JPS63152045A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To eliminate the need for a means for impressing an external magnetic field to the titled medium by forming projections consisting of a 1st perpendicularly magnetized film at specified intervals onto a substrate and forming a recording layer consisting of a 2nd perpendicularly magnetized film and protective layer consisting of dielectrics thereon. CONSTITUTION:The projections 2 which consist of the 1st perpendicularly magnetized film having magnetic anisotropy in the direction perpendicular to the film plane are formed at the specified intervals onto the substrate 1, then the recording layer 3 consisting of the 2nd perpendicularly magnetized film and the protective layer 4 consisting of the dielectrics are formed in this order thereon. The projections 2 consisting of the perpendicularly magnetized film formed on the substrate 1 and the recording layer 3 consisting of the 2nd perpendicularly magnetized film are previously magnetized in the same perpendicular direction, by which the recording layer 3 is initially magnetized in one direction. A bias magnetic field is impressed by the magnetization of the projected parts to the recording layer 3 part existing between the projections 2 in the direction opposite from the direction of the initial magnetization. Inverted magnetic domains are thereby formed only by the heating up by laser beam projection without requiring the means for impressing the external magnetic field to the medium.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a recording medium used in a magneto-optical memory, and more specifically, the present invention relates to a recording medium used in a magneto-optical memory. The present invention relates to a magneto-optical recording medium in which information can be recorded by creating inverted magnetic domains in a region irradiated with a light beam such as a laser, and which can be read out using the magneto-optic effect.

(Prior Art) Optical memory is attracting attention as a type of large-capacity file memory. Among them, magneto-optical memory has the advantage that recorded information can be rewritten, and is therefore being actively researched in various places. As the recording medium, Tb, G
Amorphous magnetic thin films fabricated by combining rare earth metals such as d, Py, and Ho with transition metals such as Fe, Co, and Ni have high recording sensitivity, no grain boundary noise, and magnetic properties perpendicular to the film surface. It is considered the most promising because it has the advantage of being able to easily produce a film with magnetic anisotropy.

Conventionally, information is recorded and erased on such a recording medium as follows. Recording involves irradiating a unidirectionally magnetized recording medium with a laser beam to raise the medium temperature above the cue temperature Tc or compensation temperature Tcomρ, and forming reversed magnetic domains using an externally applied magnetic field and a demagnetizing field of the recording medium. It is done by doing. Erasing is performed by applying an external magnetic field with a polarity opposite to that during recording and uniformly irradiating the recording medium with a laser beam with the same intensity as during recording, so-called batch erasing. As a result, the magnetization state of the recording medium returns to the initial state before recording.

(Problems to be Solved by the Invention) When recording on a conventional magneto-optical recording medium as described above, in addition to the optical system that generates the laser beam, an external magnetic field applying means is essential. The configuration of magneto-optical recording and reproducing devices has tended to be complicated.

An object of the present invention is to provide a magneto-optical recording medium that can apply a bias magnetic field without requiring an external magnetic field applying means.

(Means for Solving the Problems) The magneto-optical recording medium of the present invention has protrusions made of a first perpendicularly magnetized film having magnetic anisotropy arranged on a substrate at regular intervals in a direction perpendicular to the film surface. A recording layer made of a second perpendicularly magnetized film and a protective layer made of a dielectric material are then formed in this order.

(Function) By magnetizing the protrusion made of the perpendicularly magnetized film formed on the substrate and the recording layer made of the second perpendicularly magnetized film in the same perpendicular direction, the recording layer is initially magnetized in one direction. At the same time, a bias magnetic field is applied to the portion of the recording layer between the projections in a direction opposite to the initial magnetization due to the magnetization of the projections.

(Example) Next, an example of the present invention will be described in detail using the drawings. FIG. 1 shows a cross-sectional configuration diagram of an embodiment of a magneto-optical recording medium according to the present invention. A CoCr alloy film (
Composition: Made of a perpendicular magnetization film such as Cog, 85coO, +s>, trapezoidal protrusions 2 with a height of about 3000λ and a width of about 4000 are formed at a pitch of about 1 μm, and on top of these, a second perpendicular magnetization film is formed. The thickness of the recording layer 3 is 3000 mm.
Human TbFeCo alloy film (composition: Tbo, zz (Feg
, gcol), and 0.78), and a Si3N4 film having a refractive index of 2.0 and a thickness of 800 nm is formed as the protective layer 4 in this order.

