direction is perpendicular to the substrate surface and the direction of easy magnetization is parallel to the substrate surface in a high temperature region generated by heating.

In the magnetic recording medium according to the first aspect of the present invention, as shown in FIG. 1, the magnetic anisotropy at the high temperature is on the substrate surface (or on the substrate) as an auxiliary layer between the substrate and the recording layer. A magnetic layer having a magnetic characteristic that changes from a direction perpendicular to an in-plane direction to a film surface of a film body formed on the substrate. That is, the auxiliary layer has magnetic properties such that it exhibits in-plane magnetization in a high-temperature region formed by light irradiation or heating by a heat source, and exhibits perpendicular magnetization in a region other than the high-temperature region. A two-layer structure composed of an auxiliary layer having such magnetic properties and a recording layer having perpendicular magnetization exhibits perpendicular magnetization at room temperature. Therefore, the magnetic recording medium of the present invention is substantially equivalent to a single-layer perpendicular recording film in a low-temperature or room-temperature atmosphere, is resistant to thermal fluctuations, and has excellent information storage durability.

On the other hand, when recording and reproducing information, for example,
When the temperature of the auxiliary layer is increased by light irradiation or heating by a heater, the auxiliary layer exhibits in-plane magnetization. Therefore, the magnetic recording medium of the present invention including the two-layer structure including the auxiliary layer and the recording layer functions as a two-layer perpendicular magnetic disk when recording and reproducing information. Therefore, as described in the section of the related art, at the time of recording, it is possible to reliably record information even with a low magnetic field, and at the time of reproduction, a reproduced signal with low noise and large signal strength is obtained.

In the present invention, the magnetic material constituting the auxiliary layer is preferably a ferrimagnetic material such as a rare earth-transition metal alloy. Such a ferrimagnetic material can adjust its magnetic properties so that it exhibits in-plane magnetization in a high-temperature region and perpendicular magnetization in a region other than the high-temperature region. Examples of the ferrimagnetic material include at least one element of Fe, Co, and Ni, and Gd, Tb, Dy, Ho, and E.
A magnetic material containing at least one element of r, Tm, Yb, and Lu is preferable, and in particular, at least one element of Fe, Co, and Ni, and Gd, Tb,
A magnetic material containing at least one element of Dy, Ho and Lu is more preferable. More specifically, G
dFeCo, TbFeCo, DyFeCo, HoFeC
o and LuFeCo.

As described above, when the auxiliary layer is formed using a ferrimagnetic material, it is desirable that the compensation temperature is appropriately adjusted so that the magnetization does not face the in-plane direction at room temperature. More preferably, the compensation temperature is adjusted so as to be 0 ° C. or less.

In the magnetic recording medium according to the first aspect of the present invention, the thickness of the auxiliary layer is preferably 10 nm to 200 nm.
If the film thickness is less than 10 nm, it is difficult for a sufficient magnetic flux to pass through the auxiliary layer, so that the function as the auxiliary layer may be insufficient. If the thickness of the auxiliary layer is more than 200 nm, the smoothness of the surface of the magnetic recording medium may be impaired.

FIG. 3 is a graph showing the temperature dependence of the magnetic anisotropy of a GdFeCo film which is an example of the magnetic material forming the auxiliary layer. In the graph of FIG. 3, the vertical axis indicates anisotropic energy, and the horizontal axis indicates temperature. The anisotropic energy of the GdFeCo film is composed of a perpendicular magnetic anisotropy constant (energy) Ku generated based on the atomic arrangement of the film and a demagnetizing anisotropy energy 2πMs ² depending on the shape. As can be seen from the graph of FIG. 3, the behavior of the perpendicular magnetic anisotropy constant (energy) Ku and the demagnetizing anisotropy energy 2πMs ² depending on the shape differ with the temperature change. In general, when the temperature is increased from room temperature, the perpendicular magnetic anisotropy constant Ku monotonically decreases almost linearly and becomes zero at the Curie temperature. On the other hand, the demagnetizing anisotropy energy 2πMs ² once becomes zero at a temperature (compensation temperature) in the course of the low temperature to the Curie temperature Tc for the following reason, and is non-linear with respect to the temperature. The reason why the demagnetizing anisotropy energy 2πMs ² once becomes zero between the room temperature and the Curie temperature Tc is based on the fact that the GdFeCo film is a ferrimagnetic material. That is, since the magnetization directions of the Gd site and the FeCo site having different temperature dependencies are opposite to each other, they are expressed by the vector sum of both magnetizations at a temperature at which both magnetizations have the same magnitude. This is because the magnetization Ms of the film becomes zero.

