JP2659708B2 - Magneto-optical memory media - Google Patents

Description

The present invention relates to a method for forming a magnetization pattern by perpendicular magnetization,
The present invention relates to a double-sided magneto-optical memory medium for recording information, and for example, relates to a medium structure suitable for being applied to a magneto-optical memory medium made of a rare earth-transition metal amorphous alloy.

2. Description of the Related Art In recent years, as a large-capacity memory such as a computer, a so-called optical disk that records and reproduces information using light has been known. Among these optical disks, a magneto-optical disk using the magneto-optical effect has attracted attention as an erasable, that is, rewritable optical disk.

This magneto-optical disk forms a minute magnetization pattern that is magnetized in the vertical direction using a laser beam on a thin film of an amorphous compound of a rare earth (Gd, Tb, Dy, etc.) or a transition metal (Fe, Co, etc.). The pattern is read out using the Faraday effect or the Kerr effect.

FIG. 5 shows a sectional structure of a double-sided magneto-optical disk. In this case, the magneto-optical media 3 and 4 are coated on one surface of the two glass substrates 1 and 2, respectively.
3 and 4 are adhered on the layer via an adhesive 5 and the glass substrates 1 and 2
Has a structure for protecting the magneto-optical media 3 and 4.

FIG. 6 illustrates a method of recording information on such a magneto-optical disk, in which a laser beam 8 condensed by a lens a is irradiated onto a position of the magneto-optical medium 3 where information is to be recorded. The temperature of the magneto-optical medium 3 in this portion is increased. In this way, while the temperature of the magneto-optical medium 3 is raised, an upward auxiliary magnetic field indicated by an arrow 6 in the figure is applied from the outside, and the magnetization direction of the magneto-optical medium 3 is aligned upward. Delete the information remaining in the

Next, the direction of the auxiliary magnetic field is reversed, and a downward auxiliary magnetic field indicated by an arrow 7 is applied, and at the same time, the laser beam 8 is modulated and irradiated in accordance with the recording information, and the portion of the magneto-optical medium hit by the laser beam is irradiated. Information is recorded by reversing only the direction of magnetization of No. 3.

When the information recording on the magneto-optical medium 3 on one side is completed by the above-described method, the magneto-optical disk is turned over next, and
Information is recorded on the magneto-optical medium 4 on the reflection surface in the same manner.

In this case, as shown in FIG. 7, the direction of magnetization of the magneto-optical medium 3 where information is recorded (indicated by an arrow 11) and the direction of magnetization of the magneto-optical medium 4 where information is recorded (indicated by an arrow 12) The direction of the magnetization of the magneto-optical medium 3 where the information is erased (indicated by an arrow 9) and the direction of the magnetization of the magneto-optical medium 4 where the information is erased (indicated by an arrow 9) are opposite to each other. .

Problems of the prior art In the above-described double-sided magneto-optical disk, the holding force on both sides is generally the same. Therefore, when it becomes necessary to erase all the information recorded on one or both sides arbitrarily selected, an external magnetic field of a coercive force greater than the coercive force of the magneto-optical medium is applied to uniformly magnetize the information and collectively collect the information. Cannot be erased. This is because the directions of magnetization (indicated by arrows 9 and 10) of the magneto-optical media 3 and 4 from which information has been erased should be opposite to each other as described above. When a magnetic field having a strength equal to or greater than the coercive force of the magneto-optical medium is externally applied to the magneto-optical medium, the directions of the magnetizations of the magneto-optical media 3 and 4 are the same, and the correct magnetization cannot be erased.

In addition, in the method of collectively erasing information by applying such a strong magnetic field, it is natural that magnetization extends to both the front and back surfaces and it is difficult to erase only one surface.

Such a problem can occur commonly with a magneto-optical medium made of a rare earth-transition metal amorphous alloy or another material.

Object of the Invention Therefore, an object of the present invention is to provide a magneto-optical memory medium having a magneto-optical medium layer formed on both front and back surfaces, and to effect the recording information on only the arbitrarily selected side on the recording information on the other side. It is an object of the present invention to provide a structure of a magneto-optical memory medium capable of erasing the entire surface without giving a defect.

