JPS6374147A - Recording method for magneto-optical disk - Google Patents

Abstract

PURPOSE:To enable overlap writing and to improve the efficiency of a treatment by laminating two magnetic films which consist of ferrimagnetic materials and are shifted in magnetic characteristics and projecting laser beams having different powers thereto. CONSTITUTION:A bias layer 2 consisting of terbium iron having large coercive force is formed on a substrate and further, a recording layer 3 consisting of dysprosium.iron having a low compensation temp. and Curie temp. is formed thereon. The layer 2 is first kept magnetized in the specified direction at a ordinary temp. The light 5 of the L power for heating at the compensation temp. or below and the light 4 of the H power for heating near to the Curie temp. shown in the figure (c) are projected to the layer 3 on which the information shown by and in the figure (a) is written in order to record the information of the figure (b) to said layer, then the magnetization direction of the layer 2 in the irradiated part changes to and the magnetization of the layer 3 is inverted as well by electrostatic coupling, by which the figure (d) is obtd. the magnetization of the layer 2 is inverted and the information is written in overlap in the direction of the figure (e) when the layer is cooled after the irradiation. The efficiency of the treatment is thereby improved.

Description

[Detailed Description of the Invention] [1 Already Required] As a new information recording method for a magneto-optical disk, recording is performed on a disk substrate composed of a stacked bias layer and recording layer, which have been perpendicularly magnetized in one direction in advance. When the recording layer is heated to near the Curie temperature, the bias layer is heated only below the compensation temperature by a laser pulse, and when the recording layer is heated above the Curie temperature, the bias layer is heated above the compensation temperature. A recording method for magneto-optical disks in which binary information is recorded by selectively irradiating laser pulses with a power that is heated to below temperature.

[Industrial application field]

The present invention relates to a new recording method for magneto-optical disks.

A magneto-optical disk is a memory that uses laser light to record high-density information. Like an optical disk, it has a large storage capacity, can record and read without contact, and is unaffected by dust. It has certain characteristics.

Here, an optical disk is a read-only memory that uses a low-melting point metal as a recording medium and records and reproduces information by the presence or absence of holes (pits).
y), whereas magneto-optical disks are developed for rewritable memory (eraserble memory).
It is currently being developed as a memory.

(Prior art) Magneto-optical disks are made by forming a film of an amorphous rare earth-transition metal alloy on a disk-shaped transparent substrate made of plastic or glass using a vacuum evaporation method or a sputtering method. A disk substrate is manufactured by creating a recording layer, and then providing a protective film on top of this.

Here, polymethyl methacrylate (
Transparent plastic substrates such as polycarbonate (abbreviated as PC) or glass substrates are used, and in the case of plastic substrates, concentric or spiral guide grooves (pre-groups) are formed by molding. ing.

On the other hand, in the case of a glass substrate, a technology has been developed to create a substrate with guide grooves by coating an ultraviolet curing resin on the resin, pressing a mold onto it to form grooves, and curing it by irradiating ultraviolet rays through the glass substrate. has been used.

Next, the recording layer is made of a perpendicularly magnetized film showing ferrimagnetism made of rare earth-transition metals, such as terbium-iron-cobalt (Tb Fe Co), gadolinium-terbium iron (Gd Tb Fe), etc., as described above. It is formed by vacuum evaporation method, sputtering method, etc.

Further, the protective film is made of silicon oxide (Sin) or the like.

To record information on a magneto-optical disk with such a structure, a laser beam focused by a lens is irradiated from the side of the transparent disk substrate while a vertical magnetic field is applied, and the temperature of the irradiated part of the perpendicularly magnetized film is adjusted. This is done by utilizing the fact that the temperature rises to reach the Curie temperature, and the magnetization is reversed in the direction of the magnetic field.

Furthermore, information is erased by applying a magnetic field in the direction opposite to the direction of magnetization at the recording position, and by irradiating and heating the material with laser light to reverse the magnetization to its original direction.

In order to erase recorded information and write other information at this position using such conventional recording/erasing methods, it takes one rotation to erase the information, one rotation to reverse the magnetic field, and one rotation to write the information. Requires rotation and overwriting (0νer-wr
The problem is that it cannot be done.

Here, the reason why overwriting is not possible is because the inductance of the coil for applying the magnetic field is large, and the magnetic field cannot be reversed at high speed.

[Problem that the invention seeks to solve]

As described above, in order to erase recorded information and write other information at this position using the conventional method, one rotation is required to erase the information, one rotation is required to reverse the magnetic field, and one rotation is required to write information. The problem is that it cannot be overwritten like magnetic tape.

[Means for solving problems]

The above problem is solved by forming a bias layer made of a ferrimagnetic material and magnetized perpendicularly in a certain direction on a substrate having a guide groove for the laser beam, and a recording layer made of a ferrimagnetic material like the bias layer. However, the recording layer in the guide groove is heated to near the Curie temperature by irradiation, the bias layer is heated by a laser pulse with a power that is only heated below the compensation temperature, and the recording layer is heated above the Curie temperature and the bias layer is heated to a temperature close to the Curie temperature. This problem can be solved by a magneto-optical disk recording method in which binary information is recorded by selectively irradiating a laser pulse with a power that heats the layer above the compensation temperature and below the Curie temperature.

[Effect]

The present invention utilizes the characteristics of ferrimagnetism as a method for overwriting.

