JPH0743417B2 - Method and apparatus for detecting magnetic internal property of superconductor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for detecting a magnetic internal property of a superconductor, and more particularly, to a magnetic property inside a superconductor.
It aims to detect it easily and accurately.

(Prior Art) With the discovery of a series of new oxide high-temperature superconductors that began in 1986, research on their application progressed, and as a result, much consideration has been given to conventional metal-based superconducting materials. Attempts have been made to use superconductors in fields that did not exist. As a typical example, for example, bulk permanent magnets {13th Japan Society for Applied Magnetics Proceedings 23P E-4 (198
9)}, inductors (23P E-7), fluxgate magnetic field sensors (23P E-8), magnetic shield materials of various shapes, and magnetic bearings. These products are used as they are in bulk form, not as wire rods or tapes in which conventional metal-based superconductors are used, and therefore macro magnetic properties as bulk are important.

By the way, when using a superconductor as a wire or tape material as in the past, the critical current density (J _c ) in a magnetic field is the most important characteristic, and while maintaining a stable state as a superconductor, Efforts have been made to improve J _c . However, when it is used in the bulk state as described above, not only J _c but also the magnetic properties of the bulk as a whole and its uniformity become a problem. When used in bulk, when the magnetic field becomes higher, the so-called flux jump, in which the external magnetic flux penetrates into the sample all at once from the part where the pinning force of the magnetic flux is weak, is extremely likely to occur, as well as the demagnetizing effect. Therefore, a portion where the magnetic field becomes extremely strong locally is formed depending on the shape of the sample, and the penetration of magnetic flux starts from that portion. Therefore, it is extremely important to know the macroscopic magnetic flux distribution inside the superconductor in the magnetic field in order to develop a material suitable for the application of the product and to determine an appropriate shape of the product.

Generally, the magnetization of a superconductor does not have a uniform magnetic moment over the entire sample as in a normal magnetic material, but is non-uniform depending on the pinning force of the magnetic flux inside the material. Therefore, information such as the magnetic flux distribution and gradient inside the sample cannot be obtained by the usual magnetic measurement method in which only the averaged value is obtained over the entire sample.

As a method of directly observing such a magnetic flux change inside the superconductor, a decoration method has been often used. In this method, fine particles of ferromagnetic material such as Fe and Co are vapor-deposited on a superconductor sample in a low temperature magnetic field, and a replica on which the magnetic flux line lattice pattern of the sample is transferred is observed with an electron microscope. You can see the state of the line grid. This method is extremely convenient for observing individual magnetic flux line gratings in the range of about 1 to 10 μm, but the distribution of the magnetic flux line gratings over the entire bulk or a wide range, its magnetic field,
It is not possible to dynamically observe temperature dependence. Therefore, it cannot be used for the purpose of detecting macroscopic magnetic flux behavior of the entire bulk when used as a material.

As a method for measuring a macroscopic magnetic flux distribution and a change in magnetic flux distribution that cannot be observed by the decoration method, there are a method using a Hall element and a method utilizing a Faraday effect which is one of magneto-optical effects.

The former method using the Hall element is to place the Hall element on the superconductor and measure the magnetic flux on the surface while moving the element (eg Jpn.J.Appl.Phys.26).
(1987) L1348} can obtain only one-dimensional information with a single operation, and the measurement resolution is low at 0.5 to 1 mm.
It is far from being suitable for material development.

The latter method using the Faraday effect was originally developed for observing the intermediate state of the first-class superconductor, and as shown in FIG. Europium chalcogenide, which becomes a ferromagnetic substance in
A composite film d of a mixed crystal system of EuO or EuS and EuF ₂ is vapor-deposited, and polarized light passing through the polarizer a is irradiated from above. Magnetic flux passes through the normal conducting portion of the sample, and the polarization plane of the magnetic film deposited on the sample rotates due to the Faraday effect. When this reflected light is observed through the analyzer b, the portion through which the magnetic flux passes g The part h that is not so and the part h that is not can be observed as a black and white contrast {H.Kirchner, Phys.Stat.Sol. (A) 4
(1971) 531}.

Fig. 5 shows the method of observing the intermediate state. When this is applied to a type II superconductor, the magnetic flux distribution in the mixed state can be observed, and the magnetic gradient is changed from the strength of the black and white contrast. You can estimate {HU Habermeier et a
l.Phys.Stat.Sol. (a) 50 (1978) 187}.

