JPS6352354A - Thermomagnetic recording method - Google Patents

Abstract

PURPOSE:To attain an overwriting with a simple constitution by switching and modulating the heating state in accordance with a signal to be recorded and forming signal magnetization on a first magnetic thin film to record the signal in a cooling process. CONSTITUTION:A thermomagnetic recording medium 10 is used which has first and second magnetic thin films 3 and 4 magnetically coupled and laminated and includes a layer-built film having a part where respective magnetic moments of the first and second magnetic films 3 and 4 are coupled in opposite directions. A first heating state where the thermal magnetic recording medium 10 is heated to a temperature T1, which is higher than the Curie point Tc1 of the first magnetic thin film 3 and does not cause the inversion of the magnetic moment of the second magnetic thin film 4, and a second heating state where the medium 10 is heated to a temperature T2, which is higher than the temperature Tc1 and is high enough to invert the magnetic moment of the second magnetic thin film 4, are modulated in accordance with the information signal to be recorded to heat the thermomagnetic recording medium 10, and this medium is respective heating states is cooled to record binary information.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B1 Overview of the invention C0 Prior art 0 Problems to be solved by the invention E1 Means for solving the problems F1 Effect G. Example G-1. Structure of thermomagnetic recording medium G-2, transition of magnetization state G-3, change of magnetization state according to temperature G-4. Override condition G-5, magnetized lie for reproduction/storage G-6. Specific example G-7 of thermomagnetic recording medium, Other practical examples H8 Effect of the invention A, Industrial application field The present invention relates to a magneto-optical recording method or a thermomagnetic recording method. The present invention relates to a method for performing high-pressure recording using a magnetically expelling recording medium having a film.

B9 Summary of the Invention The present invention provides a method for performing magnetomagnetic recording on a thermomagnetic recording medium having a CH magnetic double layer film obtained by stacking magnetically coupled first and second magnetic thin films. (Before recording, the direction of the magnetic moment of the second magnetic thin film of the magnetic double-layer film is aligned in one direction, and the temperature of the second magnetic thin film is approximately equal to or higher than the Curie temperature T of the first magnetic thin film; The temperature T1 at which no reversal of the magnetic moment occurs, and this temperature T1
Switching and modulating the state to i in accordance with the signal to be recorded so that the second magnetic thin film is heated to a temperature T2 which is sufficient to reverse the magnetic moment of the second magnetic thin film. By recording and forming signal magnetization in at least the first magnetic gt film during the cooling process from each of these temperatures T or Tz, overriding is possible using a convenient method of modulating the heating temperature of the medium. .

C0 Conventional technology In a magneto-optical recording method or a thermomagnetic recording method, a recording medium having a magnetic GT film such as a perpendicular n-oxide film is so-called initialized by aligning the magnetization direction in advance in one direction perpendicular to the plane. is applied, and by forming bits having perpendicular magnetization opposite to the CJ-forming force direction by local heating such as laser beam irradiation, binarized information is recorded.

In the future, in El air recording or thermomagnetic recording methods,
Prior to rewriting information, a process of erasing recorded information (corresponding to the above-mentioned initialization) is required, and recording at a high transfer rate cannot be realized. In contrast, several so-called override methods have been proposed as recording methods that do not require such an independent erasing process. Among the override type thermomagnetic recording methods, methods that are considered promising include, for example, an external magnetic field modulation method in which the polarity of an external magnetic field to the medium is switched and reversed according to an information signal, and A two-head method is known in which an erasing head is provided. The external magnetic field modulation method is, for example, as disclosed in Japanese Patent Laid-Open No. 60-48806, etc., in which a heating beam is applied to an amorphous ferrimagnetic thin film recording medium having an easy fn axis perpendicular to the film surface. Recording is performed by applying a magnetic field with a polarity corresponding to the state of the input digital signal to the irradiation area.

D1 Problems to be Solved by the Invention By the way, when trying to perform high-speed recording with a high information transfer rate using the external magnetic field modulation method as described above, for example, M)
An electromagnet that operates on the lz order is required, and it is difficult to manufacture such an electromagnet, and even if it could be manufactured, it would be impractical due to the large amount of power consumption and power consumption. In addition, the two-head method described above requires an extra head, and the two heads must be installed apart, placing a heavy burden on the drive system. It has the following disadvantages.

