JPH0361379A - Manufacture of cobalt alloy - Google Patents

Abstract

PURPOSE:To manufacture the cobalt alloy having excellent magnetic characteristics by incorporating an electroless plating bath for forming a cobalt alloy with the alkali salt of tripolyphosphate as a complexing agent. CONSTITUTION:An electroless plating bath used for forming a cobalt alloy is incorporated with cobalt ions, a reducing agent for cobalt ions, a complexing agent for cobalt ions, a complexing assistant, a pH conditioner, a pH buffer and the other addition agents. At this time, as the complexing agent, the inorganic alkali salt of tripolyphosphate is used, and as its quantity to be added, the cobalt ions:the complexing agent=about 1:(2 to 15) is regulated by the total mol ratio to the cobalt ions. Furthermore, as the alkali salt of tripolyphosphate, sodium tripolyphosphate, potassium tripolyphosphate or the like are used, and an inorganic complexing agent such as the alkali salt of pyrophosphoric acid can jointly be used. By using the electroless plating bath, the cobalt alloy provided with excellent magnetic characteristics (coercive force) can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a cobalt alloy having excellent magnetic properties such as coercive force. This cobalt alloy is suitable as a magnetic storage medium that is coated on the surface of a magnetic disk, telephone card, etc., or as a magnetic medium that is coated on the surface of a nonmagnetic material in order to exert a magnetic field acting force on the nonmagnetic material.

<Conventional techniques/techniques> As shown in Figure 5, it has long been known that the magnetic properties (coercive force) of cobalt alloys change depending on the phosphorus content (see "Electroless Mechanism" published by Maki Shoten). (See page 70.7! of “Tsuki”).

FIG. 6 shows a chart of magnetic properties when the phosphorus content is 3 wt%. +1 (coercive force Hc = 7700e, squareness S'' = 0.83, squareness ratio R
s=0.78) was the highest value of the cobalt alloy film obtained by electroless plating.

This cobalt alloy is obtained through the following electroless plating process.

A℃ base material - Zn substitution plating (double substitution) - + Ni alloy plating - Cobalt alloy plating <Problem to be solved by the invention> However, (1) Recently, magnetic storage media have been required to have higher magnetic properties ( In particular, recording density) is required, but the above-mentioned cobalt alloy cannot sufficiently meet this requirement.

(2) To improve magnetic properties, Ni, Cr, W, Fe
It is conceivable to add metals such as as a third component.

However, when the cobalt alloy is made into a ternary system,
Since a consistent alloy structure is continuously precipitated, it is extremely difficult to adjust the plating bath compared to a cobalt-phosphorus binary alloy.

(3) On the other hand, sputtering has recently become a trend in the technology for forming cobalt alloy magnetic films for magnetic storage media. A typical manufacturing process of a magnetic storage medium using the sputtering method is shown below.

Aluminum substrate - Ni-P base film → Cr other metal base film - Cobalt alloy sputtered magnetic film - Corrosion-resistant adhesion reinforcement film -
Sputtered C (carbon) protective film This is because the cobalt alloy film formed by sputtering has an excellent coercive force Hc = 12270e, squareness S''~0.90, and squareness ratio Rs = 083, as shown in Figure 7. Furthermore, this sputtering method has the advantage that magnetic materials having different alloy compositions can be produced.

However, this sputtering method still has some problems that need to be solved.

The main problems in terms of economy include the slow deposition rate of the cobalt-based alloy, the generation of dust within the sputtering equipment, the extremely expensive equipment, and the increased production costs due to low yields and low operating rates. In terms of technology, the magnetic properties of most films formed by heat treatment deteriorate, except for special sputtering methods. Among these, the phenomenon of deterioration of magnetic properties due to the heat treatment described above is serious and significantly reduces the performance of magnetic storage media.

