JPH038023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magneto-optical storage element that records, reproduces, and erases information using laser light.

<Prior Art> In recent years, research and development of optical memory devices that can satisfy various demands such as high density, large capacity, and high speed access have been actively promoted. Among various optical memory devices, magneto-optical memory devices that use perpendicularly magnetized films as storage materials are attracting attention because they can erase information that is no longer needed and re-record new information.

However, while having the above advantages, magneto-optical storage devices have the disadvantage that the reproduction signal level is low.
In particular, in the so-called Kerr effect reproduction method in which information is reproduced using reflected light from a magneto-optical storage element, it is difficult to increase the signal-to-noise ratio (S/N) because the Kerr rotation angle is small. Therefore, conventional efforts have been made to increase the Kerr rotation angle by improving the magnetic material of the recording medium or by forming a dielectric film of SiO or SiO ₂ on the recording medium. As an example of the latter, it has been reported that the Kerr rotation angle was increased from 0.7 degrees to 3.6 degrees by forming a SiO film on a MnBi magnetic film. (J.APPl.Phys.
Vo145no8August1974). However, when forming a dielectric film on such a magnetic film, the amount of reflected light decreases as the Kerr rotation angle increases, resulting in a substantial S/N ratio.
has increased only about twice. Also, SiO and
Merely forming a dielectric film such as SiO ₂ cannot provide substantial protection against corrosion if there is a risk of corrosion in the magnetic material, and since the recording bit diameter is approximately 1 μm, small If dust or dirt adheres to the dielectric film, it will become impossible to detect the bit, so use glass or transparent resin with a thickness of about 0.5 to 2.0 mm to make it a practical recording element. It is desirable to do this, and by doing so, the effect of increasing the Kerr rotation angle (and thus increasing the S/N ratio) cannot be expected to be as great as the theoretical value.

In addition, since high-density recording is a basic requirement for optical memory devices, the recording bit diameter is as described above.
The diameter is approximately 1 μm, so servo technology such as focus servo and track servo is essential in the recording, reproducing, and erasing processes. Otherwise, the recording device would be complicated and sophisticated and would not be suitable for practical use. Particularly when applying track servo, it is desirable to have a servo guide track adjacent to the signal recording track (this is especially necessary for recording, reproducing, and erasing).

<Purpose> The present invention was made in view of the above points, and an object of the present invention is to increase the magneto-optical effect without reducing the amount of reflected light, and also to form a guide track for a servo. It is an object of the present invention to provide a magneto-optical memory element in which there is no risk that a certain magnetic thin film will be substantially corroded.

<Examples> Next, specific examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partially enlarged side sectional view of a magneto-optical memory element according to an embodiment of the present invention.

In the figure, reference numeral 5 denotes a support substrate, on which a reflective film 4 of Al, Au, Ag, etc. is formed. A dielectric film 3 such as SiO ₂ is disposed on the reflective film 4, and GdTbFe, GdTbFe, etc. are disposed on this dielectric film 3.
A perpendicularly magnetized film of an amorphous ferrimagnetic material made of a rare earth element such as SmTbFe, TbFe, GdDyFe, TbCo, or GdCo and a transition metal is formed in a strip shape as a recording track 2. For example, when the magneto-optical storage element is a disk, the recording track 2 has a concentric or spiral shape. The supporting substrate 5 on which the reflective film 4, the dielectric film 3, and the recording track 2 have been formed in this way is connected to the transparent substrate 1 made of glass or synthetic resin via a spacer 6.
A section 7 of an appropriate size is provided, and the section 7 is
are filled with gas and then bonded. As a gas
Use _N2 or Ar gas. In this configuration, the guide track is the gas body section between the recording tracks 2. That is, the guide track and the recording track 2 are distinguished from each other by the difference in reflectance between the magnetized film 2 and the reflective film 4. The magnetic film 2 forming the recording track 2 is sufficiently thin, so that the reproducing light incident on the magnetic layer is reflected by the Kerr effect from the magnetic surface, passes through the magnetic film, is reflected by the reflective layer 4, and returns to the magnetic film. Due to the combination of the Faraday effect caused by passing through the light, the rotation angle increases several times compared to the rotation angle due to the Kerr effect alone, and the amount of returned light hardly decreases, so the S/N ratio increases greatly.

