JP2000182232A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mitigate the temperature dependency of magnetization and to reduce the fluctuation of reproducing signal by providing at least >=2 layers of magnetic layers each having different magnetization, coercive force and the temperature dependency, forming each magnetic layer to have the magnetic compensation temperature of about room temperature and magnetically bonding the magnetic layers with each other. SOLUTION: A magnetic recording medium is provided with a substrate 1 composed of a material such as glass and the magnetic layer 2 formed on the substrate 1 to hold information. The magnetic layer 2 has a double layer structure composed of a 1st magnetic layer 3 having a temperature equal to or above the magnetic compensation temperature and a low temperature, at which the magnetization reaches maximum and a 2nd magnetic layer 4 having a temperature equal to or above the magnetic compensation temperature and a high temp., at which the magnetization reaches maximum. The 1st magnetic layer 3 is composed of a TbCo alloy film and the 2nd magnetic layer 4 is composed of a TbFeCo alloy film. In such a case, each of the TbCo alloy film and the TbFeCo alloy film is a magnetic body having the compensation point at room temperature. A rare earth-transition metal alloy film high in perpendicular magnetic anisotropy is preferably used as the magnetic body used for the 1st magnetic layer and the 2nd magnetic layer.

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 for use in a recording apparatus that performs recording and reproduction using a magnetic action while heating a recording medium.

[0002]

2. Description of the Related Art In the field of magnetic recording, the following recording / reproducing methods have been generally used. In this recording / reproducing method, a ferromagnetic material such as CoCrTa is used as a magnetic film formed on a magnetic recording medium. Then, at the time of recording, information is recorded by applying an external magnetic field using a recording magnetic head, and at the time of reproduction, the information is reproduced by detecting the direction of magnetization of a magnetic recording medium using a reproducing magnetic head.

Further, as a recording / reproducing method different from the above-mentioned method, the following recording / reproducing method has been proposed. In this recording / reproducing method, a ferromagnetic material such as CrO ₂ is used as a magnetic film formed on a magnetic recording medium. Then, at the time of recording, information is recorded by applying an external magnetic field using a recording magnetic head while irradiating a laser beam to reduce the coercive force,
At the time of reproduction, information is reproduced by detecting the magnetization direction of the magnetic recording medium by the reproducing head in the same manner as described above.

However, in these two recording / reproducing methods, the width of the recordable / reproducible track is limited by the width of the magnetic head, and there is a limit in increasing the recording density by reducing the track pitch.

Therefore, for example, Patent No. 2617025
The following recording / reproducing method is disclosed in Japanese Unexamined Patent Application Publication No. H11-64131. In this recording / reproducing method, a ferrimagnetic material having a compensation point near room temperature is used as a magnetic film formed on a magnetic recording medium. Then, at the time of recording, the temperature of the track to be recorded is raised, and information is recorded by applying an external magnetic field using a recording magnetic head. At the time of reproduction, the temperature of the track to be reproduced is raised, and Information is reproduced by detecting the direction of magnetization.

The magnetization of the magnetic recording medium used in this recording / reproducing method is substantially zero at room temperature, increases with an increase in temperature, reaches a maximum at a certain finite temperature, and returns to zero again at a temperature higher than the high Curie temperature. Has dependency. Further, the coercive force of this magnetic recording medium shows a large value at room temperature, monotonously decreases when the temperature rises from the room temperature state, and becomes zero at the Curie temperature.

Therefore, when the temperature of a track to be recorded on a magnetic recording medium is raised by using a heating means such as a laser beam, the coercive force is reduced only in the region where the temperature is raised, and the magnetic field applied by the recording magnetic head is lower than the applied magnetic field. Become smaller. By utilizing this, it is possible to perform recording only in an area heated by a laser beam or the like, that is, only in an area smaller than the width of the recording magnetic head.

[0008] Even during reproduction, when the temperature of a track to be recorded on the magnetic recording medium is raised, only the magnetization of the heated region increases. At this time, since the adjacent track remains substantially at room temperature, the leakage magnetic flux from the adjacent track becomes substantially zero. Therefore, signals from tracks narrower than the reproducing magnetic head can be detected.

