JPH03156903A - Manufacture of joined ferrite - Google Patents

Abstract

PURPOSE:To suppress the instability of a boundary between polycrystalline ferrite and single crystal ferrite by a method wherein one or more elements selected among Ca, Zr, Ta, K, Cs and Rb and added to the polycrystalline ferrite and the mixture is baked and then the single crystal ferrite is bonded to the baked polycrystalline ferrite by thermocompression bonding. CONSTITUTION:One or more elements selected among Ca, Zr, Ta, K, Cs and Rb are added to polycrystalline ferrite and the mixture is baked. The respective elements may be added to the polycrystalline ferrite, for example, by a method wherein oxides, carbonates, hydroxides, organometal compounds, etc., of the respective elements are added to the powder of polycrystalline ferrite and the mixture powder is press-molded and sintered in a process afterwards. Then, single crystal ferrite is bonded to the molded and sintered polycrystalline ferrite by thermocompression bonding. With this constitution, a joined ferrite which has little instability of the boundary, single-crystallization of the polycrystalline ferrite and grain growth created at the time of thermocompression bonding can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a bonded ferrite I used as a core material of a magnetic head.

[Summary of the Invention] The present invention involves adding at least one of Ca, Zr, and TaK Cs Rb to the polycrystalline ferrite to be used in advance when bonding and integrating single-crystal ferrite and polycrystalline ferrite by hot pressing. This is intended to suppress single crystallization and grain growth of polycrystalline ferrite at the bonding interface.

[Prior Art] For example, in magnetic heads used in video tape recorders, monocrystalline ferrite and polycrystalline ferrite are used in the magnetic core, instead of conventional single-crystal ferrite heads, in order to reduce sliding noise and improve the CN ratio. The head structure is being switched to a composite head using bonded ferrite.

The composite head has a single-crystal ferrite with high saturation magnetic flux density on the front gap side and a polycrystalline ferrite with high magnetic permeability on the hack gap side, making it possible to perform high-density recording despite its simple structure. It has the advantage of exhibiting excellent electromagnetic conversion efficiency.

The bonded ferrite used as the magnetic core in the aforementioned composite head is usually made by temporarily bonding mirror-polished single-crystal ferrite or polycrystalline ferrite with water or nitric acid, and then applying pressure and heat treatment in a reducing atmosphere such as nitrogen. (so-called hot pressing).

However, when hot bonding is performed using such a method,
Single crystallization and grain growth of polycrystalline ferrite occur at the interface between single-crystal ferrite and polycrystalline ferrite, and a phenomenon in which the interface moves randomly is often observed.

This movement of the interface must be suppressed as much as possible since it causes sliding noise.

Under these circumstances, the applicant of the present application first applied
In Japanese Patent No. 14311, a technique was proposed in which an oxide magnetic thin film was interposed at the interface between single crystal ferrite and polycrystalline ferrite to suppress movement of the interface. It has been confirmed that when the oxide magnetic thin film is interposed, grain growth at the interface is suppressed due to the discontinuous grain growth phenomenon.

[Problem to be solved by the invention] By the way, in manufacturing bonded ferrite, it is of course required to suppress the above-mentioned interface movement, but at the same time, it is also required to increase productivity as much as possible and reduce manufacturing costs. It is natural that

From this point of view, the formation of the oxide magnetic thin film is as follows:
It is disadvantageous in terms of capital investment and productivity. That is, in order to form the oxide magnetic thin film, a sputtering device and the like are required, which requires a large amount of equipment investment, and
An extra step is added to the bonding process, and film formation also takes a long time, resulting in a decrease in productivity.

Therefore, the present invention was proposed in view of the above-mentioned conventional situation, and is capable of suppressing the movement of the interface between single crystal ferrite and polycrystalline ferrite, and is also excellent in terms of productivity and manufacturing cost. An object of the present invention is to provide a method for manufacturing a bonded ferrite.

[Means to solve the problem]

As a result of extensive research over a long period of time in order to achieve the above object, the inventors of the present invention have previously added Ca and Z to polycrystalline ferrite.
If either Cs or Rb is added to r, Ta, and fired, single crystallization and grain growth during hot pressing are suppressed, and therefore it is possible to join by following the usual process. We have come to the conclusion that

The manufacturing method of the present invention was completed based on this knowledge, and includes Ca in polycrystalline ferrite.

The method is characterized in that at least one of Cs and Rb is added to Zr, Ta, and fired, and then a single crystal ferrite is joined and heat-pressed.