Constitution of the Invention In order to achieve the above-mentioned object, the main means adopted by the present invention is, in summary, a magneto-optical medium having a magneto-optical medium layer formed on both front and back surfaces. Are magneto-optical memory media according to the point that they are constituted by compositions having different coercive forces.

A typical example of the composition of such a magneto-optical medium is a rare-earth-transition metal-based amorphous alloy. The above-described adjustment of the coercive force is performed, for example, by appropriately setting the compensation point composition. be able to.

As described above, since the coercive force of the magneto-optical medium is different between the front surface and the back surface, first, a magnetic field having a magnetic field strength between the high coercive force and the low coercive force of the different coercive force is applied to one surface. The recorded information on the surface with the lower coercive force is completely erased.
Subsequently, the temperature of the entire magneto-optical memory medium is appropriately increased, and the compensating point temperature of the magneto-optical memory medium on the side where the coercive force is set to be relatively low is first changed to increase the coercive force of this surface. Conversely, in the state where the compensation point temperature of the surface that was initially high coercive force was changed to decrease the coercive force of that surface, and thus the state of the coercive force of the front and back surfaces was reversed,
By applying an external magnetic field, which is set at the intermediate magnetic field strength between the newly set high and low coercive force, to the entire magneto-optical memory medium, only the recorded information on the surface with the first high coercive force can be completely covered. to erase. At this time, when the two magnetic fields are formed, by setting the direction of the magnetic field to the opposite direction with respect to the magneto-optical memory medium (inverting the optical disk), the directions of the erased magnetic fields on the front surface and the back surface are reversed. Direction. By performing one or both of the two magnetizations described above, it is possible to completely erase the recorded information on both sides or any one side of the magnetic recording memory medium without affecting the other side. it can.

Embodiment Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a characteristic diagram showing the relationship between the coercive force and the rare earth composition of the rare earth-transition metal amorphous magnetic medium according to one embodiment of the present invention, and FIGS. 2 (a) and 2 (b) show the rare earth-transition FIG. 3 is a characteristic diagram showing the temperature dependence of the coercive force of the metal amorphous magnetic medium, and FIG.
FIG. 4 is a characteristic diagram showing the composition dependence of the compensation point temperature of the Co film, and FIG. 4 is a characteristic diagram showing the temperature dependence of the coercive force in the same medium.

The following embodiments are merely specific examples of the present invention and do not limit the technical scope of the present invention.

In the following embodiments, the structure of the magneto-optical disk shown in FIGS. 5 to 7 will be described as an example.

In the following embodiment, for example, the medium composition of the magneto-optical medium 3 on one surface is set to be a rare-earth-excess medium and set to the state A shown in FIG. 1 having a relatively low coercive force. Further, the medium composition of the magneto-optical medium 4 on the other surface is set to B or C, which is close to the compensation point composition and has a high coercive force. In the following description, the case of the high coercive force state B will be described.

In a double-sided magneto-optical disk having such a medium composition, when the recorded information on the surface in the state A is entirely erased without affecting the other surface in the state B, the external information at the time of erasing is required. The magnetic field strength H is set to _Ha <H < _Hb and applied to the entire surface of the magneto-optical disk. As described above, since the strength of the external magnetic field at this time is lower than the coercive force _Hb on the surface side in the B state, the magneto-optical medium 4 on the side in the B state has no magnetic influence. However, the recording information on the surface side in the state A on the other side is completely erased, and its direction is unified in the direction indicated by the arrow 9 in FIG.

Next, when it is desired to completely erase only the recording information on the surface side in the state B, the magneto-optical memory medium is inverted and the temperature is raised by ΔT as a whole. The temperature rise ΔT is such that the surface which was initially in the state A having a relatively low coercive force becomes a state A ′ (see FIG. 2 (a)) having a high coercive force near the compensation point temperature, The other surface, which was in the state B near the compensation point temperature, is set so as to be in the state of B 'having a low coercive force (see FIG. 2B). By increasing the ambient temperature by ΔT in this way, the level of the coercive force on the front surface and the back surface is reversed, and Hb ′
An external magnetic field H 'satisfying <H'<Ha'is applied to the entire surface of the magneto-optical disk. Here, Ha ′ and Hb ′ represent the temperature ΔT, respectively.
2 shows the coercive force of the magneto-optical disks 3 and 4 in the state where the magnetic disks 3 and 4 have been lifted up.