According to the recording / reproducing method as described above, high-density recording / reproducing can be performed without being limited by the width of the recording / reproducing magnetic head.

[0010]

In such a recording / reproducing method, in order to keep the reproduction signal constant, the magnetization is almost zero at room temperature and the magnetization in the temperature rising region is constant, that is, when the temperature is higher than room temperature. It is required that the magnetization does not change near the temperature at which the magnetization becomes maximum. However, in the actually manufactured magnetic recording medium, the change in magnetization with respect to temperature is sharp near the temperature at which the magnetization is maximum, and it is difficult to make the reproduction signal constant.

[0011] Therefore, although an attempt was made to precisely control the temperature, an expensive heating device with a controller had to be used, and furthermore, a time for keeping the temperature constant was required, and reproduction was not performed at a high speed. There was a problem that it could not be done.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to increase the temperature of a track to be recorded during recording and to apply an external magnetic field from a recording magnetic head. By this, information is recorded, and at the time of reproduction, the temperature of the track to be reproduced is increased, and the temperature dependence of the magnetization is moderated in the magnetic recording medium in which reproduction is performed by the reproduction magnetic head, thereby increasing the temperature. An object of the present invention is to provide a magnetic recording medium in which reproduction signal fluctuations due to temperature fluctuations are small.

[0013]

In order to solve the above-mentioned problems, in a magnetic recording medium of the present invention, at the time of recording, a track to be recorded is heated, and an external magnetic field is applied from a recording magnetic head. Information is recorded by
At the time of reproduction, a track to be reproduced is heated, and a magnetic recording medium on which reproduction is performed by a reproduction magnetic head is provided with at least two or more magnetic layers having different magnetization, coercive force, and temperature characteristics. The magnetic compensation temperature of the magnetic layer is approximately room temperature, and the magnetic layers are magnetically coupled to each other.

Conventionally, as a magnetic layer of a magnetic recording medium, 1
A layered structure was used. In such a magnetic layer having a one-layer structure, the temperature dependence of the magnetization of a rare earth element usually used as a constituent component is sharp, so that the magnetization is greatly increased by a temperature change when the temperature is raised. Was fluctuating. In this regard, according to the above configuration, at least two magnets having different magnetization, coercive force, and temperature characteristics are provided.
Since the magnetic layer includes at least two magnetic layers and the magnetic layers are magnetically coupled to each other, the temperature dependence of magnetization can be moderated as a whole of the magnetic layer. Also, by appropriately selecting the type of each magnetic layer, it is possible to provide a magnetic recording medium having the optimum magnetization and coercive force and its temperature characteristics for recording and reproduction.

The above-mentioned magnetic coupling means magnetostatic coupling or exchange coupling. Magnetostatic coupling means coupling coupled by Coulomb force, and exchange coupling is quantum mechanically atomic. It means a tightly bound bond in the size order.

In the magnetic recording medium of the present invention, it is preferable that each of the magnetic layers has a maximum magnetization temperature different from each other at a magnetic compensation temperature or higher.

According to the above arrangement, two or more magnetic layers having different maximum magnetization temperatures at or above the magnetic compensation temperature are magnetically coupled to each other. The magnetic recording medium having a moderate temperature characteristic can be provided. When reproduction is performed using such a magnetic recording medium having a moderate temperature characteristic near the maximum value of the magnetization, even if there is some temperature fluctuation,
A reproduced signal having a stable S / N (Signal-to-Noise ratio) can be obtained.

The above maximum magnetization means the magnitude of the magnetization which becomes maximum above the magnetic compensation temperature, and the maximum magnetization temperature means the temperature at that time.

The magnetic recording medium of the present invention is further characterized in that the difference between the maximum magnetization temperatures of the magnetic layers is 5 ° C. or more and 80 ° C. or less.

