JPS5924275A - Method and apparatus for measuring magnetostriction - Google Patents

Abstract

PURPOSE:To accurately measure the change of magnetostriction due to temp. change through the measurement temp. change by the measurement of constant of small magnetostriction, by detecting the brightness change of interference fringe based on a change amount caused by magnetostriction by a photo-voltage conversion apparatus such as a solar cell or the like as voltage variation. CONSTITUTION:Interference fringe generated when laser beam is reflected on the upper surface of a lower quartz interference plate S2 and the under surface of an upper quartz interference plate S1 is subjected to electric conversion by using a solar cell S.C. to be detected by a voltmeter V.M. When a magnetic field is applied by solenoid 3 or heating is applied, interference fringe obtained from a specimen 1 prior to applying a magnetic field and heating is displaced from interference fringe from the specimen 1 undergoing the change caused by magnetostriction and a temp. and the voltage difference of both of them is based on the extension and contraction of the specimen 1 caused by magnetostriction and the temp. When the variation amount DELTAl of the specimen 1 is smaller than the 1/4 wavelength of before and after the magnetic field is applied and the max. value Vmax and the min. value Vmin measured by heating the specimen 1 are substituted for a formula to obtain constant of magnetostriction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the magnetostriction constant of a magnetic material, particularly when the magnetostriction constant is Δl/1. The present invention relates to a magnetostriction constant measuring method and device that can accurately measure even very small materials of ≦1×10 2 .

Magnetostriction is a phenomenon in which a slight deformation (strain) occurs when a ferromagnetic material is magnetized, and the magnetostriction constant.

Δl/1locΔe: amount of deformation of the ferromagnetic material, lO: length of the ferromagnetic material). There are two methods for measuring the magnetostriction constant: one is to convert the dimensional change due to magnetostriction into capacitance, and the other is to fix a strain gauge such as a strain gauge to a ferromagnetic material and measure the resistance change of the strain gauge. Are known.

However, in any of the above measurement methods, the lower limit of measurement is I×10 or more and 6D, for example, when the magnetostriction constant is Δl/1, such as for magnetic materials such as soft ferrite and various amorphous materials.
．． If ≦1×10 2 , it cannot be measured, and no other method has been found to be able to measure it.

Therefore, in this invention, the magnetostriction constant is ΔlAo≦lXl0−
The object of the present invention is to provide a measuring method and apparatus that can measure the magnetostriction constant of a magnetic material that is extremely small and has extremely high measurement accuracy.

That is, this invention combines the interference fringes of the reflected light of a laser beam of wavelength λ incident on a pair of quartz interference plates brought into contact with the upper and lower surfaces of a ferromagnetic sample (length lo) in the magnetization direction, and A photovoltaic converter such as a solar cell measures the brightness change of the interference fringes based on the movement difference between the interference fringes of the reflected light of the laser beam and the amount of change (Δe) due to magnetostriction when a magnetic field is applied with or without heating. It is detected as a voltage change, and the amount of magnetostriction change (Δl) of the above sample is determined based on the deviation of the output voltage.
This is a magnetostriction measurement method whose gist is to calculate the magnetostriction constant (Δl/1lo). With this measurement method, Δ
l/j? .

It is possible to measure a small magnetostriction constant of ≦1×1O, which is impossible with conventional methods, and it is also possible to accurately measure magnetostriction changes due to changes in salinity.

This magnetostriction measuring method will be explained in detail below based on the drawings of the magnetostrictive measuring device according to the present invention. FIG. 1 is an explanatory diagram showing the optical path of the magnetostriction measuring device, and FIG. 2 is a detailed diagram of the sample and the quartz interference plate. Further, here, an example is shown in which a device for heating the ferromagnetic sample to be measured is attached.

A laser light source (Q-L) is used as the light source, and here H6-
It is a Ne laser. The optical path begins with a laser light source (Q, L
) is refracted in the horizontal direction by the glass plate (T1), converged by the lens (L), refracted again by the prism (P), and held still by the ferromagnetic sample facing downward. A solenoid (3) for applying a magnetic field to the sample (1) is also provided in the furnace (2). This sample (1) was polished so that the upper and lower surfaces in the magnetization direction had a parallelism of 102 m or less.

The two quartz interference plates are such that the lower quartz interference plate (S,) has parallel upper and lower surfaces, and the upper quartz interference plate (Sl) has an upper surface with a predetermined slope relative to the lower surface. Interference plate (S+)
Sample (1) is placed between (8g). In addition, the heating furnace (
A glass plate (Ti) is placed in the upper opening of 2), through which the laser beam passes.