The present invention has been made in view of the above circumstances, and aims to provide a thermomagnetic recording method that allows easy rewriting (override recording) by simply controlling the addition of pQ to the medium by laser light or the like. shall be.

Means for Solving the E1 Problem In order to solve the above-mentioned problems, the thermomagnetic recording method according to the present invention is such that the first and second magnetic thin films are magnetically coupled and laminated, 1. Using a thermomagnetic recording medium including a laminated film having a portion in which the magnetic moments of the second magnetic thin films are coupled in opposite directions to each other, the temperature of the first three magnetic films is approximately equal to or higher than the Curie temperature TC1, and A first heating state in which the second CD magnetic thin film is heated to a temperature T1 at which reversal of the magnetic moment does not occur, and a temperature T2 which is equal to or higher than the temperature TC1 and sufficient to reverse the magnetic moment of the second magnetic thin film. Binary information is recorded by heating the heating n-air recording medium by modulating the second heating state according to the information signal to be recorded, and cooling it in each of the above heating states. It is characterized by recording.

By modulating the intensity, irradiation time, etc. of the heating beam such as the F1 action laser beam in accordance with the information signal to be recorded, so-called override of recording can be easily performed.

G. Example FIG. 1 shows a change in magnetization state due to temperature change to explain an example of the present invention, and FIG. 2 schematically shows a cross-sectional structure of a recording medium used in the example. ing. In FIG. 1, each τ magnetization of the magnetic double-layer film in the recording medium of FIG. 2 is shown in a simplified manner, and the states of these magnetizations change depending on the temperature and external magnetic field.

That is, in FIG. 1, the first and second magnetic thin films 3.
A laminated film <"
A first heating state in which the l-type bilayer film 5) is heated to a temperature T1 that is approximately equal to or higher than the Curie temperature Tc3 of the first magnetic thin film 3 and at which magnetization reversal does not occur in the second magnetic thin film 4; , a second heating state in which the temperature T e 1 or more is heated to a temperature T2 sufficient to reverse the magnetization of the second magnetic thin film 4, in accordance with the information signal to be recorded. By cooling the thermomagnetic recording medium from the heated state, recorded magnetization is formed in the thermomagnetic recording medium.

G-1. Structure of thermomagnetic recording medium First, the structure of the thermomagnetic recording medium (or magneto-optical recording medium) used in the embodiment of the present invention will be briefly explained with reference to FIG. First and second magnetic thin films 3.4 are applied to one surface (lower surface in the figure) of a transparent substrate 1 such as a glass plate or an acrylic plate via a transparent dielectric material Pi2 that serves as a protective film or an interference film. A magnetic double-layer film 5 consisting of the following is formed in a laminated manner.

A dielectric film 6 serving as a protective film is deposited on the surface (lower surface in the figure) of the magnetic two-layer film 5. Note that the dielectric film 2 and the dielectric film 6 may be omitted, or the dielectric film 6 may be omitted.
may be a metal film.

Here, the first and second (1
Various magnetic materials can be considered as the magnetic film 3.4, but in Honji Umeri 11, Nd, Sm, Gd, T
one or more rare earth metals (RE) such as b, Dy, and Ho in an amount of X = 10-40 atm%;
One or more types of transition metals (TM) such as Cr, Mn, Fe, Co, Ni, Cu, etc. 1-x=9
Amorphous alloy RE, T composed of 0 to 60 atm%
M,−, is set. Small amounts of other elements may be added. In this RE-T~1 amorphous alloy Eft material, except when RE is \d, Sm, the magnetic moment of RE and the magnetic moment of T~1 are coupled antiparallelly, and as a result In addition to exhibiting so-called ferrimagnetism, the net magnetization is the difference between the sublattice magnetizations of RE and TM (the sum of the sublattice magnetizations when considering the positive and negative depending on the direction of magnetization). When rare earth gold polishing (RE) is composed of either Nd or Sm, or a mixture of these,
The magnetic moment of RE and the magnetic moment of T~1 are coupled in parallel to each other and exhibit so-called ferromagnetism. In this case, the net magnetization is the sum of the RE and TM sublattice magnetizations. In this embodiment, a case where RE is Gd, ..., Tb, Dy, or Ho will be explained.