Here, the effective anisotropic energy as a film
Gi Keff is the perpendicular magnetic anisotropy constant Ku and demagnetizing anisotropy
Energy 2πMs²Keff = Ku-2πMs²  It is represented by When Keff> 0, the film shows perpendicular magnetization.
However, when Keff <0, the film exhibits in-plane magnetization.

The temperature dependence of Ms and Ku can be controlled by changing the composition ratio of the material constituting the film. Therefore, when the composition of the material constituting the auxiliary layer is selected such that the compensation temperature is lower than room temperature as shown in FIG. An auxiliary layer showing magnetization is obtained. If a recording layer exhibiting perpendicular magnetization is provided on such an auxiliary layer, the two-layer structure composed of the auxiliary layer and the recording layer exhibits perpendicular magnetization and is effectively equivalent to a single-layer perpendicular recording film. When the temperature of the auxiliary layer is increased by light irradiation or heating by a heater or the like, the auxiliary layer exhibits in-plane magnetization, so that two-layer perpendicular recording consisting of a recording layer and an in-plane magnetic layer (auxiliary layer) is performed. Functions as a membrane.

As described above, the magnetic recording medium according to the first aspect of the present invention effectively functions as a perpendicular magnetic disk having a two-layer structure at the time of recording and reproducing information, and in the information holding state, that is, at room temperature. When left unattended, it effectively functions as a perpendicular magnetic disk having a single-layer structure, so that the problems described in the section of the prior art can be solved.

According to a second aspect of the present invention, on a substrate:
A magnetic recording medium comprising a recording layer having perpendicular magnetic anisotropy and heated during recording and reproduction of information, comprising an auxiliary layer between the recording layer and the substrate, wherein the auxiliary layer has an easy magnetization direction. The magnetic recording medium is characterized in that it has an in-plane direction and has magnetic properties such that the magnetization increases as the temperature increases from room temperature.

In the magnetic recording medium according to the second aspect of the present invention, the direction of easy magnetization is an in-plane direction as an auxiliary layer between the substrate and the recording layer, and as shown in FIG. A magnetic layer having sufficiently small magnetization and magnetic properties such that the magnetization increases with increasing temperature from room temperature is provided. That is, the auxiliary layer has magnetization in an in-plane direction in a high-temperature region formed by light irradiation or heating by a heat source, and has no magnetization in a region other than the high-temperature region, that is,
This is equivalent to a state where the auxiliary layer is not magnetically present.
Therefore, the magnetic recording medium according to the second aspect of the present invention also includes
Similarly to the magnetic recording medium of the first embodiment, at the time of recording and reproducing information, the magnetic recording medium substantially functions as a vertical magnetic disk having a two-layer structure. Since it functions as a perpendicular magnetic disk having a single-layer structure, the problems described in the section of the prior art can be solved.

