JP2828092B2 - Thermomagnetic recording medium and thermomagnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to a thermomagnetic recording medium,
It relates to a thermomagnetic recording method. [0002] 2. Description of the Related Art Information bits (magnetism) are generated by magneto-optical interaction.
Information is recorded on the recording medium from which the
In the thermomagnetic recording method, the magnetic thin film by the perpendicular magnetization film is used.
For a recording medium with a film, the direction of magnetization is perpendicular to the film surface.
Perform a so-called initialization that aligns in one straight direction in advance,
A bit with perpendicular magnetization opposite to this magnetization direction is
By forming by local heating such as the light irradiation, 2
It records the coded information. In this thermomagnetic recording method, information is written
Prior to replacement, erase the recorded information (the first
Process), that is, time is required for erasure.
However, recording at a high transfer rate cannot be realized. Against this
However, such an independent erasure process does not require time.
-Various recording methods using the bar light method have been proposed.
You. Among the overwrite type thermomagnetic recording methods,
The methods that have been envisaged are, for example,
The magnetic field modulation method and the erasing head in addition to the recording head
A two-head method is known. External magnetic field modulation and
Is disclosed, for example, in Japanese Patent Application No. 60-48806.
Amorphous with easy magnetic domains perpendicular to the film surface
Of heating beam to porous ferrimagnetic thin film recording medium
The magnetic field of the polarity corresponding to the state of the input digital signal current
Recording is performed by applying a field. [0004] However, as described above,
High-speed recording with high information transfer rate by simple external magnetic field modulation method
For example, if you try to record
Magnets are required, making it difficult to manufacture such electromagnets.
Even if it can be manufactured, power consumption and heat generation are large and practical
There is a problem that it is not a target. In the two-head method,
Requires extra heads, separates the two heads
And the burden on the drive system is large,
It has problems such as poor economy and not suitable for mass production.
You. [0005] The present invention relates to a heating temperature of a medium by laser light or the like.
Easy rewriting, ie, over
-Lighting was enabled to solve the above-mentioned problems.
Things. [0006] The present applicant has first solved such a problem.
A thermomagnetic recording method to be solved is disclosed in Japanese Patent Application No. 61-1949.
No. 61 and Japanese Patent Application No. 61-194962.
Provided. The thermomagnetic recording methods proposed in these applications are
A laminated structure of first and second rare earth-transition metal magnetic thin films
Application of a required first external magnetic field using a thermomagnetic recording medium
Is below the Curie temperature T of the first magnetic thin film._C1Over
The first magnetic thin film does not cause reversal of the sublattice magnetization.
Temperature T₁A first heating state of heating to a temperature T_C1Above
And sufficient to reverse the sublattice magnetization of the second magnetic thin film
Second temperature T_TwoAnd the second heating state for heating
Switching modulation according to information to be tried, for example, "0", "1"
Then, during the cooling process, the exchange coupling force of the first and second magnetic thin films
The direction of the sublattice magnetization of the first magnetic thin film to the second magnetic thin film.
For example, "0",
A recording bit (magnetic domain) of "1" is formed on the first magnetic thin film.
And a second external magnetic field or a second magnetic field.
The compensating temperature is changed from room temperature to the second temperature T._Two
At room temperature by choosing to be between
The sub-lattice magnetization of the second magnetic thin film is caused only by the external magnetic field of
Get overwrite enabled state by inverting
Is to do so. In this case, a special process (time) for erasure is performed.
High transfer rate without the need for
Or the two-head method described above, or an external magnetic field modulation method
Various problems in the case of formulas can be solved. In the present invention, these Japanese Patent Application Nos.
No. 04961 and Japanese Patent Application No. 61-194962
Taking advantage of the thermomagnetic recording method according to the application,
Omission or reduction of the above-mentioned second magnetic field in this case
, And therefore, the equipment that implements the recording method,
Thermomagnetic recording medium that can be simplified
And a thermomagnetic recording method. [0009] SUMMARY OF THE INVENTION Thermomagnetic recording according to the present invention
The medium includes first, second, and third magnetic thin films, and second and second magnetic thin films.
A second and a third magnetic thin film provided between the third magnetic thin film
Fourth magnetic thin film having a Curie temperature lower than the Curie temperature of
And The fourth magnetic thin film is the fourth magnetic thin film.
At temperatures lower than the Curie temperature of the film, the second and third magnetic
Exchange coupling force for indirectly exchange coupling thin films is maintained
Above the Curie temperature of the fourth magnetic thin film.
The exchange coupling force of the third magnetic thin film is cut off.
You. A thermomagnetic recording method according to the present invention is a
First, second and third magnetic thin films, and second and third magnetic thin films
Curie of the second and third magnetic thin films provided between the films
And a fourth magnetic thin film having a Curie temperature lower than the temperature.
Information to be recorded on a thermomagnetic recording medium
Modulates the power of the laser light in the
Temperature lower than the Lee temperature and higher than the Curie temperature
Exchange coupling between the second and third magnetic thin films by switching the temperature
Information is recorded by partially interrupting the force. In the method of the present invention described above, recording is to be performed.
The laser beam is modulated according to the information, and the key of the fourth magnetic thin film is modulated.
Temperature below the Curie temperature or above this Curie temperature
Information is given only by giving the first and second heating states (heating temperature).
Information is recorded and overwriting is possible.
You. In the present invention, the second and third magnetic thin films 2 and
Magnetic coupling between the second and third magnetic thin films between
Fourth magnet with a function to switch on and off
By adopting a structure and a method in which a thin film is provided,
And record information reliably at the second heating temperature.
