JPS6187242A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a photomagnetic recording medium which has a high S/N ratio and permits high-density recording and high-speed recording by forming said medium so as to have a photomagnetic recording layer consisting of an alloy added with specific elements and a low coercive force material layer consiseting of an alloy added with specific elements and forming a non- magnetic material layer having a specific thickness therebetween. CONSTITUTION:The photomagnetic recording medium has the photomagnetic recording layer consisting of the alloy composed of elements of at least >=1 kinds of Ce, Pr and Nd as well as Fe and impurities or said alloy added further with elements of >=1 kinds among Ti, Zr, Ta, Hf, Nb, W, Y, Mo, B and Si or the alloy added further with elements of >=1 kinds among Cr, Co, Cu, Ni and Mn and the low coercive force material layer of which the coercive force is <=1/5 the coercive force of the photomagnetic recording layer and <=100 coersted and which consists of the alloy composed of Fe, Ni and impurities or the alloy added further with elements of >=1 kinds among Cu, Cr, Mo, Mn, V and W. The non-magnetic layer having <=100 nanometer thickness if formed between the magnetic recording layer and the low coercive force material layer.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a magnetic recording device having an axis of easy magnetization in a direction perpendicular to the film surface, and from which information can be read using magneto-optic effects such as the magneto-optic Kerr effect. It's about the medium.

[Prior art]

Research on magneto-optical memory is said to have its beginnings in 1957, when recording was performed on an MnB1 thin film using a hot pen, and the written magnetic domain was observed using the magneto-optic effect. After that, research was conducted mainly on the MnB1 system, but laser light sources,
However, in the 1970s, advances in optical information processing related technology and research into new magnetic recording materials such as amorphous rare earth transition metal alloy thin films began. GcL, which is described in patent application publication No. 56-37607.

Heavy rare earths such as Tb, Dy, and HO, as well as Pe and Co.

Amorphous alloy thin films with transition metals such as N1 have been developed. These materials generally have the following characteristics.

Gd? Materials that perform recording and reproduction using magnetic compensation points such as θ and Gdoo have a small coercive force, and when high-density recording is performed, the recorded magnetic domain cannot be kept stable, and the composition dependence of the magnetic compensation point is large. There are drawbacks such as difficulty in obtaining a thin film that is uniform in area. TI) ae.

Materials such as Dyke that perform recording using a single point of the polarization have disadvantages such as poor optical reproduction characteristics due to a smaller rotation angle of the plane of polarization due to the magneto-optic effect compared to materials that perform compensation point recording. be.

Japanese Patent Publication No. 56-126107. GdTbPe or GdTt) described in 1983-94948? Diversify like eOo etc. Alternatively, there are methods to improve the properties by improving the production method as reported in the 27th Research Meeting of the Japan Society of Applied Magnetics, Material 27-5 NHx Basic Research, but heavy rare earths are present in small quantities and expensive, so they are not practical. It is unsuitable for conversion.

As described in Japanese Patent Application Laid-open No. 58-20047, a method of forming a multilayer structure to increase the magneto-optic effect has also been carried out.

However, since these reduce the reflectance of the medium, sputtering is used to manufacture recording media made of the heavy rare earth transition metals, which has drawbacks such as the increase in the magneto-optic effect does not directly improve the S/N ratio. However, when producing targets for sputtering, heavy rare earth transition metals are difficult to alloy, so it is difficult to obtain large targets.

〔the purpose〕

The present invention has been made to improve these drawbacks, and its purpose is to provide a magneto-optical recording medium that has a high S/N ratio, stable high-density recording, high-speed recording, and is easy to manufacture.

〔overview〕

The present invention provides a magneto-optical recording medium in which recording and reproduction is performed by irradiating light onto a magneto-optical recording layer in which the direction of magnetization is perpendicular to the film surface and has a binary value of either upward or downward. ) + praseodymium (Pr) I neodymium (Nd
), iron (Pe), and impurities, or the alloy further contains titanium (T).
i) 1 zirconium ("r) t tantalum (Ta), hafnium (If) 1 niobium (Nb), tungsten (W)
), yttrium (Y), molybdenum (Md), boron (
B), an alloy to which at least one element among silicon (Si) is added, or chromium (Cr),
A magneto-optical recording layer made of an alloy containing cobalt ('') and at least one element selected from copper (Cu), dikel (Ni), and manganese (Mn), and a magneto-optical recording layer that has a coercive force. An alloy consisting of iron (Pe), nickel (Ni) and impurities, or copper ((!u)) in an amount of less than one-fifth and less than 100 oersteds.

Chromium ('r) + molybdenum (Mo), manganese ('n) l vanadium (V), tungsten (W)
a low coercive force material layer made of an alloy to which at least one or more elements are added, and a nonmagnetic layer with a thickness of 100 nanometers or less between the magnetic recording layer and the low coercive force material layer. It is characterized by the fact that it has been formed.

