JP2668014B2 - Magnetic multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic material for a noise filter.

[0002]

2. Description of the Related Art The relative magnetic permeability μr (f) of a magnetic material is μr ′.
(F) −j · μr ″ (f), where μr ′ corresponds to the effective relative magnetic permeability and μr ″ corresponds to the loss. Where j = (-
1) ^1/2 and f are frequencies. A noise filter using a magnetic material utilizes a noise suppression effect due to loss of the magnetic material. Since a noise filter is required to have a large impedance and resistance, a magnetic material for the noise filter needs to have a large | μr | and μr ″. The noise of 30 to 300 MHz is regarded as a problem, and it is desired to realize a filter having an excellent noise suppression effect in this frequency band.Mn-Zn ferrite {μr ′ (0) = 1500} which is a conventional material The frequency characteristics of the relative permeability and the frequency characteristics of the impedance are shown in FIGS. 8 and 9 (Junnosuke Uetano: “Electromagnetic Environment Engineering Information” p. 152, published H4.6.30, extra edition, Mimamatsu Data System). In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents relative magnetic permeability. In FIG. 9, the horizontal axis represents frequency, and the vertical axis represents impedance. ｜ Z
| Impedance, R represents the resistance, X _L is the reactance, viewed in the material characteristic value (Ω / m). In the conventional material, μr ′ (0) is small, and as the frequency increases, μr ′ (0) increases.
Since r ′ and μr ″ decrease, | Z |, R do not become so high. Therefore, in order to obtain a sufficient noise suppression effect, it is necessary to increase the volume of the magnetic material, and the component size is large. There is a problem of becoming.

[0003]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned drawbacks, and has as its object to solve the problem of the conventional magnetic material for a noise filter, which has a low impedance and low resistance, and has a high impedance. Another object of the present invention is to provide a magnetic multilayer film exhibiting high resistance.

[0004]

According to the present invention, there is provided a magnetic multilayer film comprising a sheet-like magnetic material and a sheet-like non-magnetic insulator alternately laminated on a substrate. The thickness of the magnetic body is 1/10 to 10 times the skin depth, and the thickness of the non-magnetic insulator is equal to or greater than a thickness capable of maintaining electrical insulation between the magnetic bodies. Is the most important feature. Here, the skin depth δ is δ = {2ρm / (2πf · μr ′ · μ ₀ )} ^1/2 (2) where ρm is the resistivity of the magnetic material, f is the frequency, and μ ₀ is the magnetic permeability of the vacuum. It is. The material composition and structure are different from the conventional materials.

[0005]

According to the present invention, the thickness of the magnetic body is set to one skin depth.
By making the ratio from 1/0 to 10 times, the effect of suppressing noise due to eddy current loss can be used to the maximum.

[0006]

Next, an embodiment of the present invention will be described. FIG.
FIG. 1 is a view showing an embodiment of a magnetic multilayer film of the present invention. The magnetic multilayer film has a multilayer structure in which a sheet-like magnetic body 1 and a sheet-like non-magnetic insulator 2 are alternately stacked on a substrate 3. I have. The thickness of the magnetic body is set to be 1/10 to 10 times the skin depth, while the thickness of the non-magnetic insulator is set to a thickness that can maintain electrical insulation between the magnetic bodies. .

Next, specific experimental examples will be described. 2 shows the tm / δ dependence of the relative magnetic permeability (μr ′, μr ″). In FIG. 2, the horizontal axis represents tm / δ and the vertical axis represents the relative magnetic permeability. Used a CoZr amorphous alloy having μr ′ (0) = 5000 and resistivity (ρm) = 120 μΩcm, where tm is the thickness of the magnetic material and δ is the skin depth.
δ is expressed as ρ = [2ρm / {2πfμr ′ (0) μ ₀ }] ^1/2 (1) using ρm and the magnetic permeability μ _{0 of} vacuum. μr ′ and μr ″ are both normalized by μr ′ (0). μr ″ becomes a large value due to eddy current loss when tm / δ is in the range of 0.1 to 10. From this, it is understood that a large noise suppression effect can be obtained by setting tm to a thickness of about 1/10 to about 10 times δ.