Therefore, when manufacturing magnetic storage media such as magnetic disks using the sputtering method, the formation of protective films on the magnetic film is limited to sputtering methods that do not have thermal effects or other methods that allow cold processing. As a result, the entire manufacturing process must be carried out cold. Furthermore, when using a magnetic storage medium, the magnetic properties deteriorate due to heat caused by friction with the magnetic head during startup and shutdown. Therefore, there is a need for a magnetic film that does not deteriorate under the influence of heat.

In addition, when this cobalt alloy is formed on the surface of non-magnetic material bars, plates, wires, 'f3, etc. and used as a magnetic medium material, it is likely that there will be problems due to thermal effects or accidental temperature rise in normal environments. It is necessary to form a magnetic medium that does not deteriorate due to thermal effects.

Therefore, the present invention has developed a cobalt alloy that not only has superior magnetic properties than cobalt alloys obtained by conventional electroless plating, but also has higher performance than cobalt alloys obtained by sputtering using only the cobalt-phosphorous binary elements. The purpose is to provide a manufacturing method for.

<Problems to be Solved by the Invention> As a result of intensive studies to achieve the above object, the present inventor has discovered that a cobalt alloy obtained by electroless plating using a specific plating bath can be obtained by sputtering. It has magnetic properties equivalent to or better than that of
They also discovered that their magnetic properties further increase when heated, and completed this invention.

That is, the present invention is characterized in that a cobalt alloy is produced by electroless plating using a plating bath containing an alkali tripolyphosphate salt as a complexing agent.

Detailed explanation of the method The present invention will be described in detail below.

The plating bath of the present invention used to form this cobalt alloy consists of: ■ cobalt ions, ■ cobalt ion reducing agent, ■ cobalt ion complexing agent, ■ complexing aid, ■ pH adjuster, and ■ pH buffer. *Contains other additives.

■Cobalt ion.

Cobalt ions are usually added in the form of salt and are added in the plating bath IIl from 0.01 to 0.0. Contains 18 mol/fl.

■Reducing agent for cobalt ions, Common sodium hypophosphite is used as the reducing agent for cobalt ions. The amount added is 0.1 to 0.5 mol/vert.

■Complexing agent for cobalt ions The complexing agent for cobalt ions is an alkali salt of an inorganic salt of tripolyphosphoric acid, which is specially mentioned in the present invention.
2-15. More preferably, the ratio is 1:6 to 13. If the molar ratio of the complexing agent is less than 2, the cobalt salt cannot be sufficiently complexed. On the other hand, if the 0101 ratio of the complexing agent exceeds 15, the complexing becomes excessive and the plating precipitation deteriorates, which is not preferable.

This complexing agent can be used in combination with an inorganic complexing agent such as an alkali birophosphate salt (see Table 4).

When using tripolyphosphate alkali salt and birophosphate alkali salt together, the mixing ratio of both is the former; the latter -1-8
: It is preferable to set it as 1. More preferably 5 to 7:
It is 1.

Examples of the alkali salt of tripolyphosphate include sodium tripolyphosphate and potassium tripolyphosphate.

Examples of birophosphate alkali salts include sodium birophosphate and potassium pyrophosphate.

■Complexing aid.

As the complexing aid, an alkali phosphite salt, which is specially mentioned in the present invention, is used. This complexing aid is added as necessary, and the addition improves the magnetic properties of the cobalt alloy. The amount added is not particularly limited, but from the viewpoint of improving magnetic properties and economical efficiency, the ratio of complexing agent to complexing agent is 1:0.5 to 5 in terms of 111O1 to the above complexing agent. . More preferably l: 1.5 to 3.5.

Examples of the alkali phosphite salts include sodium phosphite dihydrate, Itsukiwado, dipotassium phosphite, and the like.

■pf (adjusting agent).

The pH adjuster is selected from common acids such as sulfuric acid, hydrochloric acid or phosphoric acid, alkali salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonium hydroxide. Then, the plating bath is adjusted to the required pH.

■PH buffering agent: One type of pH buffering agent is selected from the usual ammonium sulfate, ammonium chloride, ferric acid, and silica sand, or 2f! if necessary. It is used in combination with Group I or higher, and the amount added is 0.15 to 0.811 Iol/42.

