KR950000744B1 - Apparatus for measuring magnetization - Google Patents

Abstract

The apparatus measures the magnetizing quantity generated when applying the magnetic field to the magnetic substance. An oscillator (1) provides the saw wave to magnetizing coils (C1,2) through a DC amplifier (2) to apply the magnetic field (H) to a specimen (S). And an oscillator (3) provides the sinusoidal wave to Helmholtz coils (F1,2) through an AC amplifier (4) to apply the AC magnetic field (Ha) to the specimen. Then the specimen generates the torque (T) which is converted to the electric signal by a piezo electric sensor (5). The magnetic field detected by a Hall sensor (G) is provided to a gauss meter (10).

Description

Magnetization measuring device

1 is an overall configuration diagram of the present invention.

2 is a front view showing the main portion of FIG.

3A and 3B are a plan view and a front view of the piezoelectric sensor unit 5. FIG.

4 is a magnetization curve diagram of each sample measured by the present invention.

* Explanation of symbols for main parts of the drawings

1: triangle wave oscillator 2: DC amplifier

3: oscillator for sample driving 4: AC amplifier

5: piezoelectric sensor unit 6: preamplifier

7: tuning amplifier 8: phase detector

9: low pass filter 10: gauss meter

11: circular fixing plate for insulation 12: circular rotating plate for insulation

13, 14, 15: phosphor bronze plate 16, 17: piezoelectric sensor

18, 19: rubber plate 20, 21: sample holder

C1, C2: Electromagnetism Coil S: Sample

Ha: AC magnetic field T-connection rod

F1, F2: Helm Holtz Coil for Torque Generation

L: Magnetic field for torque H-sample magnetization

I: Magnetization M: Electronic

The present invention relates to a magnetization measuring apparatus, and more particularly, to an apparatus for measuring the amount of magnetization I generated in a magnetic body when the external magnetic field H is applied to the magnetic body.

In general, a vibrating sample magnetometer (VSM) has been used as a measuring instrument for measuring the amount of magnetization. It is a device that measures magnetization by induction electromotive force generated in the adjacent detection coil by vibrating the magnetized sample. Samples are required, the device is complex, vibration-resistant and expensive.

The present invention has been invented in view of the above-described problems, and an apparatus for measuring magnetization by measuring a torque generated by a piezoelectric sensor when applying a micro magnetic field of alternating current perpendicular to the magnetization direction of a magnetized micromass magnetic sample. Its purpose is to provide a magnetization measuring device that is easy to operate, has high sensitivity, easy to replace a sample, and is very economical.

According to the present invention for achieving the above object, the magnet sample (S), which is a magnetic material, is disposed at the center of the magnetization coil (C1) (C2) of the sample magnetization electromagnet (M), and the magnetization coil (C1) (C2) described above. Helmholtz Coil (F1) (F2) for generating torque vertically on the axis of the axis, and connecting the piezoelectric sensor unit (5) with a connecting rod (T) to the disc sample (S), triangular wave oscillator The output signal of (1) passes through the DC amplifier (2) and is supplied to the magnetization coils (C1) and (C2) described above to apply the magnetic field (H) to the sample (S). The sinusoidal wave passes through the AC amplifier 4 and is supplied to the torque generating Helmholtz coils F1 and F2, and an alternating magnetic field Ha is applied to the sample S to the sample S. Torque (L) is generated, the torque (L) is converted into an electrical signal by the piezoelectric sensor unit (5) connected to the connecting rod (T), and then sequentially through the preamplifier (6) The output terminal (Mo) through a tuning amplifier (7) for noise reduction, a phase detector (8) converted to a positive polarity voltage, and a low pass filter (9) for removing harmonic alternating current components. A magnetic field signal H for magnetization measured by the Hall element G placed next to the sample S is detected by the Gaussian 10 and output to the output terminal Ho. It consists of.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

1 is an overall configuration diagram of the present invention, Figure 2 is a front view showing the main portion of Figure 1, Figure 3 (a) (b) is a plan view and a cross-sectional view of the piezoelectric sensor portion 5, Figure 4 is a present invention The magnetization curve of each sample measured by.

The triangular wave generated by the triangular wave oscillator 1 is current amplified by the DC amplifier 2 and supplied to the magnetization coils C1 and C2 of the sample magnetization electromagnet M to supply the sample magnetization magnetic field H to the sample S. To apply.

In addition, the signal generated from the oscillator 3 for driving the sample is current amplified by the AC amplifier 4 and supplied to the torque generating Helmholtz Coil (F1) (F2) to the alternating magnetic field (S). The torque L is generated in the sample S by applying Ha). At this time, the frequency of the AC current matches with the resonance frequency of the piezoelectric sensor so that the resonance improves the sensitivity.