With the above configuration, the laser beam is reflected by the upper surface of the upper quartz interference plate (Sl) and the upper quartz interference plate (Sl).
) and is split into a pair of reflected lights that are reflected at the upper surface of the lower quartz interference plate (S2) and the lower surface of the upper quartz interference plate (Sl), and the pair of reflected lights form interference fringes. It passes through a prism (P), a lens (L), a glass plate (To), and passes through a magnifying glass (L, M) of a telescope to set and measure the observation point of interference fringes, and is converted into a photovoltage. reach the vessel.

Here, electrical conversion is performed using solar cells (S, C) with high electrical conversion efficiency, and the voltage is detected as a voltage using a digitally displayed voltmeter (V, M).

The detected voltage signal is recorded or processed by a computer (c
, p).

On the other hand, when a magnetic field is applied by the solenoid (3) or when the sample (1) is heated, a laser beam is incident on the sample (1) and a reflected light is obtained. The interference fringes of the reflected light and the interference fringes from the sample (1), which have undergone changes due to magnetostriction and temperature, are displaced, and the voltages obtained at this time also differ. This is based on magnetostriction, which is the expansion and contraction of sample (1) due to temperature.

Generally, interference fringes are bright in the direction of mutual reinforcement and dark in the direction of destructive interference, but as shown in Figure 2, the length of the sample (1) is 1.
．． In this case, the optical path difference between the above pair of reflected lights is 2go, and if this optical path difference (2Ao) is approximated (2no:λn) to an integer multiple of the wavelength λ of the laser beam used, the color of the interference fringes becomes dark. Correspondingly, the output voltage from the solar cells (S, C) is low, and if the optical path difference is 2n'o (n +-!-)X, the output voltage will be high, corresponding to the bright color of the interference fringes. .

Therefore, the magnetostriction of sample (1), expansion and contraction due to temperature change, that is, the amount of change (Δl) is expressed by the following equation (1).

2 (λn in Jo 21'oki (n+1)λ λ/4 in 11'-11o in Δl ......
・・・・・・・・・(1) On the other hand, sample (1) has magnetostriction of 9m
The output voltage changes due to changes in the brightness of the interference fringes of the reflected light, and the maximum value (Vmax) and minimum value (V
min). The output voltages before and after applying the magnetic field are vl and v2
If so, it is necessary to consider the relationship between the output voltage change amount IVIV21 and the maximum and minimum output voltages.

In addition, the amount of change in output voltage obtained is different depending on the case of a ferromagnetic material with a large magnetostriction constant and the case of a material with a small magnetostriction constant such as soft ferrite.
It is necessary to heat it to about 8°C to 8°C, but the former does not require heating.

Therefore, first, a method for calculating the amount of change (Δl) due to magnetostriction in the latter case where the magnetostriction constant is small, such as soft ferrite, will be explained.

Here, from equation (1), if the amount of change (Δl) of sample (1) is smaller than the 1/4 wavelength of the laser beam, the output voltage will be the maximum value (Vmax) or the minimum value, as shown in Figure 8. (Vm'in) or not at all. When passing only the maximum value (Vmax), set Vmln, and also set the minimum value (Vmin)
If only passing through, it is necessary to measure vmax,
Furthermore, if the maximum value and minimum value are not passed at all, Vm
It is necessary to measure both ax and Vmin, and it is important to heat the sample for the above measurements.

The output voltage (Vl), (Va) before and after applying the magnetic field, and the maximum value (Vmax) or minimum value (V
By substituting min) into equation (2), the amount of change in the sample (Δl) is obtained, and from equation (3), the magnetostriction constant is obtained.

(B) Next, change in the sample! ! i (Δl) is 1 of the laser beam
/4 wavelength, the change in output voltage 11VI V21 passes through VmaX or Vmin, or both. When passing only Vmin above, it is necessary to measure Vmax, and also Vmax.
When passing only max, it is necessary to measure Vmln. Further, if the sample passes through both Vmax and Vmin, it is not necessary to measure Vmax and Vmin, but when measuring the above-mentioned Vmax and Vmin, it is necessary to heat the sample.

The output voltages V, , V before and after applying the magnetic field, and VmaX obtained by measuring as above are expressed in the following equation (4), and (2).

By substituting Vmin obtained by measuring v2 into the following equation (5), the magnetostriction constant can be obtained.

