JP2001011616A - Alloy target for magneto-optical recording, its production and regenerating method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the magnetic permeability of an alloy target for magneto- optical recording composed of a rare earth metal-transition metal alloy, moreover to reduce the content of oxygen in the target and furthermore to facilitate the regeneration of the alloy target for magneto-optical recording. SOLUTION: This alloy target for magneto-optical recording is a planar body contg. R (one or more kinds among Tb, Dy, Gd, Sm, Nd, Ho, Tm and Er) and T (transition metals such as Fe, Co and Ni), having a substantially homogeneous sintered structure and having <=3 magnetic permeability and >=8 mm thickness. This is produced by a process of melting rapid cooling pulverizing baking under pressure by a high frequency furnace or a crucible furnace. After the use of this target, mechanical pulverizing is executed to obtain regenerated alloy powder, this regenerated alloy powder and the alloy powder before the baking under pressure in the above process are mixed, and this is baked under pressure and therefore can be made into a target once more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sputter target composed of a rare earth metal-transition metal alloy used as a magneto-optical recording material, a method for producing the same, and a method for reproducing the same.

[0002]

2. Description of the Related Art A recording layer of a magneto-optical recording medium has a Tb-F
An amorphous material made of a rare earth metal-transition metal alloy such as e-Co is preferably used. Such a recording layer is
Usually, it is formed by a magnetron sputtering method. In the magnetron sputtering method, it is necessary to leak the magnetic flux from the magnetic field generating means disposed on the back side of the target to the front side through the target. Therefore, when the magnetic permeability of the target is high, the magnetic flux passing through the target increases, and a sufficient magnetic field strength due to the leakage magnetic flux cannot be obtained. Therefore, in a target having a high magnetic permeability, it is necessary to secure a leakage magnetic flux by reducing the thickness.

[0003] However, if the target is thin, the sputtering time per target becomes short. For this reason, the frequency of performing the evacuation again by opening the sputtering chamber and exchanging the target is increased, which leads to an increase in cost due to a reduction in productivity. When a target is manufactured by a sintering method, it is necessary to grind an oxidized region near the surface after sintering for commercialization. Since the amount of grinding is about 1 mm regardless of the thickness of the target, the thinner the target, the higher the proportion of the area that is discarded without contributing to the sputtering, which also increases the cost.

With respect to a target for forming a recording layer of a magneto-optical recording medium and a method of manufacturing the same, for example, the following proposals have been made.

(I) Japanese Patent Publication No. 64-2177 discloses that
By melting a rare earth metal and a transition metal in an arc melting furnace to form an alloy ingot, pulverizing the alloy ingot, and molding the obtained alloy powder by hot pressing,
A method for producing an alloy target material is described. In this publication, wet pulverization in an organic solvent is performed,
Since the final particle size of the powder is as small as 1 to 10 μm, oxidation of the powder proceeds, and the characteristics are deteriorated. Also, in the same publication, the alloy ingot is manufactured by arc melting, but in the arc melting, since the raw material powder is melted by scanning the arc, the molten metal is gradually cooled after passing the arc, As a result, precipitation of Fe occurs. For this reason, the magnetic permeability of the target becomes high, so that the target cannot be made thick, and the life per target becomes short. In the example of the publication, a target having a thickness of 1.2 to 1.3 mm is manufactured.

(Ii) Japanese Patent Publication No. 1-19448 discloses that
The finely divided rare earth metal and the finely divided iron group metal are mixed, and the resulting mixture is subjected to hot forming at a temperature lower than the liquid phase manifestation temperature of the metal component system in the resulting mixture to obtain a dense mixture. A compact is formed, and then heated for a short time at a temperature equal to or higher than the liquid phase development temperature of the metal component system present in the compact, thereby forming an intermetallic compound of a rare earth metal and an iron group metal, and an iron group metal simple substance. A method for producing a target material having a mixed structure with the following. This target material contains 30 to 50% by weight of a rare earth metal, and the balance is an iron group metal.
The effect of the publication is to provide a high-strength sputtering target material that produces a magneto-optical recording medium having a stable composition and a low oxygen concentration.