〔Example〕

The basic structure of the present invention is shown in FIG. 1(α) and FIG. 1(b). 11 is a substrate, 12 is a magneto-optical recording layer, 15 is a low coercive force material layer, and 14 is a nonmagnetic layer.

In this case, the substrate is a transparent substrate made of glass, plastic, etc., and the optical head for reading and writing faces the substrate and reads and writes through the substrate. However, this is not essential, and the substrate has a low coercive force. There is no problem in reading and writing by forming a material layer/magneto-optical recording layer, or a low coercive force material layer/nonmagnetic layer/magneto-optical recording layer, and placing an optical head facing the magneto-optical recording medium side with respect to the substrate. Furthermore, the present invention provides the above-mentioned
The present invention is not limited only to the structure, and there is no problem in providing a protective film, an antireflection film, a multiple interference enhancement film, a transparent conductive film, etc.

The present invention will be described in detail below using the drawings.

Example 1 A well-cleaned glass was used as the substrate 23 of the medium having the structure shown in FIG. 2.
As No. 1, OuMOFeNi permalloy 10001 was formed. The coercive force of the OuMOFeNi film is approximately 7 oersted, and it is designated as sample portion 1. For comparison, sample portion 2 is prepared by forming At 10001 by sputtering instead of the permalloy film described above.

In the medium having the structure shown in FIG. 2(b), as in (1), 23 is a glass substrate, 22 is an NdFeT1 film, and 21 is a c
uMoIFeNiM, 24 is a dielectric layer 810. a
ooX is formed. This is 310mm between the NaPeTi film and the glass substrate. By forming a film, the Kerr rotation angle is enhanced. This will be referred to as sample section 3. For comparison, the sample portion 4 was prepared by forming 10ooX of At by sputtering instead of the OuMolFeNi permalloy.

(3.) In the medium having the structure shown in FIG. 2(C), 23 is a glass substrate, 22 is a NaFeTi film, and 21 is an O
uMoFeNi bar voi, 24 is a Sin film.

25 is S10. The film is formed between the NdFeB film and the Permalloy film, and has a thickness of 100 mm. This is designated as sample section 5, and for comparison, the sample section 6 is designated as sample section 6 in which Permalloy is replaced with an At film.

A medium having the structure shown in FIG. 2(d), 26 is a PMM.
This is the A-board with guide grooves having a false spacing of 1.6μ and a depth of 700 prongs. Also, as in (1), 22 is NdFe
The Ti film 21 is OuMoFeN1 permalloy. This is designated as sample N117.

For comparison, a sample N118 was prepared in which an At film was formed instead of the permalloy film.

In a medium having the structure shown in FIG. 2 (=), the same PMMA as in (4) was used as the substrate 26, and S i O, /1114 F e T ilou M as in the sample part 5 of (2) was used.
Sample part 9 is made of oFeNi permalloy,
For comparison, Sample 10 is a sample Na9 in which Permalloy is changed to At.

Sample Na11 was prepared using a medium having the structure shown in FIG. For comparison, sample N
The sample portion 12 is made of permalloy of l111 with At.

In the medium having the structure shown in Fig. 2 (α), sample N1 of (1)
1L1 (!uMO?eNi) is made into MoMnFeNi as the sample portion 13. The coercive force of this MOMnFeNi is about 5 oersteds.

In the medium having the structure shown in FIG. 2 (eL), the OuMoFeNi of the sample part 1 in (1) is (!uor7eNi) as the sample part 14. The coercive and magnetic force of this OuOr'FeNi is about 6 oersteds. .

Amorphous NdF (1) in a medium with the structure shown in Figure 2 (α)
Sample part 15 is made of eTi made of amorphous PrlFeTa with a thickness of 500^, and for comparison, sample part 16 is made of permalloy of sample part 15 with hL.

Amorphous NdF (1) in a medium with the structure shown in Figure 2 (α)
Oe with thickness 500A? Sample N1117 is made of eZrOo, and sample part 18 is made of sample N1117 made of permalloy for comparison.

In the medium having the structure shown in Fig. 2 (α), the sample Na of (1)
A sample portion 19 is made of NdFeT1 of No. 1 as NdPrFeMo, and a sample portion 20 is made of permalloy of sample 19 as hL for comparison.

In the medium having the structure shown in Fig. 2 (α), sample part 1 of (1)
Na? sTi to Nd? The sample part 21 is made of aNbCr, and for comparison, the permalloy of sample m21 is made of At and sample N[L22.

Sample N1123 is a medium having the structure shown in FIG. 2(i) in which NdFeT1 of sample part 9 in (5) is changed to Tbye, and for comparison, sample part 24 is a medium having the structure of sample Na23 in which Permalloy is changed to At.