In the magnetic recording medium according to the second aspect of the present invention, the magnetic material forming the auxiliary layer is preferably a ferrimagnetic material such as a rare earth-transition metal alloy. Such a ferrimagnetic material can adjust its magnetic properties such that the direction of easy magnetization indicates an in-plane direction from room temperature to a high temperature, the magnetization is small at room temperature, and the magnetization increases as the temperature increases.
Examples of the ferrimagnetic material include Fe, Co, and Ni.
At least one element of Gd, Tb, Dy,
At least one of Ho, Er, Tm, Yb and Lu
Magnetic materials containing various kinds of elements are preferred, and in particular, F
e, at least one element of Co and Ni;
A magnetic material containing at least one of r, Tm, Yb and Lu is preferred. More specifically, E
rFeCo, TmFeCo, YbFeCo and LuFe
Co or the like.

As shown in FIG. 5, when the auxiliary layer is formed by using such a magnetic material and selecting the composition so that the compensation temperature becomes room temperature, the saturation magnetization is sufficiently small near room temperature. This is almost equivalent to a state where the auxiliary layer does not exist. That is, at room temperature, it can be effectively a single-layer perpendicular recording film. On the other hand, when the magnetic recording medium is heated by laser light irradiation or a heater to raise the temperature of the auxiliary layer to, for example, around 200 ° C., the saturation magnetization of the auxiliary layer increases,
In addition, since it shows in-plane magnetization, a two-layer perpendicular recording film can be formed.

In the magnetic recording medium according to the second aspect of the present invention, the thickness of the auxiliary layer is preferably from 10 nm to 200 nm.
If the film thickness is smaller than 10 nm, it is difficult for a sufficient magnetic flux to pass through the auxiliary layer, so that the function as the auxiliary layer may be insufficient. If the thickness of the auxiliary layer is more than 200 nm, the smoothness of the surface of the magnetic recording medium may be impaired.

Since the magnetic recording media of the first and second embodiments are effectively single-layer perpendicular recording media at room temperature, they are resistant to the application of an unintended magnetic field from the outside and have a stable magnetization state. High in nature. In addition, when the temperature of the magnetic recording medium is increased by irradiating light or heating with a heater at the time of recording information, the two-layer structure including the recording layer and the auxiliary layer is effectively in-plane. A two-layer perpendicular recording film having an auxiliary layer is obtained. Therefore, recording with a low magnetic field becomes possible, and overwriting becomes easy. Also, at the time of reproduction, when the temperature of the auxiliary layer is raised by heating the medium by light irradiation or a heater or the like, and the auxiliary layer functions as an in-plane magnetic layer, the film surface generated in the recording layer having perpendicular magnetization is formed. Since the demagnetizing field in the vertical direction decreases, the leakage magnetic flux leaking from the recording layer to the outside increases. For this reason, when such a recording magnetic domain is reproduced using a reproducing magnetic head, the magnetic flux flowing into the magnetic head becomes large, and as a result, a large reproducing output is obtained.

In the magnetic recording media according to the first and second aspects of the present invention, the recording layer is preferably made of a metallic magnetic material having a polycrystalline structure. The recording layer is, for example, C
o, Cr, Pt, Ta, Nb, Ti and Si
Wherein the alloy preferably has ferromagnetic properties. Such an alloy has a large leakage magnetic field due to a large saturation magnetization, and can increase the obtained reproduction signal. Further, since the boundaries between the recording magnetic domains are clearly clarified, they are suitable for minute recording.

The thickness of the recording layer is preferably 5 nm to 40 nm. If the film thickness is smaller than 5 nm, the recording state may become unstable due to thermal fluctuation demagnetization.
If the thickness is larger than m, the crystal grains tend to be large and noise tends to increase.

The substrate of the magnetic recording medium of the present invention is preferably made of a material having a light transmitting property. Thus, when heating the medium by light irradiation, light can be incident from the substrate side. As such a substrate material, for example, a plastic material such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin, a reinforced glass, and a ceramic can be used.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the magnetic recording medium according to the present invention will be described, but the present invention is not limited thereto.

