JP2792115B2 - Method of forming ferrite film and ferrite substrate - Google Patents

Description

The present invention relates to a spinel type widely applied to magnetic recording media, magneto-optical recording media, magnetic heads, magneto-optical devices, microwave devices, magnetostrictive devices, magneto-acoustic devices, etc. The present invention relates to a method for forming a ferrite film in producing a ferrite film and a ferrite substrate on which a ferrite film is formed by the method.

2. Description of the Related Art Ferrite plating is, for example, as described in JP-A-59-111929, by contacting an aqueous solution containing at least ferrous ion as a metal ion with a solid surface, and contacting the solid surface with FeOH. ⁺ Or other metal hydroxide ions are adsorbed, and then the adsorbed FeOH ⁺ is oxidized to obtain FeOH 2 ⁺ , which causes a ferrite crystallization reaction with the metal hydroxide ions in the aqueous solution, This means that a ferrite film is formed on the solid surface.

Conventionally, the ferrite film has been homogenized and the reaction rate has been improved based on this technology (JP-A-60-140713).
Japanese Patent Application Laid-Open (JP-A) No. 61-179877 discloses a method of forming a ferrite film on various solids by imparting surface activity to the surface of a solid. Gazette or JP-A-61-222924
Gazette).

The ferrite plating may be of any type as long as the solid to form a film has resistance to the above-mentioned aqueous solution. Furthermore, since the reaction is carried out through an aqueous solution, a spinel ferrite film can be produced at a relatively low temperature (below the boiling point of the aqueous solution). Therefore, the limited range of the solid is smaller than that of other ferrite film fabrication techniques.

A ferrite substrate is used as a substrate for various types of magnetoelectric elements (such as a magnetoresistive element or a Hall element) to increase sensitivity to magnetism.

Problems to be Solved by the Invention However, as described above, various improvements have been proposed for the homogeneity of the ferrite film, or the generation rate of the ferrite film, but the magnetic properties of the obtained ferrite film have been described above. All methods were inadequate. That is, sufficient magnetic properties as spinel type ferrite, especially properties as a soft material are not obtained. For this reason, there has been a major problem regarding application to various electronic components and the like.

The coercive force of the ferrite film is, for example, about 100 as shown in Metal Surface Technology VOL.38, No.9, 1987 P.1.
Oe or more, and magnetite and Mn and Zn-containing (MnZn-based) ferrites have almost the same size.

When a ferrite substrate is used as a substrate for various magnetoelectric conversion elements (such as a magnetoresistive element or a Hall element), for example, a sintered ferrite substrate is porous, so that the surface is rough and many defects such as pinholes are present. There is a problem when a thin film element is formed on the surface.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for reducing iron ions.
In this method, a solution containing 002 mol / or less is brought into contact with a substrate to deposit a ferrite film on the substrate surface.

The present ferrite film is formed on various substrates to form a ferrite substrate having a ferrite film.

Action According to the method described above, that is, 0.002 mol /
By contacting the solution containing the following with the substrate and forming a ferrite film on the surface of the substrate, excellent magnetic properties, which were not obtained by a method using a solution having a concentration outside the above range, and dense and surface properties were obtained. A good ferrite film can be formed. Therefore, when a ferrite film is formed on various substrates, when used as a substrate, it is dense (fewer pinholes), has good surface properties (surface roughness comparable to that of ordinary glass), and has a sufficient soft ferrite. Since it has magnetic characteristics, for example, the sensitivity of various magnetoelectric conversion elements to magnetism can be improved.

Examples Hereinafter, examples of the present invention will be described.

The basic part of the method for forming a ferrite film of the present invention is as follows.
Mostly the same as known methods.

However, in the present invention, since a solution containing 0.002 mol / or less of iron ions is supplied to the substrate, a ferrite film having a very small coercive force (high magnetic permeability) can be obtained. Moreover, the obtained ferrite film has very few pinholes and has a surface roughness equivalent to that of ordinary glass. The cause for these phenomena is not clear.

