JP2729962B2 - Magneto-optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical recording medium, and more particularly, to a magneto-optical recording medium having a recording material having an excellent magneto-optical effect as a recording layer.

[Related Art] In recent years, a magneto-optical recording medium that writes information on a magnetic domain by writing a magnetic domain on a magnetic thin film using a thermal effect of light and reads information using a magneto-optical effect has attracted attention. .

2. Description of the Related Art Conventionally, as a magnetic material used for a magneto-optical recording medium, a material made of an amorphous alloy of a rare earth metal and a transition metal has been known. A magneto-optical recording medium using such an amorphous alloy magnetic material generally has a thickness of about 0.1 to 1 μm on a substrate such as a polycarbonate plate by a method such as vacuum deposition and sputtering of a magnetic material, for example, a Tb-Fe alloy. To form a magnetic layer. However, since the amorphous alloy magnetic material, particularly the rare earth metal component, is susceptible to oxidative corrosion, there is a major drawback that the magneto-optical characteristics of the magnetic film deteriorate with time, and this oxidative corrosion is further reduced by light and heat during recording. Will be promoted. In addition, the amorphous alloy magnetic material has a disadvantage that it is easily crystallized by heat, and therefore, its magnetic properties are easily deteriorated.

Further, since a magnetic film made of an amorphous alloy magnetic material has a low transmittance in a laser oscillation wavelength region, recorded information is read by a magneto-optical effect due to reflection on the surface of the magnetic film, that is, a Kerr effect. Since the rotation angle is generally small, there is also a problem that the reproduction sensitivity is low.

The applicant has previously noted that magnetoplumbite-type barium ferrite is a metal oxide that has excellent stability over time and has a light-transmitting property in a laser light wavelength region, so that the Faraday effect can be used. A magneto-optical recording medium provided with a magnetic layer made of a magnetic material represented by the formula (A) or (B) has been proposed (JP-A-59-45644).

_{MeM x M y Fe 12-p} O 19 (A) ( wherein, Me is at least one element selected from the group consisting of Be, Pb, Sr and Sc, and M is Co, Mn, T
It is at least one element selected from the group consisting of i, Zn, Al, Sn, Cu, Cr and Mg, provided that p = x + y (y = 0) 1.2 ≦ p ≦ 2) CoM _z Fe _2-z O ₄ (B) (wherein M is as described above, provided that 0.75 ≦ z ≦ 1.
3) BaFe ₁₂ O ₁₉ has a large magnetic anisotropy, but has a small magneto-optical effect, and is therefore insufficient as a magneto-optical recording material. BaFe
By substituting part of the Fe atom of ₁₂ O ₁₉ with Co, the magneto-optical effect can be increased. However, since trivalent Fe is replaced by divalent Co, it is necessary to compensate for the charge. Here, when charge compensation is performed by substituting a part of Fe atoms with a tetravalent metal, there is a problem that the crystal magnetic anisotropy is reduced.

To solve this problem, the present applicant has proposed a magneto-optical recording material in which part of Ba of magnetoplumbite-type barium ferrite is replaced with La, and part of Fe is replaced with Co. No. 62-119760).

[Problems to be Solved by the Invention] However, although the magneto-optical recording material disclosed in JP-A-62-119760 has a good balance between the magneto-optical effect and the magnetic anisotropy, as shown in FIG. Faraday effect) is still insufficient.

The present invention has been made in view of the above points, and an object of the present invention is to provide a magneto-optical recording material having a sufficiently large magneto-optical effect.

[Means for Solving the Problems] According to the present invention, magnetoplumbite ferrite
Magneto-optical recording in which a part of M of MFe ₁₂ O ₁₉ (M: at least one of Ba, Sr, and Pb) is replaced by Ce and a part of Fe is replaced by a metal element which becomes monovalent or divalent ion A magneto-optical recording medium using a material as a recording layer is provided.

The magneto-optical recording material used for the recording layer of the magneto-optical recording medium of the present invention is represented by the following general formula (1).

(However, MI: at least one of Ba, Sr, and Pb MII: a metal element that becomes a monovalent or divalent ion such as Mn, Co, Ni, Cu, Zn, etc. 0 ≦ X ₁ ≦ 1, 0 ≦ X ₂ ≦ 2) Further, in order to improve various characteristics of the magneto-optical recording material represented by the above general formula (1) as a magnetic recording layer, MI
May be further substituted with MIII, and a part of Fe may be further substituted with MIV to obtain a magneto-optical recording material represented by the following general formula (2).

(However, MI and MII have the same meanings as in the above general formula (1). MIII: Rare earth elements other than Ce such as La or Ca, Bi, etc. MIV: Ti, Nb, Ta, In, Ga, Al, Cr, etc. Metal element 0 <X ₁ + X ₃ ≦ 1, 0 <X ₂ ≦ 2, 0 ≦ X ₄ ≦ 4) Here, since MI is a divalent ion, this is represented by Ce, which is a trivalent or tetravalent ion. In order to replace the trivalent Fe
It should be noted that charge compensation is required by substitution with a divalent or divalent MII.

