JPS62226450A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the noise level generated from a medium and to improve the S/N thereof by constituting an amorphous photomagnetic recording layer having the direction of magnetization perpendicular to the film plane of a pre scribed compsn. and impurities. CONSTITUTION:Elements of at least one kind among Be, Ge, Sr, and Si are added to a rare earth transition metal which is the main compsn. of the amorphous photomagnetic recording layer in which the direction of the magnetization is perpendicular to the film plane and has a binary value of either upward or downward. Such recording layer is constituted of the compsn. expressed by the following formula and impurities: (rare earth transition metal)100-a(BwGexSrySiz)a, 0<a<=15at%, 0<=w<=1, 0<=x<=1, 0<=y<=1, 0<=z<=1, w+x+y+z=1. The rare earth among the rare earth transition metals contains at least 1 kinds of Nd and Sm and at least >=1 kinds among Gd, Tb, Tb, and Dy. The transition metal contains at least >=1 kinds of Fe and Co.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the composition of a magneto-optical recording layer of a magneto-optical recording medium.

[Conventional technology]

Research on magneto-optical memory began in 1957 when all recording was carried out using a hot pen on a MnB1 thin film, and 4! ! It is said to have its origins in the observation of injected magnetic domains using the magneto-optical effect. Inspired by the subsequent development of lasers,
Although intensive research has been carried out mainly on MnB1-based materials, the development of optical information processing-related technologies in the 1970s and 1970s prevented practical application because laser light sources and their utilization technology were immature. Research is progressing on new magnetic F4 film materials represented by four amorphous rare earth transition metal alloy films, including GdFe, TbFe, DyFe, and GdC.
Alloy membranes such as o have been developed. These materials generally have the following characteristics.

Compensation point recording magneto-optical recording media such as GdFe and GdCjo have a larger Kerr rotation angle (θk) than Curie single-point recording magneto-optical recording media, and although they have excellent optical reproduction characteristics, they have a small coercive force ( (several hundred oersteds) It is not possible to stably obtain minute bits with a diameter of about 1 μm.

In addition, magneto-optical recording media for Currie single point recording such as TbFe and Dyke have a large coercive force (several kilo Oersteds) and can stably obtain minute bits with a diameter of about 1 μm, contrary to the above, but the Kerr rotation angle is It had drawbacks such as being small and having poor optical reproduction characteristics.

What are the drawbacks of these binary alloy thin films? To compensate, two methods have been tried in the past.

1) Convert into 6 elements or 4 elements. If lined up, binary GdFe
GdTbFe takes advantage of TbF'e's strengths and moans about its shortcomings.
Methods of diversification such as ternary alloys or GdTbFeOo A-element alloys. (Delegraph Gakken i, OPM2) A method to create a multilayer structure. A current visitor layer is placed on the recording medium to increase the Kerr effect due to multiple reflections.

(Eng.Kli:E Trans Magh MAG-16
(1980) 1194) (S56, Aki Li Applied Physics Society Proceedings,
9 P-P-q (19s 1) 12b) More recently, G6. Rather than using only heavy rare earth metals such as Tb and Dy, light rare earth metals such as Nd and Sm are used in addition to these heavy rare earth metals.
Attempts have been made to add

This addition of Na and sm has the effect of diluting Gd, Tb, Dy, etc., and can reduce the amount of expensive Tb, Gd, Dy, etc. in stool by 77%. Furthermore, θ becomes slightly larger.

[Problem that the invention seeks to solve]

With conventional technology, the problems have been solved little by little.

In other words, by increasing the Kerr rotation angle, the carrier was raised and c/H was improved. Furthermore, by adding light rare earth metals (Nd, sm), expensive Tb, Gd, Dy
etc., could be reduced. As θ also became thicker, the C/N (ratio of carrier to noise) of the medium also increased.

However, as the practical application approaches, it becomes necessary to increase s O/N f a little more. In other words, the current C/
N is about 50 dB, which is at a practical level, but considering the margin t for product variations, about 55 dB is required. Therefore, two methods can be considered to improve the C/N. One is to increase θk by -j- to increase the carrier level. However, it is currently impossible to increase θ any further due to its relationship with Curie@degrees. Another means is to completely reduce the noise level.

