JP2707561B2 - Artificial lattice magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an artificial lattice magneto-optical recording medium having a perpendicular magnetization film applied to, for example, a rewritable magneto-optical disk. [Summary of the Invention] The present invention relates to a thin film layer A mainly composed of a rare earth-transition metal.
And a thin film layer B mainly composed of a rare earth metal, and a periodic lamination structure of two or more layers is adopted. By specifying the composition and film thickness relationship of each thin film layer, the Kerr rotation angle θ _K -the hysteresis of the magnetic field H is determined. An artificial lattice magneto-optical recording medium comprising a perpendicular magnetization film having a good loop square shape is constructed. [Related Art] In recent years, the development of magneto-optical recording media has been rapidly active. As a medium capable of obtaining practical characteristics of this magneto-optical recording medium, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-73746, a rare-earth-transition metal alloy thin film has attracted attention. This type of magneto-optical recording medium is generally
A configuration is adopted in which a perpendicular magnetization film made of a rare earth-transition metal alloy is formed. However, the magneto-optical recording medium according to such a configuration, the magnetic flux - magnetic hysteresis loop, poor squareness, such Kerr hysteresis loop, large Kerr and rotation angle theta _K, it is difficult to obtain a high coercive force Hc. Further, in order to obtain a coercive force Hc that can be practically used, it is necessary to select the film composition very close to the composition selected so that, for example, room temperature is set as the compensation temperature. Was very narrow. [Problems to be Solved by the Invention] The present invention can provide an artificial lattice magneto-optical recording medium using a perpendicular magnetization film having a square shape of a Kerr hysteresis loop and excellent magneto-optical characteristics. The problem of narrowing the practical range of the composition as a whole film, that is, the apparent composition is solved. [Means for Solving the Problems] The present invention has a periodic structure in which a thin film layer A and a thin film layer B are alternately laminated on at least one or more layers on a substrate, and is arranged in a direction perpendicular to the film surface. A perpendicular magnetization film having an easy axis of magnetization is formed. Each composition of the thin film layers A and B is represented by R ^I , R ^II , S ^I , S
When represented by ^II and M, Has become general ^{formula, x I + y I = 100} , 50x I 100, 0y I 50, 0i40, x II + y II = 100, 50x II 100, 0y II 50 A, the element group R ^I and R ^II Is at least one or more elements of Gd, Tb, Dy, Ho, and the element groups S ^I and S ^II are
It is at least one or more of the rare earth elements including Sc and Y other than the element groups R ^I and R ^II , and the element group M is Fe, Co,
At least one element of Ni, and the thin film layer A
, And B are a (ａ) and b (Å), respectively, and the relationship between the film thicknesses is (a, b) in an ab orthogonal coordinate system.
As shown in FIG. 1, the relationship between the two film thicknesses is
Point (a) (10,4), point (b) (50,40), point (c) (13
0,13) Further, a perpendicular magnetization film is formed within a range connecting the coordinate points of points (a) and (10,4). [Operation] Points (a) and (b) between the above-mentioned thin film layer A and thin film layer B
(C) According to the magneto-optical recording medium having the perpendicular magnetic film having the artificial lattice structure of the periodic laminated structure in the range surrounded by (a), the magnetic compensation temperature Tcomp of the magneto-optical recording layer, that is, the perpendicular magnetic film, is set to room temperature. It has been confirmed that the average composition as a whole, that is, the apparent composition range, which can be selected to a certain extent, is widened, and that magneto-optical properties such as an improvement in the square shape of the car hysteresis curve, an improvement in the coercive force Hc, etc. It is. That is, in the configuration of the present invention, the magnetic coupling between the R ^II magnetic atoms of the thin film layer B and the M magnetic atoms of the thin film layer A is weakened, so that the R ^II magnetic atoms of the thin film layer B have a supermagnetic effect depending on the position of the stack. The spin of the R ^II atom is inclined, and therefore, even if the magnetic film contains a large amount of R ^II atoms and the crystal layer B appears between the rare earth-transition metal thin film layer A, the film surface as a whole is It exhibits excellent magneto-optical characteristics having a magnetic anisotropy perpendicular to. [Embodiment] A magnetron sputtering apparatus may be used for producing an artificial lattice magneto-optical recording film having a periodic structure in which thin film layers A and thin film layers B according to the present invention are alternately stacked. In this sputtering apparatus, for example, as shown in FIG. 2, a base (1) that rotates about an axis 0-0 'is provided in a bell jar (not shown), and the base (1, for example) is provided on the lower surface thereof. A substrate (2) composed of a smooth glass substrate constituting a magneto-optical recording medium is arranged. And this base (2)
At equal angular intervals about the axis 0-0 ', ie, 18
Two sputter sources (3) and (4) are arranged while maintaining an angular interval of 0 °. These sputtering sources (3) and (4)
A mask (5) for regulating the sputter position of the metal sputtered by the sputter sources (3) and (4) is arranged between the substrate and the base (1), that is, the base (2). The sputtering sources (3) and (4) have the respective metal targets (6) and (7) of the thin films A and B described above, respectively. These targets (6) or (and) (7)
When the corresponding thin film A or (and) B is a composite (alloy), it can be an alloy target according to this composition, for example, a single metal body or an alloy body on another single or alloy body. The pellets can be loaded to have the required composition as a whole. (8) and (9) show magnets. And the target (6) while rotating the base (1)
DC sputtering is performed on the substrate (2) through the windows (5a) and (5b) of the mask (5) with (7) as the negative electrode side. In this way, while rotating the base (1), a perpendicular magnetization film having a thickness of 200 to 10,000 、, for example, 5000 と し て is formed on the base (2) as a whole to obtain a target magneto-optical recording medium. Make it. This sputtering has a residual gas pressure of 1.0
The operation is performed at × 10 ⁻⁶ torr and Ar gas pressure of 5 × 10 ⁻³ torr. Example 1 A perpendicular magnetization film, that is, a magneto-optical recording film was formed on a substrate (2) made of a smooth glass plate by the above-described sputtering method. In this case, Tb _19.3 Fe _72.6 Co _8.1 constituting the thin film layer A was used as the target (6), and Tb constituting the thin film layer B was used as the target (7). The thickness tA of each thin film layer A on the substrate (2) is 130 °, the thickness tB of each thin film layer B is 13 °, and both thin film layers A and B are repeatedly laminated so that the total thickness is about 5000 °. did. The average composition of the entire perpendicular magnetization film obtained in this way is Tb
_20.6 (Fe ₉₀ Co ₁₀ ) _79.4 . Comparative Example 1 The same method as in Example 1 was used, but the target was TbFeCo having almost the same composition as the average composition of the magnetic film of Example 1.