For example, as shown in FIG. 3, a laser beam R for recording or reproducing is incident on the thermomagnetic recording medium 10 having such a laminated structure from the side of the transparent substrate L shown in FIG. The side of the dielectric film 6 that will become a film, or the transparent substrate l
From the side, the magnetic field H due to the 11 stones 11, 12 etc. in Fig. 3.
H, is applied. In FIG. 3, magnet 11 and if
Although the stones 12 are placed spaced apart from each other, they may be placed next to each other as will be described later, or may be the same magnet. The example shown in FIG. 3 shows a disk-shaped 261-degree recording medium 10, and the disk-shaped recording medium 10 is rotationally driven by a spindle 16 of a drive motor 15. Although the figure shows an example in which the magnets 11 and 12 have different magnetic poles, they may have the same polarity as described later.

The magnetization state of the magnetic double-layer film 5 obtained by stacking the magnetic a-films 3.4 made of the RE-7M alloy material is as follows for each of the three films 3.4.
In the temperature range below the Curie temperature T, TC2 of 4, it is possible to take four shapes GA-D as shown in FIG. It is assumed that the easy magnetization axes of both thin films 3.4 are perpendicular to the plane (so-called perpendicular Ml film), but at least one of them may be a perpendicular magnetization film.

In Figure 4, state A and state B are the magnetic properties of the first layer)
The directions of the magnetic moments (solid arrows in the figure) of each T to 1 of the first film 3 and the second layer magnetic thin film 4 are the same, and each RE
The directions of the magnetic moments (dashed arrows in the figure) are the same. On the other hand, in state C and state 3 in FIG.
The magnetic moment of each TM of the layer thin film 3 and the second layer 3 film 4 (solid line arrow in the figure) and the magnetic moment of each RE (broken line arrow) are directed in opposite directions, and near the interface between the eyebrows. There is a region (so-called domain wall) in which the directions of the magnetic moments of , TM, and RE change by 180°. This region or domain wall is the interface domain wall 7
The interface (J-wall energy (σw erg/cmz per unit area) is stored in this part.

G-2, Monization-like, stop transition Here, the magnetic energy EA per unit area of each state A-D in Fig. 4 when an external magnetic field H (Oe) is applied.
SE3, EC, and E can be approximately described by the so-called Zeeman energy and the above-mentioned interfacial domain wall energy density σ5.

E a −M s + h + HM s z h 2
HE m = M s lh lH + M S Z
h z HEC= MS, h, H-~13□h, H
+a.

E o = M s + h + H = M s z
h t H + σ1 Both units are (erg/cm2) In these formulas, ~1. 1 and 2 respectively indicate the saturation magnetization Ms (emu/cm') of each magnetic film 3.4, and h, , and ht indicate the H thickness (cm) of each thin film 3.4. Saturation magnetization M is RE (rare earth metal) sublattice magnetization M
It is the value obtained by subtracting the TM (transition metal) sublattice magnetization MTM from IE, and is the amount defined by the following formula. That is, generally MS=1 to 1. □-M1. ! However, in the present invention, it is defined as M3=M*i-Myx. Therefore, when M1≧MTH, M.

≧0, and if M RE < M 714, ~1.
<Becomes 0.

Further, the squareness ratio of both thin films 3.4 is assumed to be 1, and the external magnetic field H is calculated assuming that the direction of the magnetic field H in FIG. 4 is positive. However, in reality, the squareness ratio is not necessarily required to be 1. The magnetic energy of each of the above states A to D is approximately determined using the Zeeman Efurgi and the above σ, and more precisely, considering the stray magnetic field from adjacent magnetic domains (bits) J↓ Although it is necessary to do so, the present invention t'
It is omitted in the 8th book.