As a result, the surface in the state A 'having a high coercive force is not magnetically affected at all, and only the magneto-optical medium 4 on the surface having changed to the low coercive force is entirely in the direction indicated by the arrow 12 in FIG. It is magnetized and the recording is erased on one side.

In the above-described embodiment, the case where the entire recording information is erased from both sides of the magneto-optical media 3 and 4 has been described. However, by performing only one of the steps, the recording and erasing on only one side may affect the other side. It is possible to do without.

Further, in the above embodiment, the case where the medium composition is set on the rare-earth excess side from the compensation point composition on both sides (A, B) has been described as an example. The setting (C) is similarly realized.

3 and 4 show rare earth elements according to another embodiment of the present invention.
FIG. 2 is an explanatory diagram of a magneto-optical medium including a Gd—Co film, which is an example of a transition metal alloy. FIG. 3 is a characteristic diagram showing the composition dependence of the compensation point temperature of the Gd-Co film, and FIG. 4 is A (Co: 77%).
7 is a graph showing the temperature dependence of the coercive force in a Cd—Co film having two compositions, ie, a state of Cd (Co: 78%) and a state of C (78%).

If the two medium compositions A and C are selected as A (Co: 77%) and C (Co: 78%) across the compensation point temperature as shown in Fig. 3, the temperature dependence of the coercive force of each medium The characteristics are as shown in FIG. Therefore, if it is desired to erase only the surface having the composition of A, the external magnetic field H is set to 50 <H <200 (O
e). When it is desired to erase only the surface having the composition of C, the external magnetic field H may be set to 50 <H <300 (Oe) while ΔT = about 19 ° C. and the medium temperature is raised.

Further, in the Gd-Co film, other than the above composition,
Is 75 to 77% and Co is 78 to 79% as C, it can be used as a magneto-optical memory medium. However, if the compositions of A and C are too far apart, the temperature change ΔT must be increased, which is inconvenient. When ΔT exceeds 100 ° C., the coercive force of the medium having the composition C becomes high in a high temperature state, which is not preferable in terms of recording characteristics. If the distances are too close, there is no difference in the temperature characteristics of the coercive force, and the object of the present invention may not be achieved.

Effects of the Invention As described above, the present invention provides a magneto-optical memory medium having a magneto-optical medium layer formed on both front and back surfaces, wherein the magneto-optical medium on each surface is formed of a composition having a different coercive force. Since it is a characteristic magneto-optical memory medium, it is possible to perform erasure of recorded information only on an arbitrarily selected surface or on both surfaces in a short time without affecting recorded information on the other surface. .

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the relationship between the coercive force of the rare earth-transition metal amorphous magneto-optical medium and the rare earth composition, and FIG. 2 is a characteristic diagram showing the temperature dependence of the coercive force of the rare earth-transition metal amorphous magneto-optical medium. FIG. 3 is a characteristic diagram showing the composition dependence of the compensation point temperature of the Gd-Co film, FIG. 4 is a characteristic diagram showing the temperature dependence of the coercive force in the medium, and FIG. 5 is an embodiment of the present invention. Showing a schematic sectional configuration of the magneto-optical memory according to FIG.
FIG. 7 is a conceptual diagram for explaining a method of recording information on a magneto-optical disk, and FIG. 7 is a conceptual diagram showing a magnetic pattern of the magneto-optical disk after recording. (Explanation of symbols) 1,2: glass substrate 3,4: magneto-optical medium 5: adhesive, 6,7: direction of magnetic field 8: laser beam 9,10,11,12 ... magnetization Direction a ... Lens.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiteru Murakami 22-22, Nagaikecho, Abeno-ku, Osaka-shi Inside Sharpe Co., Ltd. (72) Inventor Kenji Ota 22-22 Nagaikecho, Abeno-ku, Osaka City Inside Sharpe Co., Ltd. (56) References JP-A-60-7634 (JP, A)

Claims (1)

(57) [Claims] 1. A magneto-optical memory medium having a magneto-optical medium layer formed on both front and back surfaces, wherein the magneto-optical medium on each surface is formed of a composition having a different coercive force.