In other words, the recording medium used as the recording layer of a magneto-optical disk is a ferrimagnetic material, and when a magnetic field is applied to align the magnetization in a certain direction, the temperature is raised from room temperature as shown in Figure 3. As the temperature approaches the compensation temperature determined by the composition of the material used, the strength of magnetization (M) decreases, while the coercive force (Hc) increases and reaches a maximum state.

Then, the direction of magnetization is reversed and gradually increases after reaching the compensation temperature, and decreases again as it approaches the Curie temperature. At the Curie temperature, it becomes a paramagnetic material, so Hc becomes O.

The present invention makes use of the ferrimagnetic characteristics that change with the compensation temperature as a boundary, and a magneto-optical disk is composed of two ferrimagnetic layers having different magnetic characteristics on a substrate.

That is, as shown in FIG. 1, the magneto-optical disk according to the present invention is constructed by laminating a bias IW2 and a recording layer 11J3 on a substrate 1, and the necessary conditions for the bias layer 2 are as follows: (1) Compensation The temperature is above room temperature; (1) The coercive force Hc is high at room temperature.

On the other hand, the necessary conditions for recording Ji3 are: (1) The compensation temperature is low, even if it is below room temperature.

■ The Curie temperature is low and can be easily reached by low power laser irradiation.

is necessary.

The present invention uses two magnetic films with different magnetic properties and performs overwriting by irradiating them with laser beams of different powers. First, a method for recording and erasing information will be explained.

First, the bias layer 2 is magnetized in a certain direction, for example, in the ↑ direction at room temperature.

In this case, the magnetization directions of the recording layer 3 on the bias layer 2 are all oriented in the ↑ direction due to magnetostatic coupling. (
(a) Next, the coercive force (Hc) of the recording layer 3 is applied to the optical disk in this state.
) and is sufficient to heat the bias layer 2 to a temperature above the compensation temperature and below the Curie temperature (Tc) (hereinafter referred to as H power) 4, the bias layer 2 in the irradiated area becomes magnetized. is reversed and becomes the direction of ↓,
Due to the magnetostatic coupling, the magnetization of the recording N3 in the upper part is also directed in the ↓ direction.

(The above figure b) Next, when the laser irradiation is finished and the temperature is lowered, the magnetization of the bias N2 is reversed at the compensation temperature and returns to the normal direction as shown in Figure 3, but the temperature of the recording layer 3 is lower than that of the bias layer 2. Since the temperature drops first, if the compensation temperature is lower than room temperature, the reversal does not occur, but the coercive force is recovered and the recording pattern in the ↓ direction remains as it is, and recording is performed. (The above is C in the same figure) Next, when erasing information magnetized in the ↓ direction, write S!
If the bias N2 is irradiated with a laser power (hereinafter referred to as L power) 5 that is sufficient to lower the coercive force Hc of Fi3, but does not heat it above the compensation temperature, the Hc of the recording layer decreases, and as a result, the bias layer Due to the magnetostatic coupling of , magnetization reversal occurs, and the magnetization of the recording layer is oriented in the ↑ direction and erased.

(The above is d in the same figure) [Example] The recording layer was made of dysprosium with a Tc of 70°C.
Iron (Dy Fe), and as a bias layer) Terbium iron (Tb Fe) with C of 5 KOe or more at room temperature
A semiconductor laser was used as the laser beam, and the laser beam was focused to a bit diameter of 1 μm using a lens.

FIG. 4 is an explanatory diagram of the overwriting method according to the present invention, and it is assumed that information as shown by ↓ and ↑ is initially written in the recording layer 3 as shown in FIG. 4(a).

In order to record information as shown in the same figure (b), the power of the light 5 corresponds to ↓ and ↑ as shown in the same figure (c).
When the magneto-optical disk is irradiated with the H-power light 4, the direction of magnetization of the bias layer 2 in the irradiated part changes to ↓, and the magnetization of the recording layer 3 is also reversed due to magnetostatic coupling (see d in the same figure). As cooling progresses after the completion of cooling, the magnetization of only the bias layer is reversed? The overwriting ends when aligned in the direction of . (E) [Effects of the Invention] As described above, by implementing the present invention, overwriting becomes possible, and thereby information processing efficiency can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a magneto-optical disk according to the present invention, Fig. 2 is a cross-sectional view explaining the recording and erasing method according to the present invention, and Fig. 3 is a temperature characteristic of magnetization strength and coercive force of a ferrimagnetic material. FIG. 4 is a sectional view illustrating the overwriting method according to the present invention. In the figure, 1 is the substrate, 2 is the bias layer, 3 is the recording layer, 4 is H power, 5 is L power, and the left part is Ueto 1 Koyorirot λ holding te 4th 2's λ piece carpet broom 1 Figure 1 Too hundred men's bow j 2 f Toru fortune-telling cheap Hi 5@shi light and beast man anal arrogance rtc rod 2 to

Claims (1)

[Claims] a bias layer made of a ferrimagnetic material and magnetized perpendicularly in a certain direction on a substrate having a laser beam guide groove;
A recording layer made of ferrimagnetic material is formed in the same manner as the bias layer, and when the recording layer is heated to near the Curie temperature by irradiation, the bias layer is heated only to a temperature below the compensation temperature using a laser pulse of such power. and, when the recording layer is heated above the Curie temperature, the bias layer is selectively irradiated with two types of laser pulses that are heated above the compensation temperature and below the Curie temperature to record binary information. A recording method for magneto-optical disks.