JPS6115308A - Photomagnetic recording material - Google Patents

Abstract

PURPOSE:To obtain the titled material having a good heat stability and a large C/N ratio by composing a rare earth-iron group amorphous film so that it has a high rare earth element concentration by determining the ratios of plural kinds of specified elements to be within a range of the predetermined value respectively. CONSTITUTION:The photomagnetic recording material is composed of the material of a rare earth-iron amorphous magnetic film composition which includes high concentration of rare earth elements whose composition formula is expressed by RaTbMc. Element R is at least one kind of element selected out of a group consisting of Cd, Tb, and By and T is at least one kind of element selected out of a group consisting of Nd, Eu, Ho, Er, Tm, Tb, Y, Nb, Ni and Al, M is at least one kind of element selected out of a group consisting of Fe and Co. Furthermore, a+b+c=100, 35.5<=a<=45, 0<=b<=15.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magneto-optical recording material capable of recording, reproducing, and erasing information using a laser beam. , improve performance index, and regenerate S
The present invention relates to a magneto-optical recording material with a /N ratio or a C/N ratio as described above.

[Background of the invention]

Recently, magneto-optical recording, which has high density, large capacity, and allows arbitrary reading and rewriting of information, has been attracting attention. In magneto-optical recording, a magnetic thin film (perpendicularly magnetized film) with an axis of easy magnetization perpendicular to the film surface is used, and by creating reversal magnetic domains at arbitrary positions by irradiation with a light beam, the direction of magnetization can be changed. Correspondingly, binary information such as PA1"° and "°0" is recorded. On the other hand, reading out the binary signal after such inversion recording usually involves the polar Kerr effect or the Faraday effect. It is done by using it.

Conventionally, as such magneto-optical recording media, perpendicular magnetization films such as MnB1-based crystalline thin films, rare earth-transition metal-based amorphous thin films, and single crystal thin films represented by garnet have been proposed. Among them, rare earth-transition metal-based amorphous thin films are currently considered the most promising because they have no grain boundaries, have low media noise, and are easy to fabricate over large areas. As these rare earth-transition metal-based amorphous thin films, Co-based Gd-C
o type (Japanese Patent Publication No. 57-34588), Tb-Fe type (Japanese Patent Publication No. 52-31703) as Fe-based amorphous thin film.
), Gd-Fe system (JP-A-57-34588), Tb-Gd-Fe system (JP-A-56-1269C1)
Publication No. T), Gd-Dy-T b -Fe system (Japanese Unexamined Patent Publication No. 5
7-120254), T'b-Fe-Co, Dy
Alloy systems such as the -Fδ-Co system (Japanese Unexamined Patent Publication No. 58-73746) are currently being researched and developed, and the Kerr rotation angle due to the residual magnetization of the film itself has been improved to 0.3°.

However, these amorphous films tend to change significantly over time, have poor thermal stability, have poor corrosion resistance, and have a short lifespan.Furthermore, the Curie point is generally low, about 150°C or less, and requires strong power to read out signals. There were drawbacks such as the inability to increase the S/N ratio using laser light.

[Purpose of the invention]

An object of the present invention is to provide an amorphous magneto-optical recording material that has a Kerr rotation angle that is one tenth larger, provides a high reproduction S/N ratio, and has high thermal stability.

[Summary of the invention]

Rare earths are attracting attention as candidates for magneto-optical recording materials.
Conventionally, iron group amorphous films have a concentration of textile elements of 15 to 30 atomic percent for binary systems and 15 to 35 atomic percent for ternary systems, and within this composition range, the magnetization decreases at the film surface. , and a relatively large Kerr rotation angle was obtained. However, when obtaining a reproduced signal using the magneto-optic effect, increasing the power of the laser beam
It has been known for a long time that the N ratio increases, but in the above rare earth element composition range, the Curie temperature Tc or compensation temperature Tcomp is low, so if the power of the laser beam is increased too much, the Kerr rotation angle will decrease. , it is not possible to increase the S/N ratio.

Therefore, the present inventors have investigated various conditions for obtaining a perpendicularly magnetized film with a rare earth-iron group amorphous magnetic film composition containing a high concentration of rare earth elements, such that a higher Curie temperature or compensation temperature can be obtained than in the past. As a result of this study, we have arrived at the present invention.

