JPH02306445A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To allow the direct overwriting of information even with a small modulation magnetic field by holding the regions where the recording of information is not executed and which are adjacent to the regions where the recording of the information is executed in magnetic recording layers into a degaussing state. CONSTITUTION:This magneto-optical recording medium executes the recording of the information by irradiating the magnetic recording layers with the convergent light of a specified intensity or modulated according to the recording information simultaneously with the impression of the magnetic field modulated according to the recording information. The regions 102 where the recording of the information is executed and which are adjacent to the regions 101 where the recording of the information is executed in the magnetic recording layers are previously put into the degaussing state. Then, floating magnetic field intensity from the regions 102 is nearly zero and, therefore, the relation ¦HW¦=¦HE¦ of the magnetic field (HW) and the erasing magnetic field (HE) approximately holds and the modulation magnetic field in the magnetic field modulation recording system is lowered. The direct overwriting of the information even with the small modulation magnetic field is possible in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magneto-optical recording in which information is recorded by the interaction between the thermal energy of convergent light such as a laser beam and a magnetic field, and is reproduced by the magneto-optic effect. In particular, the present invention relates to a magneto-optical recording medium that allows direct override using a magnetic field modulation method.

[Prior Art] Conventionally, as a magneto-optical recording medium used for magneto-optical recording capable of direct override using a magnetic field modulation method, one in which a thin film of an alloy such as TbFeCo or DyFeCo is used as a magnetic recording layer has been used. For example, JP-A No. 63-
In the example of the magneto-optical recording medium for magnetic field modulation disclosed in No. 217548, TbFe is deposited on a transparent substrate with a thickness of about 1.2 mm.
A dielectric layer such as Si3N4 is formed on both sides of the Co layer, and a protective coat is further provided. As disclosed in Japanese Unexamined Patent Publication No. 51-107121, the magnetization direction of the magnetic recording layer is generally aligned in one direction in advance before use.

[Problems to be Solved by the Invention] Incidentally, in the magnetic field modulation method, it is necessary to modulate the magnetic field according to the recorded data, but in order to directly override information on a conventional magneto-optical recording medium, two steps are required.
It is necessary to modulate a relatively large magnetic field of about 00 to 3000 e at high speed. However, increasing the number of turns of the coil to obtain such a large magnetic field increases the inductance of the coil, making it extremely difficult to achieve high-speed magnetic field reversal. Therefore, there is a problem that direct override of information cannot be realized at a practical speed.

The present invention is intended to solve these problems, and its purpose is to provide a magneto-optical recording medium that allows direct overwriting of information even with a small modulated magnetic field.

[Means for Solving the Problems] The magneto-optical recording medium of the present invention applies a magnetic field modulated according to recorded information and simultaneously irradiates a magnetic recording layer with a fixed intensity or focused light modulated according to recorded information. In a magneto-optical recording medium in which information is recorded by
It is characterized in that the area where information is not recorded is in a demagnetized state. The recording magnetic field (Hu) and erasing magnetic field (
It is determined by the size of HE). In the case of a transition metal-rich magnetic recording layer, the relationship 1Hul<IHEI generally holds, so the modulation magnetic field strength in the magnetic field modulation method is IME
I or more is required. This is because the direction of the stray magnetic field from the part of the magnetic recording layer that is not used for recording is in the writing direction, so it is superimposed on the recording magnetic field and the erasing magnetic field and acts as an offset magnetic field. Therefore, lHi+1=lH
At EI, the modulated magnetic field strength is at its minimum.

FIG. 1 is a diagram showing the configuration of the present invention, and shows the magnetic recording layer viewed from above. Now, if the area 102 of the magnetic recording layer where no information is recorded, which is adjacent to the area 101 where information is recorded, is demagnetized, the stray magnetic field strength from the area 102 will be almost zero, so l Hul =
I HEI approximately holds true, and it becomes possible to reduce the modulation magnetic field strength in the magnetic field modulation recording method.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 2 schematically shows a cross section of a magneto-optical recording medium which is an example of the present invention. In FIG. 2, a disk substrate 201 is a transparent glass substrate with a diameter of 130 mm and a thickness of 1.degree. 2 mm, and is provided with a spiral guide groove for tracking, although not shown in the figure. An interference layer 202 with a thickness of 9 nm made of Al-3t-N is placed on the substrate side with a magnetic recording layer 203 with a thickness of about 30 nm in between, and the same <Al-
A protective layer 204 made of 3i-N and having a thickness of 25 nm was provided.