The Kerr effect was measured for the above 23 types of samples.

To measure the Kerr effect, we apply a magnetic field of 10 kA to the sample to create a remanent magnetized state and use a He-Ne gas laser (e.g.
, length 632.8 nanometers). The measurement results are shown in Table 1.

In samples 1 to 12 of (1) to (6), all structures using OuMolFeNi permalloy have hL
Compared to this, the Kerr rotation angle has increased by almost twice. Also(
7) OuMo in sample 15 and sample 14 of l(8)
'Even when permalloy other than FeNi was used, the hL of sample 2 increased by about twice as much.

In (9) to (12>, Pr1!eTa is used as the recording layer.
, 0eFeZrCo, NdPrFeMo, Nd? eNb
In the case of using Cr, the liquor rotation angle became larger.

(15) measured the Kerr rotation angle using Tb''Iθ, which has been conventionally used as a magneto-optical recording medium, as a recording layer, and even in this case, the Kerr rotation angle increased by about 1.5 times.

Note that magneto-optical recording media to which (!r, Ni, Ou, and Mu are added) have the same effect as the addition of Co in sample 21, have excellent weather resistance, and have an axis of easy magnetization perpendicular to the film surface. Met.

Here, as a specific example of the peNi-based low coercive force material layer, O
uMol[FsNi, 0uOr? eNi.

Although the present invention has been described in detail using MnMolFeNi, the present invention is not limited thereto.
rFeNi +Mo0uOr'VIFeNi.

VFeNi, WFeNi, Or'I! eNi,0ura
The low coercive force material layer described in the second claim, such as Ni or MoFeNi, has exactly the same effect.

Example 2 The relationship between the coercive force of the low coercive force material layer and the Kerr rotation angle was investigated. The results are shown in Figure 3. In FIG. 3, the horizontal axis is the coercive force, and the vertical axis is the Kerr rotation angle. All samples used are shown in Figure 2 (α)
has the structure, α is glass/NdFeTi/F
eNi permalloy, b is glass/N dF a T
i/M o F e N i, c is glass/T
b? @ / F e N i Permalloy.

The Kerr rotation angle increases as the coercive force of the low coercive force layer decreases for all three species α, h, and c. However, when the coercive force reaches about 100 acetade, it becomes equivalent to that provided with an AA reflective layer (d, t in the figure). Furthermore, when the coercive force becomes larger, the Kerr rotation angle becomes smaller than that of AA. This is because Permalloy has a smaller reflectance than hL.

Example 3 Using an optical head capable of magneto-optical recording and reproduction, Fig. 4 (-)
The frequency characteristics were investigated using the media structure shown in the figure.

A semiconductor laser with a laser wavelength of 780+m was used.

Disc rotation speed is 1800 rpm * radius 5 cI
n was fixed, and the writing frequency was varied. Reading and writing were performed from the board side. The substrate was polycarbonate 41 with groups, and a thin film as shown in Table 2 was formed to have a three-layer structure. The first layer is hLki42 with 80 OA, the second layer is
The layer is the magneto-optical recording layer 43 and the AS third layer is a conventional hL reflective film or is it made by this invention? The aNi-based low coercive force material layer 44 is MoMn? eNi, 500A
The film thickness was set to . The forming means was Do magnetron sputtering. Figure 4 shows the 0/Nratio for each write frequency in each magneto-optical recording medium
A>. 0/N ratlo was increased by providing the FeNi-based low coercive force material layer according to the present invention compared to the conventional case where non-magnetic Kl was used as a reflective film. Additionally, Oe during Ire according to the present invention.

? In a magneto-optical recording medium containing at least one of r and Nd, the effect was even greater, and the writing frequency characteristics were dramatically improved.

Example 4 A medium with the structure shown in Fig. 2 (1) was prepared, and the recording power was varied using the thickness of the nonmagnetic intermediate layer between the magneto-optical recording layer and the low coercive force material layer as a parameter. /N ratio was investigated.

The medium is OuM as 21 low coercive force material layers in Figure 2 (1).
o? eNi perm oi 1oooX.

1001A of Nd1FeTi as the magneto-optical recording layer of 22
, 24 multi-reflection layers S10. Form 900 linings,
25 as a non-magnetic intermediate layer, from 100 to 1o
I created one that changed even ooX. For each thickness of the non-magnetic intermediate layer, O for the writing laser power
/N ratio is shown in Figure 5. S10. As the thickness increases, the O/N ratio becomes saturated at low laser power. In other words, writing sensitivity is improved. However, S10. 2
When the thickness is increased to 000X, the laser power at which the C/N ratio is saturated is low, but the saturation value of the O7N ratio is also low.

For this reason, it is desirable that the thickness of the nonmagnetic intermediate layer be equal to or less than that of the magneto-optical recording layer.