The present invention is intended to solve all of these problems, and its purpose is to reduce the noise level generated from the medium. The goal is to provide a material (medium) that can increase the signal-to-noise ratio ((!/N) without reducing the signal strength as much as possible).

[Means to solve all problems]

The magneto-optical recording medium of the present invention has an amorphous magneto-optical recording layer in which the direction of magnetization is perpendicular to the film surface and has a binary value of upward or downward.
In a magneto-optical recording medium that performs recording, reproduction, and erasing by irradiating light, B and Ge are added to the rare earth transition metals that are the main composition of the amorphous magneto-optical recording layer.

The percentage indicates that at least one element among Sr and Si is completely added and the composition and impurities are as shown below.

(Rare earth transition metal) too-a (EwGexGryS
iz)aOkuα≦15at%, 0<W≦1, ≦Y≦1. 0≦Y≦1, W+X+Y+z=1 [Operation] Conventional media G4Fe, TbF'e, DyF'
e, GdO.

Rare-earth transition metal alloy thin films such as these are originally amorphous, so it is thought that there are no grain boundaries that cause media noise. However, when looking at the electron beam diffraction images of these rare earth transition metal thin films, although they are not completely amorphous, rings are actually observed, although they are unclear. This seems to be because a part of the film is crystallized or in a state close to crystallization. Furthermore, HoCo membrane? When viewed using a high-resolution Seiko microscope, it is observed that some crystallization does exist. (J
, App4Vo1.57. AI, 15Aprit1
985) Therefore, according to the present invention, in the rare earth J-transfer metal,
By adding at least one element among B, Ge, Sr, and Si, the noise from the medium is further reduced than that of conventional media, and the noise from the medium is reduced.
It can be made bigger.

[Example 1] FIG. 1 is according to the present invention. FIG. 3 is a diagram showing the composition dependence of C/N when Get is added to an IJdDyE'eOO alloy thin film. Furthermore, Figure 2 shows the Kerr rotation angle of PA71&
: Dependency diagram, measured from the substrate side.

A sputtering method was used to produce the medium, and a PC board with a pitch of 1.6 μm and a groove depth of 700 A was used. The target was NaDyFe (all Ge chips were placed on a 3O alloy target, and the film was formed by DC magnetron sputtering. The film forming conditions were an initial vacuum of I
After exhausting the air to below, set the Ar pressure to f 2 mTorr,
It has a power of 100W. Furthermore, what is the composition of the target? Using.

(Ndo, is Dy O,7B)zs (F
130.5 0Oo, 5)tt 3°C% The structure of the medium is shown in FIG. 4 PC base, 5 is aluminum nitride and silicon nitride composite film 1000A, 6 is NdDyFe
In the CoGe film 400A, 7 is a composite film 1000A of 00A nium film and silicon nitride.

The purpose of sandwiching the NdDyFeOoGe film with a composite film of aluminum oxide and silicon nitride is to ensure long-term reliability of the medium, and has no inherent meaning with respect to the present invention.

First, we will explain the entire diagram in Figure 1. The media loading and reading conditions are Write Power 3mW, ReaaPo
wer 1mW.

Bias magnetic field 4000s, frequency 1MHz, &M speed 2
．． 5m/scc, hand width 30KHz. 1
is the carrier ((3), and 2 is the carrier to noise ratio (C
/N).

6 is noise (N). From this figure, C! /N is G
The amount of e added has increased to about 8 at% (9
dB improvement). If you look a little more closely, you can see that although the carrier level remains the same, the noise level has decreased, so C
/ N has become dog-like. It can be seen that when the amount of Go added is further increased, the C/N decreases because the carrier level decreases, although the noise level does not change. However, if the amount of Ge added is less than 15 at It can be seen that the dependence on the amount of Ge added to the carrier is the same.In other words, there is no change in θ up to 8 at% Ge addition.
If it exceeds %, it is decreasing. Similarly, the Kerr rotation angle shown here is not the original Kerr rotation angle of NdDyFeoo, but is enhanced and increased by the composite film of aluminum nitride and silicon nitride. Naturally, the tendency is exactly the same when no enhancement is made with a dielectric film.