The configuration of the recording medium is basically composed of a substrate 1, an underlayer 2, and a magnetic recording layer 3 as shown in FIG. 1, but the underlayer 2 is not necessarily required. A protective layer, a dielectric layer, and the like may be provided.

Further, it is preferable to appropriately provide a guide track for guiding a laser beam during recording and reproduction on the substrate.

In the magneto-optical recording medium shown in FIG. 2, an underlayer 2, a magnetic recording layer 3, and a reflective layer 4 are formed on a substrate 1 having guide tracks.
Are sequentially laminated. Writing and reproduction of information can be performed by irradiating a laser beam from the substrate 1 side as shown by arrows in the figure, and reproduction can be performed using reflected light.

As the substrate 1, a glass substrate such as quartz glass, high silicate glass, borosilicate glass, or aluminum silicate glass, a metal substrate such as an Al alloy, or a single crystal substrate such as Si or GGG can be used. As the underlayer 2, a C-axis oriented film of ZnO, a (111) oriented film of a crystal having a spinel structure, or the like can be used. Thickness is 0.0
About 2 to 0.1 μm is preferable. The magnetic recording layer is made of a magnetic material represented by the above formula (1) or (2) and has a thickness of
0.05 to 0.5 μm is preferred.

In order to produce the magneto-optical material represented by the general formulas (1) and (2), carbonates, oxides, etc. of the constituent metals are mixed and pulverized, put into a mold having an appropriate shape, molded, and then heated to a high temperature. Should be sintered.

In order to provide the recording layer of the magneto-optical recording medium of the present invention, for example, the recording layer is represented by the above general formula (1) or (2) on a substrate or, if necessary, a substrate provided with an underlayer. The target of the magneto-optical material to be deposited is formed by a method such as vacuum deposition, sputtering, or ion plating as described above.
It is carried out by attaching it to about 0.05 to 0.5 μm.

Reflective film 4 is Cu, Al, Ag, Au, Pt, TeO X, TeC, SeAs, Te
It is formed by depositing As, TiN, TaN, CrN, cyanine dye, phthalocyanine dye, etc. on the target surface to a thickness of about 500 to 10,000 で by a method such as vacuum deposition, sputtering, or ion plating. The reflection film is provided for the purpose of reflecting the laser light transmitted through the magnetic film and increasing the Faraday effect and the reflectance by transmitting the laser light again through the magnetic film.

Recording and reproduction to and from the magneto-optical recording medium can be performed by irradiating a modulated or polarized laser beam to the perpendicularly magnetized recording layer as in the conventional case. For example, the recording layer is selectively irradiated with a laser beam under application of a magnetic field, the irradiated portion is heated to a temperature higher than the Curie temperature, the coercive force is reduced, the magnetic reversal is performed, and a recording bit is formed to record information. This information is read by irradiating the recording layer with polarized light of a laser and detecting a difference in Faraday rotation angle.

[Examples] Next, the present invention will be described with reference to examples.

Example 1 A C-axis oriented film of ZnO was oriented on a quartz substrate, and the following formula While varying MI, MII, the X ₁ in was measured Faraday rotation angle (lambda = 780 nm), its value MI, almost unaffected by MII elements, now a solid line in Figure 3. However, when Co is used for MII and X ₂ ≒ X ₄ , the Faraday rotation of Co itself is relatively large, and the rotation direction coincides with Ce, so the Faraday effect is further increased. It became like the broken line inside.

[Effect of the Invention] The magneto-optical effect (Faraday effect) of the magnetic recording layer increases, and in proportion to this, the reproduction C / N as the magneto-optical memory improves. This makes it possible to reduce the error rate as a digital memory and record a video signal as an analog signal. There are advantages such as reducing the load on the pickup head and leading to cost reduction.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are configuration diagrams each showing an example of the magneto-optical recording medium of the present invention, and FIG. Relationship between X ₁ and the Faraday rotation coefficient theta _f in (solid line)
And is a graph showing the relationship between the Faraday rotation coefficient theta _f and X ₁ in the case of using Co as MII. Fig. 4 is B
is a graph showing the relationship between _{a 1-X La X Co X} Fe 12-X X in O ₁₉ and Ferade rotation factor theta _f. DESCRIPTION OF SYMBOLS 1 ... Substrate with a guide track, 2 ... Underlayer, 3 ... Magnetic recording layer, 4 ... Reflection layer

Claims (1)

(57) [Claims] 1. A part of M of a magnetoplumbite type ferrite represented by the following formula: MFe ₁₂ O ₁₉ (M: at least one of Ba, Sr, and Pb) and a part of Fe are replaced with Ce. A magneto-optical recording medium having a recording layer made of a magneto-optical recording material substituted with a metal element which becomes a divalent or divalent ion.