[0007] However, the target materials described in the publication include:
Since there is a phase composed of a simple substance of the iron group metal, the magnetic permeability increases. For this reason, it becomes impossible to increase the thickness of the target material, and the life per target material is shortened. In the example of the publication, a target material having a thickness of more than 2 mm was not manufactured. Further, in the method described in the publication, it is necessary to pulverize the rare earth metal, but since the rare earth metal has high ductility and is difficult to pulverize, oxygen is easily mixed in the pulverization. In fact, in the example of the publication, the oxygen content of the target material is 1.5 atomic% or more, which is not small.

(Iii) Japanese Patent Publication No. 2-48623 discloses a mixed structure comprising 10 to 50 atomic% of a rare earth metal and the balance being substantially a transition metal and comprising at least three phases. An alloy target for magneto-optical recording in which the phase is an intermetallic compound phase of a rare earth metal and a transition metal is described. This alloy target is produced by sintering an alloy powder produced by a reduction diffusion method. The publication states that it is possible to provide an alloy target having advantages such as being hard to crack, dense, having a uniform composition, having a sufficiently low oxygen content, and being inexpensive.

However, the presence of the three phases means that there is a phase with a higher transition metal concentration. Since the phase having a high transition metal concentration has high magnetic permeability, the target cannot be thickened, and the life per target becomes short. The publication does not disclose the proportions of the three types of phases, but in the examples of the publication, the thickness is 3.
Since a target exceeding 5 mm was not manufactured, it is considered that the magnetic permeability is increased. In the same publication, an alloy powder composed of a transition metal single phase and an intermetallic compound phase surrounding and covering the transition metal phase is produced by a reduction diffusion method, and this is sintered to produce a target. In this method, the used target is pulverized and cannot be reused as a target raw material, so that it is difficult to reduce the raw material cost.

(Iv) Japanese Patent Publication No. 3-6218 discloses a sintered composite target material comprising rare earth metal particles, transition metal particles, and a reaction diffusion layer of both. According to the publication, the effect is that the transverse rupture strength is large, the impact resistance is good, the oxygen content is small, and the sputtering rate is high.

[0011] However, the sintered composite target material described in the publication contains a large amount of transition metal particles, so that the magnetic permeability increases. For this reason, it becomes impossible to increase the thickness of the target material, and the life per target material is shortened. In the example of the publication, a target material having a thickness of more than 5 mm was not manufactured. Further, in the production method described in the publication, it is necessary to pulverize the rare-earth metal in order to use the rare-earth metal particles as a raw material, but since the rare-earth metal has high ductility and is difficult to pulverize, oxygen is easily mixed in during the pulverization. .

(V) Japanese Patent Publication No. 3-54189 discloses that
A method of regenerating a target material by filling irregularities on the surface of the target material formed by use in a magnetron sputtering apparatus is described. Specifically, first, the irregularities are filled with a supplementary powder of the same material as the target material. Next, hot isostatic pressing or hot forging is performed to obtain a compact having a replenishment powder of high density. Subsequently, by performing a heat treatment, the target material and the compact are firmly bonded by diffusion. The target material thus reclaimed is composed of a used target material portion, a powder compact, and a diffusion bonding portion formed at the boundary between these portions. The quality is the same.

However, in the method described in the publication, the compositional deviation of the sputtered film due to the compositional variation in each part is liable to actually occur.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the magnetic permeability of a magneto-optical recording alloy target comprising a rare earth metal-transition metal alloy. Another object of the present invention is to reduce the oxygen content of such an alloy target for magneto-optical recording. Another object of the present invention is to facilitate reproduction of an alloy target for magneto-optical recording.

[0015]