When the difference between the maximum magnetization temperatures of the respective magnetic layers is 80 ° C. or higher at a temperature higher than the magnetic compensation temperature, the maximum magnetization is reduced by about 80% as compared with a case where the magnetic layer is composed of one layer, for example. , Which is not preferable as a characteristic of the magnetic recording medium. Therefore, if the difference between the maximum magnetization temperatures of the respective magnetic layers is set to 80 ° C. or less as in the above configuration, the temperature distribution near the maximum value of the magnetization becomes gentle and a sufficiently large reproduction signal can be obtained. A magnetic recording medium can be provided. By setting the temperature difference of the maximum magnetization to 5 ° C. or more, a gradual temperature change can be more effectively extracted.

In the magnetic recording medium of the present invention, it is preferable that the magnetic layer is made of an amorphous alloy composed of at least one of Fe and Co and a rare earth element.

In general, it is known that an alloy of a 3d transition metal and a rare earth element has a large perpendicular magnetic anisotropy.
Therefore, as in the above configuration, the 3d
By using an amorphous alloy composed of at least one of transition metals Fe and Co and a rare earth element, a magnetic layer having high perpendicular magnetic anisotropy can be obtained.

Thus, a magnetic recording medium suitable for perpendicular magnetic recording capable of high-density recording can be realized.

In the magnetic recording medium of the present invention, the rare earth element preferably contains at least one of Tb, Dy, and Gd.

In general, it is known that an alloy of a 3d transition metal and a heavy rare earth element has a large perpendicular magnetic anisotropy. Therefore, as in the above configuration, for the magnetic layer,
By using an amorphous alloy containing at least one of Fe and Co, which are 3d transition metals, and at least one of Tb, Dy, and Gd, which are heavy rare earth elements, the perpendicular magnetic anisotropy can be further improved. A high magnetic layer can be obtained.

Thus, a magnetic recording medium suitable for perpendicular magnetic recording capable of high-density recording can be realized.

In the magnetic recording medium of the present invention, it is preferable that the magnetic layer is made of the same alloy having a different composition ratio.

In general, the rare earth constituting the magnetic layer
Transition metal alloy films can continuously change the temperature characteristics of magnetic properties, specifically, the temperature dependence of magnetization and coercive force, by continuously changing the composition of rare earth elements and transition metal elements. . Therefore, by using the above-described configuration, it is only necessary to change each target input power when forming the same alloy-based film having a different composition ratio, and it is not necessary to switch targets.

Thus, it is possible to easily form a multilayer film having different maximum temperatures of magnetization.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view showing a schematic configuration of a magnetic recording medium according to the present embodiment. This magnetic recording medium includes a substrate 1 made of a material such as glass, and a magnetic layer 2 formed on the substrate 1 and holding information. The magnetic layer 2 is composed of a first magnetic layer 3 having a low temperature at which the magnetization is maximum above the magnetic compensation temperature and a second magnetic layer 4 having a high temperature at which the magnetization becomes maximum above the magnetic compensation temperature. Has a two-layer structure. The first magnetic layer 3 is made of a TbCo alloy film, and the second magnetic layer 4 is made of a TbFeCo alloy film. Note that the TbCo alloy film and the TbFeCo alloy film
It is a magnetic material having a compensation point at room temperature.

Here, the magnetic material used for the first magnetic layer 3 and the second magnetic layer 4 will be described. Normally, magnetic materials having a compensation point at room temperature include rare earth-transition metal alloy films, iron garnet films, and the like. Among them, as a magnetic material suitable for perpendicular magnetic recording capable of high-density recording, a rare earth-transition metal alloy film having high perpendicular magnetic anisotropy is used for the first magnetic layer 3 and the second magnetic layer 4. It is preferable as the magnetic material used.