From the above, it has been found that by adding NdDyFe0OKGo, it is possible to reduce the noise level of the medium and relatively increase the O/Ni power.

In addition, here, the composition of the alloy target of NdDyFe0O is (Ndo, es D7o, J2a (Fe O, 5Q
□ There were o, s h2 at% targets all around, but are there targets with other composition ratios? Will it have the same effect if I use it? show.

Specifically, the composition ratio is that of an arrow.

(N(io, o+ D7o, es ) is (F
eo, a COo, s )yi at %(N
d4D7+, s ) 211 (Fe@, @OOo,
z )72at%(N(io4D7o,s)am
(F'eo, * COo, 5) tz at %
(Ndo, zs D7o, ys)+s (F13
0. l Coo, 5) ss at X(N(io,
es D7o, ti ) go (F13 o, s
Co o,s ) so at X(Ndo, 1s
D7o, yi)xi (Feo, 1COo, 5)is
atX As we refine the experimental conditions further, NdDyFe0o
The composition having the effect of Ge addition to the alloy target was in the following range.

(Nd4D7+-t)m(F's,-ncon)too
−rBa<t≦(14,10≦m≦40at%0≦n
≦1 Naturally, the addition of Ge is effective up to 15 at% of the total.

[Example 2] Next, the results when B was added to the NdDyFθCo alloy thin film are shown. The experimental method, the construction of the medium 211, etc. were the same as in Example 1. The composition of the NdDyFe Co alloy target used was also the same as in Actual Gun Example 1. FIG. 4 shows the composition dependence of 0/N on B addition, and FIG. 5 shows the composition dependence of σ on B addition.

In Fig. 4, 8 indicates carrier < C), 9 indicates C/N, and 10 indicates noise (N [-). From this figure, s C!/N increases to about 8aJ% with the amount of B added ( 10(L
Improvement of B). 418th! i! 1% From Figure 5, Example 1
The exact same thing can be said. In other words, as B(1) VJS is added, the noise level of the medium decreases and becomes relatively 0.
7 N will improve. And the C/H peak has B of 8
at%, and if B is added at 15at%i, the C/N of the medium with only NdDyFsCO (no B addition)
It can be made larger.

[Example 5] Next, the results when sr' (FA was added to the NdDyFe (3o alloy thin film) are shown. The experimental method, medium structure, target composition, etc. are the same as in Example 1. Figure 6 shows C/ Sr of H
FIG. 7 is a diagram showing composition dependence on addition of Sr in θ. In FIG. 6, 11 is carrier (C), 12 is O/N, and 1'3 is noise (N). From this figure, the voltage applied to C/Nf'j:Sr is 8at
% (improvement of 8 dB). Figure 6,
As can be seen from FIG. 7, the same thing as in Example 1 can be seen. In other words, the noise level of the medium decreases with the addition of Sr.1. O/N is relatively improved. The peak of C/H is near 8atX of Sr, and if Sr is added up to 15at%, the O/N can be made larger than that of the medium containing only N(LD7fFθCO (no Sr addition)).

[Example 4] Next, the results will be shown when 4 was added to S' in the NdDyF'eCo alloy 4 film. The experimental method, medium #It structure, target composition, etc. were the same as in Example 1. Figure 8 is C/N a
r! In the diagram of composition dependence on addition, @9 diagram is 81 for θ.
FIG. 3 is a diagram of composition dependence on addition.

14 in Figure 8 is a carrier (C), 15 is O/N.

16 indicates noise (N)t-. From this figure, C/N is S
The amount of addition of l has increased to about 8 atX (7 d
Improvement of B). From FIGS. 8 and 9, the same thing as in the first embodiment can be said. In other words, the addition of Si lowers the noise level of the medium and relatively improves the C/N.