This and other objects are achieved by any one of the following constitutions (1) to (9). (1) A target used when a recording material for magneto-optical recording is formed by a magnetron sputtering method, and R (R is Tb, Dy, Gd, Sm, Nd, Ho,
20 to 30 atomic% of a rare earth metal element selected from at least one of Tm and Er, and the balance substantially T (T is a transition metal element and at least one of Fe, Co and Ni) ), An alloy target for magneto-optical recording which is a plate-like body having a substantially homogeneous sintered structure, a magnetic permeability of 3 or less, and a thickness of 8 mm or more. (2) The alloy target for magneto-optical recording according to (1), wherein the thickness is 10 mm or more. (3) The alloy target for magneto-optical recording according to (1) or (2), wherein Cr is contained in the T. (4) The alloy target for magneto-optical recording according to any one of (1) to (3), wherein the oxygen content is 1000 ppm or less. (5) Fe ₃ Tb type crystal phase accounts for 88% by volume of the entire crystal phase
The alloy target for magneto-optical recording according to any one of (1) to (4) above. (6) The method for producing an alloy target for magneto-optical recording according to any one of the above (1) to (5), wherein R and T are such that R / (R + T) is 20 to 30 atomic%. And melted in a high frequency furnace or crucible furnace, then quenched to obtain a quenched alloy, mechanically pulverized in a non-oxidizing atmosphere to obtain an alloy powder,
A method for producing an alloy target for magneto-optical recording, wherein the alloy powder is sintered by pressurizing in an inert gas atmosphere or under vacuum. (7) 90% by weight or more of the alloy powder has a particle size of 45 to 4
(6) The method for producing an alloy target for magneto-optical recording according to the above (6), which is 25 μm. (8) After using the alloy target for magneto-optical recording according to any one of the above (1) to (5), the alloy alloy is mechanically pulverized in a non-oxidizing atmosphere to obtain a reclaimed alloy powder. Is melted in a high-frequency furnace or crucible furnace, and then quenched to obtain a quenched alloy.The quenched alloy is mechanically pulverized in a non-oxidizing atmosphere to obtain an alloy powder. A method for reproducing an alloy target for magneto-optical recording, comprising a step of sintering a mixture of the above-mentioned and the above-mentioned reproduction alloy powder by sintering under pressure in an inert gas atmosphere or vacuum. (9) The method for reproducing an alloy target for magneto-optical recording according to the above (8), wherein R / (R + T) of the mixture is 1.02 to 1.08 times R / (R + T) of the reproduced alloy powder.

[0016]

In the present invention, a rare earth metal and a transition metal are melted by high frequency melting to form a molten metal, which is quenched, pulverized, and then fired under pressure to obtain a target. In the present invention, in order to use a high-frequency furnace or a crucible furnace for melting the rare earth metal and the transition metal,
Unlike the conventional method using arc melting, precipitation of a single transition metal is not substantially observed. In addition, since the alloy is rapidly cooled during alloying, there is almost no precipitation or growth of a transition metal phase. For this reason, the target of the present invention has a single sintered structure of a rare earth metal-transition metal alloy, and has low magnetic permeability.

Further, in the present invention, since particles having a large diameter are obtained at the time of pulverization, mixing of oxygen is reduced, so that a target having a low oxygen content is realized.

Further, by appropriately selecting the conditions of the pressure sintering, it is possible to suppress the increase in the magnetic permeability and the oxygen content due to the sintering and to increase the sintering density. A hard-to-break target is realized.

In the target regenerating method of the present invention, after using the target of the present invention, the target is first pulverized to obtain a regenerated alloy powder. The reclaimed alloy powder is introduced into the above-described target manufacturing process of the present invention, and a new alloy powder obtained by pulverizing the quenched alloy is mixed with the reclaimed alloy powder. Thereafter, pressure baking is performed in accordance with the above-described manufacturing process to obtain a reproduction target. Since the target of the present invention has a substantially homogeneous sintered structure, the alloy powder obtained by pulverizing the used target and the novel alloy powder have substantially the same structure. Therefore, reproduction of the target is extremely easy, and there is almost no deterioration or change in characteristics due to reproduction.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Target The target of the present invention is used when a recording material for magneto-optical recording is formed by a magnetron sputtering method.

The target of the present invention is R (R is Tb,
A rare earth metal element selected from at least one of Dy, Gd, Sm, Nd, Ho, Tm, and Er)
0 to 30 atomic%, preferably 20 to 26 atomic%. The balance is substantially T (T is a transition metal element, Fe,
At least one of Co and Ni).
If the content of the rare earth metal is too large, it is difficult to be crushed, so that it is liable to be oxidized in the manufacturing process, and the characteristics of the recording layer of the magneto-optical recording medium deteriorate. On the other hand, if the content of the rare earth metal is too small, good characteristics cannot be obtained as a magneto-optical recording material, and the ratio of the transition metal increases, leading to an increase in magnetic permeability.

The ratio of Fe + Co + Ni in T is preferably at least 85 at%, more preferably at least 90 at%. If this ratio is too low, the characteristics as a magneto-optical recording material will be low. The ratio of Fe in T is preferably at least 80 atomic%. If this ratio is too low, the characteristics as a magneto-optical recording material will be low. Fe, Co, Ni
As a transition metal element other than, Cr is preferable. Since Cr is effective in improving corrosion resistance and pulverizability, T
e, Co, Ni and Cr are preferable.