Further, in this rare earth-transition metal alloy film, one or more rare earth elements of Dy and Tb are contained,
An alloy film containing at least one of Fe and Co as a transition metal element is preferable. As such an alloy film, for example, DyF
e, binary alloy films of DyCo, TbFe, TbCo, etc.,
DyFeCo, TbFeCo, DyTbCo, GdTb
Ternary alloy films such as Co, DyTbFeCo, GdTbF
Examples include a quaternary alloy film such as eCo and GdDyFeCo. However, the material is not limited thereto, and any material composition may be used as long as the magnetic material satisfies the following first to fourth conditions. It does not matter.

First, as a first condition, in the magnetic material used for the above-mentioned first magnetic layer 3 and second magnetic layer 4, it is necessary that the total magnetization becomes almost zero near room temperature. Since the total magnetization becomes almost zero near room temperature, the leakage magnetic field from the region where the temperature is not raised can be made almost zero. That is, it is possible to reproduce only the signal from the region where the temperature is raised, and it is possible to improve the S / N.

As a second condition, the magnetic material used for the first magnetic layer 3 and the second magnetic layer 4 needs to have a sufficiently large coercive force at room temperature. Specifically, the coercive force at room temperature is preferably larger than the recording magnetic field of the recording head. Further, in order to improve the stability against disturbance, the coercive force at room temperature must be 5%.
More preferably, it is KOe or more.

As a third condition, the magnetic material used for the first magnetic layer 3 and the second magnetic layer 4 needs to have a large maximum value of magnetization at room temperature or higher. In order to obtain a sufficient signal strength, the maximum value of the magnetization is 5
It is preferably at least 0 emu / cc. In order for the temperature of the magnetic material to be uniformly increased by heating with a semiconductor laser, the temperature at which the magnetization becomes maximum is 100 ° C. to 250 ° C.
It is preferred that

As a fourth condition, the magnetic material used for the first magnetic layer 3 and the second magnetic layer 4 has a coercive force of less than the magnetic field of the recording magnetic head at a finite temperature equal to or higher than room temperature. It is necessary to become. Specifically, when the temperature of the magnetic material is raised by a semiconductor laser, it is preferable that the coercive force at the temperature of 200 ° C. or higher during recording be equal to or less than the magnetic field of the recording magnetic head.

As will be described later in detail, the temperature characteristics of magnetization can be made closer to a desired shape by magnetically coupling the first magnetic layer 3 and the second magnetic layer 4. Here, magnetic coupling means magnetostatic coupling or exchange coupling, magnetostatic coupling means coupling coupled by Coulomb force, and exchange coupling is quantum mechanically in the order of the atomic size. A tightly bound bond is meant.

In this embodiment, the first magnetic layer 3 and the second
The difference in magnetic compensation temperature from the magnetic layer 4 is about 50 ° C. Further, in the present embodiment, as shown in FIG. 1, the first magnetic layer 3 is formed on the substrate 1 and the second magnetic layer 4 is further laminated thereon, but the present invention is not limited to this. Instead, the configuration may be such that the second magnetic layer 4 is formed on the substrate 1 and the first magnetic layer 3 is further laminated thereon.

Here, the procedure for manufacturing the above magnetic recording medium will be described. First, in order to form the first magnetic layer 3 and the second magnetic layer 4 in a continuous process, a target made of each element of Tb, Fe, and Co is arranged in a chamber of a sputtering apparatus. The target made of each element is provided with a shutter corresponding to the target. By opening and closing each shutter, a film having a desired component is formed.

Then, the above-mentioned substrate 1 is mounted on a substrate holder, cooled with water, and the inside of the chamber is evacuated to 2 × 10 ⁻⁴ Pa or less, and then the pressure is adjusted to 0.7 Pa by introducing Ar gas. Then, magnetron sputtering is performed while rotating the substrate 1 at a speed of 60 rpm using Tb, Fe and, if necessary, Co as targets, to obtain the first magnetic layer 3.
Then, the second magnetic layer 4 is formed continuously.

When the first magnetic layer 3 is formed, the power applied to each target is 158 W for the RF power of the Tb target and 300 W for the DC power of the Co target.
And When the second magnetic layer 4 is formed, the RF power of the Tb target is 266 W and the DC power of the Fe target is 126
The DC power of the W and Co targets was set to 300 W.

