JPH0536517A - High frequency magnetic material - Google Patents

Abstract

PURPOSE:To obtain high Q at a frequency region of a UHF band or higher. CONSTITUTION:Where X of a general formula of CO2 (Ba1-xSrx)3 Fe24O41 refers 0.1 to 0.6, Ba of CO2Ba3Fe24O41 is substituted by Sr. An amount to be substituted is made small at a relatively low frequency and as the frequency is raised, the amount to be substituted is made larger, whereby a high frequency magnetic material having optimum composition for a frequency to be used can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency magnetic material, and more particularly to a high frequency magnetic material suitable for an inductor used in a high frequency region of 100 MHz or more.

[0002]

2. Description of the Related Art Inductors are used in a range of several hundred MHz
Is expanding into the high frequency range. Conventionally, Ni-Zn type ferrite has been mainly used for the high frequency coil, but problems such as self-resonant frequency occur when the frequency becomes high, and it is considered to use a ferlock sprayer or the like. However, it has hardly been put to practical use. Further, in the high frequency region, it has been considered to use an air-core coil by using a non-magnetic material, but it is difficult to obtain a high inductance and Q when using a non-magnetic material.

[0003]

SUMMARY OF THE INVENTION The present invention aims to improve the composition of cobalt-barium type ferrite, which is a type of ferro sprayer, to obtain a high Q and a magnetic material which can be used in a high frequency range. It is a thing.

[0004]

The present invention solves the above problems by improving the composition of a hexagonal magnetic material, that is, a ferroscopic planar magnetic material.

That is, the magnetic material of the present invention is characterized in that the composition represented by the general formula Co ₂ (Ba _1-x Sr _x ) ₃ Fe ₂₄ O ₄₁ satisfies 0.1 ≦ X ≦ 0.6. ..

[0006]

[Function] By substituting a part of Ba of Co ₂ Ba ₃ Fe ₂₄ O ₄₁ with Sr, the Q in the high frequency region can be improved. Further, a high μQ product can be obtained within the above composition range.

[0007]

EXAMPLES Examples of the present invention will be described below.

First, a method of manufacturing a high frequency magnetic material according to the present invention will be described. CoO, BaCO ₃ , SrCO as materials
₃ , Fe ₂ O ₃ were weighed so as to have a predetermined composition, and mixed in a ball mill for 20 hours. This was calcined at a temperature of 1200 ° C. for 2 hours, and the calcined product was pulverized with a planetary ball mill. A binder and the like were added to the mixture, the mixture was molded, and the mixture was baked at a temperature of 1200 to 1300 ° C for 2 hours to obtain a material according to the present invention.

The characteristics of the magnetic material for high frequencies according to the present invention were measured by the commonly used short-circuit coaxial method. With the dimensions before firing, the outer diameter was 25 mm, the inner diameter was 18 mm, and the thickness was 5 mm, and a toroidal core was obtained and various properties were measured. The measurement frequencies were 50MHz, 100MHz, 300MHz and 500MHz.

The above measurement results will be described below.
FIG. 1 is an explanatory diagram showing changes in Q at each frequency. X, that is, the amount of Ba replaced by Sr is plotted on the horizontal axis, and Q at that time is plotted on the vertical axis. 0.1 ~ at 50MHz
Q greatly improved in the range of 0.3, and began to decrease when it exceeded 0.3. When the amount of substitution increased, Q decreased to a state close to that without substitution. At 100MHz, the tendency is almost the same, but the degree of Q decrease is small even if the substitution amount increases.

In the high frequency region of 300 MHz, Q increased as the amount of substitution increased up to X of 0.3, and Q decreased when the amount of substitution increased at a peak. However, 50MH
The amount of decrease is small compared to the examples of z and 100MHz, and there is almost no change above 0.5. It is the same that Q increases as the replacement amount increases even at 500MHz, but X
It peaked when was 0.6, and there was almost no change above that.

From the above results, it has been found that with respect to Q, the effect becomes remarkable in the range where the substitution amount is small in the low frequency range, and the substitution amount is increased as the frequency becomes higher. From this, a high Q can be obtained by selecting the replacement amount according to the band used as the inductor.

FIG. 2 is an explanatory diagram showing changes in μ × Q at each frequency. X, that is, the substitution amount of Ba with Sr is plotted on the horizontal axis, and the value of μ × Q at that time is plotted on the vertical axis. At 50MHz, the value decreases as the replacement amount increases. As shown in FIG. 1, the fact that the value decreases despite the improvement of Q indicates that the magnetic permeability μ decreases. However, the trend has changed at 100MHz.
That is, the value increases up to X of about 0.2, and decreases with increasing substitution amount with the peak at that value.

In the high frequency region of 300 MHz, the value increases as the amount of substitution increases up to X of 0.3, and the value decreases when the amount of substitution increases at a peak. However, 50MHz
Compared to the 100MHz example, the amount of decrease is smaller,
It does not become smaller than the value when it is not replaced. The same is true at 500MHz, but there is a peak when X is 0.5. There is little change above 0.5.

From the above results, the μQ product characteristic is not so effective in the low frequency range, and is more effective as the frequency becomes higher. Further, it was found that the effect is produced at the point where the substitution amount is large as the frequency becomes high. From this, a high μQ product can be obtained by selecting the replacement amount according to the band used as the inductor.

From the two measurement results, the magnetic material according to the present invention is effective in the frequency band of about 100 MHz or more.
In the relatively low range of about 0 MHz or less, the substitution amount X is 0.1 to
The effect becomes remarkable when it is set to about 0.3. On the other hand, it is more effective to increase the substitution amount X in the high frequency region of 300 MHz or more. That is, it is desirable to select in the range of 0.3 to 0.6.

From the above results, it is necessary to set the range of the substitution amount X to be less than the range in which the influence of the decrease of the magnetic permeability μ becomes large. As mentioned above, it depends on the frequency, but 0.
If it exceeds 6, there is no effect of increasing Q,
Since the Q product decreases, it is preferable to set the range to 0.6.

[0018]

According to the present invention, an inductor having a large Q can be obtained in a high frequency region of 100 MHz or more, and a magnetic material having a relatively large μ can be obtained. As a result, a magnetic material for an inductor having a large inductance and a high Q value suitable for a frequency band from the UHF band to a higher frequency band can be obtained.

The magnetic material according to the present invention can be widely used not only as an inductor but also as a magnetic material in a high frequency region.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of Q characteristics of a magnetic material according to the present invention.

FIG. 2 is an explanatory diagram of μQ product characteristics of a magnetic material according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Sakakura 828 Hinohara, Tamagawa, Tamagawa-mura, Hiki-gun, Saitama Toko Co., Ltd. Tamagawa factory

Claims (2)

[Claims] 1. A high-frequency magnetic material having a composition represented by the general formula Co ₂ (Ba _1-x Sr _x ) ₃ Fe ₂₄ O ₄₁ and having 0.1 ≦ X ≦ 0.6. 2. A magnetic material for a high frequency inductor, wherein 0.1 ≦ X ≦ 0.6 in a composition represented by the general formula Co ₂ (Ba _1-x Sr _x ) ₃ Fe ₂₄ O ₄₁ .