Next, when the coercive force or magnetization reversal (R field of the first layer thin film 3 is Hc + (Oe) and the magnetization reversal magnetic field of the second layer thin film 4 is Hcz (Oe), first the (n sex 3
The energy required to invert M9゜3 into filtration, that is, the coercive force energy E + (erg/cm") is:
E+=2 l Ms+ : h+Hc+ Similarly, the energy E z (erg/cm") required for the second layer magnetic thin film 4 to reverse magnetization is E2"'2 l
Msz: expressed as hzHC2.

The magnetization state is from 1 (=A-D) to j (=A-D, l≠")
In order to transition to
The condition is that it is larger than E. For example, the necessary conditions for transitioning from state EA to state B are: E
l"CI"2 IM control, given as H,2.

G-3. Changes in magnetization state in response to temperature With reference to FIG. .

First, it is assumed that a portion of the magnetic double-layer film 5 in the recording medium 10 to be recorded is at room temperature T and in a state GA in FIG. 1. Recording is performed by irradiating a laser beam onto a portion of the magnetic double-layer film 5 in this state GA, and by modulating and controlling the intensity or irradiation time of the laser beam at this time according to the recording signal. , heating temperature T of the two-layer film 5
is selectively controlled to be switched to either the first temperature T1 or the second temperature T. Here, the first temperature T
1 is a temperature that is approximately equal to or higher than the Curie temperature TC1 of the first three-magnetic film 3 and at which magnetization reversal of the second three-magnetic film 4 does not occur due to an external magnetic field H1, which will be described later. The temperature is higher than the temperature T3 and is sufficient to reverse the magnetization of the second magnetic film 4 by the external magnetic field H1. That is, an external magnetic field H1 by the magnet 11 shown in FIG. The HA field is sufficient to reverse the magnetization of the thin film 4.

After such heating is completed, magnetization appears in the first magnetic thin film 3 when the temperature T of the two-layer film 5 becomes TCl, but the direction of magnetization is determined not by the Zeeman energy but by the difference between the two layers. So-called exchange coupling force becomes dominant. That is, at the temperature T (near Tc+) at which the spontaneous magnetization of the first magnetic thin film 3 appears, the external magnetic field H+ and the interfacial domain wall energy σ between the eyebrows are The saturation magnetization M S + and film thickness h1 of the magnetic thin film 3 of No. 1 are selected. Therefore, when the medium temperature T becomes Tc1, the magnetization state is either %A or 6B, which is the direction of magnetization of each layer of the magnetic double-layer film 5. When the temperature is T1, the state is A, and when the temperature during heating is T, the state is jGB.

Further, the recording portion of the medium is cooled, for example in a chamber? W
When it reaches about T, the part of shape OA becomes t3A, the same magnetization state as the original initial state, and the part of shape IB becomes GB, the direction of magnetization is opposite to the original initial state. But the third
As shown in the figure, by applying an external magnetic field H2 to the recording medium 10 near room temperature T8 by the magnet 12, which satisfies the conditions detailed in section G-4 of this specification, the second (
The direction of rl of the J-type thin film 4 is reversed, and the magnetization state of the magnetic double-layer film 5 becomes the state 9C in FIG. 4.

Next, heat (heating) is applied to 4 of the magnetic double layer film 5 of the recording medium
When heating is applied to the recorded portion in the ffi state C, the magnetization of the first τn thin film v3 disappears when the portion exceeds the temperature TCl, and the state returns to the above state. It becomes the same (n state) as when heated from becomes the above-mentioned state B, so a recording magnetization state corresponding to these heating temperatures T I and T 2 is obtained.The recording portion of the shape 6B is at least in the state d before the next rewriting (override) operation. (transitioned to
The direction of magnetization of the second magnetic three-layer film 4 is aligned in the same direction as Akiyama A.

In this way, the magnetic moments of the first and second magnetic thin films 3.4 of the magnetic double-layer film 5, which are coupled to each other by Cn gas, are arranged in the recording portion (corresponding to the portion of shape g A) in the same direction. , the recording portions whose magnetic moments are in opposite directions (corresponding to the portion in state C) are modulated and heated to the respective heating temperatures T, , T according to the information signal, thereby producing the original state. A new magnetization state can be recorded regardless of the magnetization state of the magnetization state, and so-called override can be realized.