On top of that, a reflective layer 205 made of AI with a thickness of 40 nm is formed, and further made of ultraviolet curing resin with a thickness of about 10 μm.
A protective coat layer 206 was provided.

As an example of the present invention, the composition of the magnetic recording layer 203 is Nd6.
A magneto-optical recording medium made of Dy22F e62coIO (at%) was produced. Although the magnetic recording layer 203 was manufactured by sputtering, the entire surface of the disk was in a multi-domain demagnetized state.

Next, the recording/reproducing characteristics of this magneto-optical recording medium using an optically assisted magnetic field modulation recording method were evaluated.

A method of recording information will be explained using FIG.

That is, as shown in FIG. 3(b), convergent light from a semiconductor laser continuously emitted from the disk substrate 201 side is irradiated to heat the magnetic recording layer 203 to a temperature close to the Curie temperature, thereby lowering the coercive force. At the same time, a magnetic head placed on the protective coat layer 206 side is used to generate a recording signal (see FIG. 3(a)).
) The polarity of the magnetic field applied to the recording medium is shown in Figure 3 (c
). As a result, the magnetization of the magnetic recording layer is reversed only in areas where the coercive force of the magnetic recording layer is small enough to reverse the magnetization by the applied magnetic field, and a magnetic domain pattern corresponding to the recording signal is formed in the magnetic recording layer ( FIG. 3(d)) Recording of information is completed.

Here, the medium is rotated at 1800 revolutions per minute, and the recording radius is 5.
7 mm, recording laser power of 5 mW, and magnetic field modulation frequency of 3.7 MHz. For comparison, similar recording was performed on a magneto-optical recording medium having the same configuration, the magnetic recording layer of which was previously magnetized in one direction. FIG. 4 shows the dependence of the carrier-to-noise ratio (CNR) of the reproduced signal on the intensity of the modulated magnetic field when the medium recorded in this manner is reproduced with a reproduction laser power of 1 mW. Although the medium of the embodiment of the present invention has a saturation CNR lower by about 1 dB than the comparative example, the modulation magnetic field strength required for saturation is about 1000e lower, and good recording can be performed with a modulation magnetic field of 500e.

Note that similar results were obtained when not only the magnetic field but also the laser beam was modulated according to the recording signal during recording.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a magneto-optical recording medium in which information can be directly overridden even with a small modulated magnetic field in a magnetic field modulation recording method. As a result, it is possible to easily achieve a higher data transfer rate, which has been a problem with magnetic field modulation methods. Note that such an effect is not only obtained with the magneto-optical recording medium having the structure and configuration shown in the examples of this application, but also with a magneto-optical recording medium using other materials and configurations. Needless to say.

[Brief explanation of drawings]

FIG. 1 is a plan view of a magnetic recording layer showing the configuration of the present invention. 101...Data recording section 102...Non-recording section FIG. 2 is a diagram showing the configuration of a magneto-optical recording medium in an embodiment. 201...Disk substrate 202...Interference layer 203...Magnetic recording layer 204...Protective layer 205...Reflection layer 206...Protective coat layer Figure 3 shows information recording by magnetic field modulation method. Diagram to explain. FIG. 4 is a diagram showing the dependence of carrier wave-to-noise ratio on modulated magnetic field strength. that's all

Claims (1)

[Claims] In a magneto-optical recording medium in which information is recorded by applying a magnetic field modulated according to the recorded information and simultaneously irradiating the magnetic recording layer with a fixed intensity or focused light modulated according to the recorded information, the magnetic recording layer A magneto-optical recording medium characterized in that an area where information is not recorded adjacent to an area where information is recorded is in a demagnetized state.