The above element is produced as follows.

A reflective film 4 and a dielectric film 3 such as SiO ₂ are formed on a supporting substrate 5, and a strip-shaped recording track 2 is formed by a perpendicular magnetization film, and a recording element having a four-layer structure and a transparent substrate 1 are connected to each other. A structure is adopted in which they are overlapped with a spacer 6 in between. Then, the gap 7 between the recording track and the protection plate is filled with N ₂ or Ar gas.

In this embodiment, the guide track is a transparent portion between the recording tracks 2, and the guide track and the recording track are distinguished from each other by the difference in reflectance between the recording track 2 and the reflective film 4.

In addition to the configurations of the above-described embodiments, various configuration changes are possible within the scope of the gist of the present invention.

For example, the magnetic material is not limited to the above-mentioned amorphous ferrimagnetic material, but may also be a crystalline perpendicularly magnetized film such as MnBi, MnBiCu, or EuO.

Further, in the above embodiment, a dielectric film 3 is formed between the recording track 2 made of a magnetic film and the reflective film 4, and the dielectric film performs thermomagnetic recording of information on the recording track 2 using a laser beam. This dielectric film is provided to prevent heat from escaping to the reflective film 4 due to thermal conduction, and if the energy of laser light or the like is sufficient, the dielectric film may be omitted.

Furthermore, the recording track 2 and the guide track do not necessarily have to be in the form of parallel strips, and track numbers and information for dividing the tracks into sectors may be included.

Of course, the present invention is not dependent on the manufacturing method; for example, the recording track may be formed by an etching method or by a powerful laser beam. Furthermore, by forming a magneto-optical storage element having a similar structure on the back side of the support substrate 5 in FIG. 1, it is also possible to double the storage capacity by utilizing both sides of the recording element.

As described above, in this embodiment, by providing a reflective film, the Kerr effect caused by reflection on the magnetic thin film and the Faraday effect caused by passing through the magnetic thin film are combined, so that the incident laser beam The rotation angle of the wavefront is increased compared to the rotation angle caused only by the Kerr effect, and therefore signals with good S/N can be recorded and reproduced. In addition, since a dielectric film is interposed between the strip-shaped magnetic thin film and the reflective film, the heat generated when thermomagnetic recording is performed on the magnetic thin film using laser light is absorbed by the reflective film. Dissipation can be prevented.

<Effect> A support substrate provided with a reflective film and a magnetic thin film and a transparent substrate filled with N ₂ or Ar gas
Since the magnetic thin film is bonded with the magnetic material, corrosion of the magnetic thin film can be substantially prevented, and as a result, it is possible to provide a magneto-optical storage element that does not change over time and has high reliability in recording and reproducing. Furthermore, since the magnetic thin film serving as the recording track is formed into a band shape and the recording tracks are separated from each other by being filled with the above-mentioned gas, heat is transferred from the recording track irradiated with the laser beam to the adjacent recording track. Since it does not escape, thermomagnetic recording can be performed efficiently with less laser power.

[Brief explanation of the drawing]

FIG. 1 shows a partially enlarged side cross-sectional view of an embodiment of a magneto-optic storage element according to the present invention. In the figure, 1: substrate, 2: recording track, 3: dielectric film, 4: reflective film, 5: support substrate, 6: spacer, 7: gap.

Claims (1)

[Scope of Claims] 1. A first substrate, a reflective film provided on the first substrate, a magnetic thin film having a perpendicular easy axis of magnetization formed in a band shape on the reflective film, and a second substrate. In the magneto-optical memory element, the first substrate provided with a reflective film and a magnetic thin film and the second substrate are bonded with a gap between them, and the gap is filled with N ₂ or Ar. A magneto-optical memory element characterized by being filled with gas.