When the thickness of the non-magnetic insulator is small, a current flows between the magnetic layers due to dielectric breakdown or the like, and the thickness of the magnetic layer becomes apparently larger than the above set value, so that a sufficient noise suppressing effect can be obtained. become unable. Therefore, it is necessary to set the thickness of the nonmagnetic insulator to a thickness that can maintain electrical insulation between the magnetic bodies. Experimental results when using SiO ₂ as the nonmagnetic insulator are shown below. FIG. 3 shows a frequency characteristic of the relative magnetic permeability.
A thick NiFe alloy was used. In this frequency range, the skin depth δ is 0.16 to 1.6 μm, which is sufficiently thicker than the NiFe layer thickness. Therefore, if the SiO ₂ layer is only to keep the electrical insulation of the NiFe layers, to the vicinity of the ferromagnetic resonance frequency 650MHz of NiFe, .mu.r 'is constant, .mu.r "is the .SiO ₂ layer thickness 5nm should become a low value , 30
It can be seen that μr ′ decreases and μr ″ sharply increases from around MHz, resulting in incomplete electrical insulation.
With an iO ₂ layer thickness of 50 nm, the ferromagnetic resonance frequency is 650 MH
It can be seen that μr ′ is constant up to the vicinity of z, the increase in μr ″ is suppressed, and the electrical insulation is almost maintained. With the SiO ₂ layer thickness of 100 nm, the insulating effect becomes more reliable.
When SiO ₂ is used as the nonmagnetic insulator, it can be seen that the electrical insulation between the magnetic bodies can be almost completely maintained by setting the layer thickness to several tens of nm or more.

Next, μr ′ (0) = 500 as a magnetic material
Experimental results are shown for a magnetic multilayer film using a CoZrNb amorphous alloy having 0, ρm = 120 μΩcm and SiO ₂ as a nonmagnetic insulator. The skin depth δ is 30 to 300
It is 0.4 to 1.4 μm in MHz. The thickness of the SiO ₂ layer is 0.1 μm, which can maintain electrical insulation between the magnetic materials.
Set to. As the CoZrNb layer thickness tm, δ / 10 ≦
FIGS. 4 and 5 show the frequency characteristics of relative permeability and impedance when set to 2 μm that satisfies tm ≦ 10δ. In FIG. 4, the horizontal axis represents frequency and the vertical axis represents relative permeability. In FIG. 5, the horizontal axis represents frequency and the vertical axis represents impedance. 8 and 9, the value of μr ′ (0) is large, and the decrease of μr ′ and μr ″ with the increase of the frequency is gradual. Therefore, | μr at 30 to 300 MHz. |, Μ
r "takes a large value, and | Z |, R also take a large value.
In this example, | Z |
Is obtained. The frequency characteristics of impedance when tm is 0.04 μm and 14 μm, which are outside the range of δ / 10 ≦ tm ≦ 10δ, are shown in FIGS. 6 and 7, respectively. FIG.
7 and FIG. 7, the horizontal axis represents frequency, and the vertical axis represents impedance. At tm = 0.04 μm, | Z | is large but R is small, while at tm = 14 μm, | Z
Both | and R have small values, and a sufficient noise suppression effect cannot be expected.

[0010] The magnetic material may be Fe, Ni, Co.
On the other hand, as a nonmagnetic insulator, SiO ₂ , AlN, Al ₂ O ₃ , BN, Ti
Even if N and SiC are used, the same effect as described above can be obtained. As described above, the magnetic multilayer film according to the present invention has an improvement in that it exhibits higher impedance and higher resistance than the conventional material.

[0011]

As described above, the magnetic multilayered film according to the present invention has high impedance and resistance in the frequency band of several tens MHz to several hundreds MHz, which is regarded as a problem in the electromagnetic environment, and has a low noise suppressing effect. It has the advantage of being superior. Therefore, the present magnetic multilayer film is useful as a magnetic material for a noise filter.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the dependence of the relative magnetic permeability of CoZrNb on the thickness of a magnetic layer.

FIG. 3 is a diagram showing frequency characteristics of relative magnetic permeability when the thickness of SiO ₂ is changed.

FIG. 4 shows CoZrNb / SiO ₂ (2 μm / 0.1 μm)
m) A diagram showing frequency characteristics of relative magnetic permeability in the multilayer film.

FIG. 5: CoZrNb / SiO ₂ (2 μm / 0.1 μm)
m) A diagram showing frequency characteristics of impedance in the multilayer film.

FIG. 6 shows CoZrNb / SiO ₂ (0.04 μm / 0.
1 μm) is a diagram illustrating frequency characteristics of impedance in a multilayer film.

FIG. 7: CoZrNb / SiO ₂ (14 μm / 0.1 μm)
m) A diagram showing frequency characteristics of impedance in the multilayer film.

FIG. 8 is a diagram showing frequency characteristics of relative permeability in a conventional material (Mn—Zn ferrite).

FIG. 9 is a diagram illustrating frequency characteristics of impedance of a conventional material (Mn—Zn ferrite).

[Explanation of symbols]

 1 magnetic material 2 non-magnetic insulator 3 substrate

Claims (1)

(57) [Claims] 1. A magnetic multilayer film comprising a substrate and a sheet-like magnetic material and a sheet-like non-magnetic insulator alternately laminated on a substrate, wherein the thickness of the magnetic material is 1/10 of the skin depth. Wherein the thickness of the non-magnetic insulator is not less than a thickness capable of maintaining electrical insulation between the magnetic bodies.