The target may contain at least one of unavoidable impurities such as Al, Si, Ca, Mg, C, and S. The total content of these elements is preferably 0.1 atomic% or less.

The target of the present invention is a single-structure sintered body substantially free of a rare earth metal phase and a transition metal phase, and composed of crystal grains of a rare earth metal-transition metal alloy.

Rare earth metal-transition gold constituting the target
Alloys mainly consist of Fe_ThreeIt is a Tb type crystal phase. This
Or, the target usually contains Fe_{twenty three}Tb₆Type crystal phase
Or Fe_TwoA Tb type crystal phase is included. Fe_{twenty three}Tb₆Type crystal
The phase generally has a low Tb content (about 25 atomic%).
Below), and Fe_TwoThe Tb-type crystal phase generally contains Tb.
Appears when the amount is large (about 25 atomic% or more). all
Fe in the crystalline phase_ThreeThe ratio of the Tb type crystal phase is preferably 8
8% by volume or more, more preferably 92% by volume or more
is there. Observe the cross section of the target with a scanning electron microscope.
Then, Fe_ThreeIn the matrix phase composed of Tb type crystal phase
And Fe_{twenty three}Tb₆Type crystal phase or Fe_TwoTb type crystal phase
Dispersed tissue structure is observed. Identification of these phases and
The quantification was performed by X-ray diffraction and EPMA (electron
What can be done by the probe microanalysis)
it can. In X-ray diffraction, Fe_ThreeTb type, Fe_{twenty three}Tb₆Type,
Fe _TwoSubstantially no crystal phases other than Tb type are observed.

From the results of the EPMA measurement, it is considered that Co, Ni, and Cr contained in the target have replaced the Fe sites of the respective crystal phases.

In the target of the present invention, it is preferable that the presence of an α-Fe phase is not recognized in X-ray diffraction.

In the present invention, since it is preferable to perform firing at a temperature at which grain growth does not occur, as described later, the average crystal grain size of the target reflects the diameter of the alloy powder used as a raw material.

The target of the present invention has almost no crystal grain boundaries.

The magnetic permeability of the target of the present invention is 3 or less,
Preferably it is 2.5 or less. If the magnetic permeability is too high, the magnetic flux leaking from the target surface during magnetron sputtering is reduced, so that the target cannot be thickened, and as a result, the productivity of the magneto-optical recording medium decreases as described above. . At present, the smallest commercially available target has a magnetic permeability of about 5, but the target of the present invention has a magnetic permeability of 3 or less. Also,
At the time of magnetron sputtering, the same or higher magnetic field strength can be obtained on the target.

The magnetic permeability of the target of the present invention is 1 or more, usually 1.5 or more.

The target of the present invention is a plate-like body, and its thickness is not particularly limited. However, the target of the present invention has a low magnetic permeability and can be made thick. Specifically, even if the thickness is 8 mm or more, the leakage magnetic field intensity on the target can be increased during magnetron sputtering, and even if the thickness is 10 mm or more, a sufficient leakage magnetic field intensity can be obtained. However, in order to obtain a sufficient leakage magnetic field strength, the target thickness must be 12
mm or less is preferable. The planar shape of the target may be any of a circle, an ellipse, and a square. The diameter or minor diameter of the target is usually about 120 to 260 mm.

The target of the present invention is manufactured by a method described later, so that oxygen is less mixed in the manufacturing process. Therefore, the oxygen content can be reduced to 1000 ppm or less,
It is easy to make it 600 ppm or less.

The sintered density of the target is preferably 95
% Or more, more preferably 98% or more. According to the manufacturing method described later, such a high sintering density can be easily obtained. Since the target of the present invention has sufficient mechanical strength due to its high sintering density, it is unlikely to crack in the target bonding step when it is installed in a sputtering apparatus. The sintering density in this case is the ratio of the density of the sintered body to the theoretical density.

Next, a method of manufacturing the target of the present invention will be described.

Alloying Step First, a rare earth metal and a transition metal are prepared so that the ratio thereof becomes the above-mentioned target composition.

