JPH02230535A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent thermal interference and to reduce the laser power for recording by successively forming a dielectric film, first magnetic film, second magnetic film, dielectric film and reflecting film in this order on a substrate, or alternatively, a dielectric film, second magnetic film, first magnetic film, dielectric film and reflecting film. CONSTITUTION:The first magnetic film 3 has low Curie point and high coercive force at room temp., while the second magnetic film 4 has relatively high Curie' point and lower coercive force at room temp. compared to the first magnetic film 3. These films generate exchange bonding force in a two-layer structure and constitute the perpendicularly magnetized film on the substrate 1. The medium has such a structure that from the substrate, the dielectric film 2, first magnetic film 3, second magnetic film 4, dielectric film 5 and reflecting film 6 are successively formed or in alternative order, the dielectric film 2, second magnetic film 4, first magnetic film 3, dielectric film 5 and reflecting film 6. By this method, no thermal interference occurs in the medium. The obtd. medium has high C/N and reliability and requires smaller laser power for recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Industry] The present invention relates to a magneto-optical recording medium having a rare earth metal-transition metal perpendicularly magnetized film.

[Conventional technology]

Magneto-optical disk memory is approaching the stage of practical application.
Adopt reflective film horizontal structure (1st edition Journal of Applied Magnetics, Vol.
．． 11. , No. 2, P213, 1987) or M
Signal quality has also been improved by making the O film two-layered (Optical Memory Symposium 86 Proceedings, p. 45).

[Problem to be solved by the invention]

However, when the MO film is made into two layers, the total thickness of the MO layer itself is less than IOOOA, and the shortest domain length is 3.
When writing a 7MHz (1.800rpm) signal, there is a drawback that the signal cannot be clearly written due to thermal interference with adjacent signals.In order to reduce thermal interference to this MO2 layer film, A1 If a reflective film such as
In addition to the thickness of 1,000 mm, there was a drawback that the recording laser power increased due to the increased heat capacity of the reflective film.

Therefore, the present invention is intended to solve the two consecutive drawbacks,
The object of the present invention is to provide a medium with a two-layer film structure in which thermal interference does not occur and the power of a recording laser can be reduced.

[Means to solve the problem]

(1) Low Curie point (TL) and high coercivity at room temperature (
Replacement of a two-layer structure consisting of a first magnetic film with H H) and a second magnetic film with a relatively high Gury temperature (T++) and low coercivity (I{L) at room temperature compared to this magnetic layer. In a magneto-optical recording medium having a perpendicularly magnetized film on a substrate, the configuration of the medium is a dielectric film, a first magnetic film, a second magnetic film, a dielectric film, and a reflective film when viewed from the substrate side. It is characterized in that, starting from the film or substrate side, it has a structure of a galvanic electric film, a second 6II magnetic film, a first magnetic film, a dielectric film, and a reflective film.

(2) The magnetization direction of each of the first magnetic film and the second magnetic film maintains the same direction from room temperature to the Curie temperature.

(3) It is characterized in that the thickness of the first magnetic film and the second magnetic film can be removed by 500 people or less.

[Effect]

In order to maintain the characteristics of the MO2 layer film structure and reduce thermal interference, it is better to reduce the total thickness of the MO2 layer film and add a reflective film. However, since the enhancement effect due to the thinning of the MO film and the reflective film is affected, the direction of magnetization of each magnetic film in the two layers of the MO film must be adjusted so as not to disturb the Faraday effect of the laser light that has passed through the MO film. must remain in the same direction. Furthermore, in order to utilize the Faraday effect, it is necessary for light to pass through the M○ layer, and the MO film must be a thin film with a thickness of 500 or less.

〔Example〕

In order to confirm the effects of the present invention, a magneto-optical recording medium having a structure as shown in FIG. 1 was prepared by sputtering.