The torque (L) is transmitted to the piezoelectric sensor unit (5) by the connecting rod (T) is converted into an electrical signal and input to the preamplifier (6), after removing the noise by the tuning amplifier (7), the phase Phase detection by the detector (8), converted into a DC voltage of + and-polarity, the harmonic current components are removed by the low pass filter (9), and then output to the output terminal (Mo), Y axis of the oscilloscope and XY recorder Mark on.

In addition, the magnetic field signal H for magnetization measured by the Hall element G placed next to the specimen S is detected by the Gauss meter 10 and its output is output to the output terminal Ho. The magnetization curve is obtained by being displayed on the X axis.

Next, the magnetization measuring agent according to the present invention will be described in detail.

When the DC current through the triangular wave oscillator 1 and the DC amplifier 2 flows to the electromagnet magnetizing coils C1 and C2, the magnetization H for the sample magnetization in the coil axis direction in the horizontal direction is Generated and the sphere or disc sample S placed at the center of the electromagnet magnetizing coils C1 and C2 is magnetized by the magnetic field H for the magnetization of the sample by the electromagnet M, and thus the magnetization amount I. Has

Amplified alternating current passing through the sample driving oscillator 3 and the AC amplifier 4 flows to the torque generating Helmholtz coils F1 and F2 perpendicularly to the magnetic field H for the sample magnetization. When the magnetic field (Ha) is applied to the sample (S), the torque (L) is generated in the sample (S) due to the sample magnetization magnetic field (H) and the micro-AC magnetic field (Ha),

L =-(I × Ha) υ ... (1)

Relationship is established. (Where υ is the volume of the sample)

When the torque L is measured by the torque detection piezoelectric sensor unit 5 using the piezoelectric element, the magnetization amount I can be obtained by the above formula (1).

At this time, in order to increase the sensitivity, the frequency of the AC magnetic field (Ha) is matched with the resonance frequency of the piezoelectric sensor unit (5).

3 shows a piezoelectric sensor unit, which is configured to operate only for torque and not to side forces such as bending, and to protect piezoelectric sensors 16 and 17 which are relatively fragile.

Reference numerals 11 and 12 denote circular circular plates for insulation and circular rotary plates for insulation, respectively, which support the piezoelectric sensors 16 and 17, deform only to torque, and exhibit a large resistance to side force. (14) and (15) are supported.

Reference numerals 18 and 19 support the piezoelectric sensors 16 and 17 described above, and are attached to the fixed plate 11 and the rotating plate 12 as rubber plates for absorbing and mitigating strong impacts.

The piezoelectric sensors 16 and 17 are connected in series so as to add an electromotive force generated against the twist in the same direction. In addition, the sample support (20, 21) made of phosphor bronze at the end of the connecting rod (T) elastically supports the sample to facilitate the removal of the sample (S).

In general, the iron core material of the electromagnet (M) mainly uses a silicon steel sheet heat-treated 24 hours at a temperature of 800 ℃ in a nitrogen atmosphere. The pole diameter of the iron core (Pole) is 26mm, the pole spacing is fixed to 20mm.

Two circular coils wound 660 times of 0.8mm diameter polyester coated wire were connected in parallel to obtain a resistance of 2.2Ω at room temperature. The relationship between the magnetization current i and the generated sample magnetization magnetic field H is 500Oe / A, and a maximum magnetic field of 4000Oe is obtained by the current of 8A, and the linearity is good.

In addition, the residual magnetic field is 4Oe or less.

In addition, in the above-described torque generating helmholtz coils (F1) (F2), since the sample (S) mainly used a disc sample, a square-shaped Helmholtz coil having a cross section of 16 mm x 8 mm was used, and a 0.12 mm diameter 100 wire wound wires each with DC resistance of 15Ω. The maximum value of AC voltage is 2V.

In the above-described direct current and alternating current magnetization power sources, the electromagnet magnetization coils C1 and C2 are samples generated by supplying a bipolar DC magnetization power amplified by the DC amplifier 2 to the triangular waves generated by the triangular wave oscillator 1. The magnetization magnetic field H is applied to the sample S, and the sine wave signal generated by the above-described torque generator oscillator 3 is supplied to the torque generating helmholtz coils F1 and F2 by the AC amplifier 4. The amplified alternating magnetization power is supplied to apply the alternating magnetic field (Ha) generated to the sample (S).

The period of the triangular wave described above was 60 seconds to reduce the hysteresis effect of the XY recorder, and the frequency of the oscillator 3 for sample driving was varied from 200 to 2000 Hz so that the resonant frequency of the piezoelectric sensor unit 5 was about 405 Hz. Adjust to match.

The power amplification transistor was forcedly cooled by using a low noise air cooling fan, and the maximum output of the DC amplifier 2 was ± 20 V and ± 10 A.

In addition, in the signal detection system, the piezoelectric sensor unit 5 used a bipolar type using a Rochelle salt crystal, which was 4 mm wide, 1.5 mm thick and 17 mm long, and supported only to respond to torque.