[0033]

Embodiment 1 FIG. 6 is a schematic sectional view of a magnetic recording medium according to the first embodiment of the present invention. The magnetic recording medium 100 has a structure in which an auxiliary layer 2, an underlayer 3, a recording layer 4, a protective layer 5, and a lubricant layer 6 are sequentially laminated on a substrate 1. Substrate 1
It is a disk-shaped tempered glass substrate having a diameter of 2.5 inches. On such a substrate, an auxiliary layer 2, an underlayer 3, and a recording layer 4
Were sequentially formed as follows by a DC magnetron sputtering method. The substrate temperature during sputtering is about 2
The temperature was set to 00 ° C. The target was a 6-inch target, and the discharge argon gas pressure was set to 3 × 10 ⁻³ Torr (about 399).
× 10 ^-3 Pa) and 1 kW of electric power was supplied.

Under these conditions, an amorphous ferrimagnetic material GdFeCo is formed on the substrate 1 as the auxiliary layer 2 to a thickness of 100 nm.
m. The compensation temperature was adjusted to −50 ° C. by adjusting the composition of GdFeCo. In the auxiliary layer 2 whose composition has been adjusted in this way, the anisotropic energy exhibits temperature dependence as shown in the graph of FIG. The direction of easy magnetization of the auxiliary layer 2 is a direction perpendicular to the film surface from the compensation temperature to 80 ° C. That is, in this temperature range, the auxiliary layer is a perpendicular magnetization layer. In the temperature range from 80 ° C. to the Curie temperature of 350 ° C., the easy magnetization direction is the in-plane direction, and the auxiliary layer 2 is an in-plane magnetization layer.

Next, Ti-10 at% is formed on the auxiliary layer 2.
An underlayer 3 made of Cr was formed to a thickness of 30 nm. The underlayer 3 is a layer for controlling the crystal orientation of the recording layer 4 so that the recording layer 4 has perpendicular magnetic anisotropy. Then
On the underlayer 3, a polycrystalline Co-19 at% Cr-10a
A recording layer 4 of t% Pt was formed to a thickness of 16 nm.

Next, a protective layer 5 made of SiN was formed on the recording layer 4 to a thickness of 10 nm. The RF sputtering method was used for forming the protective layer 5. In RF sputtering, the argon gas pressure for discharge is 3 × 10 ⁻³ Torr (about 399).
× 10 ⁻³ Pa), and the input power was 1 kW. Next, a lubricant layer 6 made of perfluoropolyether is formed on the protective layer 5 by dipping to a thickness of 0.5 nm to 5 nm.
Formed. Thus, the magnetic recording medium 100 having the laminated structure shown in FIG. 6 was manufactured.

Next, FIG. 7 shows a partial schematic configuration of a recording / reproducing apparatus according to the present invention. The recording / reproducing device includes a magnetic head 2
0, a laser light source 31, an optical fiber 32, and a lens 33. Magnetic recording medium 10 manufactured as described above
0 is incorporated in such a recording and reproducing apparatus. In FIG. 7, the magnetic head 20 includes a slider 21 made of ceramics, a read / write element 22, and a support spring 23 that supports the slider 21. At the time of recording and reproducing information, the laser light emitted from the laser light source 31 is guided to the lens 33 by the optical fiber 32, passes through the substrate 1 of the magnetic recording medium 100, and is focused on a predetermined area of the recording layer. . Thereby, a predetermined region of the magnetic recording medium 100 is locally heated by the laser beam.

Here, the read / write element 2 of the magnetic head 20
A description will be given of the positional relationship between No. 2 and a region where the laser light on the magnetic recording medium is focused. FIG. 8 conceptually shows a state where the bottom of the magnetic head 20 in FIG. 7 is viewed from the substrate side of the magnetic recording medium. A reproducing element for reproducing information is shown in FIG. 8 as a reproducing magnetoresistive element (MR element) 2.
22 and shields 223 and 2 sandwiching the MR element 222.
24. On the other hand, a recording element for recording information is an inductive recording element including a recording magnetic pole 221 and a shield 224. That is, the magnetic head 20 shown in FIG. 7 is a magnetic head in which an inductive recording element and an MR-type reproducing element are combined, and the same magnetic head that is currently generally used in a hard disk drive can be used. . In FIG. 8, the laser light focusing area is a circular area 34, the size of which is the width of the recording magnetic pole 221 of the magnetic head, the width of the MR element 222, and the width of the shield 22.
It is larger than the interval between the magnetic poles including 3, 224.