And, the O/N peak is around 8atX, and
If sl is added up to 15atX, NdDy(3
It is possible to make it more compact than the O/N of the medium of only O (81 cities and Canada).

[Example 5] Furthermore, B and Go were added to the NdDyFeoO alloy thin film.
The results are shown in the case of f-soeding. The composition ratio of B and Ge is 5
0:S Oat%. The implementation method, medium structure, target composition ratio, etc. are the same as in Example 1. I1o is C/
The 11th diagram shows the composition dependence of N on B-Ge addition.
The figure is a diagram showing the composition dependence of θ on B-Ge addition. 17 in Figure 10 is carrier (0), 18 is C/N11
97) E/I, ((N)'e is shown. From FIGS. 18 and 11, the same thing as in Example 1 can be said. In other words, B-
As G is cooled, the noise level of the medium decreases, and c7y relatively improves (improvement of 9.5 dB). And, the peak of C/N is around 8 at% of B-Ge, and if B-Ge is added at 15 at and 9≦, then
It can be more user-friendly than the O/N of a medium with only NdDyFeoO (B-Go, no 4 forces).

Further, although the ratio of B-Ge used this time is that of 50:50at light, the effect of the present invention is the same regardless of the ratio of B and Ge. Furthermore, what does B −Ge alone mean?
-8r, B-8i, Ge-Br, Ge-8iBr
-81, B-G6-Br, B-Ge-8i, Ge-
8r-81, B -Go-8r-131, t'' There is no problem with the addition of a sword, and it goes without saying that the ratio thereof is also arbitrary.

Next, the composition of the amorphous magneto-optical recording layer is NdDyE'eC! o
The present invention is shown in its entirety except for the following.

[Example 6] FIG. 12 is a diagram showing the composition dependence of O/H when Ge is added to the N1TbB'eCo alloy thin film according to the present invention. FIG. 13 is a graph showing the composition dependence of the Kerr rotation angle, measured from the substrate side. method for producing the medium;
The conditions, medium structure, etc. are the same as in Example 1, and the target is N.
A Go chip is shown above on a dTbFeoo alloy target. The composition of the alloy target is as follows.

(Nao, 14Tb o, as )*vm (Fe o
, sa co 6.41) to, x at% In Fig. 12, 20 is carrier (0), 21 is C/N22 is noise (
N) Show k. From this figure, O/N shows that the male blade uf of C)e has increased to about 8 at% (improvement of 9 dfl).

From FIG. 12 and FIG. 13, the same thing as in Example 1 can be said. In other words, with the addition of Ge, the noise level of the medium decreases, and the O/N improves. Then, the peak of C/H is near 8atX for Ge, and if Ge is added up to 15atX, NdTbFeCo
The O/N of the medium can be made larger than that of the medium (with Gθ addition).

Here, the composition of the NdTbFeCo alloy target is (Ndo, sa Tbo, as) *s, s (F
'e (1, i @ coo, tl) Although kumquats were used at % of kumquats, similar effects were obtained even if other composition ratios were used. The following group is used for A-line fishing: those with acid ratios.

(Nao, o+ Tbo, sa)z@(Fe o, *
OOo,i,)yyiat%(Ndo4Tb o,s
ha (Feo, s COo, t )tt at%(
Nd0.41 Tbo, is )21 (Feo, z
C! Oo, 5) tz at% (Ndo, zi Tbo,
ys ) as (Feo, s 00o, s ) a
t%(N(io, zi Tbo, yi)to (Fe
o, s COo, s) go at% (Ndo, ziTl
)o,ys)si (f'eo,s COo,5)as
at y3 When the experimental conditions are further refined, NdTbF
The composition having the effect of adding Ge to the alloy target of eoo was in the following range.

(Ndz Tbt-z)m(1'el-nCon)
1116-0a (Z≦α5.10≦m≦40atX O≦n≦1 Naturally, the amount of Ge added is effective up to 15 at% of the total.