1 is a PC board with a 1301 groove, 2 is an AISiN dielectric film of 800, and 3 is a Gd2a. ! IF
e73. [lC O n. Ilat%MO film 150
26th person, 4 as biomembrane (T I) 22. eF
e 71! ．． llC O e. eat%MQ film 150
8, number 5 is an AISiN dielectric film of 250, and number 6 is an A1 reflective film of 400A. These films were sequentially formed without breaking the vacuum. The magnetic properties of the first magnetic film and the second magnetic film are shown in the following table.

These two magnetic films are transition metal-rich films in which the sublattice magnetization of the transition metal is more dominant than that of the rare earth metal at room temperature.

In order to compare this medium, two types were prepared: a conventional MOL layer reflective film medium and an M○2 layer medium without a reflective film. Second
The figure shows a structural diagram of the Mol layer reflective film medium. 21 is 130
PC board with φ groove, 22 is AISiN dielectric film 8'O
OA, 23 is Tb22flFe 7+! ．． tlC O
e. ea t%MO membrane 300 people, 24 AI Si
Nifj electric film 25OA, 25 is A1 reflective film 400
It is A. This is because the MO film two-layer structure in Fig. 1 has one layer (Tb
FeCo), and the thickness is also the same.
It is 0A. Next, FIG. 3 shows a structural diagram of a medium without a two-layer MO film and no reflective film. 31 is a PC board with a 130φ groove, 3
2 is the AISiN dielectric film 800, 33 is the first magnetic film, and TeGd23. lIF e rg. llc o z. a
a t%MO film 5CIOA, 34 is T as the second magnetic film
b22. eF e 72lIC O e. eat
%MO film 500 people, 35 is AISiN dielectric film 5o8.

Various electrical properties of these conventional comparative media and the media of the present invention were evaluated. FIG. 4 shows the dependence of the carrier-to-noise ratio (C/N) on the writing power. 41 is MO thin film 2
The medium of the present invention has a layer reflective film, and 42 is the conventional M○1.
43 is a conventional MO2 layered medium without a reflective film. Comparing the electrical characteristics of these three media, 41 media of the present invention can be written with lower power than the other two conventional media, and the power at which the C/N saturates is 0.7 mW from the rise, and is sharp and good.

Moreover, the C/N of the medium of the present invention is as high as 61.0 dB. On the other hand, in the conventional 42 MO single-layer reflective film medium, the C/N rise was 1.5 mW, and the C/N was 56 dB, both of which were worse than the medium of the present invention. In addition, the 42 media require more write power than the inventive media. In the case of No. 43, the MO2-layer medium without a reflective film, it took as much as 4 mW to rise the C/H, and the rise was very poor. The C/N was also 58 dB, which is lower than the medium of the present invention, and the writing power required is even higher than that of the 42 medium, which is not good at all.

All of these evaluation conditions are 1800 rpmS r4 5
mm, 3. 7MHz, duty 50%, magnetic field 200
This is at 0e.

As an evaluation item for blowing, FIG. 5 shows the dependence of C/N on the writing pulse width. 51 is a medium of the present invention with a two-layer MO thin film reflective film; 52 is a conventional medium with a MO layer reflective film;
53 is a conventional MO2-layer medium without a reflective film. Comparing these three media, the medium of the present invention has a very wide margin with respect to the pulse width and exhibits good characteristics. In other words, it can be seen that the pulse width of 48 dB or more, which is required as a drive, is most preferable, which is 40 to 150 nsec. These evaluation conditions are r=30mm, 3.7
51 media at MHz write power 5mW, 52
The medium of No. 53 has a power of 6 mW, and the medium of No. 53 has a power of 9 mW.

Furthermore, as a durability test, Erase/W r
The ite/read repeated test results are shown.

