JPH06122990A - Co-fe-b alloy electroplating film and its production - Google Patents

Abstract

(57) [Summary] [Structure] General formula, (Co _100-X Fe _X ) _BY (however, atomic%
Where 9 ≦ X ≦ 12, 0 <Y ≦ 0.2)
Fe-B alloy electroplating film. This plating film is Co ²⁺ /
Co ²⁺ and Fe ²⁺ so that Fe ²⁺ has an atomic ratio of 91/9 to 88/12
In the form of sulfate and / or chloride, and further electroplating in an acidic solution containing 1 g / liter or more of dimethylamine borane and / or trimethylamine borane. [Effect] It has a high saturation magnetic flux density, a low coercive force, a magnetostriction constant of 0 or slightly negative, and is excellent in writing and reading performance, and is suitable as a magnetic material of a thin film magnetic head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a plating film mainly used as a magnetic material of a thin film magnetic head suitable for high density magnetic recording, which has a high saturation magnetic flux density and a low coercive force.
And the soft magnetic Co-Fe whose magnetostriction constant is 0 or slightly negative
-B alloy plating film and its manufacturing method.

[0002]

2. Description of the Related Art In recent years, plated coatings have been widely used not only for decoration and anticorrosion, but also as functional coatings for electronic parts and the like. For example, a thin film magnetic head used in a model having a high recording density among fixed magnetic recording devices (hard disk drives) for computers uses a permalloy thin film produced by a plating method as a magnetic body. Permalloy is a typical soft magnetic material, and in particular, the permalloy plating film currently used is approximately 82/1.
No. 8 Ni-Fe alloy (Ni means about 82 atomic% and about 18% by weight of Fe. The same notation is used in the following description), and the magnetostriction constant is 0 or a slightly negative value. The point is that it has.

With respect to fixed magnetic recording devices (hard disk drives), demands for larger capacity and smaller size have been increasing year by year, and along with this, high recording density has progressed, and in order to further improve writing (recording) performance. , A material having a high magnetic flux density has begun to be required as a magnetic material of a thin film magnetic head. However, when the Fe content is increased in order to obtain a higher saturation magnetic flux density in the permalloy film, the magnetostriction constant becomes larger than the value of the permalloy film currently used and shows a positive value, and the read (reproduction) performance is improved. It is a major cause of instability. Therefore, the permalloy film has a limit in increasing the magnetic flux density.

FIG. 5 is a diagram showing a composition in which a magnetostriction constant is 0 in a vapor deposited film of a Co-Fe-Ni ternary alloy (Journal of
Applied Physics Vol.38 (1967) p.3409). It is fully expected that materials near the composition shown in this figure are promising as magnetic materials for thin-film magnetic heads, and U.S. Pat.
The specification of No. 216 also describes a method of plating with a Co-Fe-Ni ternary alloy having a composition with a magnetostriction constant of 0 and a high saturation magnetic flux density.

However, it is difficult to control the composition of the plating film in alloy plating containing three kinds of metal elements. Particularly, in the precipitation of a Co--Fe--Ni ternary alloy, Fe which is electrochemically base takes precedence. It belongs to the anomalous eutectoid type where it precipitates rapidly and its composition tends to change.

Of the compositions having a magnetostriction constant of 0 shown in FIG. 5, the highest saturation magnetic flux density is the composition corresponding to the Co-Fe binary alloy, which is about 90/10 of the Co-Fe alloy. It is considered good to plate with. The specification of U.S. Pat. No. 4,756,816 describes a Co-Fe alloy plating method of about 90/10, and a plating film having a low magnetostriction constant is obtained. However, there is no clear description of the value, especially the sign of the sign.

On the other hand, in order to improve the reading performance, it is necessary to have a low coercive force (that is, soft magnetism) and a small magnetostriction constant, and the development of a material using a Co-Fe-Ni ternary alloy. Is being considered. Co-Fe-Ni ternary alloy is promising as a magnetic material for thin-film magnetic heads, but as described above, it is difficult to control the composition of the plating film during manufacturing.

The Co-Fe binary alloy of about 90/10 has a low magnetostriction constant and is expected to improve reading performance.
The performance required of a magnetic material used in a thin film magnetic head or the like is that not only the coercive force is small and the magnetostriction constant is small, but also the magnetostriction constant is 0 or a slightly negative value.