As a result, by setting the iron ion concentration in the above range, there is some effect on the soft magnetic properties (low coercive force, high magnetic permeability) of the obtained ferrite film or on the fineness and surface properties of the excellent film. It seems that there is not.

Some examples of the method for forming a ferrite film of the present invention will be described with reference to the drawings.

For example, a schematic diagram of an example device is shown in FIG. Reference numeral 3 denotes a base on which a ferrite film is to be formed. 4 is the substrate 3
It is a turntable that can be attached and turned. 1
And 2 are nozzles for supplying a plating solution to the substrate 3. By selecting an appropriate nozzle, the liquid can be supplied dropwise or in a spray form. In order to minimize unnecessary reactions before the plating reaction, to reduce the variation in the characteristics of the obtained ferrite film, and to make it easier to control, it is better to prepare the liquid necessary for plating in several parts. This figure shows a case where the image is divided into two parts. Numerals 5 and 6 are tanks for storing the respective plating solutions.

Further, as shown in the figure, a portion for performing a ferrite plating reaction, such as the base 3 and the turntable 4, is partitioned by a case 7, and a non-oxidizing (for example, nitrogen) gas is sent into the case 7 to form a non-oxidizing atmosphere. . The tank 5 contains an aqueous solution (reaction solution) containing at least 0.002 mol / or less of iron ions. The tank 6 uses, for example, sodium nitrite NaNO ₂ as an oxidizing agent, and further uses ammonium acetate as a buffer or a complexing agent. An aqueous solution (oxidizing solution) containing CH ₃ COONH ₄ is charged, and the solution is supplied into the apparatus through nozzles 1 and 2 by a pump or the like. The ferrite film obtained when the reaction solution further contains Ni ions and Zn ions is a NiZn-based ferrite film, and the ferrite film obtained when Mn ions and Zn ions are further included is a MnZn-based ferrite film. Each liquid is supplied to the base 3 while being rotated by the turntable 4. The turntable 4 is heated to 50-100 ° C by a heater or the like.
Heat to In this manner, a ferrite-forming reaction is performed on the base 3 to form a ferrite film on the base 3.

FIG. 1 shows the case where the solution necessary for plating is divided into two, but a method of dividing into three solutions may be used. As a method of dividing into three liquids, for example, the first liquid is the above-described reaction liquid,
The second liquid is a liquid (oxidizing liquid) in which only an oxidizing agent for oxidizing ferrous ions is dissolved. The third solution is a solution prepared by dissolving ammonium acetate CH ₃ COONH ₄ as a buffer or complexing agent to adjust the pH during the ferrite formation reaction or to facilitate the incorporation of elements other than iron into the ferrite film. Liquid). If necessary, the pH of the solution may be adjusted by further dissolving an alkali such as ammonia water NH ₄ OH or sodium hydroxide NaOH. As a method for supplying these plating solutions to the substrate 3, a method in which the reaction solution and the oxidizing solution are alternately and repeatedly supplied while the conditioning solution is continuously supplied, or a method in which the reaction solution and the conditioning solution are supplied,
There is a method of repeatedly supplying the oxidizing liquid. What is necessary is that after supplying the reaction liquid to the substrate 3, the supply of the oxidizing liquid to the substrate 3 is then repeated.

FIG. 2 shows a schematic diagram of an apparatus according to an example of another method. The nozzle 1, base 3, rotary table 4, tanks 5 and 6, and case 7 are the same as those in FIG. However, in the present method, unlike the method shown in FIG. 1, the plating solution prepared in two parts is mixed in the mixing section 8 and the mixed plating solution is supplied to the base 3 via the nozzle 1. The mixing unit 8 selects an appropriate method such as a method in which the liquid is dropped from two nozzles, mixed with a funnel and discharged from one port, or a method in which the liquid is discharged from the nozzle 1 by combining two tubes into one. do it. By selecting an appropriate nozzle shape and structure, the liquid can be supplied to the substrate 3 in the form of a drop or a spray.