Using the recording / reproducing apparatus having the above configuration, information recording and reproduction were performed as follows. By irradiating the laser beam on the surface of the magnetic recording medium 100 by condensing it, a light irradiation area 34 is formed on the magnetic recording medium 100 as shown in FIG. In the light irradiation area 34, the temperature is about 20.
Increase to 0 ° C. Thereby, the high-temperature region in the light irradiation region of the auxiliary layer 2 exhibits in-plane magnetization as shown in FIG.
Therefore, the magnetic recording medium 100 is effectively a two-layer perpendicular recording medium. In this state, the recording magnetic pole 221 shown in FIG.
And a shield 224, a recording operation was performed by applying a recording magnetic field to the light irradiation area 34 formed on the magnetic recording medium 100.

When the light irradiation on the magnetic recording medium 100 is stopped, the temperature of the light irradiation area of the auxiliary layer decreases to near room temperature, so that the auxiliary layer becomes a perpendicular magnetization film. With the change in the easy magnetization direction, the magnetization direction of the auxiliary layer is aligned with the magnetization direction of the recording layer, as shown in a region where light is not irradiated in FIG. Therefore, the magnetic recording medium is effectively a single-layer perpendicular magnetic recording medium, and the stability of the magnetization state of the recording magnetic domain recorded in the recording layer is high. Such a magnetic recording medium has 40
High-density magnetic recording of gigabit / square inch (6.20 gigabit / square centimeter) or more is possible.

In the reproducing operation, light is focused on the surface of the magnetic recording medium to locally increase the temperature. As a result, the auxiliary layer of the magnetic recording medium becomes an in-plane magnetization layer, and the magnetic recording medium is effectively a two-layered perpendicular recording medium. Further, the leakage magnetic field generated from the recording layer was increased by the auxiliary layer of the in-plane magnetization, and information was reproduced by detecting the leakage magnetic field from the recording layer by the MR element 222.

FIG. 9 shows the recording / reproducing characteristics of the magnetic recording medium 100 manufactured in this embodiment. The graph of FIG. 9 shows the relationship between the output voltage and the recording current in the recording and reproducing operations. In the graph of FIG. 9, the output voltage indicates the output voltage detected by the reproducing element of the magnetic head, and the recording current indicates the current flowing to the recording element of the magnetic head. A conventional magnetic recording medium having no auxiliary layer ("No auxiliary layer" in FIG. 9)
), The recording current at which the output voltage is saturated is 2
0 mA, and the saturation value of the output voltage is 0.6 mV.
On the other hand, in the magnetic recording medium with the auxiliary layer manufactured in this example, the recording current at which the output voltage is saturated is 12 mA, and the saturation value of the output voltage is 1.0 mV. That is, in the magnetic recording medium of the present embodiment, the current value required for recording is 40% lower than that of the conventional magnetic recording medium, and recording is easy. The output voltage of the magnetic recording medium of the present embodiment is 66% higher than that of the magnetic recording medium of the present embodiment, and the reproducing performance is improved.

In this embodiment, GdF is used as the auxiliary layer.
Although an eCo layer was used, DyFeCo, Ho
The same effect was confirmed when FeCo or LuFeCo was used. The effect when TbFeCo was used as the auxiliary layer was not remarkable, but was effective.