The present inventor tried electroplating a Co--Fe alloy to obtain a film having a low magnetostriction constant, but as shown in FIG. 4, the magnetostriction constant is in the composition range of coercive force of several Oersted (Oe) or less. It showed a positive value (Summary of the 83rd Conference of Surface Engineering Society of Japan, 27B-4 (1991)). The composition with the smallest coercive force in a Co-Fe plating film with a low magnetostriction constant has a Co / Fe atomic ratio of about 88/12.
However, the magnetostriction constant shows a positive value. If the Fe content is further reduced, the magnetostriction constant becomes negative,
Coercive force increases.

As described above, as a plated magnetic film for a thin film magnetic head suitable for both writing and reading,
The current situation is that no alternative material for permalloy has been developed yet.

[0011]

SUMMARY OF THE INVENTION The present invention is a plating film mainly used as a magnetic material of a thin film magnetic head suitable for high density magnetic recording, which has a high saturation magnetic flux density and a low coercive force, and The magnetostriction constant is 0 or slightly negative,
An object of the present invention is to provide a plating film having excellent writing and reading performances and a method for manufacturing the same.

[0012]

[Means for Solving the Problems] As described above, in the Co-Fe plating film, the composition having a small magnetostriction constant and a slightly negative value has a large coercive force, while the coercive force is small. (Co / Fe is about 88/12), the magnetostriction constant becomes positive. In order to reduce both the magnetostriction constant and the coercive force, the present inventor has studied adding a third element to the plating film of a Co—Fe alloy and completed the present invention. The gist of the present invention is the following Co-Fe-B alloy plating film and a method for producing this film.

A soft magnetic Co—Fe—B alloy electroplating film represented by the general formula: (Co _100-X Fe _X ) _BY . However, X and Y in the above general formula, in atomic%, are 9 ≦ X ≦ 120 <Y ≦ 0.2.

Co ²⁺ / Fe ²⁺ in atomic ratio 91/9 to 88/12
Up to 10 Co / ⁺ and Fe ²⁺ as sulfates and / or chlorides, and further contains dimethylamine borane and / or trimethylamine borane in an amount of 1 g / liter or more and less than 10 g / liter and having a pH of 4 or less. A method for producing the above Co-Fe-B alloy electroplated coating, which comprises performing electroplating in an acidic bath.

[0015]

[Function] The cause and mechanism of changing the coercive force of the magnetic substance have not been clarified, but one of the factors is the crystal grain size. For melting materials, etc.,
Usually, the crystal grain boundaries suppress the interaction between magnetic moments, and thus the crystal grains often form one magnetic domain. At this time, mainly the crystal magnetic anisotropy and the shape magnetic anisotropy of the crystal grain size act strongly. The magnetic anisotropy expresses the easiness of rotation in the direction of the internal magnetization, and when the magnetic anisotropy is small, the magnetic anisotropy tends to rotate, so that the magnetic anisotropy easily becomes a soft magnetic material.
Permalloy and Sendust show typical soft magnetic properties because of their small magnetocrystalline anisotropy.

If the crystal grain size is reduced in such a state that the crystal grains form one magnetic domain, that is, the magnetic interaction is cut off, the single magnetic domain becomes smaller and the magnetization direction rotates. It becomes difficult to do so, the soft magnetic characteristics deteriorate, and the coercive force increases. For magnetic medium materials and the like, the method of decreasing the crystal grain size and increasing the coercive force by adding B and P is often adopted.

However, when the crystal grain size is further reduced, magnetic interaction is exerted between isolated crystal grains without magnetic interaction, and the magnetic domain becomes larger than the crystal grain. When the crystal grain size is sufficiently finer than that of the magnetic domain structure, the crystal magnetic anisotropy does not act, the magnetic anisotropy becomes small and soft magnetism is exhibited, and the coercive force decreases. Therefore, even a material having a large crystal magnetic anisotropy and exhibiting no soft magnetism can be a soft magnetic material by reducing the crystal grain size.

In the present invention (the invention), B is added as the third element to the Co—Fe alloy plating film in order to utilize such an effect. By adding B, the crystal grains are sufficiently fine. And the coercive force decreases. That is,
B, which was previously thought to increase coercive force,
In the present invention (invention thereof), it acts to reduce the coercive force.

The composition of the Co-Fe-B alloy plating film is (Co _100-X Fe _X ) _BY (however, in atomic%, 9 ≦ X ≦
It is necessary to be represented by 12, 0 <Y ≦ 0.2).

The reason why X is limited in atomic% to 9≤X≤12 is to make the magnetostriction constant zero or negative. Also,
The content of Y, that is, B, in atomic% was set to 0 <Y ≦ 0.2, because the coercive force was decreased when B was contained in the plating film as much as possible, while the coercive force was decreased when it was contained in excess of 0.2 atomic%. This is because the magnetic force increases.