In addition, as mentioned above, magnetic materials with a large magnetostriction constant have Vm
Passes both ax and Vmin, and Vmax, Vm
Since in is known, the magnetostriction constant of the magnetic material is as follows (6)
It is obtained from Eq.

(m: half-wave number) In addition, in this invention, the calculated magnetostriction constant has a positive sign (elongation ), and if the direction is the opposite direction, it becomes a negative sign (stripe), so there is an advantage that when measuring the maximum value and minimum value of the output voltage, it is possible to simultaneously determine whether the magnetostriction constant is positive or negative.

Examples according to the present invention will be shown below to clarify its effects.

The apparatus shown in FIG. 1 described above was used as the magnetostriction measuring apparatus, and Mn-zn ferrite with a length of 10 mm was used as the sample.

Output voltage (Vt) before and after applying a magnetic field of 40 (Oe)
Measure (■2), then increase the temperature by applying a magnetic field.
Measure the maximum value (Vmax) and minimum value (Vmin) of the output voltage when increasing the temperature by °C, input this output voltage signal to a computer, and calculate the magnetostriction constant using the above-mentioned formula set in advance. Automatic measurements were performed. As shown in Table 1, the results show that magnetostriction constants of 1×10 F or more, which cannot be measured by conventional methods, can be measured with high precision.

Chapter 1 Table

[Brief explanation of drawings]

FIG. 1 is an optical path diagram of the magnetostriction measuring device according to the present invention,
FIG. 2 is a detailed explanatory diagram of the sample and the upper and lower quartz interference plates. FIG. 8 is a graph showing the relationship between the voltage output from the solar cell and time, and shows the case of Δl-'A/4. In the figure, 1... Sample, 2... Heating furnace, 8... Solenoid, Q, L... Laser light source, L... Lens, T
1. T2...Glass plate, P...Prism, L, M.
... Magnifying glass, S, C... Solar cell, V, M... Voltmeter, c, p... Computing machine, S. - Upper quartz interference plate, S2... Lower quartz interference plate. Applicant: Sumitomo Special Metals Co., Ltd.

Claims (1)

[Claims] 1. Interference fringes caused by a laser beam of wavelength λ incident on a pair of interference plates sandwiching a ferromagnetic sample (length 40) and the amount of change (Δl) due to magnetostriction when a magnetic field is applied to the sample The luminance change due to the movement difference with the interference fringes caused by the laser beam accompanying the above is detected as a voltage change by a photovoltaic converter, and the magnetostriction change amount (Δl) is calculated based on the deviation of the output voltage, and the magnetostriction constant (ΔII/ A magnetostriction measurement method characterized by determining 1lo). 2 Interference fringes caused by a laser beam of wavelength λ incident on a pair of interference plates sandwiching a ferromagnetic sample (length lO) and a change machine (Δ4) caused by magnetostriction when the sample is heated and a magnetic field is applied.
), the brightness change due to the movement difference with the interference fringes of the laser beam is detected as a voltage change by a photovoltaic converter, and the magnetostriction change amount (Δ4) is calculated based on the deviation of the output voltage, and the magnetostriction constant (Δl/ 1. A magnetostriction measurement method characterized by determining lo). 8 Consisting of a laser light source that can obtain a laser beam of a predetermined wavelength, and a convex lens, prism, etc. that converges and refracts the V-laser beam and introduces it to the ferromagnetic sample to be measured, or through which the reflected light from the sample passes. an optical path, a lower quartz interference plate whose upper and lower surfaces are parallel to each other and on which the sample is placed; an upper quartz interference plate whose upper surface has a predetermined slope and which is placed on the upper surface of the sample; and an upper and lower quartz interference plate. A solenoid for applying a magnetic field placed around the outer periphery of the sample held still, a magnifying glass for setting an observation point for interference fringes of the laser beam reflected from the sample, and an interference fringe for the reflected light. It is composed of a solar cell that converts the voltage into a voltage, and a voltmeter that measures this converted voltage, and detects the brightness change due to the difference in movement of the interference fringes of the reflected light due to the amount of change in the sample due to magnetostriction as a voltage change, A magnetostriction measurement device characterized by determining a magnetostriction change amount based on a deviation of an output voltage. 4. The magnetostriction measuring device according to claim 8, which includes a heating furnace that houses a measurement sample that is placed between upper and lower quartz interference plates and a solenoid that applies a magnetic field to the measurement sample.