■Other additives As other additives, the following components may be used as trace additives effective in improving the magnetic properties of the deposited metal.

Metal sulfides and oxides such as zinc, iron (II), zirconium, cobalt, lanthanum, samarium, nickel, aluminum, and hydroxides and alkali aluminates of the above metals.

Aluminum represented by lanthanum acetate, manganese sulfate, manganese zirconium tartrate, zirconium sulfate, aluminum-based components such as aluminum sulfate, aluminum phosphate, potassium aluminum sulfate, sodium aluminum sulfate, aluminum oxalate, aluminum acetate, aluminum citrate, aluminum lactate, etc. The amount of compounds and other aluminum compounds used varies depending on the type of each component, but in general, 1. OXl(M5~1, OX10-'m
ol/I1. The range shall be . When the amount of l'am additive is 1. When Ox is less than 10-'mol/j2, no improvement is observed in magnetic properties (especially coercive force), and 1.
There is no need to mix more than 0XIo -'mol/x.

However, the aluminum compound among the above-mentioned trace additives exhibits special behavior. That is, by allowing the aluminum component to be present in the plating bath, it becomes possible to electrolessly plate the cobalt alloy directly onto the aluminum substrate (that is, without underplating with nickel).

Regarding the blending amount of the aluminum component, etc.,
In the specification as filed, a column titled "Addition of Aluminum Component" is provided after the "Examples" column, and will be described in detail here.

Next, a method of electroless plating using this plating bath will be explained.

(On aluminum (single aluminum, aluminum alloy) base material) Al〈nium base material - Degreasing - Removal of interfacial impurities by immersion in 15% nitric acid solution - 1st - Zn substitution plating - 3rd - Zn substitution by immersion in 25% nitric acid solution Removal of layers - Second Zn displacement plating Neutralization with monosodium bicarbonate solution - Electroless Ni alloy plating - Electroless cobalt alloy plating. This process forms a magnetic disk.

In addition, when aluminum-based aluminum is present in the plating bath, it is possible to omit the step of underplating an electroless Ni alloy onto the aluminum base material, which is performed before electroless cobalt alloy plating. With this method, a magnetic storage medium layer or a magnetic medium layer can be formed on an aluminum substrate other than the above magnetic disk substrate.

(On Cu and other metals) The first method is metal degreasing-alkaline etching-3-
Immersion in 5% hydrochloric acid or sulfuric acid solution - direct electroless cobalt plating.

The second method is metal degreasing-alkaline etching-3-5
% immersion in hydrochloric acid or sulfuric acid solution - Imposition of 4Pd catalyst group - Activation by immersion in the above hydrochloric acid or sulfuric acid solution - Direct application of electroless cobalt alloy plating.

(on semiconductors, glass, ceramics) Degreasing - Roughening with hydrogen fluoride water - Neutralization - Application of Pd catalyst substrate - Activation by immersion in the above hydrochloric acid or sulfuric acid solution - Electroless cobalt alloy plating (on plastics) (on insulating materials such as base materials) Degreasing - Unless special cases, generally roughening with a mixture of chromium trioxide and sulfuric acid - Neutralization - Addition of Pd catalyst group - Activation by immersion in the above hydrochloric acid or sulfuric acid solution - Apply electroless cobalt alloy plating.

Through this process, products such as Bribert cards such as telephone cards, cash cards, Identity 1 cards, and train tickets are formed.

<Effects of the Invention> At room temperature, the cobalt alloy thus obtained has magnetic properties that are equal to or higher than conventional cobalt alloys obtained by electroless plating, as well as those obtained by sputtering. .

Therefore, not only the performance as a 6N storage medium or a magnetic medium is improved, but also speed, lower equipment cost, higher yield, and higher operating rate can be achieved compared to the sputtering method.

Therefore, a cobalt alloy that is excellent in magnetic storage media and magnetic media can be provided at low cost.