[0021] The invention of is a method for producing an electroplating film of the invention of. The plating bath used in this method uses Co ions (Co ²⁺ ) and Fe ions (Fe ²⁺ ) as sulfates (CoSO ₄ and / or FeSO ₄ ) and chlorides (CoCl ₂ and / or FeCl ₂ ). Alternatively, any one of them (sulfate alone or chloride alone) is contained, and as an additive for supplying B, either or both of dimethylamine borane (DMAB) and trimethylamine borane (TMAB) are contained. As anions contained in the plating bath,
Only one of Cl ⁻ and SO ₄ ²⁻ may be contained, but it is preferable that both are contained.

Co ²⁺ / Fe ²⁺ atomic ratio in the plating bath (hereinafter Co
^{2 +} / Fe ²⁺ ratio) is adjusted according to plating conditions such as plating current. For example, as the plating current increases, the proportion of Fe in the plating film increases, so Fe ^{2+ in} the bath may be relatively small. However, since it does not change as much with the plating current as in the case of permalloy plating, the ratio of Co ²⁺ / Fe ^{2+ in} the plating bath is the Co / Fe atomic ratio (hereinafter Co / Fe) of the plating film to be manufactured. (Fe ratio), that is, a ratio at which the magnetostriction constant is 0 or slightly negative, or a ratio in which Fe ²⁺ is slightly smaller than that.

Dimethylamine borane (DMAB), trimethylamine borane (TMAB), or the total addition amount thereof is 1 g / liter or more and less than 10 g / liter.

FIG. 1 is a graph showing the relationship between the amount of TMAB or DMAB added and the coercive force of the obtained plating film, which is the result of the test described in Examples below.
The effect of lowering the coercive force is recognized with the addition of 0.5 g / liter,
The effect becomes particularly remarkable when the amount is 1 g / liter or more. However, the coercive force increases when the amount added exceeds 10 g / liter.

FIG. 3 is a diagram showing an intensity distribution of X-ray diffraction using CoKα rays for a plating film obtained by using a plating solution containing TMAB. The peak in the figure represents the (111) plane of a crystal with a face-centered cubic (fcc) structure. From the spread of this peak (half-value width), the amount of TMAB added should be approximately 1.5 to 3.5 g / liter. It can be said that it is preferable because the crystal grain size is reduced and the coercive force is particularly effective.

If the pH of the plating bath is higher than 4, oxidation of Fe ²⁺ and precipitation of Fe (OH) ₃ will occur, so the pH is adjusted to 4 or less. However, if it is too low, the amount of hydrogen generated becomes large, and it becomes difficult to control the thickness of the plating film. Therefore, it is preferable not to be 2 or less.

To the plating bath, for example, NaCl as an electrolytic supporting agent, sodium saccharin as a residual stress reducing agent for the plating film, and sodium dodecyl sulfate as a surfactant for improving wettability are added in appropriate amounts. desirable.

The optimum concentration range of the plating bath depends on the plating conditions,
When plating on a fine pattern such as a magnetic material of a thin film magnetic head, it is preferable to set the total metal ion concentration of the plating bath to about 0.1 to 0.4 M, though it depends on the apparatus.

The plating current is preferably ² to 10 mA / cm ² . Since the coercive force tends to decrease as the plating current decreases, it is particularly preferable to set the coercive force to ² to 3 mA / cm ² .

The temperature of the plating bath does not need to be low or high, and may be in the range of 20 to 45 ° C. About 25 ° C is suitable.

The material of the plating apparatus is preferably a non-conductive, non-magnetic material such as acrylic resin which does not react with an acidic plating bath. Vinyl chloride resin, polypropylene,
Teflon resin or the like can also be used.

The material of the anode used for plating is most preferably the same as the composition of the alloy to be plated. However, a single metal of the same element as one of the alloy elements, or an insoluble material such as platinum is used. Good.

A material to be plated such as a wafer and a magnetic head is attached to the cathode.

The above Co-Fe-B alloy electroplating film can be produced by plating the surface of a material to be plated such as a wafer and a magnetic head using the above plating bath.

[0035]

EXAMPLE A production test of a Co—Fe—B alloy electroplating film was conducted using a paddle type electrolytic cell having the shape shown in FIG.

The plating tank 1 is made of acrylic resin, the cathode 2 to which a wafer to be plated is attached is arranged in the lower part, the anode 3 is arranged in the upper part, and the paddle 4 is arranged in the plating tank 1 in the left-right direction in the drawing. Move back and forth. The temperature, pH and concentration of the plating solution are controlled in an adjusting tank (not shown), and as shown by the arrow, the pump (not shown) supplies the plating solution to the plating tank 1, and the overflowing plating solution is recovered. It is then returned to the adjusting tank. The flow rate is adjusted by the flow rate adjustment valve.