Next, the preparation is melted in a high-frequency furnace or crucible furnace (reflection furnace). In the present invention, it is more preferable to use a high-frequency furnace. In a high-frequency furnace, an eddy current is generated in a metal by putting a metal in a coil and flowing a high-frequency current through the coil. The metal generates heat due to its electric resistance and is melted to become a molten metal. On the other hand, in the above-described arc melting, the entire metal cannot be made into a molten metal because it is heated by scanning the arc. In the high-frequency melting, the entire metal can be melted, which allows rapid cooling, and the molten metal is naturally stirred, so that a homogeneous alloy with less precipitation of different phases can be obtained. In a crucible furnace, since the entire metal is heated by a heater, a homogeneous alloy close to that of a high-frequency furnace can be obtained. The melting of the metal in the high-frequency furnace and the crucible furnace is performed in a non-oxidizing atmosphere such as nitrogen gas or Ar gas.

Next, the molten metal is rapidly cooled. As the quenching method, for example, a casting method or a spraying method (gas atomizing method, single roll method, centrifugal disk method, etc.) may be used,
Among these, a casting method that is easy to reduce the cost is preferable. In the casting method, a molten metal is poured into a coolable ceramic crucible having an open top, or a horizontal split mold or a vertical split mold, and the molten metal is rapidly cooled. The space in the crucible or split mold is preferably a thin plate having a thickness of about 10 to 50 mm. It is preferable that the quenching speed is so fast that the casting is cracked and a thin plate cannot be maintained.

The quenching is performed in a non-oxidizing atmosphere such as nitrogen gas or Ar gas. In the present invention, since the molten metal is quenched and alloyed, the formation and growth of the α-Fe phase are suppressed, and an alloy having extremely low magnetic permeability can be obtained.

In order to reduce the oxygen content of the quenched alloy, it is preferable to remove a region having a large oxygen content on the surface of the quenched alloy by grinding. Grinding depth is
A depth of about 1 mm or less from the surface is sufficient.

The milling step is then mechanically pulverizing the rapidly solidified alloy, an alloy powder.
The pulverization is performed in a non-oxidizing atmosphere such as nitrogen gas or Ar gas. In the pulverization, the alloy powder having a particle size of preferably 45 to 425 μm, more preferably 100 to 200 μm is 90 μm in total.
It is performed so as to account for at least 95% by weight, preferably at least 95% by weight. If the particle size is too small, the oxygen content in the target becomes too large due to oxidation during pulverization. On the other hand, if the particle size is too large, sintering becomes difficult, so that it is necessary to raise the firing temperature in the firing step described below, which results in α-F
The e-phase is precipitated and the magnetic permeability is increased, which is not preferable. The crushing means is not particularly limited, and may be any of a coarse crusher such as a jaw crusher, a roll crusher, a cone crusher, a hammer mill, a stamp mill, and a fine crusher such as a disc mill, a brown mill, a ball mill, an attritor, a jet mill, and the like. May be used. After pulverization, if necessary, classify by sieving or the like.

Firing Step Next, a sintered body is obtained by firing the alloy powder under pressure in an inert gas atmosphere such as Ar gas or in a vacuum. It is preferable to use a hot press method or a hot isostatic press method for the pressure firing. The pressure and the temperature at the time of the pressure sintering may be determined so that a dense sintered body can be obtained and the generation and growth of the α-Fe phase can be suppressed. The firing temperature is preferably a temperature at which liquid phase sintering does not occur. In addition, in order to prevent cracking of the target, it is preferable to fire at a temperature at which grain growth does not occur.

Specifically, when the hot press method is used, the pressing force is preferably 400 kgf / cm ² or more,
The firing temperature is preferably 900 to 1200 ° C., the time for maintaining the firing temperature is preferably 5 to 60 minutes, and the rate at which the temperature is raised to the firing temperature is preferably 10 minutes.
° C / min or more. When using a hot isostatic pressing method, the pressing force is preferably 500 kgf / cm ² or more, the firing temperature is preferably 600 to 1000 ° C., and the time for maintaining the firing temperature is preferably 20. ~ 6
It is 0 minutes, and the rate at which the temperature is raised to the firing temperature is preferably 20 ° C./minute or more. If the pressure is too small, the sintered density will be low. At this time, if the sintering temperature is too high in order to secure the sintering density, the oxygen content of the target increases, and the precipitation of α-Fe causes an increase in the magnetic permeability. On the other hand, if the firing temperature is too low, the sintering density will be low, and the mechanical strength of the target will be insufficient. The reason for setting the heating rate and the firing time in the above ranges is to increase the sintering density and make the target less likely to crack. There is no particular upper limit on the pressing force, but when a general carbon mold is used as a molding frame in the hot press method, it is usually preferably 600 kgf / cm ² or less. In the hot isostatic pressing method, the pressure is preferably set to 2000 kgf / cm ² or less.