You. [0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A Thermomagnetic Recording Medium According to the Present Invention
In this configuration, as shown in FIG.
1, the second and third magnetic thin films 1, 2 and 3 are laminated
In the present invention, FIG.
As shown in the schematic sectional view, a glass plate, an acrylic plate, etc.
A protective film or an interference film is formed on one surface of the light transmitting substrate 5.
, Second and third magnetic layers through a transparent dielectric film 6
The thin films 1, 2 and 3 and the second and third magnetic thin films
A fourth magnetic thin film 4 interposed between the films 2 and 3 is formed.
Configuration. Each of the first to third magnetic thin films is a rare earth element.
-Constituted by a perpendicular magnetization film of a transition metal. And this
A dielectric film is formed on the magnetic layer formed by laminating the magnetic thin films 1 to 4.
A protective film 7 is formed by deposition. However, this
In the thermomagnetic recording medium 10, the dielectric film 6 and the protective film
7 can also be omitted. This thermomagnetic recording medium 10
Between adjacent magnetic thin films 1, 2, 4, and 3
It is magnetically coupled by exchange coupling force. In the above configuration, each of the dielectric films 6,
The fourth magnetic thin films 1 to 4 and the protective film 7 are deposited,
Alternatively, it can be formed by sputtering or the like. The magnetic thin films 1 to 4 are made of various magnetic materials.
Although it is conceivable to configure by Nd, Sm,
One kind of rare earth metal (RE) such as Gd, Tb, Dy, Ho
Class or two or more types with x = 10 to 40 atomic%, and C
transition metals such as r, Mn, Fe, Co, Ni, and Cu (T
One or two or more of M) is 1-x = 90 to 60
Amorphous alloy RE composed of_XTM_1-XBy
Can be configured. In this case, add a small amount of other elements.
It may be added. This RE-TM amorphous alloy magnetic material
Except when RE is Nd or Sm, R
Make the magnetic moment of E and the magnetic moment of TM antiparallel
And, as a result, exhibit so-called ferrimagnetism,
The net magnetization is the difference between these RE and TM sublattice magnetizations.
(When considering the positive / negative depending on the direction of magnetization,
(Sum of magnetization). Rare earth metal (RE) is Nd, Sm
If it is composed of any one or a mixture of them,
The magnetic moment of RE and the magnetic moment of TM are parallel
Combine to exhibit the so-called ferromagnetic properties, in which case the positive
The taste magnetization is the sum of the RE and TM sublattice magnetizations. For such a thermomagnetic recording medium 10,
External magnetic field H almost perpendicular to the film surface_exUnder the application of
Curie temperature T of magnetic thin film 1_c1The second magnetic field
The direction of the sublattice magnetization of the transition metal of the conductive thin film 2 to a predetermined direction
(Hereinafter, this direction is referred to as a positive direction)
T₁And the external magnetic field H_exof
Under the applied voltage, the Curie temperature T_c1The second magnetic thin film
The direction of the sublattice magnetization of the transition metal of the film 2 is determined by the external magnetic field H_exTo
Therefore, the direction is opposite to the above-described forward direction (hereinafter, this direction is referred to as the reverse direction).
Direction T)_Two Second heating by
Give the state and. Then, the first and second temperatures T
₁And T_Two From the first and second heating states
During the cooling process, the sublattice magnetization in the third magnetic thin film 3 is increased.
Of the second magnetic thin film 2 without being reversed.
Is the same as the sublattice magnetization of the third magnetic thin film 3.
Orientation, that is, the same state as the unrecorded state. The first and second heating states are thermomagnetic
Attempts to record the intensity of the laser beam on the recording medium 10
This can be done by modulating according to the information. Thus, the first and second heating states are obtained.
Of the laser beam for modulation according to the information to be recorded
Only in the first magnetic thin film 1
By the positive part and the reverse part of the lattice magnetization,
For example, binary information of "0" and "1" is recorded. At this time, as described above, the third
To reverse the direction of the sublattice magnetization in the magnetic thin film 3 of FIG.
The sub-lattice magnetization of the second magnetic thin film 2 is
This is because the orientation is the same as that of the sublattice magnetization of the film 3.
In the binary recording state, both the second and third magnetic thin films 2
And the directions of the sublattice magnetizations of the magnetic recording medium
Since the state is equivalent to the initial state of the record, the next record
In performing the first and second steps corresponding to the recorded information.
This recording is possible only by giving a heating state.
That is, a state in which overwriting is possible is obtained. The thermomagnet on which information is recorded in this manner
Reading recorded information from a magnetic recording medium, that is, reproducing
Converts the linearly polarized laser beam to the first magnetic thin film 1
Irradiate and interact with this light and magnetization
By detecting the rotation angle, the transition metal TM of the first magnetic thin film
Binary depending on whether the sublattice magnetization is in the positive direction or inversion direction, for example,
“0” and “1” are read. As described above, the thermomagnetic recording medium 10
The recording of the information is performed in the first magnetic thin film 1 by the sub-
For example, by the positive portion and the reverse portion of the lattice magnetization,
Binary information of "0" and "1" is provided.
Are in an exchange-coupled state with the first magnetic thin film 1.
Curie temperature T for the second magnetic thin film 2_C1
And T_C2The magnetization state at the following temperature is the state A shown in FIG.
To D can be adopted. In FIG. 3, first and second magnetic thin films are shown.
For only 1 and 2, each of the TM spin and RE spin
The directions are schematically shown with solid arrows and dashed arrows, respectively.