G-4. Override Conditions Next, conditions for realizing the above-mentioned override will be explained.

With an external magnetic field H2 applied as shown in Figure 1,
When the temperature T of the magnetic double layer film 5 of the medium changes, first, the Curie temperature TCl of the first magnetic thin film 3 changes from room temperature TI.
In the temperature range up to (TR≦T<Tc1), the condition that magnetization state A does not transition to another magnetization state is -2M5+b+H+-2M5zhJ+ <21Ms+l
h+)Ic+〒21M szl hJcz2Ms+h
+L-σw <21M511 h+Hc+-2M5zh
z old - σ, < 2 IM szl hJcz Also, the condition that the magnetization state 6C does not transition to another magnetization state is 2Ms+h+H++σw <21M5lh+Hc+-2
M5zhJ++σw < 21M 321 hz) Ic
It becomes z. Next, the temperature T of the magnetic double layer film 5 is set to the above temperature TC.
1 to the second heating temperature T2 (Tc,
<T<T2), the conditions under which the magnetization of the second magnetic thin film 4 is not reversed are IHll<Hcz.Furthermore, when the temperature T of the magnetic double-layer film 5 exceeds the temperature T2 (T>''rz), The conditions for reversing the sublattice magnetization of the second magnetic thin film 4 are as follows: As soon as 1"l>Hcz, the magnetic double layer film 5 of the thermomagnetic recording medium 10 is reversed in the cooling process from the heating state. The temperature T of the recording portion is approximately the Curie temperature 'rc, (first magnetic FJvJ, 3
)-t-yu')? Wff) niaL;'j (T
= Tc+), and the direction of magnetization of the first magnetic thin film 3 intersects with the so-called U conversion (the condition determined by the negative bonding force is σ□ >21M5 heat). h+lo+1 In addition, in the temperature range from below the above temperature TC1 to room temperature T (TRS T < TC+), the Era state, d
The conditions under which A does not transition to another magnetization state are the same as those in the heating process mentioned above, and the conditions under which magnetization state B does not transition to the pond magnetization state are: 2Ms+b+H++2M5zhzlL <21M511
11+Hc+-21~1jih2Hc22Ms+htL-
σw <21M5tl h+Hc+2M3zhJ+
dv <21M5zl hxHcz.

Next, at room temperature, the external magnetic field H generated by the magnet 12,
(However, the polarity of L Hz is positive in the direction of the arrow shown in Figure 1.) When Uzuki U is applied, the condition that magnetization state A does not transition to another magnetization state is -2M5+b+Hz-2Ms
zhzHz<21M911 b+Hc+°+ 2 IM
szl hzHcz-2j, mountain H2-σw <21M
s+l b+)lc+2M5zhzHz 6w <2
jMszlhJcz, magnetization state, 6B is magnetization state C
The conditions for transitioning to are: 2Ms+l'l+L+2M5zhzHz<2 IM>
+)Ic+ +21M5ZI hzl(cz2'1s+
t++)Iz-σw <21M,,l t++L+21
5□h mountain-σb>21M-1hzHcz.

Magnetic double layer W that satisfies all the above override conditions
By using 25, overriding as described above becomes possible.

Here, in the above explanation, conditions BA, B and conditions 1c
Although the change in the magnetization state is explained using GA, s and state GA, if the magnetization direction of the second magnetic thin film 4 in the initial state is to be aligned in the opposite direction to the above, the same result can be obtained using GA, s and state GA. Can be overridden.

That is, in this case, the shape 6B is the shape of the above-mentioned embodiment, and the shape G
Correspond to A, and similarly, from state A to state C,
Furthermore, while making 6C correspond to D,
By changing the definition of saturation (nization Ms to M,=Sit1.l-Mat), each of the above-mentioned override conditional expressions can be applied as is.