Furthermore, as shown in each of the Examples in Tables 1 to 3, a remarkable effect of improving the magnetic properties was observed when heated.

As a result, the formation of the protective film on the cobalt alloy is no longer limited to cold processing. For example, 510 that requires firing
Two films can be formed on cobalt alloys.

Therefore, if a magnetic storage medium made of this cobalt alloy is heat-treated in advance, its magnetic properties will not deteriorate even if heat is applied due to friction with a magnetic head or the like. Even when this heat-treated cobalt alloy is used as a magnetic medium, problems with temperature rise do not occur.

In other words, this cobalt alloy has a wide range of applications as magnetic storage media and magnetic media.

Furthermore, the results shown in FIG. 4 show that the cobalt alloy obtained according to the present invention has a higher recording density than the cobalt alloy formed by sputtering.

<Example> Hereinafter, an example for confirming the above effects will be described.

Tables 1 to 3 classify plating baths according to the magnitude of the coercive force Hc of the magnetic film immediately after plating. In other words, the 8000e level corresponds to Examples 1 to 8 in Table 1, the 9000e level corresponds to Examples 9 to 14 in Table 2, and the t0000e level corresponds to Examples 15 to 2 in Table 3.
0. In addition, Table 4 shows Examples 21 and 22 in which alkali tripolyphosphate and alkali birophosphate were used together as complexing agents. Comparative Example 1 shows the case where an alkali pyrophosphate was used alone as a complexing agent.

Although not shown in the table, in the plating bath of each example, 4.5 x ammonyl potassium tartrate 0.5 water was added.
Contains 10""++ol/fl.

Using the plating baths shown in Tables 1 to 4, electroless plating was applied to an aluminum disk (its surface is smooth), which had been previously plated with N and -P alloy, and the cobalt alloy film of the example was applied. Formed. Then, the magnetic properties of each disk were measured using a vibrating magnetometer.

The results are shown in each table.

Incidentally, FIG. 1 is a chart showing the magnetic properties of the disk electrolessly plated in the plating bath of Example 6. "adjJ in Figure 1 is the value corrected for the magnetic influence of the N-P alloy base plating applied to the same disk."
"jTH" is a chart showing the magnetic characteristics of the disk after correction and heating.Similarly, adj in FIG.
adJTH in Fig. 2 is the case when the plating bath of Example 13 is used, adJ in Fig. 3, adJ in Fig. 3,
TH is the case where the plating bath of Example 15 was used.

From the above germination, it can be seen that the magnetic properties of the cobalt alloys of each of the above examples are superior to those of the cobalt alloys obtained by conventional electroless plating before heating. It can also be seen that the magnetic properties of the cobalt alloys obtained from the plating baths shown in Table 3 are superior to those of the cobalt alloys obtained by sputtering.

After heating, the cobalt alloy films of each example showed improvement in magnetic properties.

Further, FIG. 4 shows the results of a recording density reproduction test using the same disk as in FIG. 3 (using the plating bath of Example 15). For example, the results show that the S/N value is 30.6 dB at 30 KFRPI, which indicates that the cobalt alloy film of the example can obtain a higher recording density than the cobalt alloy film obtained by the sputtering method. .

Note that the surface of the disk subjected to the sputtering method is roughened by texturing, whereas that of the embodiment has a mirror surface.

Addition of Aluminum Component> In conventional electroless plating methods, it has been considered impossible to form a cobalt alloy directly on an aluminum base material. Therefore, as a typical method, aluminum base material - Zn substitution plating (double substitution) -N
After passing through the steps of i-alloy plating and cobalt alloy plating, a cobalt alloy was finally plated.

Unless the base metal of the Ni alloy was plated on the aluminum base material in advance in this manner, the cobalt alloy could not be adhered to the aluminum base material. The reasons why direct plating is not possible are that the aluminum base material easily dissolves in the plating bath, and that the metallic bond required for plating cannot be obtained due to the difference in the unit cell structure of both aluminum and cobalt metals. It is caused by

Also, when forming a cobalt alloy layer on an aluminum base material using a magnetic alloy plating method or sputtering method,
It is necessary to form a base metal such as Ni or Cr on the aluminum base material in advance.