It is shown. The magnetization volumes of both magnetic thin films 1 and 2
All easy axes are perpendicular magnetization films in the direction perpendicular to the film surface.
However, at least one of them is a perpendicular magnetization film.
Just do it. In FIG. 3, state A and state B are the first
TM spin tracks of the first magnetic thin film 1 and the second magnetic thin film 2
The TM magnetic moments and each RE spin
When the magnetic moments of RE are in the same direction
It is. In contrast, in states C and D of FIG.
The magnetic mode of each TM of the first magnetic thin film 1 and the second magnetic thin film 2
And RE have opposite magnetic moments
In the vicinity of the interface between the layers.
Direction of the magnetic moment and the magnetic moment of the RE is 1
Existence of a region that changes by 80 °, ie, the interface domain wall 9
And the interface domain wall energy (per unit area)
σ_werg / cm^Two) Is stored. A thermomagnetic recording device for performing the thermomagnetic recording
The device is, for example, as shown in FIG.
For example, recording on a disk-shaped thermomagnetic recording medium 10
The laser beam R for reproduction is transmitted from the light transmitting substrate 5 of FIG.
Incident on the side of the protective film 7 or the substrate 5
For example, a magnet 21 and, if necessary, a magnet 22 are provided.
And the magnetic field H_exas well as
H_subIs applied. In FIG. 4, a magnet 21 and a magnet 22 are shown.
Are arranged apart from each other, but adjacent to each other
Can also. Also, as described later, the magnetic field H_subEliminates
In this case, the configuration is such that the magnet 22 is omitted. Disk shape
The thermomagnetic recording medium 10 has a rotating shaft 26 of a drive motor 25.
To be driven to rotate. And the laser
The power of light R is modulated according to the information to be recorded.
Then, the laser beam irradiation part of the thermomagnetic recording medium 10 is
Second temperature T₁And T_TwoTo be heated to
You. Next, an embodiment of the present invention will be described.
However, the present invention is not limited to these examples.
Needless to say. [Embodiment 1] A description will be given with reference to FIG. Figure
Fig. 5 schematically shows the process of changing the magnetization state due to the temperature change.
It was done. This embodiment will be described with reference to FIG.
As described above, the first to third magnetic thin films are formed on the light transmitting substrate 5.
1 to 3 are formed, the second magnetic thin film 2 and the third magnetic thin film
4 and a fourth magnetic thin film 4 is provided between each of the magnetic thin films 1.
Are composed of ferrimagnetic TM-RE alloy magnetic thin films.
This is the case. These magnetic thin films 1 to 4 are so-called DC
Light transmissive substrate 5 using a guntron sputtering device
Above, directly, that is, omitting the formation of the dielectric film 6
RE-TM ferrimagnetic thin film is formed by sputtering sequentially
Done. These magnetic thin films 1 to 4 exchange RM and TM.
It was formed so as to be laminated on each other. And the upper third
800 .mu.m thick, for example, Si on the magnetic thin film 3._ThreeN_Four, Al
N, SiO_Two, SiO, MgF_TwoProtective film 7 made of
Formed. The first and second media 10 in this embodiment
The magnetic thin films 1 and 2 of each
Temperature T_C1And T_C2At each temperature up to
It is assumed that the film is a child magnetization dominant film, a so-called TM rich film.
The third magnetic thin film 3 is heated from room temperature to the heating temperature T.₁
Up to the RE sublattice magnetization dominant film, so-called RE rich film
And The first to fourth magnetic thin films 1 to 4 respectively
Curie temperature of T_C1~ T_C4Then T_C1<T_C2        ‥‥ (1) T_C4<T_C2, T_C3  ‥‥ (2) T_C4≤T_C1        ‥‥ (3) To be selected. The thickness of the fourth magnetic thin film 4 is
Curie temperature T of the magnetic thin film 4_C4Second at higher temperature
And the exchange force between the third magnetic thin films 2 and 3 can be sufficiently shut off.
To a small thickness, for example, 100 °
You. In the first embodiment, as shown in FIG.
Next, states A and C shown in FIG.
Or, the portion by B, that is, the first magnetic thin film 1
The formation of the positive and reverse directions of TM spin
This is a case where information is recorded. In FIG. 5, each magnetic thin film
Arrows described in 1-3 schematically indicate the direction of TM spin.
The magnetization in each of the magnetic thin films 1 to 4 is shown in FIG.
M_S1~ M_S4Indicates that each of the thin films 1 to 4 is a ferrimagnetic thin film.
Magnetic moment and RE in each of the magnetic thin films 1 to 4
This corresponds to the difference between the magnetic moments. In this example, in the initial state, for example, state A,
That is, the TM spin directions of the first and second magnetic thin films 1 and 2
The directions are both in the positive direction, and at this time, the third magnetic thin film 3
Further, the TM spins of the first and second magnetic thin films 1 and
It is assumed that it is in the same direction as that of 2. Now, this room temperature T_RFrom the initial state A in
Temperature T is first temperature T₁Alternatively, the second temperature T_TwoHeat up
You. This first temperature T₁Is approximately the key of the first magnetic thin film 1.