Furthermore, in addition to the addition of Ge, B,
Sr, Si, B-Ge, B-8r, B-8i,
Ge-8r, Go-191, 5r-8i, B-
Ge-8r, B-Go-8i, Ge-8r-8i
.

It goes without saying that even those to which B-Ge-8r-817 is added are acceptable, and the ratio thereof is also arbitrary.

[Example 7] Figure 8g14 is a diagram showing the composition dependence of C/H when all Ge is added to the anlGdFeco alloy thin film according to the present invention. FIG. 15 is a graph showing the composition dependence of the Kerr rotation angle, measured from the base & side. method for producing the medium;
The conditions, medium structure, etc. are the same as in Example G, and the target is 8.
Ge chips are placed on an mGaF3 Co alloy target. The composition of the alloy target was kumquat.

(Sm11.I GdO, @ ) 37 (FeLSI
C00, @*)71 at% In Figure 14, 23 is carrier (C), 24 is C/N25 is noise (N)'! Shown below. From this figure, the amount of Go added in O/N is 8 at')
The noise level of the medium decreases by 75 fL with the addition of Ge. C/N is relatively improved.The C/H peak is near 8 at% Ge, and G
If e is added up to 15 at%, BmGdFeO
The C/N can be made larger than the C/N of the medium with only 0 (without Go addition).

In this case, the composition of the SmGdFeCo alloy target is (Smo, *G(io,5)ty(Feats
C! 0 ats ) 73 at % was used, but the same effect can be obtained even if all targets with composition ratios other than this are used. Specifically, it has the following composition ratio.

(Smo, o 5Gda, 1g) 11 (Feo,
scQ 11.1) tt at% (Sm11.4
G(1o,s)am (Fe,m0Oo,t)tta
t% (8mo4i Gdo, is )ts (F
eocooa, 5) yt at % (Smo, xi
Gdo,ys)ti (Feo,1COo,5)as
at% (Smo, zsGdo, ys) 26 (Fe
o,s C! Oo, s) go at X(Smo, 1s
Gdo,ti)ss (re(,,100a,s) a
s at% When the experimental conditions are further refined, SmGdFe
The composition having the effect of adding Ge to the Co alloy target was in the following range.

(SmtGdt-t)m(Fet-n con)t
oo-mo(z<o, s, 1o≦m≦40 at%0
≦n≦1 Naturally, the amount of Ge added is effective up to a total of 15 at. Furthermore, in addition to Ge addition, similar to the above-mentioned disaster example,
B, Sr, Si, E-Ge, B-8r, B-
8i, G.

-8r, Ge-8i, 5r-81, B-Ge-8r, B
-Ge-8i.

G e-8r-8i, B-G e-8r-8i 'I
It goes without saying that there is no problem even if F is added, and the ratio thereof is also arbitrary.

Similarly, in this example, NdDyFe0o, NdTbFe0o
, SmGdFaCo, but NdGdF
eCo, SmDyFeCo.

SmTbFe0o, NbSmDyFeC! o, Nd
The present invention is effective if the composition contains a transition metal in an alloy of heavy rare earth metals and heavy rare earth metals, such as SmTbFeCo. When the medium F' used in the example with one 46-light beam was observed with a mirror imager, all of the electron beam diffraction images were complete halo patterns, and no unclear rings were observed.

〔Effect of the invention〕

As described above, according to the invention, B is added to the rare earth transition metal that is the main composition of the amorphous optical recording layer.

By adding at least one element among Ge, Br, and Si, the noise level of the medium can be completely reduced, and the O/N ratio can be improved.

However, what is shown in this example is only a PC base version.
There is no problem in using a resin base such as PMMA or epoxy A4 IF, or a glass substrate with grooves made of ultraviolet curing resin or a glass substrate plate itself may be used. In addition, the structure of the medium may be three or four layers, and the dielectric material may be a composite film of aluminum nitride and silicon nitride, a single film of aluminum nitride, a single film of silicon nitride, or a single film of silicon nitride.
5102. Even if S10°ZnS or the like is used, the present invention will not be impaired in any way.

