JPS62201355A - Three-dimensional magnetic anisotropy measuring instrument for sample - Google Patents

Abstract

PURPOSE:To easily and speedily measure three-dimensional magnetic anisotropy by inserting a sample into a cavity resonator and rotating both relatively, and measuring variation in resonance frequency or in Q value. CONSTITUTION:Coaxial waveguides 2 and 3 are connected to both ends of the cavity resonator 1. A partition wall which has a small hole in the center is provided between the resonator 1 and a converter 3 to serve as the end wall of the resonator 1, and a disk 8 is inserted rotatably into the slit between the resonator 1 and converter 2 as the partition wall between the resonator 1 and converter 2. A small hole is bored in the center of the disk 8 and electric vibrations in the converter 2 leak into the resonator from the small hole to excite the resonator 1. Further, a cut is made in the disk 8 from the peripheral side and the sample is inserted through the cut. A shift in the resonance frequency of the resonator 1 between when the sample is placed and when not and variation in the Q of the resonator 1 are measured while the directions of the sample are changed to measure three-dimensional magnetic anisotropy.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an apparatus for measuring three-dimensional magnetic anisotropy in magnetic products such as magnetic tapes and magnetic disks.

Conventional technologyMagnetic tapes and magnetic disks are made by mixing fine ferrite powder with a binder and applying it to a plastic sheet.The fine ferrite powder is acicular crystals, and when applied, the viscosity of the binder causes the crystals to form. There is a tendency for the directions to be somewhat aligned (orientation).

The orientation of this ferrite fine particle should have an impact on the performance of magnetic tapes, etc., but since there has been no on-site measurement method to measure the degree of orientation, active research and management of the orientation of ferrite fine particles is also required. It had not been done. Recently, as a high-density recording method on magnetic tape, a method of magnetizing in a direction perpendicular to the tape surface has been adopted. In this case, it is desirable that the needle-shaped ferrite fine particles be oriented perpendicularly to the tape surface. Such orientation can be achieved by applying a magnetic field perpendicular to the sheet surface before the ferrite coating dries and solidifies, but in this case there has been no way to easily and quickly check the degree of orientation achieved.

C2 Problems to be Solved by the Invention The present invention solves three problems for magnetic products such as magnetic tapes and magnetic disks.
The object of the present invention is to provide an apparatus that can easily and quickly measure dimensional magnetic anisotropy.

21 Means for solving the problem A slit is provided across the cavity at a portion corresponding to the antinode of the magnetic field in the electromagnetic vibration within the cavity, and a sample is placed in this slit. Measures the three-dimensional magnetic anisotropy of the sample by changing the direction of the sample and measuring the shift in the resonant frequency of the cavity resonator before and after placing it, the change in the Q of the cavity resonator, etc. It is something to do.

3. Effect Conventionally, the properties and characteristics of waveguides and cavity resonators have been described as being in a vacuum.

The actions and characteristics of waveguides and cavity resonators are basically determined by the speed of electromagnetic waves, and since the speed of electromagnetic waves is given by 1/F, there is no magnetic field inside the cavity resonator. If the body exists, the state of electromagnetic vibration within the cavity resonator will change compared to when there is no magnetic body. The present invention focuses on this point.

In order to express the magnetic properties of the sample including hysteresis, the magnetic permeability μ is expressed as the complex magnetic permeability μ −iμ″.