When the first magnetic layer 3 and the second magnetic layer 4 are formed under the above conditions, the composition of the first magnetic layer 3 is Tb
₂₃ Co ₇₇ and the composition of the second magnetic layer 4 is Tb ₂₆ Fe ₂₂ C
o ₅₂ . In addition, each number represents an atom at%. The first magnetic layer 3 and the second magnetic layer 4 were formed so as to have a thickness of 100 nm.

As a comparative example, a magnetic recording medium in which a TbCo single layer film having the same composition as that of the first magnetic layer 3 was formed on the substrate 1, and the second magnetic layer 4 was formed on the substrate 1.
And a magnetic recording medium on which a TbFeCo single layer film having the same composition as in Example 1 was formed.

FIG. 2 shows a magnetic recording medium according to this embodiment,
That is, the magnetic recording medium in which TbCo and TbFeCo are laminated on the substrate 1 and the magnetic recording medium of Comparative Example 2
Types of magnetic recording media, that is, a magnetic recording medium having a TbCo single layer film formed on a substrate 1 and a TbFeC
6 is a graph showing temperature characteristics of magnetization in a magnetic recording medium having a single-layer film formed thereon. In FIG. 2, the horizontal axis indicates temperature, and the vertical axis indicates a value obtained by normalizing the magnetization by the maximum magnetization at or above the magnetic compensation temperature. Also, the graph of the magnetic recording medium on which the laminated film of TbCo and TbFeCo is formed is indicated by a thick line, the graph of the magnetic recording medium on which the TbCo single layer film is formed is indicated by a broken line, and the graph of TbFeC is shown.
o Graph of the magnetic recording medium with a single-layer film
Each is shown.

As shown in FIG. 2, in the magnetic recording medium according to the present embodiment, the temperature dependence of the magnetization is relaxed near the maximum value of the magnetization as compared with the magnetic recording media according to the two comparative examples. You can see that there is.

When reproduction is performed using the magnetic recording medium according to this embodiment, the change in reproduction intensity can be suppressed to a range of about 10% even with a temperature change of about 50 ° C.
On the other hand, when reproduction is performed using the magnetic recording media in the two comparative examples, a change in reproduction intensity fluctuates by about 10% with a temperature change of about 35 ° C. That is, according to the magnetic recording medium of the present embodiment, when reproducing, the temperature of the reproducing area on the magnetic recording medium fluctuates due to disturbance such as a change in laser power applied to the magnetic recording medium or a change in room temperature. However, a more stable reproduction signal can be obtained.

Next, the temperature at which the magnetizations of the first magnetic layer 3 and the second magnetic layer 4 were maximized was changed so that the reproduction intensity did not fluctuate over a wider temperature range. Specifically, the maximum value of Mr was changed by changing the composition ratio of Fe and Co in the second magnetic layer 4. The Tb composition ratio was adjusted so that room temperature was the compensation point temperature.

As a result, if the temperature at which the respective magnetizations become maximum differs between the first magnetic layer 3 and the second magnetic layer 4 by 80 ° C. or more, the maximum value of the magnetization of the magnetic layer 2 becomes larger. Was found to be reduced to 80% or less as compared with the configuration composed of a single layer. In this case, since the magnitude of the reproduced signal is reduced, it has been found that it is not suitable as a magnetic recording medium. Further, in order to extract a gradual temperature change, it was more effective to set the temperature difference of the maximum magnetization to at least 5 ° C. or more.

Therefore, in order for the temperature distribution near the maximum value of the magnetization to be gentle and to obtain a sufficiently large reproduction signal, the first magnetic layer 3 and the second magnetic layer 4
And the temperature difference at which each magnetization is maximum is 5 ° C.
It is preferable that the temperature is not less than 80 ° C.

In this embodiment, the thickness of the entire magnetic layer 2 is set to 200 nm, but the present invention is not limited to this. However, in order to record information uniformly on the magnetic layer 2 by the recording head, it is preferable to set the thickness of the entire magnetic layer 2 to 300 nm or less.