Using a single alloy target, a magneto-optical recording film was formed on the glass substrate (2) by sputtering. FIGS. 3A and 3B show the measurement results of the hysteresis loop curves of the Kerr rotation angle θ _{K with} respect to the magnetic field H of each recording film obtained in Example 1 and Comparative Example 1 described above. As is clear from the comparison between the two curves, the curve of Example 1 is superior to the curve of Comparative Example 1 in the square shape of the Kerr hysteresis loop. In the case of Example 1, the Kerr rotation angle θ _{K was} 0.42 °, which was a great improvement as compared with θ _K = 0.36 ° of the uniform alloy film of Comparative Example 1 having the same composition. Example 2 A magneto-optical recording film formed by repeatedly laminating a thin film layer A made of TbFeCo and a thin film layer B made of Tb using the sputtering apparatus described in FIG. Formed on a glass substrate (2). In this case, each sample was manufactured by changing each thickness of each of the thin film layers A and B. The relationship between the thickness of each of the thin film layers A and B of each of these samples is plotted with a circle in FIG. In each of these samples, it was confirmed that a perpendicular magnetization film was formed within the range surrounded by the solid line a in FIG. 4 to form a magneto-optical recording medium. Although according to the same method as in Example 3 Example 1, the ratio t _A / t _B of the thickness t _B of the thickness t _A of Tb ₁₉ Fe ₇₃ Co ₈ film layers A and Tb thin layer B, respectively 3/1 indicates when set to 1/1, the measurement result of the coercive force Hc for t _a in Figure 5. According to this, a high coercive force is obtained over a wide laminated structure region, that is, an overall apparently wide composition.
It can be seen that Hc is obtained. Example 4 In samples 1 to 5 obtained by the same method as in Example 1 except that the relationship between the thin film layers A and B and the thickness thereof was changed, a perpendicular magnetization film was obtained. According to each of the embodiments described above, it is understood that a target magneto-optical recording medium can be obtained within the range surrounded by the coordinate points (a), (b), (c), and (a) in FIG. Was. In each of the above-described examples, a case has been described in which the thin film layers A and B in the magnetic film having the laminated structure have the same composition, but the thin film layers A and B are alternately arranged. However, both or one of each of the thin film layers A and B is composed of two or more thin films having a composition satisfying the conditions of each of the thin film layers A and B described above. Each of the thin film layers A and B can be formed by a single layer or a stack of thin films. That is, basically, the thin film layers A and B are repeatedly formed.
And A ₁ and A _2, take a configuration such as the Toka _{A 1 -B-A 2 -B-} A 1 ··· and _{A 1 -A 2 -B-A 1} -A 2 -B ··· obtain. [Effects of the Invention] As described above, according to the present invention, a high Kerr rotation angle θ _K , a high coercive force Hc, and an apparent composition of a magneto-optical recording medium excellent in a square shape of a Kerr hysteresis loop can be changed from a wide range of compositions. Since it can be selected, it is possible to produce a magneto-optical recording medium having various characteristics such as optimal mechanical and magnetic properties suitable for the use mode and use conditions, for example, which brings a great advantage in practical use.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows thin film layers A and B of a magneto-optical recording medium according to the present invention.
FIG. 2 is a configuration diagram of an example of a sputtering apparatus used for producing a magneto-optical recording medium according to the present invention. FIGS. 3A and 3B are Kerr rotation angle-magnetic field curve diagrams, respectively. FIG. 4 is a diagram showing the film thickness relationship between the thin film layers A and B which can constitute the perpendicular magnetization film. FIG. 5 is a diagram showing the coercive force Hc and the thin film layer A.
FIG. 5 is a diagram showing a relationship with the thickness of the hologram. (2) is a substrate, and (6) and (7) are targets.

Claims (1)

(57) [Claims] The thin film A and the thin film B are alternately laminated in at least two layers, and each composition of the thin film layers A and B is represented by R ^I , R ^II , S ^I ,
When represented by S ^II and M, the thin film layer A is The thin film layer B is Has become general ^{formula, x I + y I = 100} , 50x I 100, 0y I 50, 0i40, x II + y II = 100, 50x II 100, 0y II 50 A, the element group R ^I and R ^II is at least one or more of Gd, Tb, Dy, and Ho, and the element groups S ^I and S ^II are S elements other than the element groups R ^I and R ^II.
at least one or more of the rare earth elements containing c and Y; the element group M is at least one or more of Fe, Co, and Ni; and each of the thin film layers A and B When the film thicknesses are a (Å) and b (Å), respectively, and the relationship between the film thicknesses is represented by (a, b) in the ab orthogonal coordinate system, the relationship between the two film thicknesses is (10,4), (Five
An artificial lattice magneto-optical recording medium comprising a perpendicular magnetization film within a range connecting the coordinate points (0, 40), (130, 13), and (10, 4).