The magneto-optical recording material of the present invention is represented by the composition formula RaTbMc, where R is substantially at least one element selected from the group consisting of Gd, Tb, and Dy, and T is Nd, '
Eu, Ho, Er, Tm, Yb, Y, Nb
, Ni, A/, M is at least one element selected from the group consisting of Fe, Go, and a + c = 10
It is a rare earth metal-iron group amorphous alloy perpendicular magnetization film satisfying 0.35.5<a<45, 0(b(15). It is more preferably 36(a(38).

In the alloy film of the present invention, in order to raise the Curie temperature or compensation temperature to 150°C or higher, which is higher than the conventional one, the amount a of R needs to be 35.5 atomic percent or more, but if it is too large, Writing with semiconductor laser light becomes impossible (or a perpendicularly magnetized film cannot be obtained).
The content must be 45 atomic percent or less. In order to obtain strong perpendicular magnetic anisotropy on the film surface within the compositional concentration range a of the rare earth metal element R in the present invention as described above, it can be achieved by sputtering or vapor deposition. To obtain this, a high-concentration argon gas atmosphere of 20 to 100 m Torr, an atmosphere of either nitrogen or oxygen gas alone, or a mixed gas atmosphere in which one or more nitrogen or oxygen gases are mixed into an argon gas at a partial pressure. It is preferable to perform sputtering or vapor deposition in a medium. This is thought to be because the rare earth metal elements react with these gases and create some kind of nonmagnetic region in the alloy film, thereby inducing strong perpendicular magnetic anisotropy.

Further, when a film is formed by sputtering or vapor deposition in these gas atmospheres, a part of the rare earth metal element whose spin is antiferromagnetically coupled to the iron group element becomes nonmagnetic due to oxidation or the like. Therefore, the appearance is higher and the compensation composition shifts to the side of the composition containing more rare earth metal elements, so that a perpendicular magnetization film can be obtained even in a film with a composition containing more rare earth metal elements. For example, Figure 4 is a diagram showing the Tb concentration dependence of the saturation magnetic flux density 4πMs of a TbXCo+oo-x amorphous film prepared by RF sputtering in pure Ar gas and Ar10z gas. be. In the figure, the solid line indicates the case of fabrication in pure Ar gas, and the dotted line indicates the case of fabrication in Ar + 02 gas. T in membrane
The amount of non-magnetization of b is shown. From the figure, it can be seen that when the film is formed in an Ar/O2 mixed gas atmosphere, the compensation composition moves by ΔX toward the higher Tb concentration side. This is because Tb atoms were made non-magnetic by this amount. Figure 5 shows TbXc in an Ar+02 mixed gas atmosphere using the RF sputtering method.
FIG. 7 is a diagram showing a change in the amount of demagnetization ΔX/X of Tb atoms with respect to oxygen partial pressure P02 when an oloo-x amorphous film is produced. From the same figure, the amount of demagnetization increases rapidly as the oxygen partial pressure increases, and after passing about 0.13 X 1O-4 Torr, the increase becomes gradual, and the amount becomes 0.16 X 1O-4 Torr.
orr is about 50%. However, if a portion of the rare earth element R represented by R is too large and becomes non-magnetic by oxidation etc., the film properties will deteriorate, so the amount to be de-magnetized is 5 to 60%, more preferably 20 to 50%. It is preferable to keep it within the range of . In addition, in order to adjust the recording and playback sensitivity of the °C1 film as needed,
A part of d, Tb, DV is replaced with N of other rare earth constituent elements T.
By substituting 15 atomic percent or less with at least one of d, Eu, Ho, Er, 'Sm, Yb, and Y, the performance as a magneto-optical recording medium can be optimized. Furthermore, by substituting a portion of Fe or Co of the iron group constituent element M with at least 15 atomic percent or less of at least one of Nb, A/, and Ni, the figure of merit of the magneto-optical recording material can be increased to 4. Increasing the crystallization temperature TX without deteriorating θK (R is reflectance, θ is Kerr rotation angle),
Corrosion resistance can be improved.

Furthermore, in the present invention, the rare earth element R constituting the film is
By forming an amorphous film using at least two of Gd, Tb, and Dy as amorphizing elements, the Curie temperature or compensation temperature can be further increased, and the Kerr rotation angle can be increased. In addition, by substituting Fe with Co or Co with Fe at 50 atomic percent or less, the magnetic moment of the iron group elements that contribute to the Kerr rotation angle can be increased (and furthermore, the magnetic moment of the iron group elements, which are other constituent elements in the present invention By replacing element R with another type of rare earth element, the Kerr rotation angle can be further improved and at the same time the Curie temperature -
By optimizing this, recording and playback sensitivity can be greatly improved.