G-5. Magnetization state for reproduction/storage By the way, in order to perform override, the recording state of the signal (direction of magnetization of the first magnetic thin film 3) is required as described above.
Regardless, it is necessary to align the orientation of the stone R of the second magnetic three-layer film 4 in the same direction, and each N of the magnetic double-layer film 5 (the first and second magnetic thin films 3.4 ) of the sub-lattice (there are recorded portions where the depletion direction is the same and recording portions where the depletion direction is opposite to each other. However, during playback or storage of the recording medium, such Efa dichotomy occurs. If there is an antiparallel portion where the sublattice magnetization directions of the five layers are opposite to each other, the following disadvantages occur.

That is, first of all, if the sublattice magnetization of each thin film 3.4 is in the above-mentioned antiparallel state, the thickness of the first thin film 3 must be increased in order to improve the reproduction characteristics. From the calculation of the cR process, it is better to have a thicker film thickness h2 of the second three films 4, so the film thickness of the magnetic double layer film 5 becomes considerably thicker, and a high output laser is required to perform the above heating. However, it is currently difficult to supply such a high-output laser.

Further, even when stored at room temperature or the like, if the sublattice magnetization of each layer of the magnetic double-layer film 5 is in an antiparallel state, it is unstable against magnetic fields and heat. Furthermore, this antiparallel state is a state in which only one magnetic thin film 3 carries information, and when reproducing using the Kerr effect, information can only be read from this thin film 3 side. If the Curie temperature TC2 of the second thin film 4 is higher than the Curie temperature TCI of the first thin film 3 (Tc+<TCx) as shown in FIG. Generally, 0.2 is larger (
Since θ is 1 and θ is 2), the S/N ratio will be better if the signals are successively output from the second thin film 4 side, but such readout cannot be performed if the above-mentioned antiparallel state remains. For this reason, when playing back or saving a recording medium, the second
It is desirable that the sublattice magnetization direction of the three films 4 be the same as the sublattice magnetization direction of the first thin film 3.

To explain the conditions for this, the magnetization shape G in Figure 1 is
A third external magnetic field H, (in FIG. 1, the direction of the arrow of the external magnetic field H1 is assumed to be positive) is applied to the magnetic recording medium having the recording portions A and C, and the magnetization state Bc is changed to the magnetization state. The conditions for transitioning to B are 2M! +b+Ht+σw <21M5lh+Hc+2M
Bhz)Is+σw>21MSihJcz. In addition,
At the same time, the condition for the magnetization state GA not to transition to other magnetization states fiB, C or D: 2M5+h+Hz-2MszhzHz<21Ms, l
hIHc+ + 21M5zl hzllcz-2M
3. h1H3-σ-< 21M311 h+Hc+2M
5zh mountain - σw <21M321 hz) fez is of course necessary.

It is necessary to satisfy these conditions at the operating temperature or the medium temperature during reproduction, but in addition to the third external magnetic field H3, it is also necessary to
That is, when the external magnetic field H2 shown in FIG. 1 is applied, the following conditions must be satisfied in addition to the above conditions. Here, the direction of the external magnetic field HIIX is the same as the direction of the external magnetic field H3, and H,
It is assumed that there may be cases where First, magnetization, r3 A
The condition that does not transition to another magnetization state is Hl in the above conditional expression.
It can be obtained by replacing 1 with H98. Next, the conditions for the magnetization state B that has been transitioned from the above state C to not transition to another state are as follows: 2-3 mountains H*x + 2M5zhz Hax < 21M
sl h+lb+ + 21M 32111zflcz
2Ms+l'11H,, -σw <21M5. l fi
+Hc+2M5zbzH,, -σ-< 21M5zl
bzHct.

In this explanation of the magnetization state for reproduction/storage, changes in the magnetization state are also explained using states HA, B, and state C. However, the direction of magnetization of the second magnetic thin film 71 in the initial state is When aligning in the opposite way to the above, states A, 3 and state gH
A similar transition of the magnetization state is also possible using Bp. That is, in this case, state B is the state of the above embodiment, GA
Similarly, the shape part A is made to correspond to B, the state go to C, and the state C to D, and the magnetization state at the end of the override is set to the magnetization state BA suitable for reproduction and storage.
This is to increase the number of transitions.