Curie temperature T_C1The external magnetic field H described above and described below_exBy
Temperature at which reversal does not occur in the magnetization of the second magnetic thin film 2
And Second temperature T_TwoIs the first temperature T₁Higher,
In addition, the TM sublattice magnetization of the second magnetic thin film 2 is changed to an external magnetic field H_ex
Of the second magnetic thin film 2 which is sufficient to
Curie temperature T_C2The above temperature is set. Such a temperature T₁Or T_TwoHeating to
After completion, the temperature T becomes T_C1When it goes down
Magnetization appears in the first magnetic thin film 1 and the direction of the magnetization
As regards the determination, the so-called exchange between the magnetic thin films 1 and 2
Make the binding force dominant. That is, the first magnetic
Temperature (T (T) at which spontaneous magnetization of the conductive thin film 1 appears._C1Nearby) smell
And roughly σ_w1> 2 | M_S1| H₁H_ex  ‥‥ (5) In order to satisfy the condition, the external magnetic field H_exAnd interface between layers
Domain wall energy σ_w1Magnetization of the first magnetic thin film 1 with respect to
M_S1And film thickness h₁Is selected. In this way, the medium
Temperature T is T_C1When the magnetization state is lower than
The direction of the TM sublattice magnetization of the first and second magnetic thin films 1 and 2 is
Either the state A or the state B of FIG.
And the temperature at the time of heating is T₁When heating to state A
Temperature is T_TwoIt becomes the state B at the time of. In FIG. 5, a state E indicates that the temperature T is equal to the first temperature.
Degree T₁And the magnetization of the first magnetic thin film 1 disappeared
In the cooling state, the temperature T becomes substantially the first temperature.
Curie temperature T of magnetic thin film 1_C1When it comes to the following,
As described above, the first magnetic thin film 1 has the TM
The exchange coupling force of the thin film 2 and that of the second magnetic thin film 2
The magnetization direction becomes the same, which is the initial state A in FIG.
Thus, for example, a recording portion of “0” is formed. Also, FIG.
In the state F, the temperature T is the second temperature T_TwoThe temperature is raised to
The magnetization of the first and second magnetic thin films 1 and 2 does not disappear once
Decreases in the magnetic field H_exThe TM sub-type of the second magnetic thin film 2
Lattice magnetization is magnetic field H_exIn this state,
In this case, the presence of the fourth magnetic thin film 4 causes the second and third magnetic
That the exchange coupling force between the conductive thin films 2 and 3 is interrupted
Therefore, the TM sublattice of both magnetic thin films 2 and 3 as shown in state F
The directions of the magnetizations can be opposite to each other. And
Further, the temperature T is the Curie temperature T of the first magnetic thin film 1._C1Nearby
When approaching, the exchange coupling force of the second magnetic thin film 2 causes
The first magnetic thin film 1 has the same direction as the second magnetic thin film 2,
A state G occurs in which the TM sublattice magnetization in the inversion direction occurs. No.
The fourth magnetic thin film 4 between the second and third magnetic thin films 2 and 3
Is the direction of the sublattice magnetization of the second and third magnetic thin films 2 and 3
Are opposite to each other, and the interface domain wall 9 is generated.
You. Further, from this state G, the temperature T is changed to the room temperature T._R
When it cools down, the conditions of Expressions 12 and 13 described below are satisfied.
A state B or state C is set depending on the setting. At this time the first
Of the TM sublattice magnetization of the magnetic thin film 1
Therefore, for example, information “1” is recorded. When the state C is reached, the first
And the TM sublattice at the interface between the second magnetic thin films 1 and 2
When the magnetization, that is, the TM spin is reversed,
A plane domain wall 9 will be generated. Here, from state G to state B,
C is determined or determined by the following conditional expression. Here,
The thickness of each of the third and fourth magnetic thin films 2, 3 and 4 is represented by h_Two,
h_ThreeAnd h_FourAnd the magnetization is M_S2, M_S3And M_S4And
Magnetic force is H_C2, H_C3And H_C4And h_Four≪h_Two, H
_ThreeAnd M_S4・ H_C4≪M_S2・ H_C2, H_S3・ H_C3And
In addition, the interface magnetic wall effect between the first and second magnetic thin films 1 and 2 is obtained.
Energy density as σ_w1And the second and third magnetic thin films 2 and
Domain wall wall energy density between_W2Then, the third
The conditions under which the magnetic thin film 3 does not undergo magnetization reversal are:   σ_W2-2M_S3・ H_Three・ H_ex<2M_S3・ H_Three・ H_C3  ‥‥ (11) Becomes The transition condition from the state G to the state C is as follows. Becomes Furthermore, the transition condition from the state G to the state B is: Becomes Therefore, the above equations (11) and (12) are
When conditions satisfying both are given, the external magnetic field H_ex
At room temperature even if no external magnetic field is applied.
State C will be obtained. On the other hand, the above equations (11) and (13) are both
If satisfied, transition from state B to state C at room temperature
To do so, as shown in FIG.
Other external magnetic field H_subWill be required. this
In this case, this magnetic field H_subIs Is set to satisfy. Now, the above conditional expression (15)
Focuses only on equation (14) when
Then   H_sub> H_c2+ (Σ_W1/ 2M_S2・ H_Two)-(Σ_W2/ 2M_S2・ H_Two)                                                           ‥‥ (16) Becomes Then, by the transition to the state C described above,
Thus, the magnetization directions of the second and third magnetic thin films 2 and 3,
That is, the direction of the TM spin is in the state A in the initialized state.
In this case, the forward direction is the same,
When rewriting information, the temperature change according to the written information
Key, that is, the first and second temperatures T₁And T_TwoTemperature to
When ascending, the state is the same as from the initialization state
The transition to E enables overwriting. Embodiment 2 In Embodiment 1 described above, the room temperature T
_RFrom the second temperature T_TwoUp to the compensation point T_compDoes not exist
Each magnetic thin film 1 and 2 is constituted by the TM-RE magnetic thin film.