To the rare earth-iron group amorphous film of the present invention described above, 10 atomic percent or less of a nonmetallic element such as B or Si or a transition metal element such as a platinum group element other than the constituent elements of the present invention is added. By doing so, the film properties such as magnetic properties, Curie temperature, crystallization temperature, corrosion resistance, etc. can be further optimized depending on the application.

The element T is Nd, Eu, Ho, Er, Sm,
Yb, Nb, A/.

The effect of adding transition metal elements such as Y, Ni, B, Si, and platinum group elements to rare earth-iron group amorphous films is not limited to alloy films within the composition range of the present invention, but generally all rare earth elements A similar effect can be obtained with a rare earth-iron alloy film having a wide composition range of 5 to 45 atomic percent. Especially Nb,
Ru element is effective in raising the crystallization temperature, increasing thermal stability, and improving corrosion resistance.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using Examples.

In the amorphous alloy film of the present invention, one of the iron group elements Co and Fe, which is the main component of the alloy film, is formed into a disk with a diameter of about 110 mm, and the other iron group element, rare earth metal Element Gd
, Tb, at least one element of DV, Nd
, Sm, Nb, Ni, and Az by sputtering using a composite target in which 5×5 square plates are arranged so that the area ratio has a predetermined composition, or by sputtering with a predetermined composition. The alloys were arc melted in vacuum and then electron beam evaporated using these alloys. In the case of RF sputtering method,
The pressure of Ar gas is 50 to 100 m Torr, or the pressure of Ar gas containing 10% 02 is 5 to IQ m
The test was carried out under conditions of 100 W of input high-frequency power at Torr. In addition, in the case of magnetron sputtering method, Ar
The pressure of Ar gas containing scum, 10% N2, or Ar gas containing 5% 02 is 10 to 100 m Torr,
The test was conducted under the condition of input high frequency power of 5Kw. Furthermore, in the case of electron beam evaporation, the oxygen pressure is 1 to 15
Vapor deposition was performed in an atmosphere of −7 Torr. As mentioned above, in the case of Ar gas alone, by increasing the gas pressure,
Also 02. By sputtering or vapor deposition in a gas containing an active gas such as N2, a part of the rare earth element R referred to in the present invention is made nonmagnetic by oxidation, etc., and spin coupling of rare earth atoms from the sublattice of the ferrimagnetic material is caused. By removing the rare earth element R and moving the compensation composition to the higher concentration side of the rare earth element R, a perpendicularly magnetized film can be obtained at a higher concentration side than in the past.

The perpendicular magnetic anisotropy energy Ku of the film thus produced showed a value in the range of 1 to 15×110 5 er//Cc.

FIG. 1 is a table showing the Kerr rotation angle θK, coercive force Hc, Curie temperature Tc, compensation temperature Tcomp, and crystallization temperature TX of a typical film produced by the method described below.

As is clear from the same table, the concentration of rare earth element R is 35
．． 5 atomic percent or more, Curi temperature Tc or 15
0°C or more, compensation temperature Tcomp is near room temperature, Kerr rotation angle θK is 0.24 degrees or more, coercive force Hc is l koe or more,
An amorphous film suitable for a magneto-optical recording material having a crystallization temperature Tk of 420''C or higher has been obtained.

FIG. 2 is a diagram showing the composition dependence of the Kerr rotation angle of a typical amorphous film produced by the method described above.

Curve 1 in the figure is a Tb36-X GdXFe64 amorphous film, curve 2 is a Tb38FC62,...XC0X amorphous film,
Curve 3 is the Tb18GdlBFe64XCoX amorphous film, curve 4 is the Tb38Co62-xFeX amorphous film, and curve 5 is the Kerr rotation angle θ as a function of As is clear from the figure, in the amorphous alloy film of the present invention, denoted by RaTbMc, the concentration of the rare earth element, denoted by R, is set to 35.5 atomic percent or more. It can be seen that the Kerr rotation angle θK can be further improved in an alloy film in which the remainder is an iron group element represented by M.

Figure 3 shows the Tb36 pe59 of the present invention shown in Figure 1.
#55 amorphous gold film (curve 7), Tb36 Fe5g N
b5 amorphous alloy film (curve 8) and conventional Tb25, Fe
75 is a diagram showing the results of comparing the state of deterioration of perpendicular magnetic anisotropy energy Ku due to heat treatment with that of the 75 amorphous alloy film (curve 6).゛The experiment was conducted by annealing at 200°C in an Ar atmosphere for +11 hours each time, measuring Ku(t) at that time, and calculating the initial value Ku(01) as Ku(t)/Ku(0). As is clear from the figure, the Tb-Fe-Ae gold alloy curve 7) of the present invention, the Tb-Fe-
It can be seen that the Nb alloy (curve 8) exhibits excellent thermal stability.