Therefore, the manufacturing cost of forming a cobalt alloy layer on an aluminum base layer increases. Therefore, the present inventor has made extensive studies on a method of electroless plating a cobalt alloy directly onto an aluminum substrate and a plating bath used therein.

Conventionally, the following two reasons can be considered as reasons why it is not possible to electrolessly plate a cobalt-based alloy directly onto an aluminum base material.

First cause: Cobalt ions cannot be deposited because aluminum metal, which is a diamphoteric metal, easily undergoes a chemical reaction with acid or alkali and dissolves, violently generating hydrogen.

Second cause: While aluminum metal has a face-centered cubic lattice, the cobalt metal, which is the main component of the cobalt alloy to be plated, usually has an α-type dense cubic lattice, so the plating reaction starts. However, because the lattice structures of both metals are different, the metal bond required for plating at the interface cannot be obtained.

The present inventor has discovered that the above two causes can be solved by dissolving an appropriate amount of aluminum ions in the plating bath in advance (hereinafter referred to as the "second invention").

In other words, in order to prevent the dissolution of the aluminum metal, which is the primary cause, if an appropriate amount of aluminum-based ions are dissolved in the electroless cobalt plating bath in advance, the aluminum base material can be immersed in the plating bath. It was found that the aluminum substrate did not dissolve when This phenomenon is
Unlike the previously known methods of preventing elution by passivating the aluminum interface with nitric acid groups or preventing dissolution by forming a lake, this method does not inhibit the electroless plating reaction.

In order to solve the second cause of mismatch in the unit cell structure between aluminum and cobalt metals, if aluminum ions are present during plating, they will be formed by the arrangement of cobalt atoms that first precipitate at the aluminum interface. The ultra-thin film layer is not α-type cobalt with an m-close cubic lattice structure,
It was discovered that cobalt changes to β-type cobalt, which has a face-centered cubic lattice structure, and has the same lattice structure as aluminum, resulting in strong surface metal bonding to the interface of the aluminum base material. As a basis for inferring the formation of β-type cobalt, they place importance on the well-known fact that when r-cobalt metal undergoes hydrogen reduction in the form of an oxide, it becomes β-type cobalt. This can be inferred based on the fact that the unit cell structure of cobalt is J, which is the same face-centered cubic lattice as that of aluminum metal.

The possibility of the formation of β-type cobalt is due to the precipitation principle of electroless plating with the following precipitated metal M and reducing agent R in the initial stage of cobalt formation as explained above. e Grave Mn + ne → MO or 2H" + 2e- = H2 is occurring, and the oxidation reaction caused by 08 in the formula appears to temporarily change the cobalt atom to cobalt oxide, and furthermore, this cobalt oxide In addition to the influence of H" shown in the above reaction, the influence of hydrogen during the substitution reaction of Zn-4 cobalt in the substituted Zn layer previously formed on the aluminum base material, and also the influence of hydrogen on the aluminum base material. Due to the synergistic effect with the influence of nascent hydrogen generated in the dissolution reaction, β is immediately and strongly reduced.
The phenomenon of degeneration into cobalt type can be inferred. The formation of β-type cobalt by this oxidation and reduction continues until the ultra-thin film finishes covering the aluminum base material surface, but after that, normal α-type cobalt is deposited on the β-type cobalt, forming a cobalt alloy layer. form.

Therefore, only the closest bonding interface of the cobalt alloy becomes β-type cobalt, and as a result, it is presumed that a strong metallic bond between the face-centered cubic lattice structures, which is the same as that of aluminum metal, is obtained.