[0044]

Embodiment 2 An embodiment of a magnetic recording medium according to the second aspect of the present invention will be described below. The magnetic recording medium manufactured in this example has the same laminated structure as the magnetic recording medium manufactured in Example 1 (see FIG. 6), and the amorphous magnetic material of the auxiliary layer 2 is made of ErFeCo. Except for Example 1,
It was produced in the same manner as described above. ErFeCo has an in-plane direction of easy magnetization from room temperature to high temperature. The compensation temperature of the auxiliary layer 2 was set to 40 ° C. by adjusting the composition of ErFeCo. As a result, as shown in FIG. 5, the magnetic characteristics of the auxiliary layer 2 have a very small saturation magnetization near room temperature, and the saturation magnetization increases as the temperature is increased.

This magnetic recording medium is also incorporated in the recording / reproducing apparatus shown in FIG. 7 to record and reproduce information as in the first embodiment. First, the recording operation will be described. At the time of recording, a laser beam is condensed and irradiated on the magnetic recording medium to locally heat the magnetic recording medium. In a region where the magnetic recording medium is irradiated with light, the medium temperature is about 2 ° C.
Increase to 00 ° C. Thereby, the saturation magnetization increases in the high temperature region of the light irradiation region of the auxiliary layer, and as shown in FIG. 2, a state in which the in-plane magnetization layer is formed effectively. Accordingly, the magnetic recording medium is effectively a two-layer perpendicular recording medium, and a magnetic path is formed by the recording layer, the auxiliary layer of in-plane magnetization, and the recording magnetic head, so that even if the magnetic field from the recording head is low, it is ensured. A recording magnetic domain can be formed in the recording layer. When the light irradiation is stopped, the temperature of the light-irradiated region of the auxiliary layer returns to around room temperature, so that the saturation magnetization of the auxiliary layer becomes very small. Therefore, magnetically, the existence of this auxiliary layer can be ignored,
As shown in the area where light is not irradiated in FIG. 2, the magnetic recording medium of this embodiment is effectively a single-layer perpendicular recording medium. Therefore, the stability of the magnetization state of the recording magnetic domain recorded in the recording layer is high. Similarly to the magnetic recording medium of the first embodiment, the magnetic recording medium of the present embodiment is 40 gigabits / bit.
High-density magnetic recording of square inches (6.20 gigabits / square centimeter) or more is possible.

In the reproducing operation, light is condensed and irradiated on the surface of the magnetic recording medium to locally heat a region of the magnetic recording medium where information is to be reproduced. As a result, a high-temperature region is formed in the light-irradiated region of the auxiliary layer of the magnetic recording medium. In such a high-temperature region, its saturation magnetization increases and exhibits in-plane magnetization. Therefore, during a reproducing operation, such a magnetic recording medium is effectively a two-layer perpendicular recording medium, and the leakage magnetic field from the recording layer is increased by the auxiliary layer having in-plane magnetization. Then, the leakage magnetic field from the recording layer is changed to the MR element 22 in FIG.
The information is reproduced by detecting at step 2.

The magnetic recording medium of the present embodiment in which recording and reproduction have been performed as described above has a current value required for recording reduced by 40% as compared with the conventional magnetic recording medium, and has a low magnetic field strength. But the information was recorded without fail. Regarding the output voltage, the magnetic recording medium of the present embodiment has a higher output voltage.
0% higher, and the reproduction signal increased. That is, the recording and reproducing performance of the magnetic recording medium of this example was improved.

In this embodiment, ErF is used as the auxiliary layer.
An eCo layer was used, but TmFeCo, Yb
It was confirmed that the same effect can be obtained when using FeCo or LuFeCo and setting the compensation temperature near room temperature. Further, it was also effective when a film using any one of Er, Tm, and Yb as the rare earth element and using Fe or Co as the transition metal was used as the auxiliary layer. Therefore,
Needless to say, it is also effective when the auxiliary layer is formed by combining these elements.