In general, the amorphous alloy film containing a large amount of the rare earth element R (R≧35°5 atomic percent) of the present invention is different from the conventional amorphous alloy film containing a small amount of the same rare earth element (R (3.5 atomic percent)).
It also has better corrosion resistance than .

Next, Tb3 with high rare earth element concentration obtained by the present invention
The reproduction light power dependence of a 6Fe53Co1□ perpendicularly magnetized film and a conventional Tb25Fe75 perpendicularly magnetized film with a low rare earth concentration was investigated. As a result, the output-to-noise ratio C/N during reproduction is lower than that of the conventional Tb25 Fe75 perpendicularly magnetized film.
．． At 5 mW or more, the C/N is saturated and only 47 dBL can be obtained, whereas the Tb36 Fe53 Co of the present invention
With the No. 11 perpendicular magnetization film, the reproduction light could be increased to 2.5 mW, and as a result, a high C/N value of 55 dB was obtained. At this time, the measurement frequency f was 1 MHz, the measurement bandwidth Δf was 3QkHz, and the bit length was 13 μm.

As described above, in general, the amorphous perpendicular magnetization film with a high concentration of rare earth element R of the present invention has a higher C It can be seen that /N is obtained.

Although not explained above, when Dy is added alone as the R element, Eu and Ha are added as the T element.

The same results as above can be obtained when Er, Yb or Y is added.

〔Effect of the invention〕

As is clear from the above explanation, the amorphous perpendicular magnetization film with a high rare earth element concentration of the present invention has better thermal stability than the conventionally reported amorphous perpendicular magnetization film with a lower rare earth element concentration. , larger playback output/noise ratio (C/
It can be seen that this is an excellent magneto-optical recording material that can obtain N2).

[Brief explanation of the drawing]

FIG. 1 is a table showing the Kerr rotation angle, coercive force, Curie temperature compensation temperature, and crystallization temperature of a typical amorphous perpendicularly magnetized film of the present invention, and FIG.
+ Tb38F"62 X CoX+ Tb18 G
d17-5 Fe64-X CoX+Tb3B Co6
2 X FeX, T')+9 Dy18 Co63-
A diagram showing the dependence of the Kerr rotation angle on the X concentration in the X FeX amorphous perpendicularly magnetized film. Tb
36Fe59M5. A diagram showing the change in perpendicular magnetic anisotropy energy with respect to annealing time when a Tb36Fe59Nb5 amorphous perpendicularly magnetized film is annealed at 200°C in an Ar atmosphere, Figure 4. Tb with a saturation magnetic flux density of 4πMs when produced by RF sputtering in dust and Ar+02 mixed gas
A diagram showing the 4 degree dependence, Figure 5 is a graph showing Tb)Hcolo in an Ar + 02 mixed gas atmosphere by RF sputtering.
Oxygen partial pressure Po2 when producing o-X amorphous perpendicular magnetization film
FIG. 2 is a diagram showing changes in the amount of demagnetization of Tb atoms with respect to FIG.

Claims (1)

[Claims] 1. The compositional formula is represented by Ra Tb Mc, where R is Gd, T
b, at least one element selected from the group consisting of Dy, T is Nd, Eu, Ho, Er, Sm, Yb, Y
, at least one element selected from the group consisting of Nb, Ni, and Al; M consists of at least one element selected from the group consisting of Fe and Co; and in atomic percent, a+b+c=100, 35.5<a<45
, 0<b<15, and is characterized by being predominantly amorphous. 2. The magneto-optical recording material according to claim 1, wherein the R is at least two elements selected from the group consisting of Gd, Tb, and Dy. 3. The magneto-optical recording material according to claim 1, wherein the M is composed of two elements, Fe and Co. 4. In the magneto-optical recording material according to claim 1, the R consists of at least two elements selected from the group consisting of Gd, Tb, and Dy, and the M consists of two elements, Fe and Co. A magneto-optical recording material characterized by: 5. Claims 1, 2, 3, or 4
3. The magneto-optical recording material according to item 1, wherein 5 to 60% of the element represented by R is contained in a non-magnetic state. 6.Claim 1, 2, 3 or 4
3. The magneto-optical recording material according to item 1, wherein 20 to 50% of the element represented by R is contained in a non-magnetic state.