In the second embodiment, the second magnetic thin film 2
FIG. 6 shows the saturation magnetization M_SAnd the coercivity is indicated by the broken line curve.
Force H_cAs shown in FIG.
-Temperature T_C2The following second temperature T_TwoCompensation point T between
_compAnd T_compRE sublattice magnetization dominates at lower temperatures
It shows the characteristics of a so-called RE-rich film,_comptaller than
Characteristic of so-called TM rich film
It is composed of a magnetic film exhibiting properties. Heat in this case
Configuration example of each magnetic thin film 1 to 4 constituting the magnetic recording medium 10
Are shown in Table 1. [0042] [Table 1]Then, in this case, the room temperature T_RThe first magnet at
Force σ between the conductive thin film 1 and the second magnetic thin film 2_W1Is 1.
7erg / cm^TwoThus, the second magnetic thin film 2 and the third magnetic thin film
Exchange force σ of membrane 3_W2Is 2.5 erg / cm^TwoMet.
Using the thermomagnetic recording medium 10 having this configuration, the first temperature
T₁= 150 ° C., second temperature T_Two= 250 ° C
Information recording was performed by the same operation as in Example 1. FIG.
The magnetization state in each process in this case is shown. In FIG.
The same reference numerals are given to the portions corresponding to and the duplicated description is omitted.
In FIG. 7, each state A, E, F, G and
The solid arrows attached to the magnetic thin films 1, 2, 3 in FIG.
The M spin or TM magnetic moment, and the dashed arrow is R
Indicates the E spin, or TM magnetic moment. And
According to the second embodiment, the first temperature T₁Heating and cooling
In the recall process, the transition from state A or C → state E → state A
This causes, for example, a bit of “0” to
The second temperature T formed on the thin film 1_TwoHeating and cooling
State A or C → state F → state G → state C
This causes a “1” bit to be written.
It was confirmed that it would fit. That is, in this case, in FIG.
External magnetic field H at line a_exRoom temperature T_Rso
Coercive force H of second magnetic thin film 2_C2Is H_C2<H_exBecome
As a result, the expression (12) can be satisfied,
In this case, as shown in FIG.
The external magnetic field H_exExternal magnetic field H other than_subDon't give
The transition can be made directly. In the description of the first and second embodiments,
In this case, the transition between the states A, B, and C described in FIG.
In the case where the value information is recorded, the state shown in FIG.
The same information can be recorded by the transition between A, B, and D.
Can also be. That is, in this case, FIG. 5 and FIG.
State A to state B, state B to state A, and state C to
What is necessary is just to correspond to the state D. As described above, the thermomagnetic recording medium 10
Between the second magnetic thin film 2 and the third magnetic thin film 3.
A fourth magnetic thin film 4 is disposed on the fourth magnetic thin film 4.
Therefore, the temperature T based on the recorded information₁Or T_Two At
Magnetic connection between the second magnetic thin film 2 and the third magnetic thin film 3
Switch between the connected and disconnected states
Temperature T_Two External magnetic field H at_exBy the first
2 can reliably perform the reversal of the magnetic thin film 2
is there. Next, the above-described fourth magnetic thin film 4 is provided.
The case of a thermomagnetic recording medium with no
To illustrate. Reference Example 1 In this reference example, the external
Magnetic field H_exOnly given. In this reference example,
The magnetic recording medium 10 used includes first, second and fourth magnetic recording media.
Magnetic thin films 1, 2 and 3;
As the coercive force H_cThe relationship between the temperature characteristics of FIG.
As shown by the curves 81 to 83, it becomes the recording bit coercive layer.
The first magnetic thin film 1 is at room temperature T_RShows high coercive force at
The magnetic thin film 2 has a Curie temperature of the first and third magnetic layers.
The highest magnetic thin film 1 compared to the thin films 1 and 3
The characteristic that the sublattice magnetization does not reverse near the Lie point is
To be elected. For example, the Curie temperature T of the first magnetic thin film 1_C1
It has a coercive force of about 1 kOe even in the vicinity. The first magnetic thin film 1 is a so-called TM-rich film
Or an RE-rich film. First to third
Curie temperature T of each magnetic thin film 1-3_C1~ T_C3Is T_C3<
T_C1<T_C2Is selected. Second and third magnetic thin films 2 and 3
And 3 are also TM rich film or RE rich film.
It does not matter whether or not the second magnetic thin film 2 has its Curie point.
T_C2If the vicinity is a TM-rich film, the third magnetic thin film
3 is the Curie point T_C3Immediately below is an RE-rich film.
2 magnetic thin film 2 is T_C2In the case of a RE-rich film in the vicinity
T_C3Immediately below, the third magnetic thin film 3 is a TM-rich film. each
Table 2 shows the composition, film thickness, and characteristics of one example of the magnetic thin films 1 to 3.
You. [0050] [Table 2]In this case, the first and second magnetic thin films 1 and
No. 2 is Fe-rich under the respective Curie temperature
TM rich, and the third magnetic thin film 3 is Tb rich
In other words, when the recording is RE rich,
The procedure will be described with reference to FIG. Even in this case, FIG.
In each of the magnetic thin films 1 to 3 in each state,
Ishi indicates the magnetic moment as a solid arrow,
Schematically shows the magnetic moment with a dashed arrow. In this case, the first and second data for binary recording
Temperature T of 2₁And T_TwoIs the first temperature T₁about,
Curie temperature T of the first magnetic thin film 1_C1For example, close to T₁
≒ 170 ° C. and the second temperature T_TwoAbout the second magnetic
Curie temperature T of the conductive thin film 2_C2For example, close to T_Two$ 270
° C. Now, at room temperature T_RFor example, in the initialization state,
The first and second magnetic thin films 1 and 2 have their respective TM sublattice magnetizations.