[Brief explanation of drawings]

Figure 1 shows the composition dependence of O/N when all Ge is added to the NdDyFe(!o alloy thin film. Figure 2 shows the composition dependence of
7 is a diagram showing the composition dependence of the Kerr rotation angle when Gei is added to the 7F'θCO alloy R film. Figure 3 is a structural diagram of the medium. Figure 4 shows the composition dependence of C/N when B is added to the NdDyF'000 alloy thin film. Figure 5 11i NdD
yFeC. FIG. 3 is a diagram showing the composition dependence of the Kerr rotation angle when B is added to the alloy thin film. Figure 6 shows N(LD7F13Co alloy thin film with Sr).
A diagram of the composition dependence of O/H when adding . Figure 7 is N
dA diagram showing the composition dependence of the Kerr rotation angle when Sr is added to the D7FθOo alloy thin film. Figure 8 is a diagram showing the dependence of O/N on the composition when 81 is added to the NdDyFeC0 alloy thin film. FIG. 9 is a diagram showing the composition dependence of the Kerr rotation angle when 81 is completely added to the NdDyFeoO alloy thin film. FIG. 10 is a diagram showing the composition dependence of O/N when B-Gei is added to a NdDyFeCo alloy thin film. Figure 11 is N
Figure 12 shows the composition dependence of the Kerr rotation angle when B-Ge' (+-) is added to the dDyFeoo alloy thin film.
A diagram of the composition dependence of C/N when Ge is added to a FeC0 alloy thin film. The 15th factor is a diagram showing the composition dependence of the Kerr rotation angle when Ge is added to the NdTbFeCo alloy thin film. 8g14 figure is SmGdFeC! A diagram of the composition dependence of C/N when Gekm is added to the o alloy thin film. Figure 15 shows Sm
FIG. 4 is a graph showing the composition dependence of the Kerr rotation angle when all Ge is added to the 04F'eCO alloy thin film. 1... Carrier ((3) 2... Carrier to noise ratio (G/N) 3... Noise (N) 4... PC board 5... Composite film of aluminum nitride and silicon nitride 6 −
NdDyFeCoGe film 7... Composite film of aluminum nitride and silicon nitride 8.
...Carrier (,0) 9...Ratio of carrier to noise (0/N) 10...Noise (N) 11...Carrier (c) 12...Ratio of carrier to noise (a/N) )13...
Noise (N) 14... Carrier (C) 15... Carrier to noise ratio (07M) 16...
・Noise (N) 17...Carrier (0) 18...Ratio of carrier to noise (0/N) 19...
・Noise (N) 20...Carrier (c) 21...Ratio of carrier to noise (C/N) 22・
...Noise (,N) 23...Carrier (0) 24...Ratio of carrier to noise (C/N)25...
・Noise (N) More than 1 1'ffl Violet 2 II Le 4 1 Ku Convex Figure S Figure E) Figure 'I'
/! ; SrW%ノ7m Name SFigure 5" lo 6 , S,...,%J\ 1 Figure 10 Figure 111 Figure 12 Name 13

Claims (3)

[Claims] (1) The direction of magnetization is perpendicular to the film surface and is either upward or downward.
In a magneto-optical recording medium in which recording, reproduction, and erasing is performed by irradiating light onto an amorphous magneto-optical recording layer that takes a value, B, G
1. A magneto-optical recording medium characterized in that it is doped with at least one element among e, Sr, and Si and has the following composition and impurities. (Rare earth transition metal)_1_0_0_-_α(BwGex
SrySiz) α0<α≦15at%, 0≦w≦1 0≦x≦1, ≦Y≦1 0≦z≦1, W+X+Y+Z=1 (2) The rare earth of the rare earth transition metals is Nd, S
at least one light rare earth metal of m;
2. The magneto-optical recording medium according to claim 1, further comprising at least one heavy rare earth metal selected from among d, Tb, and Dy. (3) The transition metal among the rare earth transition metals is Fe,
The magneto-optical recording medium according to claim 1, characterized in that it contains at least one type of Co.