Further, FIG. 3 shows a schematic diagram of an apparatus as an example of another method. The nozzle 1, base 3, rotary table 4, tanks 5, 6, case 7, and mixing section 8 are the same as those in FIG. The preheating section 9 is a different part of the method. In other words, in the present method, unlike the method shown in FIG.
After heating to below the boiling point of the solution, the mixture is mixed in the mixing section 8 and the mixed plating solution is supplied to the substrate 3 via the nozzle 1. As a method of preheating the solution only, the plating solution may be supplied to the substrate 3 separately by two nozzles after the plating solution is preheated by the preheating unit 9 except for the mixing unit 8, for example.

The above-described example is a method using an oxidizing agent. For example, a mixed gas of nitrogen and oxygen or air may be supplied into the case 7 without using the oxidizing agent, and the case 7 may be oxidized by oxygen.

FIG. 4 shows a schematic view of an apparatus according to an example of another method. Substrate
3. The tanks 5, 6 and the mixing section 8 are the same as in the conventional system. The plating reaction section 10 and the water bath 11 are different parts of the method. That is, in the present method, unlike the method described above, the method can be performed without using a rotary table and in a state where a plating reaction portion and the like are isolated from gas. Further, a ferrite film can be deposited on a part of the gas 3. The base 3 on which a ferrite film is to be formed is incorporated in the plating reaction section 10. In the plating reaction section 10, the plating solution is physically made to uniformly flow over the surface of the substrate 3. Mixing section 8 and plating reaction section 10
By setting in the water bath 11,
Heat to 100 ° C. In this way, a ferrite film is deposited on the surface of the substrate 3 set in the plating reaction section 10.

FIG. 5 is a schematic diagram showing an example of another method. Nozzles 1, tanks 5, 6 and mixing section 8 are the same as before. Without using a turntable or a water bath,
Instead, the base 12 is used. As shown in the drawing, the base 3 is set on the base 12 at an angle. The substrate 3 is inclined at a predetermined angle so that the plating solution flows uniformly on the surface of the substrate 3, and 50 to 100
The substrate 3 can be heated to ° C. In this way,
A ferrite film is deposited on the surface of the base 3 set on the base 12. This method can be performed in the air or air.

As described above, the reaction solution of the example shown has at least
By containing 2 mol / or less, the soft magnetic properties of the ferrite film are improved (coercive force is reduced) as compared with the case where a ferrite film is prepared using a reaction solution having a concentration other than the above.

The material of the base 3 is not particularly limited. Some examples are polyimide films, various plastics such as polyethylene terephthalate (PET), metals such as copper, nickel, silver, gold, tungsten, molybdenum, platinum, palladium, iron, iron alloys, and various organic laminates. Board,
That is, there are various types of glass, ceramics, and the like, such as a laminate of paper base epoxy, glass cloth base epoxy, glass base polyester, glass cloth base tetrafluoroethylene, and the like.

Further, the surface of the substrate 3 has a center line average roughness (Ra).
When the thickness is 0.01 μm or more, the deposition rate of the film can be improved.
This works positively for FeOH ⁺ adsorption, oxidation reaction or ferrite crystallization reaction, and the fine particles generated in the aqueous solution are caught or gathered on the substrate surface,
Further, it is considered that the film growth is promoted and assisted. Also,
By having a certain degree of surface roughness,
It is considered that the substantial increase in the surface area of the substrate 3 and the increase in the area involved in reactions such as adsorption also have an effect.

Experimentally, those which are particularly compatible with ferrite film formation are those containing any one or more of oxygen, nitrogen and sulfur, or especially oxides.

Examples of the oxide include alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), beryllia (BeO), steatite (MgO · SiO ₂ ), forsterite (2MgO · SiO ₂ ), and magnesia ( Various ceramics such as MgO), titania (TiO ₂ ), titania + zirconia (ZrO ₂ ), titania + magnesia, Al ₂ O ₃ -SiO ₂ · B ₂ O ₃ , Al ₂ O ₃ -PbO · SiO ₂ · B ₂ O ₃ , Al
Includes glass ceramics such as ₂ O ₃ -MgO ・ SiO ₂・ B ₂ O ₃ , Al ₂ O ₃ −CaO ・ MgO ・ SiO ₂・ B ₂ O ₃ , metal oxides such as CuO, NiO, and iron such as ferrite Oxide.

