JPS6012767B2 - Manufacturing method of high-density Ni-Zn ferrite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing Ni--Zn ferrite, which has a high coagulation density and exhibits excellent magnetic properties in a high frequency band.

In recent years, with the development of information processing, the magnetic recording industry has made remarkable progress.

As a result, in the field of magnetic recording, improving recording density has become an even more important issue in order to cope with the increase in the amount of information, and the recording frequencies of magnetic heads used in video tape recorders, electronic computers, etc. are becoming increasingly high. There is a tendency to shift to As a result, performance requirements for the magnetic heads used in these devices have become even more demanding, and materials with even better high frequency characteristics than before have been desired.
Currently, ferrite is in practical use as a magnetic head material for the above-mentioned video tape recorders and electronic computers, and in the former, Mn--Zn hot-pressed or single-crystal ferrite is the mainstream.

On the other hand, Ni-Zn ferrite is mainly used in the latter, but it requires precision machining, so it is of course high density, and it also has magnetic properties, especially high initial permeability in the frequency band used. required. Generally, the frequency dependence of the initial magnetic permeability of ferrite (hereinafter referred to as Mu f characteristic) can be divided into a low frequency band with little frequency dependence and a band where the initial magnetic permeability gradually decreases at higher frequencies. I can think.

In the low frequency band where the Mu f characteristic is flat, the magnetization mechanism due to domain wall movement is considered to be the dominant mechanism, and the initial magnetic permeability changes depending on the crystal grain size, pore distribution, or amount of impurities in the ferrite crystal body. changes greatly. On the other hand, the frequency at which the initial permeability begins to decrease is approximately determined by the crystal anisotropy constant specific to each ferrite, and this fact is well known as the Snake limit. Looking at the current state of use of ferrite magnetic heads, it is common that they are used across a range from a flat band with a flat r-f characteristic to a band with a gradual decrease in initial permeability, and the materials used also vary. Its use requires high initial magnetic permeability. In a belt castle where the initial magnetic permeability varies greatly in this way, it is a very difficult problem to maintain it high. Conventionally, in order to focus on high initial permeability at high frequencies, the initial permeability at low frequencies (frequency bands with flat peak-f characteristics) was often sacrificed, or vice versa, and it was difficult to satisfy both at the same time. was difficult.

The present invention improves these shortcomings, obtains a sufficiently high initial magnetic permeability in the frequency band actually used as a magnetic head, and also produces high-density Ni by ordinary drilling without using special methods such as hot pressing. - A method of manufacturing Zn ferrite is provided.

The dry method is a common method for producing ferrite, but in the case of Ni-Zn ferrite, the raw material is Ni○
, Zn○, Fe203 etc. oxides or salts, sulfates,
Nitrate, carbonate, and other substances that decompose into oxides during calcination or freezing are often used.

When trying to manufacture ferrite with higher performance, it is of course necessary to use raw materials with a low content of impurities that adversely affect magnetic properties, but in addition, it is necessary to use raw materials with a low content of impurities that adversely affect magnetic properties. , it is necessary to pay sufficient attention to the shape, etc. In the normal dry method, each raw material powder is first mixed, then temporarily placed next to each other, and then crushed and molded.
Naturally, its uniformity becomes a problem. That is, the uniformity of the distribution of raw material particles in the mixed powder, the uniformity of the composition of reactants in the preliminary powder, the uniformity of the ion distribution in the baking powder, etc. are important. Particularly in the case of Ni-Zn ferrite, where Zn ferrite is formed in the early stage of sintering and takes the form of burnt stripes in which Ni ions are diffused, the difficulty of Ni ion diffusion may affect the uniformity of ion distribution. This will have a large impact on the magnetic properties. If the particle size of the raw material Ni○ or nickel compound is large, even if diffusion occurs, areas with a large amount of Ni ions or vice versa, areas with a small amount of Ni ions are likely to occur locally.
It is thought that the ion distribution becomes non-uniform. If the ion distribution is non-uniform, crystal anisotropy etc. will differ locally and domain wall motion will be hindered, so it is expected that the initial magnetic permeability in a frequency band where the rf characteristic is flat will decrease.