Are in the positive direction, that is, in the state A described in FIG.
Suppose there is. In the first embodiment, the required
External magnetic field H_exFor example, a magnetic field of only 500 (Oe)
For example, the first and second magnetic thin films 1 and 2 in state A
It is given in the same direction as the RE sublattice magnetization. In this state, the temperature T is changed to the first temperature T.₁Temperature rise
Then, T ≧ T_C3As shown in the state H in FIG.
The magnetization of the conductive thin film 3 disappears, and T ≒ T₁≒ T_C1In the
As shown in state I, this magnetic thin film 1
Decreases or disappears, but this temperature T₁And the second magnet
Since the conductive thin film 2 has a required coercive force, the external magnetic field H_exTo
Therefore, make sure that the magnetization is not reversed.
Therefore, during the cooling process from this elevated temperature, the second magnetic thin film
Initial state of the first magnetic thin film 1 by the exchange coupling force with the film 2
Each TM and RE sublattice magnetization in the same direction as state A occurs,
Returning to state A, for example, a recording portion of information "0" is formed.
You. On the other hand, the temperature T is changed to the second temperature T_TwoHeating up
Then, as shown in the state J, the magnetization of the first magnetic thin film 1 is changed.
Needless to say, the magnetization of the second magnetic thin film 2 disappears or almost disappears.
Since it disappears, during the cooling process from this temperature, the first and second
Direction of the TM sublattice magnetization of the magnetic thin films 1 and 2
World H_exIs stabilized in this direction. Soshi
Then, the temperature is further lowered to show the state K and the state L.
As shown, between the first magnetic thin film 1 and the second magnetic thin film 2
Exchange coupling force acts on the first magnetic thin film 1 and its TM
The magnetism of the second magnetic thin film 2 is aligned with the magnetization of the TM sublattice.
You. Then, the temperature is further lowered to reduce the temperature of the third magnetic thin film 3.
Curie temperature T_C3When the temperature is near, the first magnetic thin film
1 is stabilized in a state in which the magnetization state is inverted from the state A.
It is kept in state M. At this time, the third magnetic thin film 3
Coercive force in the first magnetic thin film 2 and the first and second magnetic thin films 2
The magnitude of the exchange force between the membranes 1 and 2, the external magnetic field H_exSize of
And the external magnetic field H_exThe direction of the magnetization is determined
However, in the thermomagnetic recording medium 10 having the above configuration, the external
Magnetic field H_ex= 500 (Oe), this external magnetic field H_exDirection
The magnetization is oriented. That is, in the third magnetic thin film 3,
The TM spin, that is, the TM sublattice magnetization is shown in state M.
As shown in FIG.
And the magnetization of the second magnetic thin film 2 becomes the first magnetization.
In the state M in the same direction as that of the conductive thin film 1, the second and third
A domain wall 9 is generated between the magnetic thin films 2 and 3 of FIG. But
In the configuration described above, the distance between the second and third magnetic thin films 2 and 3 is reduced.
Domain wall energy at room temperature T_RAnd the first and second magnetic thin films
The second is due to being larger than the domain wall energy between 1 and 2.
Of the third magnetic thin film 3
And the TM sublattice magnetization is aligned with that of the third magnetic thin film 3.
Room temperature T_RIt was confirmed that the state was changed to state C. this
Thus, the second temperature T_TwoIts cooling by heating to
In the process, according to the state C, ie, the recording portion of the information “1” is
It is formed. Then, the write portion of this information “1” is
In order to write the next information, the temperature T₁Ma
Or T_TwoWhen the temperature rises to
The portion A is also the TM and RE in the second magnetic thin film 2.
Are each sublattice magnetization oriented in the same direction?
In any case, the transition to state I
Then, for example, the information of “0” and “1”
Writing, that is, overwriting can be performed. In this reference example, FIG.
Binary information is recorded according to state A and state C.
In this case, state B is changed to state A shown in FIG.
The state C is changed to obtain the state D, and the binary information is recorded.
Recording can be performed, in this case,
Part magnetic field H_exIs selected in a direction opposite to the direction shown in FIG. Reference Example 2 In this reference example, the external
Magnetic field H_exOnly given. Used in this reference example
The first, second and third magnetic recording media 10 are also provided.
Having magnetic films 1, 2 and 3 as magnetic thin films 1 to 3.
Is the coercive force H_cThe relationship between the temperature characteristics is shown by the curve in FIG.
As shown in 101 to 103, the recording bit coercive layer
1 magnetic thin film 1_RShows high coercive force at
Curie temperature T_C1And the third magnetic thin film 3
Curie temperature T_C3Is the highest, and the queue of the second magnetic thin film 2 is high.
Lee temperature T_C2Those with high coercive force near
Devour. That is, each cut of the first to third magnetic thin films 1 to 3
Lee temperature T_C1~ T_C3Is T_C3> T_C2> T_C1Selected
The magnetization reversal occurs in the third magnetic thin film 3 during the information recording process.
It is selected for the material which does not change. The second magnetic thin film 2 is shown in FIG.