As an example of the knowledge of directly forming a cobalt alloy film on the above aluminum metal, there is an example using sputtering method ^L
LITOPIA Vol, 19 No. 2 FEB,
This is reported in Cobalt-Nickel Metal Thin Film Magnetic Disk 1, published in 1989. Here, Cr
It is stated that no sputtered underlayer is required;
According to this document, it is explained that an alumite-treated aluminum base material is puff-polished and a Co--Ni alloy nitride film is directly formed in an N2 atmosphere. At that time, Co-Ni-N11i was mainly orthorhombic with some hexagonal crystals mixed in, and it was described that N was released by heat treatment and it changed into a hexagonal co-Ni film. There is. The above Ill is similar to the invention of Beika 2 in that it forms a cobalt magnetic film directly on aluminum, but it is a ternary alloy and the interface of the aluminum base material is made porous by alumite treatment. This invention is fundamentally different from the invention of rice cracker 2 in that the alloy is deposited with an anchoring effect.

The invention of rice cracker 2 is characterized in that the cobalt unit crystal lattice at the nearest adjacent interface forms the same face-centered cubic structure as aluminum, creating a strong metal bond. The electroless plating bath that can be used will be explained in detail.

The plating bath contains: ■ cobalt ion, ■ cobalt ion reducing agent, ■ cobalt ion complexing agent, ■ pH adjuster, ■ p
Contains a component of the HpH buffer aluminum ion source.

(2) Cobalt ion Cobalt ion is usually added in the form of a salt and is contained in the plating bath ifl in an amount of o, oi to 0.18 mol (hereinafter referred to as 0.01 to 0.18 mol Ill).

■Reducing agent for cobalt ions, Common sodium hypophosphite is used as the reducing agent for cobalt ions. Addition amount is 0.1 to 0.511 ol/fl
shall be.

■Cobalt ion complexing agent, Cobalt ion complexing agent is usually citric acid tartaric acid,
Alkali salts of organic acids such as malonic acid, succinic acid, gluconic acid, malic acid, etc., alkali salts of inorganic acids such as birophosphoric acid, and alkali salts of inorganic acids such as tripolyphosphoric acid used in the second invention specified in the invention of rice cracker 2. Selected from salt, i Ill
or a combination of two or more types, and if necessary, an alkali salt of an inorganic acid such as phosphorous acid is used as a complexing aid. The total anol ratio of complexing agent to cobalt ion is 1:2
〜1:10, and the complexing aid molar ratio is 1:10 to 1:5.
Set to 0.

■pH adjuster, pH adjuster includes the usual acids such as sulfuric acid, hydrochloric acid, or phosphoric acid, sodium hydroxide, and potassium hydroxide.

Select from alkali salts of lithium hydroxide and alkaline ammonium hydroxide, and adjust to the required pH ■pH buffer: For the pH buffer, select from the usual ammonium sulfate and chlorinated acid, and use sand as well. I can do it.

The amount added is 0.15 to 0.8 mol/IL.

■Aluminum ion source The aluminum ion source is a component specially mentioned in the invention of rice cracker 2, and includes aluminum hydroxide, alkali aluminate, aluminum sulfate, aluminum phosphate, potassium aluminum sulfate, sodium aluminum sulfate, aluminum oxalate, and acetic acid. Aluminum compounds such as aluminum, aluminum citrate, aluminum lactate, etc.
Other aluminum compounds may be used, but
In short, it is selected from the components that dissolve at the plating bath pH and become aluminum ions, and is 0.0 in terms of aluminum ions.
It is used at a ratio of 01 to 0.25 mol/It. Here, the aluminum component is 0.001a+.

If it is less than 1/j2, the cobalt alloy will not form a metallic bond to the aluminum base material, and the alloy film will easily peel off. On the other hand, even if the amount exceeds 0.25 mol/42, there is no change in the metallic bond between aluminum and cobalt, resulting in an economical loss.3The electroless plating method using this plating bath is as follows. be.

Degreasing of aluminum base material → alkaline etching = 15%
Removal of interfacial impurities by immersion in nitric acid solution - 1st Zn displacement plating - 25% - Removal of 2nd Zn substitution layer by immersion in nitric acid solution - 2nd Zn displacement plating Neutralization with monobicarbonate solution - Electroless of the second invention Apply cobalt alloy plating.