Therefore, in order to increase the contribution of domain wall motion to the initial magnetic permeability, it is necessary to use Ni○ or a nickel compound with a particle size as small as possible to improve the uniformity of the ion distribution in the crystalline structure. Furthermore, if Ni◯ or a nickel compound having a small particle size is used, diffusion of Ni ions is facilitated, which may have the effect of promoting false silk. The present invention has been developed based on the above facts, and will be described in detail below with reference to Examples. Example 1 Table 1 and FIG. 1 show various properties of Ni-Zn ferrite when two types of Ni○, namely A and B, were used as raw materials.

The average particle diameters of the two types of Ni○ are 1.2r for A and 4.8r for B, respectively.
and B2 are samples using raw material B. All samples contained 17.7 mol% Ni0, 32.8 mol% Zn0, and F
e203 Raw materials with a blending ratio of 49.5 mol% are mixed in water or an organic solvent such as alcohol or acetone, and 1300
After being frozen at a temperature of 1,300 pm or less, the powder was pulverized using a ball mill or a vibration mill, and the resulting powder was pressure-molded and sintered in air or oxygen at a temperature of 1,300 pm or less. As is clear from Table 1 and Figure 1, Samples A and A2 using raw material A with a small average particle size are more effective than Samples B and B2 using raw material B with a large average particle size. At a ratio of 3M or lower, the initial magnetic permeability is large and the effect of the present invention is remarkable, and by using this kind of material, it is fully expected that the magnetic head characteristics will be improved.

In addition, Samples A and A2 were also excellent in grain density, demonstrating the effect of promoting grain formation due to the use of NiO having a small particle size, and the superiority of the present invention is recognized. Example 2 Table 2 shows various properties of Ni-Zn ferrite A3, & produced under the same conditions as A, B, and of Example 1 except for the compounding composition.

A3 and Horse are those using raw materials A and B, respectively, and the blended compositions of both are Ni022.7 mol% and Zn027.
8 mol% and Fe20349.5 mol%. Second
As is clear from the table, in the frequency band of 0.5 to 7.0 M ratio, B3 has a higher initial permeability than B3, and the same effect as Example 1 is observed even when the blending composition is different. Table 2 Example 3 Table 3 shows Ni-Zn when nickel oxalate is used as a raw material.
Various characteristics of ferrite C, C2 are shown.

Each raw material was blended to have the same composition as A, B of Example 1, and a sample was prepared in the same manner. Although the decomposition point of hakamate is much lower than the calcination temperature in this case, nickel oxalate is thermally decomposed at the same temperature as the calcination temperature, and the average particle size of a single particle in the token particles is The diameter was confirmed to be less than 3 Buddhas. Table 3 Again, in this case, as in Example 1 or 2, when Ni○ having a small particle size was used, excellent magnetic properties can be obtained.

As described above, if Ni○ or a nickel compound with a small average particle size of 3 μm or less is used as a raw material, the effects of the present invention can be fully exhibited, but as the average particle size becomes larger than 3 μm, the initial magnetic permeability increases. gradually decreases, and desired characteristics cannot be obtained.

Therefore, the limit of the average particle size at which the effects of the present invention are significantly exhibited is set to be 3 mm or less. If the Ni-Zn ferrite according to the present invention is actually used in a magnetic head, it is expected that head characteristics will be fully improved due to its high initial magnetic permeability, and its high density will facilitate precision processing, making it suitable for industrial use. However, the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a characteristic curve diagram showing the frequency dependence of the initial magnetic permeability of the Ni--Zn ferrite of the present invention.

Claims (1)

[Claims] 1. In a method for producing ferrite in which raw material powders are mixed, calcined, pulverized, molded, and then sintered, single particles or skeleton particles are used as the nickel oxide or nickel compound raw material powder among the raw material powders. 1. A method for producing Ni--Zn ferrite, characterized in that raw material powder is used in which the average particle diameter of the particles encapsulated in the powder is 3 μm or less.