G-6. Specific Example of Thermomagnetic Recording Medium Next, a specific example of the magnetic material used as each magnetic thin film 3.4 of the thermomagnetic double layer film 5 in the thermomagnetic recording medium 10 will be described.

Using so-called DC magnetron sputtering, a RE-7M ferrimagnetic thin film (dielectric material), which will become the first and second magnetic thin films 3. (without interposing the film 2) to form the magnetic two-layer film 5. In this case, for RE-TM ferrimagnetic thin n 3.4, RM (rare earth metal) and TM
(transition metal), and to prevent oxidation of the magnetic double-layer film 5 consisting of these magnetic thin films 3 and 4, the surface side (lower side in Fig. 2) Thickness 8
A protective film 6 of 0.00 people is deposited.

Further, the single layer film of each layer was heated under the same conditions as the two layer film 5, and the magnetic properties of each layer and the above-mentioned interfacial domain wall energy density σ were evaluated. Here, the materials, film thicknesses, and characteristics at room temperature of each of the three films 3.4 are shown in Table 1.

Table 1 For these first and second (d characteristics 1 yield 3.4), at room temperature, the RE sub-leaf magnetization is thicker than the 7M sub-lattice magnetization (RE rich), The first layer thin film 3 has a magnetic compensation point near 120°C, and the second layer thin film 4 has a magnetic compensation point near 170°C. Also, the interfacial domain wall energy density σ4 at room temperature is 2.0 (erg /co+2).

External V! L
A field of 20 kOe was applied, and the magnetization state became as shown in Fig. 4 above.
I initialized it so that it would be QA. Next, with Q and 3 kOe applied as the external magnetic field H1 in Fig. 1 above,
The sample was heated to temperature T and then cooled to room temperature. During this time, linearly polarized light with a wavelength of 830 nm was irradiated from the side of the transparent substrate 1 such as a slide glass, and the magnetization state was observed using the so-called Kerr effect. At this time, when the heating temperature T was 150° C., the magnetization state after heating and cooling was unchanged from before heating, and was in the above state, BA. On the other hand, Canada? When A degree T was 200° C., the magnetization state after heating and cooling became the above-mentioned state 6B in which the direction of magnetization was reversed for both thin films 3.4.

Next, when a magnetic field of 5 kOe as the external magnetic field H2 in FIG. 1 is applied to the sample which is in state B at room temperature, the magnetization state of the bilayer film 5 changes from state 6B to state C. It was observed that Further, even when the external magnetic field H2 was applied to the sample in state A, no change in the magnetization state was observed.

Next, the above sample, which is in state C at room temperature, was heated to the above temperature T with the above external (d field H1 applied) and cooled to room temperature, !:. , G.A.
As in the case of heating and cooling from
It was confirmed that when the temperature was 0°C, state B was reached after cooling.

Here, the two-layer film sample used for measurement was at room temperature, 50°C, and 7°C.
At each temperature of 5° C., 100° C., 1125° C., and 150° C., each override conditional expression in the above-mentioned section G-4 is satisfied. Furthermore, at other temperatures as well, Ms,
Since 1/Hc and σ8 change continuously, it is considered that they are almost satisfied. In addition, the external magnetic field required for the transition of the amorphous state at each temperature is in good agreement with the value obtained from the conditional expressions. It is clear that these conditions are suitable for realizing the magnetic recording method.

By the way, when the external magnetic field H at room temperature was changed, the magnetization state of the two-layer film 5 made of each of the magnetic thin films 3.4 shown in Table 1 changed as shown in FIG. 5. In FIG. 5, HOI represents an external magnetic field in which a transition from state to state A (or from state C to B) occurs. Similarly, )(oz is the external magnetic field when moving from state B to state 6c (or from state A to D) & HO2 is the state 6c
From c to state GA (or from state to B) i! i! Each represents the external magnetic field when moving. Note that these magnetization state transition external magnetic fields were measured using the Kerr effect. Here, from the above external (Moriba HO3) and each layer in Table 1 above, the interfacial domain wall energy density σ is 2.
It is calculated as O (erg/cm"). Also, the calculated values and measured values of Hot when using this value of energy density σ8 are in good agreement.