In the firing under pressure, after pressing,
It is preferable that after the temperature is raised and the firing temperature is maintained for a predetermined time, the pressure is released and cooling is performed.

After firing, the compositionally and structurally inhomogeneous region near the surface of the sintered body is removed by grinding to complete the sputtering target. At this time, a grinding depth of about 1 mm or less is sufficient.

Target Reproducing Method A method of reproducing a target according to the present invention will be described.

First, the bonding material is removed from the used target, leaving only the target.

The milling step is then pulverized spent target, an alloy powder.
Hereinafter, this alloy powder is referred to as reclaimed alloy powder. This pulverization is performed in the same manner as in the pulverization step in manufacturing the target.
That is, various conditions such as a pulverizing atmosphere and a preferable particle size range are the same as those in the pulverizing step in manufacturing the target.

Mixing Step Next, the reclaimed alloy powder is mixed with the alloy powder obtained in the pulverizing step in manufacturing the target (hereinafter, referred to as a new alloy powder) to obtain a mixture. Although the mixing ratio of the reclaimed alloy powder and the new alloy powder is not particularly limited, it is usually preferable that the ratio of the new alloy powder in the mixture be 10 to 80 parts by weight. Since the regenerated alloy powder has a higher degree of oxidation of the rare earth metal than the new alloy powder, if the ratio of the regenerated alloy powder is too high, the characteristics as a target become insufficient. In order to reduce the influence of the oxidation of the reclaimed alloy powder, the ratio of the rare earth metal in the new alloy powder is preferably higher than the target composition of the target. Specifically, it is preferable that R / (R + T) of the new alloy powder be 1.02 to 1.08 times R / (R + T) of the recycled alloy powder.

After the sintering step, the mixture is sintered under pressure to obtain a sintered body. Preferred conditions for the firing under pressure are the same as those in the firing step in the production of the target. Finally, the surface of the sintered body is ground to complete the reproduction target.

[0051]

EXAMPLE 1 25 atomic% of Tb, 65 atomic% of Fe, 5 atomic% of Co and 5 atomic% of Cr were mixed to obtain a total of 2 kg of raw material. After the raw material was melted by high frequency, the plane size was 200 mm x 200
The mixture was poured into a ceramic mold having a size of 0.1 mm and rapidly cooled to obtain a rapidly cooled alloy. The high frequency melting and quenching were performed in a nitrogen gas flow atmosphere.

Next, the surface of the quenched alloy was removed by grinding to a depth of 0.5 mm. As a result, the oxygen content of the entire quenched alloy became 200 ppm or less.

Next, after the quenched alloy was pulverized by a stamp mill to a diameter of 3 mm or less, the gap of the WC rotary disk of the disc mill was set to 0.4 mm, and the quenched alloy was charged into the gap to perform pulverization. By this pulverization, a particle size of 10 to 500 μm
Was obtained. This was classified using a sieve having an opening of 45 μm and a sieve having a diameter of 425 μm. The pulverization was performed in a nitrogen gas flow atmosphere.

Table 1 shows the measurement results of the particle size distribution of the alloy powder and the corresponding amounts of oxygen and Tb.

[0055]

[Table 1]

Table 1 shows that the Tb content of the alloy powder is extremely stable without depending on the particle size. Also, 4
It can be seen that the amount of oxygen is too large for the alloy powder less than 5 μm.

Next, a carbon mold is filled with alloy powder,
The temperature was increased at a rate of 15 ° C./min while applying a pressure of 00 kgf / cm ² , and hot-pressed at 1050 ° C. for 20 minutes in an Ar atmosphere. After releasing the pressure, the mixture was cooled to obtain a sintered body.

The outer peripheral surface and the front and back surfaces of the sintered body were removed by grinding to a depth of 1 mm to obtain a target. This target had a diameter of 127 mm and a thickness of 10 mm.

This target has a magnetic permeability of 2.3, an oxygen content of 550 ppm, and a sintered density of 95%.
Met. Further, with this target, there was no problem such as a crack when forming a film in the bonding step of the sputter target.