The horizontal axis is the number of E/W/R repetitions, and the vertical axis is the length of the write signal (FWHM: Full WidthHar).
f Modulation>. The test position is r=
30mm, 3.7MHz, 90nseC. 61 is a medium of the present invention with a two-layer MO thin film reflective film, 62 is a conventional medium with an MO1-layer reflective film, and 63 is a conventional medium without a two-layer MO reflective film. The writing power of the medium is 6
1 is 5 mW, 62 is 6 mW, and 63 is 9 mW. From this figure, it can be seen that the signal quality of media 61 and 62 is good with no change at all, while the signal length of media 63 gradually increases and the medium deteriorates.

Note that the MO film of the medium used in this example is GdFeCo, T
bFeCo, but in addition to these, GdTbFeCo,
DyFeCo. NdDyFeCo, NdTbFeCo,
It is possible to use a rare earth transition metal alloy film such as PrDyGdFeCo, etc., and any combination of a low Curie point high coercive force film and a high Curie point low coercive force film may be used. In addition to the AISiN film, dielectric films include Sj-N, AIN, and Zn.
Any nitride-based, oxide-based, or sulfide-based galvanic film such as S, AISiON, etc. can be used, and the reflective film can also be made of Cu. Various materials such as Ag, Pt, and stainless steel can be used.

〔Effect of the invention〕

As mentioned above, if the present invention is used, thermal interference with adjacent signals will not occur even when the shortest domain length is written.
Furthermore, a reliable medium with a high C/N ratio can be produced.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of the medium of the present invention. FIG. 2 is a structural diagram of a Mol layer reflective film medium. FIG. 3 is a structural diagram of a M O 2 )r4 medium without a reflective film. FIG. 4 is a diagram showing the write power dependence of C/N. FIG. 5 is a diagram showing the dependence of C/N on write pulse width. FIG. 6 is a diagram showing the dependence of the signal on the number of E/W/R repetitions. 1...130φ grooved PC board 2...AISiN dielectric film 800 people 3-G d 23. llF e vg. ec O
a. Tlat%MO membrane 150 people 4-T b 22. flF e 72. aco
6,lla t%MO film 150A 5...AISiN dielectric film 250 people 6...AI reflective film 400A 21...130φ grooved PC board 22...AISiN rust electric film 800 people 2 3 -Tb
F e C o M O membrane 300 people 24...AIS
iN dielectric film 250 people 25...A1 reflective film 400 people 31...130φ grooved PC board 32...AISiN rust electric film 800 people 3 3-G d
F e Co M O membrane 500 people 3 4-T b
F e C o M O membrane 500 people 35...A I
Sj. N-electroelectric film 500 people 41...Medium of the present invention with MO thin film 2-layer reflective film 42...MO1i reflective film body 43...MO 2-layer medium without reflective film 51...MO thin film 2-layer reflective Media of the present invention with film 52...
MOIJli medium with reflective film 53...MO two-layer medium without reflective film 61...MO thin film two-layer reflective film medium 62...Mo
Medium with l-layer reflective film 63...Medium without MO2-layer reflective film and above

Claims (3)

[Claims] (1) Low Curie point (T_L) and high coercive force (at room temperature)
A two-layer exchange-coupled structure consisting of a first magnetic film having a magnetic field (H_H) and a second magnetic film having a relatively high Curie point (T_H) and a low coercive force (H_L) at room temperature compared to this magnetic layer. In a magneto-optical recording medium having a perpendicularly magnetized film on a substrate, the structure of the medium, when viewed from the substrate side, includes a dielectric film, a first magnetic film, a second magnetic film, a dielectric film, a reflective film, or A magneto-optical recording medium characterized by having a structure including a dielectric film, a second magnetic film, a first magnetic film, a dielectric film, and a reflective film when viewed from the substrate side. (2) The magneto-optical recording medium according to claim 1, wherein the direction of magnetization of each of the first magnetic film and the second magnetic film remains the same from room temperature to Curie temperature. (3) The magneto-optical recording medium according to claim 1, wherein the total thickness of the first magnetic film and the second magnetic film is 500 Å or less.