In the present embodiment, the magnetic layer 2 has a two-layer structure including the first magnetic layer 3 and the second magnetic layer 4, but the present invention is not limited to this. Further, it is possible to adopt a structure of three or more layers in which magnetic layers are stacked. In this case, the temperature change near the maximum value of the whole magnetization can be designed more gently.

In the present embodiment, the first magnetic layer 3 and the second magnetic layer 4 are formed by the sputtering method. However, the present invention is not limited to this.
For example, film formation can be performed by a technique such as molecular beam epitaxy, vacuum evaporation, or ion beam evaporation.

In this embodiment, in the sputtering for forming the first magnetic layer 3 and the second magnetic layer 4,
Although a target is provided independently for each metal component, the present invention is not limited to this. For example, a method using a target formed as an alloy, or a composite in which, among components of a metal to be formed into a film, an evaporation source made of a smaller metal is placed on an evaporation source made of a metal having a larger content. Sputtering can be performed by a method using a target or the like.

The rare earth-transition metal alloy film is formed by continuously changing the composition of the rare earth element and the transition metal element so that the temperature characteristics of the magnetic characteristics, specifically, the temperature dependence of the magnetization and the coercive force are changed. Can be continuously changed. For this reason,
The same multi-component system, preferably TbFeCo, DyFeC
o, TbDyFeCo, GdTbFeCo, GdDyF
At the time of eCo film formation, it is possible to easily form a multilayer film having different maximum temperatures of magnetization only by changing the target input power without switching targets.

The magnetic recording medium according to the present embodiment
Although the magnetic layer 2 is provided only on one side of the substrate 1, the magnetic layer 2 may be provided on both sides of the substrate 1 in order to increase the recording capacity per magnetic recording medium. Absent.

The magnetic recording medium according to the present embodiment
Although the magnetic layer 2 is provided on the upper surface of the substrate 1,
If necessary, an antioxidant film and a soft magnetic film may be provided before the magnetic layer 2 is laminated. As a material constituting the oxidation preventing film, for example, AlN or SiN
The magnetic layer 2 from the substrate 1 side
Any material can be used as long as the material can prevent oxidation of the material. Further, the soft magnetic film has a function of efficiently entering the lines of magnetic force into the magnetic head when the magnetic head is constituted by a single-pole head. The soft magnetic film may be made of, for example, permalloy, but any material may be used as long as it is an in-plane magnetized film and exhibits soft magnetism.

In the magnetic recording medium according to the present embodiment, a protective layer and a lubricating layer are further provided on the magnetic layer 2 in order to improve impact resistance, abrasion resistance, and corrosion resistance with the magnetic head. It may be provided. As a material constituting the protective layer, any material may be used as long as the material has excellent wear resistance, impact resistance, and corrosion resistance. Examples of a material forming the protective layer include an amorphous carbon film, a diamond-like carbon film, a carbon nitride film, and a hydrogenated carbon film. Any material may be used for the lubricating layer as long as it reduces the frictional force between the magnetic head and the magnetic recording medium.
For example, a fluorine-based material such as perfluoropolyether may be used.

In the magnetic recording medium according to the present embodiment, a glass substrate is used as a material for forming the substrate 1. However, the present invention is not limited to this. For example, a sapphire substrate, an aluminum substrate, polycarbonate, PMMA ( Polymethyl methacrylate), a glass 2p substrate (a substrate on which a photocurable resin layer having irregularities such as grooves and pits formed on a glass substrate by a photopolymerization method), a ceramic, a silicon wafer, or the like may be used.

[0060]

As described above, in the magnetic recording medium according to the present invention, at the time of recording, the temperature of the track to be recorded is increased, and information is recorded by applying an external magnetic field from the recording magnetic head. At the time of reproduction, a track to be reproduced is heated, and a magnetic recording medium to be reproduced by a reproduction magnetic head is provided with at least two or more magnetic layers having different magnetization, coercive force, and temperature characteristics. The magnetic compensation temperature of each of the magnetic layers is approximately room temperature,
The magnetic layers are magnetically coupled to each other.