In FIG. 5, the magnetization state during recording is 9. Either A or Bc (or B, B or D)
, the external magnetic field He that satisfies the following conditions during reproduction is
By applying xa (or Hex+), it is possible to perform reproduction in which the states gA and GB are in the recording magnetization state.

Hog<Hexa<-Hot (or Hot<Hexa<Hot) In this way, the magnetization state of the magnetic double layer film 5 changes to the shape M during reproduction.
When the state is A or QB, the magnetic double layer film 5 is lower than when the state is C (or QD).
As described above, both thin films 3.4 can be used for signal readout, and the S/N ratio of the reproduced signal is improved.

This means that if the state after the override is either A or C (or BB or D), an external magnetic field Hexa (or Hexm) that satisfies the above conditions is applied.
), it is stored in the magnetized states A and B,
Playback becomes possible. However, when applying the above external magnetic field Hexa (or when applying HexB), during storage, or during playback, other external magnetic field Hexc (or Hexo
) is applied, it is necessary to also satisfy the following conditions.

)(.z <Hex(<Hox (or HOZ < HeXo < Hox)G
-7, Other Embodiments In the embodiment shown in FIG. 1, the second magnetic thin film! When IQ4 has a magnetic compensation point between room temperature and temperature T2, as shown in FIG.
It will be facing the same way.

As shown in Fig. 6, the direction of the external magnetic field H2 is
Since the direction is the same as that of 1, as shown in Figure 7, 1
．． Each of the external magnetic fields H6 and H2 using the same magnet 13
can be produced. That is, by setting the irradiation position of the laser beam R on the thermomagnetic recording 10 at the periphery of the magnet 13, the magnetic field from the magnet 13 is prevented from reaching the maximum at the laser irradiation position, and the external magnetic field H0 at this point is Smaller than the second external magnetic field H2 (Hz > H+
).

It should be noted that the present invention is not limited to the above embodiments, and for example, ferromagnetic thin films can be used in addition to ferrimagnetic thin films as each layer of the magnetic double-layer film of a thermomagnetic recording medium.

Above, a specific example of the present invention has been explained using an example in which the magnetic coupling energy between two layers is due to exchange coupling between both layers, but this magnetic coupling energy may be due to magnetostatic coupling between both layers or in addition to exchange coupling. It does not matter if it is due to a combination.

H1 Effects of the invention According to the thermomagnetic recording method of the invention, the intensity and irradiation time of a heating beam such as a laser beam are modulated according to the information signal, and the heating temperature of the medium is varied between the first and second temperatures. Information can be effectively recorded on the medium by using a simple configuration that only performs switching on the switching side.

[Brief explanation of drawings]

FIG. 1 is a magnetization state diagram for explaining the operation of an embodiment of the present invention, FIG. 3 is a schematic configuration diagram schematically showing an example of a recording device, FIG. 4 is a diagram for explaining the transition of magnetization state, FIG. 5 is a diagram showing changes in magnetization state in response to changes in external magnetic field, and FIG. FIG. 6 is a magnetization state diagram for explaining another embodiment, and FIG. 7 is a schematic configuration diagram for explaining the application state of an external magnetic field in the other embodiment. 3...First magnetic thin film 4...Second magnetic thin film 5...Magnetic double layer film 7...Interfacial domain wall

Claims (1)

[Claims] First and second magnetic thin films are magnetically coupled and stacked,
Using a thermomagnetic recording medium including a laminated film having a portion in which the magnetic moments of the first and second magnetic thin films are coupled in opposite directions to each other, the temperature of the first magnetic thin film is approximately equal to or higher than the Curie temperature T_C_1 a first heating state in which the second magnetic thin film is heated to a temperature T_1 at which reversal of the magnetic moment does not occur; and a temperature equal to or higher than the temperature T_C_1 and sufficient to reverse the magnetic moment of the second magnetic thin film. A second heating state of heating to T_2 is modulated according to the information signal to be recorded, and recording magnetization is formed in the thermomagnetic recording medium by cooling from each of the heating states. Thermomagnetic recording method.