The wafer is a sintered body of alumina (Al ₂ O ₃ ) and titanium carbide (TiC) with an alumina film formed by a sputtering method. When used, a permalloy alloy film (thickness 1000Å) is used as a base by the sputtering method. Was formed. A 99.9% Co plate was used for the anode.

The plating solution used was CoCl ₂ .6H ₂ O 38.1
g / l, CoSO ₄・ 7H ₂ O 16.9 g / l, FeSO ₄・
7H ₂ O 3-10 g / liter, TMAB or DMAB 0
10 g / liter was added, 25 g / liter of boric acid was added as a pH buffer, and the pH was adjusted to 3.00 to 3.02 with hydrochloric acid. In addition, 25 g / liter of sodium chloride, 1.5 g / liter of saccharin sodium as a residual stress relaxation agent for the plating film, and 0.1 g / liter of sodium lauryl sulfate (surfactant) were added to improve surface wetting properties. For the temperature of the plating solution, use an electronic thermostat using a Peltier element,
Adjusted within 23 ± 0.1 ℃. The flow rate to the plating tank was 5 liters per minute on average.

The test results are shown in FIGS. 1 and 2. Figure 1
Is a diagram showing the change in coercive force (Hc) of the plating film depending on the concentration of TMAB or DMAB.
In both cases, addition of 0.5 g / liter is effective and 1 g / liter
A remarkable effect was recognized by making it more than 1 liter. However, the coercive force increased again when the amount added was 10 g / liter.

FIG. 2 shows the Fe / (Co + Fe) (atomic percentage) and the magnetostriction constant of the plating film obtained by changing the plating current in the range of 2.2 to 13 mA / cm ² with the concentration of TMAB being 2 g / liter. It is a figure which shows the relationship of ((lambda)). From this figure, by changing the plating current, Fe / (Co + F
e) (atomic percentage) is 9 to 12, that is, the ratio of Co / Fe
It can be seen that the magnetostriction constant can be made 0 or negative between 91: 9 and 88:12 expressed by (Co: Fe). Further, the smaller the plating current, the lower the coercive force tends to be. At 2.2 mA / cm ² , the coercive force could be about 2 Oersted (Oe) and the magnetostriction constant could be 0 or slightly negative.

[0041]

The Co-Fe-B alloy electroplating film of the present invention has a high saturation magnetic flux density, a low coercive force, and a magnetostriction constant of 0 or slightly negative, and is a thin film excellent in writing and reading performance. It is suitable as a magnetic material for a magnetic head. This plating film can be manufactured by applying the method of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing a change in coercive force (Hc) of a Co—Fe—B alloy electroplating film produced by using a plating bath in which the addition concentration of TMAB or DMAB is changed.

FIG. 2 is a diagram showing a relationship between Fe / (Co + Fe) (atomic percentage) and a magnetostriction constant (λ) in a Co—Fe—B alloy electroplating film obtained by changing a plating current.

FIG. 3 is a diagram showing an intensity distribution of X-ray diffraction using CoKα rays for Co—Fe and Co—Fe—B alloy plating films.

FIG. 4 is a diagram showing the relationship between the Fe concentration, the coercive force, and the magnetostriction constant in the Co—Fe alloy electroplating film.

FIG. 5 is a diagram showing a composition in which a magnetostriction constant is 0 in a vapor deposited film of a Co—Fe—Ni ternary alloy.

FIG. 6 is a schematic view of a paddle type electrolytic cell used in the examples.
(a) is a plan view and (b) is a partially longitudinal side view.

[Explanation of symbols]

1: Plating tank, 2: Cathode, 3: Anode, 4: Paddle, 5: Motor

Claims (2)

[Claims] 1. A soft magnetic Co—Fe—B alloy electroplating film represented by the general formula: (Co _100-X Fe _X ) _BY . However, X and Y in the above general formula, in atomic%, are 9 ≦ X ≦ 120 <Y ≦ 0.2. 2. Co ²⁺ and Fe ²⁺ are contained as sulfates and / or chlorides so that the atomic ratio of Co ²⁺ / Fe ²⁺ is from 91/9 to 88/12, and further, dimethylamine Borane and / or trimethylamine borane 1g / l or more 10
Co-Fe- according to claim 1, characterized in that the electroplating is carried out in an acidic bath containing less than g / liter and having a pH of 4 or less.
Method for producing B alloy electroplated coating.