This target was scanned with a scanning electron microscope, X
As a result of analysis by line diffraction and EPMA, a relatively dark region observed as a matrix phase in a scanning electron micrograph was a Fe ₃ Tb type crystal phase, and a relatively bright region dispersed in the matrix phase was Fe ₂
It was found to be a Tb type crystal phase. The proportion of the Fe ₃ Tb type crystal phase among these crystal phases was 97% by volume. According to the analysis by EPMA, (Fe + Co + Cr): Tb was approximately 3: 1 in the Fe ₃ Tb type crystal phase. From this result, it is considered that Co and Cr replace the Fe site.

FIG. 1 shows an X-ray diffraction chart of this target.
Shown in In FIG. 1, the diffraction peak existing between 2θ = 41 ° and 2θ = 42 ° is derived from the Fe ₃ Tb crystal. In the analysis by X-ray diffraction, α-F
The presence of e-phase was not observed.

The homogeneity of the target in the in-plane direction and the thickness direction was examined. In the in-plane direction, the cross section is 20mm
The composition was measured by dividing the area into 32 areas, and the T between each area was measured.
The variation in the b content was examined. Further, in the thickness direction, the composition was measured by dividing the region into 10 regions each having a thickness of 1 mm, and the variation in the Tb content between the regions was examined. As a result, the Tb content in the in-plane 32 regions is 24.864 to 25.08.
The Tb content was in the range of 5 at%, and the Tb content in 10 regions in the thickness direction was in the range of 24.847 to 25.080 at%.
That is, the Tb contents were all within the range of 25.0 ± 0.2 atomic%, which proved to be extremely homogeneous. The same measurement was performed for Fe, Co, and Cr, and similar results were obtained for these elements.

When a magneto-optical recording film was formed on a substrate having a diameter of 63.5 mm by magnetron sputtering using this target to produce a mini-disc, 150,000 or more mini-discs were manufactured without replacing the target. Was possible. In addition, there was no change in the composition of the film formed at the beginning and the film formed at the end, and each film was homogeneous in the in-plane direction.

Example 2 The composition of the raw materials was 22 atomic% of Tb, 68 atomic% of Fe,
A target was prepared in the same manner as in Example 1 except that the atomic% and the Cr atomic amount were 5 atomic%.

This target has a magnetic permeability of 2.5, an oxygen content of 500 ppm, and a sintered density of 96%.
Met. Further, with this target, there was no problem such as a crack when forming a film in the bonding step of the sputter target.

FIG. 2 shows a scanning electron microscope photograph of a cross section in the in-plane direction of the target, and FIG. 3 shows a scanning electron microscope photograph of a cross section in the thickness direction. As a result of analysis by X-ray diffraction and EPMA, a relatively bright region observed as a matrix phase is a Fe ₃ Tb type crystal phase, and a relatively dark region dispersed in the matrix phase is a Fe ₂₃ Tb ₆ type. It was found to be a crystalline phase. Of these crystal phases, F
The ratio of the e ₃ Tb type crystal phase was 94% by volume. EP
According to the analysis by MA, in the Fe ₃ Tb type crystal phase, (F
e + Co + Cr): Tb was approximately 3: 1. From this result, it is considered that Co and Cr replace the Fe site.

In the analysis by X-ray diffraction, α-Fe
No phase was observed.

The homogeneity of the target in the in-plane direction and the thickness direction was examined in the same manner as in Example 1. As a result, the Tb content was within the range of 22.0 ± 0.2 atomic% in all cases, and it was found that the Tb content was extremely homogeneous. The same measurement was performed for Fe, Co, and Cr, and similar results were obtained for these elements.

When a magneto-optical recording film was formed on a substrate having a diameter of 63.5 mm by magnetron sputtering using this target to produce a mini-disc, 150,000 or more mini-discs were manufactured without replacing the target. Was possible. In addition, there was no change in the composition of the film formed at the beginning and the film formed at the end, and each film was homogeneous in the in-plane direction.

Comparative Example For comparison, a quenched alloy was produced using arc melting instead of high-frequency melting, and a comparative target was made in the same manner as in Example 1 except for this.

In this target, X-ray diffraction and EP
Analysis by MA showed the presence of the α-Fe phase, and the magnetic permeability was as large as 5.