Although the magnetic recording medium of the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. In the first and second embodiments, the laser beam is incident from the substrate side to heat the magnetic recording medium to a desired temperature. However, the laser beam is applied from the opposite side of the magnetic recording medium from the substrate (the side on which the recording layer is formed). May be applied to heat the magnetic recording medium. In this case, for example, a magneto-optical head 120 as shown in FIG. 12 may be provided in the magnetic recording / reproducing apparatus. A magneto-optical head 120 shown in FIG. 12 includes a recording / reproducing head 122 having a recording magnetic pole and an MR element on a slider 121 for flying above a magnetic recording medium.
And a lens 123 for condensing light on the magnetic recording medium
Are magneto-optical heads on which are mounted. By flying the magneto-optical head 120 on the surface of the magnetic recording medium on which the recording film is formed, recording and reproduction on the magnetic recording medium can be performed.

The means for heating the magnetic recording medium is not limited to laser beam irradiation, and the magnetic recording medium may be heated using radiant heat from a heater or the like.

[0051]

Since the magnetic recording medium according to the first aspect of the present invention has an auxiliary layer between the substrate and the recording layer that exhibits in-plane magnetization at a high temperature, the magnetic recording medium has
Recording and overwriting can be reliably performed with a low magnetic field intensity, and the obtained reproduction output can be made equal to or larger than that of a magnetic recording medium for longitudinal recording when reproducing information. Further, since the auxiliary layer exhibits perpendicular magnetization at room temperature like the recording layer, it is hardly affected by an unintended external magnetic field when information is stored, and the stability of the recording magnetic domain can be improved.

Further, since the magnetic recording medium according to the second aspect of the present invention has an auxiliary layer exhibiting in-plane magnetization in a high temperature state, like the magnetic recording medium of the first aspect, when recording information, a low magnetic field is required. Recording and overwriting can be reliably performed with high intensity, and at the time of information reproduction, the obtained reproduction output can be made equal to or greater than that of a magnetic recording medium for longitudinal recording. Further, since the magnetization of the auxiliary layer is extremely small at room temperature, the recording magnetic domains formed in the recording layer are hardly affected by the magnetization of the auxiliary layer. Therefore, when information is stored, the stability of the recording magnetic domain recorded in the recording layer can be improved.

The magnetic recording apparatus provided with the magnetic recording media of the first and second embodiments can reliably record information with a low magnetic field, so that the power consumption of the magnetic head during recording can be reduced. . Further, since the magnetic recording device has excellent thermal stability and enables high-density magnetic recording, a magnetic recording device having a large capacity and high reliability can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the concept of a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the concept of a magnetic recording medium according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between magnetic anisotropy energy and temperature in a ferrimagnetic material.

FIG. 4 is a diagram showing a relationship between magnetic anisotropy energy and temperature of an auxiliary layer of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between saturation magnetization and temperature of an auxiliary layer of a magnetic recording medium according to a second embodiment of the present invention.

FIG. 6 is a diagram schematically showing a cross-sectional structure of a magnetic recording medium according to the present invention.

FIG. 7 is a diagram schematically illustrating a mechanism of the recording / reproducing apparatus according to the embodiment.

FIG. 8 is a conceptual diagram of the bottom of the magnetic head as viewed from the substrate side of the magnetic recording medium.

FIG. 9 is a diagram showing the recording / reproducing characteristics of the magnetic recording medium of Example 1, showing the relationship between the output voltage and the recording current in the recording and reproducing operations.

FIG. 10 is a diagram for explaining a state in which a magnetic path is closed by a recording layer and an in-plane magnetization layer.

FIG. 11 is a diagram showing a state in which a magnetic path is closed by a recording layer, an in-plane magnetization layer, and a magnetic head, and a magnetic circuit is formed.