In order to improve the sensitivity to magnetism such as various thin-film magnetoelectric devices (such as a magnetoresistive device or a Hall device), if a substrate material suitable for each device is selected as a substrate suitable for forming the device, Preferably, the smoother the surface roughness of the substrate, the smoother the surface of the ferrite film formed on the surface. Even if various non-magnetic substrates are used, it is a substrate to which a ferrite film with sufficient soft properties is added, so the sensitivity to the magnetism of the element is improved, and if a NiZn-based ferrite film is formed, high resistance is obtained. In addition to this, the conductor can be formed directly on the ferrite film. That is, various devices can be manufactured without an insulating layer.

 Next, more specific examples of the present invention will be described.

(Example 1) Chloride 1 was added to ion-exchanged water (hereinafter simply referred to as water) 5.
An aqueous solution (reaction liquid) was prepared by dissolving iron, nickel chloride and zinc chloride in the amounts shown in Table 1. As another solution, an aqueous solution (oxidizing solution) was prepared by dissolving sodium nitrite and ammonium acetate in water 5 in the amounts shown in Table 1.

Using these solutions, ferrite films were prepared with an apparatus as shown in FIG. Nitrogen gas at 1.5 min / min
To obtain a non-oxidizing atmosphere.
° C was kept constant. The turntable was rotated at a speed of 400 revolutions per minute. Each solution was supplied as a spray at a flow rate of 40 ml per minute.
The substrate is a glass substrate.

Table 1 shows the results of measuring the magnetic properties of these ferrite films. This is a comparison value when the coercive force Hc of Sample No. A is set to 100, and the coercive force of Samples Nos. D to J is less than half that of Sample No. A, and is very excellent in softness. That is, the coercive force of the ferrite film obtained by the method of the present invention was usually less than half the coercive force of the ferrite film obtained so far, and the coercive force showed a very small value.

Further, the ferrite film obtained by the method of the present invention had few pinholes and had a surface roughness equivalent to that of a glass substrate.

(Example 2) The same liquid as F in Example 1 was prepared as a reaction liquid and an oxidizing liquid. The oxidized solution was further adjusted to pH = 8 with aqueous ammonia.

Using these plating solutions, ferrite plating was performed with the apparatus shown in FIGS. The substrate used was an alumina substrate subjected to glass glaze.

For comparison, the same solution as in Example 1 A was prepared and plated in the same manner.

The magnetic properties of the ferrite film obtained by the method of the present invention and the ferrite film prepared for comparison were compared.
Hc was almost the same as the result of Example 1, and the ferrite film obtained by the method of the present invention showed better soft magnetic characteristics. Furthermore, there were few pinholes and the surface was smooth.

(Example 3) A reaction solution was prepared by dissolving 0.3 g of ferrous chloride, 1.3 g of manganese chloride and 8 mg of zinc chloride in water 5. Further, as an oxidizing solution, 60 mg of sodium nitrite and 2 g of ammonium acetate are dissolved in water 5 and the pH is further adjusted with aqueous ammonia.
= 9 was prepared.

Using these plating solutions, the apparatus shown in FIG.
Ferrite plating was performed. The substrate used was a glass substrate.

For comparison, ferrous chloride 4g, manganese chloride 2 in water 5
Reaction solutions were prepared in which 6 g and 130 mg of zinc chloride were respectively dissolved. Further, as an oxidizing solution, a solution was prepared by dissolving 1.5 mg of sodium nitrite and 20 g of ammonium acetate in water 5 and further adjusting the pH to 9 with aqueous ammonia.