This target was examined for homogeneity in the in-plane direction and the thickness direction in the same manner as in Example 1. As a result, in the region divided in the thickness direction, 24 to 2
It was found that some of them did not fall within the range of 6 atomic%, and the dispersion was large. This is because α-
It is considered that a large diameter Fe-rich powder was generated at the time of pulverization because the Fe phase was formed and the α-Fe phase was hard to be pulverized, and the large diameter Fe-rich powder was gathered at a lower portion when being injected into a mold during pressure molding. Can be

When this target is used for magnetron sputtering, in order to obtain the same leakage magnetic field strength as the 10 mm thick target of the present invention manufactured in the above embodiment,
It was necessary to reduce the thickness of the target to 6 mm.

Example 3 The target used in the production of 150,000 mini disks in Example 1 was pulverized to obtain a reclaimed alloy powder.

On the other hand, when the raw material composition was Tb 26 atomic%, Fe
An alloy powder was obtained in the same manner as in Example 1, except that 64.2 atomic%, Co 4.9 atomic% and Cr 4.9 atomic% were used.
This was classified in the same manner as in Example 1 to obtain a new alloy powder.

The regenerated alloy powder and the new alloy powder were mixed at a weight ratio of 1: 1.
After hot pressing in the same manner as described above, grinding was performed to obtain a target.

When a mini-disc was manufactured using this target, as in Example 1, no change was observed in the composition of the film formed at the beginning and the film formed at the end.
Each of the films was homogeneous in the in-plane direction.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction chart of a target.

FIG. 2 is a drawing substitute photograph showing a crystal structure, and is a scanning electron microscope photograph of an in-plane cross section of the target of the present invention.

FIG. 3 is a drawing substitute photograph showing a crystal structure, and is a scanning electron microscope photograph of a cross section in the thickness direction of the target of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/00 304 C22C 38/00 304 G11B 11/105 546 G11B 11/105 546K

Claims (9)

[Claims] 1. A target used when forming a recording material for magneto-optical recording by a magnetron sputtering method, wherein R (R is Tb, Dy, Gd, Sm, Nd,
A rare earth metal element selected from at least one of Ho, Tm and Er) in an amount of 20 to 30 atomic%, and the balance substantially T (T is a transition metal element; Fe, Co
And at least one of Ni), having a substantially homogeneous sintered structure, having a magnetic permeability of 3 or less,
An alloy target for magneto-optical recording, which is a plate having a thickness of 8 mm or more. 2. The alloy target for magneto-optical recording according to claim 1, which has a thickness of 10 mm or more. 3. The alloy target for magneto-optical recording according to claim 1, wherein said T contains Cr. 4. The alloy target for magneto-optical recording according to claim 1, wherein the oxygen content is 1000 ppm or less. 5. The Fe ₃ Tb type crystal phase has a total crystal phase of 88%.
5. The alloy target for magneto-optical recording according to claim 1, which accounts for at least% by volume. 6. The method for producing an alloy target for magneto-optical recording according to claim 1, wherein R and T are set so that R / (R + T) is 20 to 30 atomic%. The obtained mixture is melted in a high-frequency furnace or crucible furnace, and then quenched to obtain a quenched alloy.The quenched alloy is mechanically pulverized in a non-oxidizing atmosphere to obtain an alloy powder,
A method for producing an alloy target for magneto-optical recording, wherein the alloy powder is sintered by pressurizing in an inert gas atmosphere or under vacuum. 7. A powder having a particle size of at least 90% by weight of the alloy powder.
7. The method for producing an alloy target for magneto-optical recording according to claim 6, wherein the thickness is 5 to 425 [mu] m. 8. After using the alloy target for magneto-optical recording according to any one of claims 1 to 5, it is mechanically pulverized in a non-oxidizing atmosphere to obtain a reclaimed alloy powder. The obtained mixture was melted in a high-frequency furnace or crucible furnace, and then quenched to obtain a quenched alloy.The quenched alloy was mechanically pulverized in a non-oxidizing atmosphere to obtain an alloy powder. A method for reproducing an alloy target for magneto-optical recording, comprising a step of sintering the mixture with the reproduced alloy powder by pressurizing and firing the mixture in an inert gas atmosphere or in a vacuum. 9. The method for reproducing an alloy target for magneto-optical recording according to claim 8, wherein R / (R + T) of the preparation is 1.02 to 1.08 times R / (R + T) of the reproduced alloy powder. .