As a result, there is an effect that the temperature dependence of the magnetization can be moderated as a whole of the magnetic layer. In addition, by appropriately selecting the type of each magnetic layer, it is possible to provide a magnetic recording medium having the optimum magnetization and coercive force and the temperature characteristics thereof for recording and reproduction. To play.

In the magnetic recording medium according to the present invention, it is preferable that each of the magnetic layers has a different maximum magnetization temperature from the magnetic compensation temperature.

Thus, by magnetically coupling two or more magnetic layers having different maximum magnetization temperatures at or above the magnetic compensation temperature, it is difficult to realize a single layer. There is an effect that a gentle magnetic recording medium can be provided. When reproduction is performed using such a magnetic recording medium having a moderate temperature characteristic in the vicinity of the maximum value of magnetization, even if there is some temperature fluctuation, the reproduction has a stable signal-to-noise ratio (S / N). This produces an effect that a signal can be obtained.

In the magnetic recording medium according to the present invention, the difference between the maximum magnetization temperatures of the magnetic layers may be 5 ° C. or more and 80 ° C.
The following configuration is preferable.

As a result, the temperature distribution near the maximum value of the magnetization is moderated, and a magnetic recording medium capable of obtaining a sufficiently large reproduction signal can be provided.

In the magnetic recording medium according to the present invention, it is preferable that the magnetic layer has an amorphous alloy composed of at least one of Fe and Co and a rare earth element.

Therefore, a magnetic layer having high perpendicular magnetic anisotropy can be obtained. As a result, it is possible to realize a magnetic recording medium suitable for perpendicular magnetic recording capable of high-density recording.

The magnetic recording medium of the present invention preferably has a configuration in which the rare earth element contains at least one of Tb, Dy, and Gd.

Therefore, a magnetic layer having higher perpendicular magnetic anisotropy can be obtained. Thereby, there is an effect that a magnetic recording medium suitable for perpendicular magnetic recording capable of high-density recording can be realized.

In the magnetic recording medium of the present invention, it is preferable that the magnetic layers have the same alloy system having different composition ratios.

Therefore, when forming the magnetic layer, it is only necessary to change the power applied to each target, and it is not necessary to switch targets. This has an effect that a multilayer film having different magnetization maximum temperatures can be easily formed.

[Brief description of the drawings]

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

FIG. 2 shows the magnetic recording medium and 2 as a comparative example.
4 is a graph showing temperature characteristics of magnetization in various types of magnetic recording media.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 magnetic layer 3 first magnetic layer 4 second magnetic layer

Claims (6)

[Claims] At the time of recording, a track to be recorded is heated, and information is recorded by applying an external magnetic field from a recording magnetic head. At the time of reproduction, information is recorded.
A magnetic recording medium in which a track to be reproduced is heated and reproduction is performed by a reproduction magnetic head, comprising at least two or more magnetic layers having different magnetization, coercive force, and temperature characteristics. A magnetic recording medium having a compensation temperature of about room temperature and magnetic layers magnetically coupled to each other. 2. The magnetic recording medium according to claim 1, wherein each of said magnetic layers has a maximum magnetization temperature different from each other above a magnetic compensation temperature. 3. The difference between the maximum magnetization temperatures of the respective magnetic layers is as follows:
3. The magnetic recording medium according to claim 2, wherein the temperature is 5 ° C. or more and 80 ° C. or less. 4. The magnetic layer according to claim 1, wherein the magnetic layer is made of an amorphous alloy composed of at least one of Fe and Co and a rare earth element.
14. A magnetic recording medium according to any one of the preceding claims. 5. The method according to claim 1, wherein the rare earth elements are Tb, Dy, and G.
The magnetic recording medium according to claim 4, comprising at least one of d. 6. The magnetic recording medium according to claim 4, wherein the magnetic layers are made of the same alloy having a different composition ratio.