Each layer is formed by magnetron sputtering. First, C
The trapezoidal protrusion 2 made of an oCr alloy film is formed in the following manner. Power density 4 w/c in Ar gas atmosphere using CoCr alloy target on glass substrate
m2, sputtering gas pressure 3.5X 10-'Pa, Co
After sputtering a Cr film to a thickness of 3000λ,
As shown in a>, a resist pattern 5 having a thickness of 2000λ and a width of 5000λ is formed at a pitch of 1 μm, and ion milling is performed using Ar at a gas pressure of 2.6×10 −2 Pa for 12 minutes. Furthermore, by stripping off the resist using oxygen plasma, a height of 3000 mm was obtained as shown in FIG. 2(b).
Spiral or concentric trapezoidal projections made of a CoCr film with a width of 40QOλ and a width of 40QOλ are formed at a pitch of about 1 μm.

The recording layer 3 TbFeCo alloy film was formed using a composite target in which Tb pieces were arranged on a FeCo target, in an Ar gas atmosphere, at a power density of 4 w/crn2 and a sputtering gas pressure of 3.
．． It is made with 5×10”Pa.

Protective layer 4 Si3N4 film is formed using a Si target and A
The power density Ow /
cm", sputtering gas pressure 2.5X 10-'Pa,
Created.

Next, a recording operation using the magneto-optical recording medium according to the present invention will be explained with reference to FIG. Perpendicular magnetization WJ of this medium, (
A protrusion 2 consisting of a CoCr alloy film) and a second perpendicular magnetization film (
By magnetizing the recording layer 3 made of TbFeCo alloy film in the same perpendicular direction (+, y direction) in advance, the recording layer 3 is initially magnetized in one direction as shown in FIG. 3(a). 8. In addition, the recording layer between these protrusions has
The bias magnetic field 7 can be applied in the opposite direction (-y direction) to the magnetization of the CoCr alloy film forming the protrusions. Therefore, as shown in FIG. 3(b), the laser beam 10 is irradiated to the portion of the recording layer between the protrusions in synchronization with the timing of magnetization in the direction opposite to the initial magnetization (<-y direction). to raise the temperature of the recording layer to above the Curie temperature (220°C
), the desired reversed magnetic domain 9 can be formed in the cooling process.

The shape and film composition, such as the height and pitch, of the perpendicularly magnetized film forming the protrusion are not limited to those described above;
It is appropriately selected depending on the recording density of the desired recording medium and the magnitude of the bias magnetic field.

The height of the protrusions is preferably several thousand angstroms, and the pitch is preferably about 1 μm. The film composition of the protrusion is CoCr
In addition to the alloy film, a perpendicular magnetization film such as barium ferrite may also be used. Furthermore, the composition of the recording layer is not limited to the one described above, and other magneto-optical recording materials may be selected as long as the coercive force 11c can be made larger than the bias magnetic field from the projections. As the protective layer made of dielectric material, S
In addition to i3N4, materials formed of AQN, SiO□, SiO, etc. to a thickness of several hundred to several thousand are used.

(Effects of the Invention) As described above, according to the present invention, a magneto-optical recording medium incorporating a unidirectional bias magnetic field applying means can be provided. Therefore, if the recording layer is initially magnetized in advance in a direction opposite to the bias magnetic field, a reversal magnetic domain can be formed simply by raising the temperature by laser beam irradiation without requiring an external magnetic field applying means. In addition, using an external magnetic field applying means that can switch the magnetic field only in the opposite direction to the present medium and the bias magnetic field, while irradiating a constant laser beam, the bias magnetic field and the magnetic field from the external magnetic field applying means are combined. It also makes recording easier.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the invention, FIG. 2 is a diagram showing a manufacturing method of the invention, and FIG. 3 is a diagram illustrating the invention in detail. In the figure, 1... Substrate, 2... Protrusion made of perpendicularly magnetized film, 3... Recording layer, 4... Protective layer, 5... Resist pattern, 6... Magnetization within the protrusion, 7... Bias magnetic field from magnetization within the protrusion, 8... Initial magnetization magnetization, 9
. . . Reversed magnetization, 10 . . . Laser beam.

Claims (2)

[Claims] (1) On the substrate, protrusions made of a first perpendicular magnetization film having magnetic anisotropy are formed at regular intervals in a direction perpendicular to the film surface, and then a recording layer made of a second perpendicular magnetization film is formed. , and a protective layer made of a dielectric material are formed in this order. (2) The magneto-optical recording medium according to claim 1, wherein the recording layer made of the second perpendicularly magnetized film is an amorphous magnetic alloy thin film.