[Effect]

When polycrystalline ferrite made by adding at least one of Cs and Rb to Ca, Zr, Ta, and fired is bonded to single crystal ferrite and hot pressurized, compared with the case when normal polycrystalline ferrite is used. As a result, single crystallization and grain growth are reduced, and movement of the polycrystalline ferrite-single crystal ferrite interface is suppressed.

〔Example) Examples to which the present invention is applied will be described below.

In this example, in order to manufacture the bonded ferrite, Ca and Zr are first added to the polycrystalline ferrite used.

One or more of Cs and Rb is added to Ta, and this is fired.

As a method of adding each of the above-mentioned elements, oxides and carbonate compounds of each of the above-mentioned elements are added to the powder of polycrystalline ferrite.

An example is a method in which a hydroxide, an organometallic compound, etc. are added in advance, and subsequent steps are performed to form, press, and sinter. Alternatively, polycrystalline ferrite powder is added to a hydroxide-containing solution of each of the above elements, an organometallic compound solution (for example, Alcolade solution 1 acetylacetone solution, etc.), a carbonate compound suspension, etc., and after filtration (dehydration), it is dried or dissolved. It is also possible to heat and dry it as it is, press it into a shape, and sinter it.

Furthermore, the above-mentioned solution may be dripped or applied onto the bonding surface or the entire surface of an unsintered ferrite powder block that has been molded and pressed, and then sintered.

Next, single crystal ferrite is joined to the polycrystalline ferrite produced as in step i1c above, and heat-pressed. The conditions for heat-pressing (temperature, pressure, etc.) can be the same as those normally used for manufacturing bonded ferrite.

When polycrystalline ferrite and single-crystal ferrite, which have been sintered with the above-mentioned elements added, are hot-pressed, the movement of the interface during bonding and the single-crystal two-grain growth of polycrystalline ferrite l- are suppressed. Less junction ferrite is obtained.

The present inventors actually produced two types of bonded ferrite using Mn-Zn polycrystalline ferrite to which K (potassium) was added and fired by the above-mentioned processing method and untreated Mn-Zn polycrystalline ferrite. .

Note that the case where the former is used is an example, and the case where the latter is used is a comparative example.

That is, after temporarily adhering mirror-finished Mn-Zn polycrystalline ferrite and single crystal ferrite, 5kg/cd
Pressure and heat treatment were performed at 1220° C. for 12 hours in a nitrogen atmosphere while applying a pressure of

The Examples and Comparative Examples are all under the same conditions except that the polycrystalline ferrite used is different.

The bonded state after the pressure and heat treatment is shown in FIGS. 1 and 2.

FIG. 1 shows a bonded state in an example, and FIG. 2 shows a bonded state in a comparative example. In both cases, the magnification is 200x.

Comparing these figures 1 and 2, it is found that when polycrystalline ferrite fired with the above-mentioned elements added is used,
That is, it can be seen that in the examples, there is little single crystallization or grain growth of polycrystalline ferrite at the single crystal-polycrystal interface. Therefore, there is little movement of the interface before and after bonding, and the interface is flat.

Similarly, when bonded ferrite was produced using polycrystalline ferrite that had been fired with the addition of Ca, Zr, Ta, Cs, and Rh, single crystallization and grain growth of the polycrystalline ferrite near the interface were suppressed. There was little movement of the interface.

In the following, specific embodiments of the present invention have been described.
It goes without saying that the present invention is not limited to this embodiment.

[Effect of the invention] As is clear from the above explanation, in the present invention,
At least II of Ca, Zr, Ta, Cs, and Rb!
! T! The polycrystalline ferrite that has been fired with the addition of
It is possible to suppress the single crystallization and grain growth of polycrystalline ferrite, and to suppress the movement of the interface.

Therefore, if the present invention is applied to, for example, manufacturing a core material of a magnetic head, it becomes possible to manufacture a magnetic head with less sliding noise.

Further, the manufacturing method of the present invention can follow the conventional manufacturing process of bonded ferrite as is, and there is no need to add any new process, which is advantageous in terms of equipment investment and productivity.

[Brief explanation of the drawing]

Figure 1 is a micrograph (200x magnification) showing the appearance of crystal grains near the interface of bonded ferrite using polycrystalline ferrite fired with K added, and Figure 2 is a photo taken using untreated polycrystalline ferrite. 2 is a micrograph (200x magnification) showing the appearance of crystal grains near the interface of the bonded ferrite.

Claims (1)

[Claims] Ca, Zr, Ta, K, Cs, Rb in polycrystalline ferrite
1. A method for producing a bonded ferrite, which comprises adding at least one of the following and firing the same, followed by bonding single crystal ferrite and heat-pressing the bonded single crystal ferrite.