FIG. 12 is a schematic configuration diagram of a magneto-optical head capable of heating a magnetic recording medium by irradiating a laser beam from a side opposite to a substrate of the magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Auxiliary layer 3 Underlayer 4 Recording layer 5 Protective layer 6 Lubricant layer 20 Magnetic head 21 Slider 22 Recording / reproducing element 31 Laser light source 33 Lens 34 Light irradiation area 100 Magnetic recording medium 221 Recording magnetic pole 222 MR element 223, 224 shield

Continuing from the front page (72) Inventor Fumiyoshi Kirino 1-1-88 Ushitora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd. (72) Koichiro Wakabayashi 1-188 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell shares In-company (72) Inventor Hiroyuki Awano 1-1-88 Ushitora, Ibaraki-shi, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Inventor Harumi Sakamoto 1-88 Ushitora, Ibaraki-shi, Osaka, Japan Inside Hitachi Maxell Co., Ltd. (72) Inventor Tomoko 1-88 Ushitora, Ibaraki-shi, Osaka, Japan Inside Hitachi Maxell, Inc. (72 ) Inventor Tsuyoshi Onuma 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell Co., Ltd. 5D006 BB01 BB02 BB07 BB08 CB07 FA09 5D091 AA10 CC11 CC30 DD03 HH04

Claims (14)

[Claims] 1. A magnetic recording medium which has a recording layer having perpendicular magnetic anisotropy on a substrate and is heated at the time of recording and reproducing information, comprising: an auxiliary layer between the recording layer and the substrate; The auxiliary layer,
A magnetic recording medium having magnetic properties such that the easy magnetization direction becomes a direction perpendicular to the substrate surface at room temperature and the easy magnetization direction becomes a direction parallel to the substrate surface in a high temperature region generated by heating. 2. A magnetic recording medium which has a recording layer having perpendicular magnetic anisotropy on a substrate and is heated at the time of recording and reproducing information, comprising an auxiliary layer between the recording layer and the substrate, The auxiliary layer,
A magnetic recording medium characterized in that the direction of easy magnetization is an in-plane direction and has magnetic properties such that magnetization increases as the temperature increases from room temperature. 3. The recording medium according to claim 1, wherein the recording layer is made of a metal magnetic material having a polycrystalline structure, and the auxiliary layer is made of a ferrimagnetic material having an amorphous structure. Magnetic recording medium. 4. The recording layer is made of an alloy mainly composed of Co, and the alloy is made of Cr, Pt, Ta, Nb, Ti.
4. The magnetic recording medium according to claim 3, comprising at least two elements selected from the group consisting of Si and Si, and exhibiting ferromagnetism. 5. The ferrimagnetic material comprises: at least one element selected from the group consisting of Fe, Co, and Ni;
The magnetic recording medium according to claim 3, further comprising at least one element selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. 6. The ferrimagnetic material comprises: at least one element selected from the group consisting of Fe, Co, and Ni;
6. The magnetic recording medium according to claim 5, comprising at least one element selected from the group consisting of Er, Tm, Yb and Lu. 7. The magnetic recording medium according to claim 6, wherein the compensation temperature of the ferrimagnetic material is near room temperature. 8. The ferrimagnetic material according to claim 1, wherein the ferrimagnetic material is Fe, C
6. The composition according to claim 5, comprising at least one element selected from the group consisting of o and Ni and at least one element selected from the group consisting of Gd, Tb, Dy, Ho and Lu. 3. The magnetic recording medium according to claim 1. 9. The magnetic recording medium according to claim 8, wherein the compensation temperature of the ferrimagnetic material is 0 ° C. or less. 10. The magnetic recording medium according to claim 1, further comprising a non-magnetic amorphous layer between the recording layer and the auxiliary layer. 11. The magnetic recording medium according to claim 1, wherein the substrate has optical transparency. 12. A magnetic recording apparatus comprising the magnetic recording medium according to claim 1. Description: 13. The apparatus according to claim 12, further comprising a light source for irradiating the magnetic recording medium with light to heat it.
3. The magnetic recording device according to claim 1. 14. The magnetic recording apparatus according to claim 13, further comprising a magneto-optical head having a lens for condensing light on the magnetic recording medium and a magnetic coil for applying a magnetic field. .