The magnetic properties of the ferrite film obtained by the method of the present invention and the ferrite film prepared for comparison were compared.
Hc was almost the same as the result of Example 1, and the ferrite film obtained by the method of the present invention showed better soft magnetic characteristics. Furthermore, the film was excellent in denseness and surface roughness.

(Example 4) Using the same plating solution as No. D, F and H of Example 1, ferrite plating was performed with the apparatus shown in FIG. The substrate used was mainly MgO.SiO ₂ , MgO, BeO, Al ₂ O ₃ -S
There are nine types: iO ₂ · B ₂ O ₃ glass ceramic base, quartz glass plate, polyimide film, stainless steel plate, copper plate, and copper-clad glass cloth base epoxy.

For comparison, nine types of substrates were similarly plated using the same solution as in No. A of Example 1.

The magnetic properties of the ferrite film obtained by the method of the present invention and the ferrite film prepared for comparison were compared.
Hc was almost the same as the result of Example 1, and the ferrite film obtained by the method of the present invention showed better soft magnetic characteristics. Further, the ferrite film of the present invention was a dense and very smooth film having a small surface roughness.

(Example 5) The same reaction solution and oxidizing solution as in Example 3 were prepared for each of 5,
Using these solutions, using the apparatus shown in FIG. 5,
Ferrite plating was performed for 2 hours on a substrate obtained by subjecting an alumina substrate to glass glaze.

For comparison, plating was performed in the same manner using the same solution as in the comparison of Example 3.

The magnetic properties of the ferrite film obtained by the method of the present invention and the ferrite film prepared for comparison were compared.
Hc was almost the same as the result of Example 3, and the ferrite film obtained by the method of the present invention showed better soft magnetic characteristics. Further, the ferrite film of the present invention was a dense and very smooth film having a small surface roughness.

(Example 6) The same reaction solution and oxidizing solution as F of Example 1
The ferrite plating was performed and ferrite plating was performed in the same manner as in Example 1 using the apparatus shown in FIG. A glass substrate was used as a substrate, and plating was performed for 2 hours. [Product of the Invention] For comparison, sintered ferrite was lapped and mirror-finished. [Comparative product] Comparing the sintered body ferrite with the substrate provided with the ferrite film obtained according to the present invention, the pinhole density is 1/1000 or less of the comparative product, and the surface roughness is the center line average roughness (Ra). ) Was 1/10 or less. That is, since the ferrite substrate of the present invention has very few pinholes and has a very smooth surface, it can be used for forming various devices without any need for mirror finishing.

Effect of the Invention According to the present invention, as described above, 0.002 mol of iron ions
By using a solution containing the following, it is possible to produce a ferrite film exhibiting better magnetic properties as a soft ferrite than using a solution outside the above range. In addition, the denseness and smoothness of the obtained film are very excellent.

Thereby, a ferrite film having magnetic properties sufficient for application to various electronic components and the like can be obtained. Furthermore, it is a very effective ferrite substrate for forming various devices.

[Brief description of the drawings]

FIGS. 1, 2, 3, 4, and 5 are schematic views of an apparatus used in an embodiment of the method for forming a ferrite film of the present invention. 1,2 ... nozzle, 3 ... substrate, 4 ... rotary table, 5,6 ... tank, 7 ... case, 8 ... mixing section, 9 ... preheating section, 10
… Plating reaction part, 11… Water bath, 12… Base base.

Claims (4)

(57) [Claims] 1. A method for forming a ferrite film, comprising: bringing a solution containing 0.002 mol / or less of iron ions into contact with a substrate to deposit a ferrite film on the surface of the substrate. 2. A ferrite film according to claim 1, wherein a solution containing an iron ion and a solution containing an oxidizing agent for oxidizing ferrous ions are mixed before contacting the substrate, and then contacted with the substrate. Method. 3. The method for forming a ferrite film according to claim 1, wherein the solution is heated to 50 ° C. to a boiling point or lower, and then the solution is sequentially brought into contact with the substrate. 4. A ferrite substrate having a ferrite film formed on a substrate surface by the method according to claim 1.