Assuming that the sample is placed at the antinode of the magnetic field within the cavity resonator,
The resonant frequency of the cavity resonator before placing the sample is fl, the Q value is Ql, and the resonant frequency and Q value when placing the sample are f.
2. Assuming Q2, A is the shape and size of the cavity resonator, the vibration mode, the shape and size of the sample, and the directional relationship with the magnetic field located)
As a coefficient determined by, it is generally arranged in the form. Since the above μ゛ and μ゛ are values in the direction of the magnetic field, by rotating the sample against the magnetic field, that is, against the cavity resonator, μ′ and μ” in various directions of the sample can be determined. .When the sample has an expanse that covers the entire cross section of the cavity resonator, the value of does not change even when the sample is rotated, and the thickness of the sample is t1. Letting the length c1 vibration mode of the system be TELof!, it is given by: In the above equation, C is the speed of light, e is the wave number within the cavity resonator, and it is practically easy to use it when e=2. T
The vibration mode of E7oQ is as shown in Figure 4. When e = 2, etc., an even number, the antinodes of the magnetic field are formed at both ends and the center of the cavity, so the sample is placed at the center of the cavity. What is necessary is to provide a slit and insert it from there. Of course, e=1 and the sample may be set on the end face of the cavity resonator. The most convenient method can be selected depending on the method of excitation of the cavity resonator and the properties of the sample.

Electricity rate ε0. The magnetic permeability is μ0, and the sample is inside the cavity resonator.In the above equation, the denominator integral is the volume integral for the entire inside of the cavity resonator, and the numerator is the volume integral for the inside of the sample.E, )-1 is when there is no sample. The electric and magnetic fields, E and H-1 are the electric and magnetic fields when there is a sample. Also, ε is the complex permittivity,
and f are the respective complex frequencies when no samples are inserted and when samples are inserted. The sample is set at the antinode of the magnetic field, but in the TE10e mode, the electric field there is O, so if the sample is sufficiently small compared to the volume of the cavity resonator in equation 1 above, the sample is set at the antinode of the magnetic field. In space, E'=E,
Since the contribution of the integral of the sample part to the integral of the entire cavity resonator in the denominator can be regarded as 0, the denominator is the electromagnetic energy within the cavity resonator that determines the cavity resonator and its vibration mode. becomes a constant. Therefore, the integral of the numerator in equation (1) is carried out depending on the shape and orientation of the sample, and μ
(A) can be found for the general case. For example, if the sample has various cross-sectional shapes such as square, rectangular or circular, or if the sample is thin such as thread-like where only the elongated direction protrudes outside the slit. The present invention is applicable even to a width shape or a shape smaller than the opening of a cavity resonator.

Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a cavity resonator with a rectangular cross section, and coaxial waveguide converters 2 and 3 are connected to both ends thereof. An input antenna 4 for cavity resonance excitation is inserted into the coaxial waveguide converter 2, and a receiving antenna 5 is inserted into the coaxial waveguide converter 3. The input antenna 4 is connected to an oscillator 6 by a coaxial cable, and the receiving antenna 5 is connected to a detection circuit 7 by a coaxial cable. Between the cavity resonator 1 and the coaxial waveguide converter 3, there is a partition wall with a small hole in the center, which serves as the end wall of the cavity resonator. A disk 8 is rotatably inserted into the slit between the cavity 1 and the coaxial waveguide converter 2, and this disk serves as a partition between the cavity resonator 1 and the coaxial waveguide converter 2.

A small hole is bored in the center of the disk 8, and the electrical vibrations inside the coaxial wave tube converter 2 leak into the cavity through this hole and excite the cavity.

FIG. 2 shows details of the disk portion. There is a step convex part 8 on the outer periphery of the disk.
a is provided, and the inner periphery of the stepped convex portion is supported by a bearing 9 fitted to the end flange of the cavity resonator 1, making the disc 8 rotatable. A gear is formed on the outer periphery of the stepped convex portion 8a, and is connected to a drive motor (not shown). A notch 10 is provided in the disc 8 from the circumferential side, and the sample S is inserted through the notch 10 while being held in a suitable holder. In this embodiment, the mode of vibration is Ee=1, and the antinodes of the vibration of the magnetic field are formed at both ends of the cavity resonator, as shown in FIG.