As shown, room temperature T_RMaterial with low coercivity
The third magnetic field where a certain magnetized state is coerced
Magnetic field H with respect to the direction of the TM sublattice magnetization of the conductive thin film 3
_exReverses the magnetization direction of the TM sublattice
TM rich or RE rich is determined
You. The first magnetic thin film 1 is RE-rich or TM-rich
Any of these may be used. An example of each magnetic thin film 1-3
Table 3 shows the composition, film thickness, and characteristics. [0060] [Table 3] In this case, the first and third magnetic thin films 1 and
No. 3 is Fe-rich water at each Curie temperature or lower.
TM rich, and the second magnetic thin film 2 is Tb rich
In other words, when the recording is RE rich,
The procedure will be described with reference to FIG. In this case as well
11 shows the TM spin in each of the magnetic thin films 1 to 3 in each state.
Or the magnetic moment is indicated by a solid arrow, and there is no RE spin.
The magnetic moment is shown schematically with a dashed arrow.
You. In this case, the first and second data for binary recording
Temperature T₁And T_TwoIs the first temperature T₁About the
Curie temperature T of the magnetic thin film 1_C1Temperature close to, for example, T
₁≒ 130 ° C. and the second temperature T_TwoAbout the second magnetic
Curie temperature T of the conductive thin film 2_C2For example, close to T_Two$ 200
° C. Now, the room temperature T_RIn the initial state in
And the second magnetic thin films 1 and 2 are in the state A described in FIG.
At this time, the TM spin of the third magnetic thin film is equal to the first and second TM thin films.
2 in the same direction as the TM spin of the magnetic thin films 1 and 2
Shall be And also in this reference example 2,
External magnetic field H_exAre the first and second in state A, for example.
Given in the same direction as the TM sublattice magnetization of the magnetic thin films 1 and 2.
You. In this state, the temperature T is changed to the first temperature T₁To the rising
As the temperature increases, the temperature T becomes T_C1Near the first magnetic thin film 1
The magnetization disappears or decreases as shown in state N.
As shown in FIG. 10 in the state of FIG.
Since films 2 and 3 have the required large coercive force,
In addition, the external magnetic field H_exOf TM and RE sublattice magnetization by
By ensuring that no inversion occurs,
In the process of cooling from this elevated temperature, the exchange with the second magnetic thin film 2 occurs.
The first magnetic thin film 1 is in the same state as the initial state A by the exchange coupling force.
The TM and RE sublattice magnetizations in each direction are generated and return to state A.
Thus, for example, a recording portion of information "0" is formed. On the other hand, the temperature T is changed to the second temperature T_TwoIe
Curie temperature T of the second magnetic thin film 2_C2Heats up near
As shown in state O, the magnetization of the first magnetic thin film 1 is
As a result, the magnetization of the second magnetic thin film 2 disappears or almost disappears.
However, at this temperature, the third magnetic thin film 3 is sufficiently large at this temperature.
Because of the coercive force, this temperature T_TwoAlso outside
Magnetic field H_exThe desired magnetization direction is not affected by
Coercive. However, regarding the second magnetic thin film 2,
Is the external magnetic field H_exThe direction of its magnetization during its cooling process
Is the external magnetic field H_exAligned to. In other words, state P
As for the TM sublattice magnetization, the external magnetic field H_exAnd in the opposite direction,
Therefore, the TM sublattice magnetization of the second magnetic thin film 2 is the third
The magnetization direction is opposite to the TM sublattice magnetization, and both magnetic thin films 2 and 3
An interface domain wall 9 is generated therebetween. And even cooler or cooler
In the cooling process, the temperature T becomes the Curie temperature T of the first magnetic thin film 1._C1
Approaching, magnetization appears in the first magnetic thin film 1.
Depending on the selection of the temperature characteristics and the film thickness of the first magnetic thin film 1
That is, the TM sublattice magnetization is the TM sublattice magnetization of the second magnetic thin film 2.
The state Q is obtained by being aligned with the direction of the lattice magnetization. further
As the temperature T is lowered, the first magnetic thin film 1 has its coercive force.
This magnetization state is coercive because the
In the configuration of No. 10, the exchange between the second and third magnetic thin films 2 and 3 is performed.
The exchange force is large, that is, the second and third magnetic thin films 2 and
3 and the first and second domain wall energies.
Energy is small.
As a result, the direction of the sublattice magnetization of the second magnetic thin film 2 is reversed, and FIG.
The state C shown by is given to form a recording portion of information "1".
Is done. Then, the write portion of this information “1” is
In order to write the next information, the temperature T₁Ma
Or T_TwoWhen the temperature rises to
C and TM in the second magnetic thin film 2
Are each sublattice magnetization oriented in opposite directions?
In either case, the transition to state N will occur.
Then, for example, the information of “0” and “1”
Writing, that is, overwriting can be performed. In the example described above, the state A and the state A
FIG. 3 shows a case where binary information is performed by C.
Are replaced with states A and C in FIG.
Binary information recording may be performed. in this case
The external magnetic field H_exIs selected in the opposite direction from FIG.
You. As described above, the first to third magnetic thin films
Even when using a thermomagnetic recording medium, binary recording
According to the present invention, the fourth magnetic thin film 4 is interposed.
By the external magnetic field H_exOf the magnetization of the second magnetic thin film
Rolling can be performed reliably. Note that in each of the above examples,
In the case where each of the magnetic thin films 1 to 4 has ferrimagnetism,
The use of ferromagnetic film
Can also. [0070] As is apparent from the above description, the present invention
According to the method of the present invention, the erasure process (time) is not required.
High transfer rate can be realized from the
Since the two-head method used is not used, the structure is simplified.
Heat treatment, regardless of external magnetic field modulation.