In addition, in Fig. 5, α is the thickness of the nonmagnetic layer of 100 mm, b is the same 200 mm, C is 5 mm, d is 100 mm, - is 20 mm
It is 00A.

〔effect〕

As shown in the above embodiments, the magneto-optical recording medium having the structure according to the present invention has a Kerr rotation angle approximately doubled and a C
/N ratio is also improved.

Furthermore, since the recording magnetic domain is stable, there is little deterioration in the C/N ratio even at high recording densities, making the medium more suitable for high-density recording.

In addition, conventional TbFa, Gd(!O, Tb?eCiO,
Compared to media containing heavy rare earths such as TbGdFe, Na, P
Materials containing light rare earth elements such as r and Ce are cheaper in material cost, and the magneto-optical recording medium according to the present invention is characterized in that the effect is greater for media containing light rare earth elements.

When sputtering is used to manufacture magneto-optical recording media, it is extremely difficult to manufacture targets for heavy rare earth transition metals; Light rare earth transition metals can be easily made into targets by melting.

Furthermore, writing sensitivity can be improved by providing a nonmagnetic intermediate layer between the magneto-optical recording layer and the low coercive force material layer. Furthermore, if the magneto-optical recording layer transmits some light, it is also possible to enhance the Kerr rotation angle between the low coercive force material layer and the magneto-optical recording layer.

[Brief explanation of the drawing]

FIGS. 1(α) and 1(b) are diagrams showing the basic layer structure of the magneto-optical recording medium according to the present invention. In (cL) and (b), 11...Substrate 12...Magneto-optical recording layer) 13...Low coercive force layer or 12...Low coercive force Layer 13... Magneto-optical recording layer, and in (b) 14... Intermediate layer. FIGS. 2(α) to 2(1) are diagrams showing the structure of a specific embodiment of the magneto-optical recording medium according to the present invention. In each figure, 21...Low coercive force layer 22...Magneto-optical recording layer 23...Substrate 24...Transparent dielectric layer 25... . . . Intermediate layer 26 . . . A substrate with guide grooves. FIG. 5 shows the effects of the magneto-optical recording medium according to the present invention. α...Glass substrate/N d Fe Ti
/ Fe in a medium with the structure of
The graph shows the Kerr rotation angle with respect to the coercive force of Ni. b...Glass substrate/Nd1FeTi/MoFa
The graph shows the Kerr rotation angle with respect to the coercive force of Mo7eNi in a medium having a structure of N1. c ”' ”-Glass substrate / T b IF e /
In a medium having a structure of FeNi] FeNi
This shows the Kerr rotation angle with respect to the coercive force. d...Glass substrate/N d7 e T 1/
Kerr rotation angle of a medium having the structure of A t. e...Glass substrate/T b Fe/A
Kerr rotation angle of a medium with structure L. FIG. 4 is a diagram showing the recording and reproducing frequency characteristics of the magneto-optical recording medium according to the present invention. (α) shows the structure of the medium used in the experiment, 41... Substrate 42... A/, N (transparent dielectric layer) 43...
. . . Magneto-optical recording layer 44 . . . A low coercive force material layer or ht. Cb) shows the ON ratio with respect to the writing frequency, and 1a to 5α and 1b to 5b in the figure are the sample numbers shown in Table 2. Figure 5 shows the O/N ratio for the writing laser power using the thickness of the non-magnetic intermediate layer between the magneto-optical recording layer and the low coercive force layer as a parameter. i1\J~, (a) (b ) Figure 1 Figure 2L Figure 2 (α) Figure 4 Figure 5

Claims (1)

[Claims] In a magneto-optical recording medium in which recording and reproduction are performed by irradiating light onto a 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, the magneto-optical recording medium is made of cerium (C).
e), an alloy consisting of at least one element selected from praseodymium (Pr), neodymium (Nd), iron (Fe), and impurities, or an alloy containing titanium (Ti).
), zirconium (Zr), tantalum (Ta), hafnium (Hf), niobium (Nb), tungsten (W),
Yttrium (Y), molybdenum (Mo), boron (B)
, an alloy to which at least one element among silicon (Si) is added, or at least one element among chromium (Cr), cobalt (Co), copper (Cu), nickel (Ni), and manganese (Mn) to the alloy. A magneto-optical recording layer made of an alloy to which elements of are added, and the magneto-optical recording layer,
When the coercive force is less than one-fifth and less than 100 oersted
(Fe), nickel (Ni), and impurities, or the alloy further contains copper (Cu), chromium (Cr), molybdenum (Mo), manganese (Mn), vanadium (V
), and a low coercive force material layer made of an alloy to which at least one element of tungsten (W) is added, and a thickness of 100 nanometers is provided between the magneto-optical recording layer and the low coercive force material layer. A magneto-optical recording medium characterized by forming the following non-magnetic layer.