As mentioned above, the effect of sample μ appears as a shift in the resonant frequency of the cavity resonator, so if the frequency is fixed at the resonant frequency when there is no sample, the frequency shift can be observed as a decrease in the detection output. be done. If a sample with a width that covers the cross section of the cavity resonator is used, A, which is a factor of shape and position, does not change due to the rotation of the sample. Therefore, while rotating the sample, the rotation angle of the disk 8 and the detection output When the relationship between .mu. and .mu. In the case of a narrow sample in which only the longitudinal length protrudes outside the slit, the value of A varies depending on the rotation angle, so the anisotropy of μ cannot be immediately determined from the record of the relationship between the detection output and the rotation angle. Calculation using equation (1) is required. If you want to cut out a sample smaller than the opening of the waveguide from the tape and measure it, you can cut it out into a circle and set it in the center of the disk 8, or you can place the sample on a non-oriented sheet. By pasting with a non-oriented adhesive or sandwiching two sheets, the shape and position factor A does not change due to rotation, so by recording the relationship between the detection output and the rotation angle in polar coordinates, it is possible to determine the three-dimensional direction. The agreement of the anisotropy is immediately apparent.

For example, in the case of a magnetic tape or disk in which fine ferrite particles are oriented in the thickness direction, sample S is cut out thinly from the tape or disk as shown in Figure 5, and the Z direction parallel to the tape or disk surface is Set it in the cavity resonator so that it is in the axial direction of the cavity resonator. The thickness of this sample is 1
Let us consider the case where the width is W, the length of the cavity resonator is 01, the cross section is aXb, and the sample is set as shown by X and Y in FIG. When the vibration mode is TE loe and &=1 and the sample is set as shown in Figure 6 Y, the magnetic flux density is equal before and after the sample along the direction of the magnetic field line H, so the magnetic field inside the sample is! (/μ. Since the magnetic field H is constant in the y direction, the numerator of the above equation (1) is \ where Ha is the maximum magnetic field strength. (2) From (3), solving the above equation for μ Furthermore, when the sample is set as shown in Figure 6 This is the case because the line integral (magnetomotive force) of the magnetic field lines going around the is also constant regardless of the presence or absence of the sample.

The strength change in the X direction of the magnetic field is Tχ 1 finger. Since the numerator of equation (1) is (μ-l), H and A are expressed as The formula represents μ in the direction parallel to the plane of the tape or disk.

G. Effects According to the present invention, a sample is inserted into a cavity resonator and the sample and cavity resonator are rotated relative to each other to change the resonance frequency or Q value (
The magnetic anisotropy of the sample in the three-dimensional direction can be determined by measuring the change in the detection output while keeping the excitation frequency constant. This type of method can be applied not only to large-shaped samples, but also to narrow-shaped samples such as magnetic tape where only the longitudinal direction protrudes from the cross section of the cavity resonator, and to samples smaller than the cross section of the cavity. Measurement of the three-dimensional magnetic anisotropy of a sample (see explanation of FIG. 5) can be performed very easily and quickly, and can greatly contribute to quality control of this flTI product.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of the device of the present invention, FIG. 2 is an enlarged vertical cross-sectional view of the main parts, FIG. 3 is a perspective view of a disk, and FIG. 4 is a TEtoe in a cavity resonator. Fig. 5 is an explanatory diagram of how to cut out a sample for measuring the anisotropy in the thickness direction of the sample, and Fig. 6 shows the state of setting the cut sample in the cavity resonator. FIG.

Claims (3)

[Claims] (1) A slit that crosses the cavity resonator is provided at a portion corresponding to the antinode position of the magnetic field within the cavity resonator, a sample is inserted into this slit, and the gap between the cavity resonator and the sample is 3-dimensional magnetic anisotropy of a sample, characterized in that a change in the resonant frequency of the cavity resonator or a change in the Q value of the cavity resonator at that time is detected. measuring device. (2) The measuring device according to claim (1), wherein the sample has a narrow shape such that only the longitudinal direction protrudes outside the slit. (3) The measuring device according to claim (1), wherein the sample has a smaller shape than the waveguide opening of the cavity resonator.