Since the output resistance of the piezoelectric sensor unit 5 is very large, the amplification is performed by the preamplifier 6 of the J-FET having a large input resistance, and then the phase detector 8 is passed through a narrowband amplifier having a center frequency of 405 Hz and Q = 5.6. Phase detection is performed by inputting to the Y terminal. The reference signal inputs an AC voltage for driving the coils of the Helmholtz coils F1 and F2 to the X terminal of the phase detector 8 via the phase adjusting circuit.

Only the DC component in the output voltage that is the product of the voltages input to the input terminals of X and Y is filtered by the low pass filter 9 and output.

Experimental Example

In order to test the performance of the present invention, the samples were selected from Metglas 2605CO, 2605SC, 2605C2, 2826MB, whose properties were published, and molded into a disc of about 2.8 mm in diameter on a commercially available 25 mm wide ribbon. The mass of each sample was measured with an electronic balance of 10 µg resolution, and the volume was calculated by the published density. The connection between the sample connecting rod (T) and the sample (S) used the elasticity of the phosphor bronze plate. When one cycle sweep time of the magnetization history curve is 60 seconds, the measurement result of each sample is the same as the third degree. At this time, the resonant frequency of the piezoelectric sensor 5 was 405 Hz. If the peak to peak value of the output voltage of the hysteresis curve shown on the XY recorder is Vpp, the following equation is established by the following equation (1).

Vpp = k " = k 'Is Hs v = k Is v ............................... (2)

Where k ", k ', and k are the device constants, respectively, and k is obtained by a sample whose Is and v are known. Table 1 is obtained by combining the experimental results.

Where Vpp is the length in the Y-axis direction of the XY recorder.

TABLE 1

From the above results, it can be seen that the error rate between the experimental value and the nominal value for saturation magnetization is within 5%. However, the value of the coercive force of the hysteresis curve is almost the same for all samples and is about 6Oe, which is excessive. And the permeability is very small because of the anti-magnetic field coming from the shape of the sample. As a result, it is possible to measure the magnetization history curve by a very simple and economic method, and it surpasses the existing VSM in terms of sensitivity. The error in the measurement of saturation magnetization is about 5%.

As described above, according to the present invention, since the torque generated in the sample is measured by the piezoelectric sensor when an alternating micromagnetic field is applied perpendicular to the magnetization direction of the magnetized micromass sample, it has a very large sensitivity. By changing the sensitivity of the piezoelectric sensor and the frequency of the AC current for sample driving to the resonant frequency of the piezoelectric sensor, a large idle voltage can be obtained and the torque acting on the sample can be measured. Simple structure and easy operation.

Claims (2)

A disc or spherical sample S, which is a magnetic material, is placed at the center of the magnetization coils C1 and C2 of the magnetization magnet M for the sample magnetization, and torque is generated perpendicularly to the axis of the magnetization coils C1 and C2. Helmholtz coils (F1) (F2) for the purpose, and connecting the piezoelectric sensor unit (5) with a connecting rod (T) to the sample (S), the output signal of the triangular wave oscillator (1) is a direct current amplifier (2) After passing through and supplying the magnetization coils (C1) and (C2), the magnetic field (H) for the sample magnetization is applied to the sample (S), and the sine wave of the oscillator (3) for driving the sample passes through the AC amplifier (4). By supplying to the torque generating Helmholtz coils (F1) (F2) by applying an alternating magnetic field (Ha) to the sample (S), the torque (L) is generated in the sample (S), where The current frequency is matched with the resonance intrinsic frequency of the piezoelectric sensor unit 5 to generate resonance to improve sensitivity, and the torque L is connected to the connecting rod T. A phase detector 8 which is converted into an electrical signal by the pre-sensor part 5 and sequentially converted into a tuning amplifier 7 for removing noise and a voltage of positive polarity (+) through a preamplifier 6. The alternating magnetic field (Ha) signal measured by the Hall element G placed in the sample S is passed through the low pass filter (9) for removing the excess harmonic alternating current component to the Gaussian meter (10). The magnetization measuring device characterized in that it is detected and output to the output terminal (Ho). 2. The piezoelectric sensor part 5 according to claim 1, wherein the piezoelectric sensor part 5 is provided with a rubber plate 18 on an inner surface of the circular fixing plate 11 for insulation, and an inner surface of the circular rotating plate 12 for insulation opposite to the fixing plate 11. A rubber plate 19 is placed on the platen to support the piezoelectric sensors 16 and 17, and to support the phosphor bronze plates 13, 14 and 15 on the inner side between the fixing plates 11 and the rotating plate 12, The magnetization measuring device, characterized in that the sample support (20) 21 is provided at the end of the connecting rod (T) connected to the outer surface of the rotating plate (12).