Modulation, for example, recording by laser light modulation
High-speed recording because of the
The simplification of the device combined with the fact that it can be configured by the light
There are many benefits, such as striking. Also,
In the present invention, as is evident from the respective embodiments described above,
By providing the third magnetic thin film 3, the external magnetic field H_exof
With binary information recording regardless of other external magnetic fields.
-Can you bring the bar light to a possible state,
Alternatively, even if not, the first embodiment described with reference to FIG.
In the transition from state B to state C, the external magnetic
World H_subIn the case of using
Nos. 1 and 2 as proposed in application No. 61-194961
2 compared with the thermomagnetic recording method using only the magnetic thin films 1 and 2.
External magnetic field H_subCan be reduced.
That is, the thermomagnetism disclosed in Japanese Patent Application No. 61-194961 was used.
In the air recording method, in the first embodiment of FIG.
Only the first and second magnetic thin films 1 and 2 are used as magnetic layers.
In this case, for example, FIG.
External magnets required for transition from state B to state C shown in
Place H_subIs H_sub> H_C2+ Σ_W/ 2M_S2h_Two‥‥ (161) Becomes On the other hand, in Example 1, the condition (1
6), both equations (161) and (1)
As is clear from comparison with equation (6), equation (16) is used.
Is σ compared to equation (161)_W2/ 2M_S2h_TwoTerm
H_subCan be reduced. Further, for example, as described above, the magnetic layer
Only the first and second magnetic thin films 1 and 2 and the second
Room temperature T_RAnd its Curie temperature T
_C2Between the compensation temperature T_compIn the compensating composition so that
The first temperature T₁,
That is, the Curie temperature T of the first magnetic thin film 1_C1In the vicinity
It is necessary to prevent the magnetization reversal from occurring in the magnetic thin film 2 of FIG.
The coercive force of the second magnetic thin film 2 at this time
H_C2Is actually about 1 kOe or more. Such conditions
Material that satisfies_RCoercivity H_C2Is about 2k
Since Oe is larger than Oe, σ_W
/ 2M_S2h_TwoThe second external magnetic field H to which the term
_subRequires a large magnetic field of at least 3-4 kOe.
In other words, such a magnetic field H_subTo medium 10
It is practically difficult to apply the device simultaneously or sequentially to the whole area
There is a point. Further, the application of Japanese Patent Application No. 61-194962 is disclosed.
Like the first, only the first and second magnetic thin films 1 and 2
Therefore, in the magnetic layer, the second magnetic layer
The thin film 2 at room temperature T_RAnd Curie temperature T_C2Compensation temperature during
Degree T_compIs used, the second external magnetic field H
_subTo the external magnetic field H_exCan be matched with practically
Magnetic field H_subIt is no longer necessary to provide
The first temperature T₁That is, the curl is applied to the first magnetic thin film 1.
-Temperature T_C1The first magnetic thin film 1 is located near the second magnetic thin film
The external magnetic field H_exIs large
Although it is less than 1 kOe at best, the room temperature T
_RThe magnetic field that causes the magnetization reversal in the second magnetic thin film 2 is
Since it is about 2 kOe or more according to the equation (161), this value
To reduce the thickness, increase the film thickness or use the second magnetic
The magnetization reversal temperature of the thin film 2 is set to the high temperature side, and the room temperature T_RAt
Magnetization M_SMay be increased, but in this case,
Problems such as an increase in recording power occur. However,
According to the present invention described above, the magnetic thin film provided with the third magnetic thin film 3 is provided.
The use of the air recording medium 10 can solve such a problem.
Peel off.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a basic configuration diagram of a thermomagnetic recording medium of the present invention. FIG. 2 is a sectional view of an example of a thermomagnetic recording medium according to the present invention. FIG. 3 is an explanatory diagram of transition between magnetization states. FIG. 4 is a schematic configuration diagram of a recording apparatus. FIG. 5 is an explanatory diagram of a magnetization process of an example of the thermomagnetic recording method according to the present invention. FIG. 6 is a temperature characteristic diagram of magnetization and coercive force. FIG. 7 is an explanatory diagram of a magnetization process of a comparative example. FIG. 8 is a temperature characteristic diagram of coercive force of each magnetic thin film example. FIG. 9 is an explanatory diagram of a magnetization process of a comparative example. FIG. 10 is a temperature characteristic diagram of coercive force of an example of a magnetic thin film. FIG. 11 is an explanatory diagram of a magnetization process according to another example of the present invention. [Description of Signs] 1 to 4 First to fourth magnetic thin films, 10 thermomagnetic recording medium, R laser beam, 21, 22, magnet, 25 drive motor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10 506 G11B 11/10 586

Claims (1)

(57) [Claims] A second magnetic thin film provided between the first, second, and third magnetic thin films;
And a fourth magnetic thin film having a Curie temperature lower than the Curie temperature of the third magnetic thin film, wherein the fourth magnetic thin film has a lower temperature than the Curie temperature of the fourth magnetic thin film. 3. The thermomagnetism is characterized in that the exchange coupling force of the third magnetic thin film is maintained, and the exchange coupling force of the second and third magnetic thin films is cut off above the Curie temperature of the fourth magnetic thin film. recoding media. 2. A second magnetic thin film provided between the first, second, and third magnetic thin films;
And a fourth magnetic thin film having a Curie temperature lower than the Curie temperature of the third magnetic thin film, modulating the power of the laser beam according to the information to be recorded. (4) Recording information by switching between a temperature lower than the Curie temperature of the magnetic thin film and a temperature higher than the Curie temperature to partially block the exchange coupling force between the second and third magnetic thin films. A thermomagnetic recording method.