As explained above, we were able to prevent the aluminum base material from dissolving in the plating bath, and in addition, we modified β-type cobalt, which has the same face-centered cubic lattice as aluminum, at the outermost bonding interface of the aluminum base material. As a result, a strongly metal-bonded cobalt alloy film could be directly formed on the aluminum substrate. This has made it possible to manufacture inexpensive aluminum magnetic materials.

This eliminates the need for plating a base metal such as a Ni alloy on the aluminum substrate, making it suitable for producing magnetic storage media and magnetic media that require flexibility. for example,
It can be used in the field of electronics (for example, 1. formation of a magnetic storage medium on a disk substrate, 2. formation of a magnetic storage medium on an aluminum card type substrate, etc.). In addition, in the field of magnetic materials, for example, 3. Aluminum rod.

It can be used for various purposes as an inexpensive magnetic medium for partially or completely forming aluminum molded products such as dough, plate, foil, and die casting.

As for the magnetic properties of the cobalt alloy plating film deposited at this time, the coercive force Hc shown in Examples 23 to 26 in Table 5 was obtained, and the highest value was HC=8910e.

The above value exceeds the value of the coercive force (Hc=7710e) of the conventional electroless plated film shown in Table 3.

[Brief explanation of drawings]

Figure 1 is a chart showing the magnetic properties of a disk electrolessly plated with the plating bath of Example 6. adJ in Figure 1 is the magnetic property of the same disk when the magnetic influence of the Nl-P alloy base plating is corrected. Chart showing the characteristics: adjTH in FIG. 1 is a chart showing the magnetic characteristics when the same disk is corrected and heated; FIG. 2 is the magnetic characteristics of the disk electrolessly plated with the plating bath of Example 13. adj in FIG. 2 is a chart showing the magnetic properties of the same disk when the magnetic influence of the base plating of N and -P alloys is corrected. adj T H in FIG. Chart showing magnetic properties when corrected and heated
The figure is a chart showing the magnetic properties of a disk electrolessly plated with the plating bath of Example 15. adj in Figure 3 shows the magnetic properties of the same disk when the magnetic influence of the Nl-P alloy base plating is corrected. adJTH in Figure 'fS3 is a chart showing the magnetic characteristics when correction and heating are performed on the same disk, Figure 4 is a graph showing the results of the recording density reproduction test, and Figure 5 is the graph of the conventional example. A graph showing the relationship between phosphorus content and coercive force in a cobalt-phosphorus alloy. Figure 6 is a chart showing the magnetic properties of a disk electrolessly plated using a conventional plating bath. Figure 7 is a chart showing the magnetic properties of a disk electrolessly plated using a conventional plating bath. A chart showing the magnetic properties of a disc subjected to this process. Patent applicant No. 4 Figure 1 Self 11; Top 1 (KFRPI) Figure %r Thickness h (Co, mg/cm2) Figure 4-2 Engraving of the sound volume, Ht magnetic car relationship diagram (No change in content) Figure H: oersted Mie weight U mult: 1 Hm: 4.953E*03 Hc: 7.714E*02 Mm: 1.599E-02 Mr: 1.241E-02 SSk: **h ***Fist0 S Umbrella: 8.269E-QI S k: 7.982E-01 S: 8.015E-01 Rs: 7.761E-01 0R0◆◆*UmbrellaUmbrella◆Engraving of the order drawing (changed in content) None) Figure H: oersted M;e snow U mult: 1 5.0DDE103 1.227E◆03 1.549E-02 1,281E-02 8,808E-01 9,005E-01 9,24BE-01 9,743E-(11 8,265E-01 Heisei horse month day

Claims (1)

[Claims] A method for producing a cobalt alloy, characterized by electroless plating using a plating bath containing an alkali salt of tripolyphosphate as a complexing agent.