Recently, a case was also reported in which a mixed crystal composite magnetic thin film of EuS / EuF ₂ was vapor-deposited and the magnetic flux distribution of YBa ₂ Cu ₃ O _x , an oxide high-temperature superconductor, was observed at a temperature of 10K. {N. Moser et al. Physica C159 (1989) 117}.

(Problems to be solved by the invention) Conventionally, as a magnetic thin film, europium chalcogenide (EuO, EuS, Eu) has been used to observe the magnetic flux distribution using the magneto-optical effect.
Only F ₂ ) have been used. This is because these materials use the property that they become ferromagnetic at low temperatures and have a large Faraday rotation angle.

However, in the conventional method, when observing the magnetic flux distribution, these magnetic films must be vapor-deposited on each sample one by one, and it is very complicated considering the labor and the removal after measurement, and the material manufacturing and the product inspection. If it is used for other purposes, the cost will be greatly increased. Moreover, since the Curie temperature of these Eu-based magnetic films is lower than the liquid nitrogen temperature (77K), it cannot be applied to the recent oxide high temperature superconductors with a critical temperature of 77K or higher. The high temperature oxide superconductor is considered to be used at liquid nitrogen temperature due to its high critical temperature, and the fact that it cannot be easily measured at 77K is a major drawback. Furthermore, since the difference between the black and white contrasts corresponding to the magnetic flux gradient in the sample is difficult to catch with the naked eye, a device for quantitatively detecting the contrast and an image processing device after that are required.

As described above, the conventional method of observing the magnetic flux distribution using the Eu-based magnetic film increases the cost due to the complexity of the measurement and is restricted by the operating temperature. It left a problem such as a need.

The present invention advantageously solves the above-mentioned problems, and can be used more easily and at lower cost than conventional ones and can be used over a wide temperature range. Moreover, the magnetic properties of a superconductor capable of more accurately grasping the internal magnetic properties can be grasped. It is an object to propose an internal property detection method together with its detection device.

(Means for Solving the Problems) That is, the present invention is to make a magnetic thin film having a striped domain structure in which the direction of spontaneous magnetization is perpendicular to the film surface in a low temperature region in close contact with the surface of the superconductor, and the magnetic field is applied to the superconductor. While applying
By irradiating polarized light from above, and by calculating the magnetic flux density distribution from the change in the magnetic domain width corresponding to the magnetic flux distribution inside the superconductor that appears in the magnetic thin film due to the magneto-optical effect associated with this polarized light irradiation, the magnetic field inside the superconductor can be determined. It is a method for detecting a magnetic internal property of a superconductor, which comprises detecting a physical property (first invention).

Further, the present invention provides a superconductor magnetic internal property detecting device comprising a superconducting material sample cooling means, a magnetic field applying means for the sample, and an observing means for the sample having at least a polarized light irradiation function. A magnetic thin film having a striped magnetic domain structure in which the direction of spontaneous magnetization is perpendicular to the film surface at least in the lower surface in the low temperature region, and the domain width of the striped magnetic domain changes corresponding to the magnetic flux distribution inside the sample. , And a thin film member that is in close contact with the mounted sample surface is installed so that it can move at least vertically, and the magnetic properties inside the superconductor are detected by obtaining the magnetic flux density distribution from the change in the magnetic domain width. It is a magnetic conductor internal property detection device (2nd invention) which consists of this.

In the present invention, the low temperature range means a temperature range of about 150 K or lower.

In the present invention, the following materials are suitable as materials for the magnetic thin film.

(1) Chemical formula: R ₃ Fe ₅ O ₁₂ or R ₃ Fe _5-x MxO ₁₂ where one or more selected from R: Bi, Y and rare earth elements, among M: Ga, Al and In One or two or more selected ones whose main composition is iron garnet represented by x ≦ 3.

The iron garnet containing Fe represented by the above chemical formula has uniaxial magnetic anisotropy and has a large Faraday effect, so that it can be a magnetic film having a striped magnetic domain.
As R, Y and rare earth elements, and further Bi can be selected. These can be used alone or in a suitable combination of two or more kinds to form a mixed composition, whereby the magnitude of spontaneous magnetization, temperature characteristics, and Faraday rotation angle can be adjusted. Can be changed. Furthermore, by substituting a part of Fe with Ga, Al or In, the magnitude of spontaneous magnetization generated by Fe can be changed. Since the effect is lost if the amount of Fe becomes too small by the substitution, the substitution amount x is set in the range of x ≦ 3.

(2) Chemical formula: AFeO ₃ Here, the main composition is a rare earth orthoferrite represented by one or more selected from A: Y and rare earth elements.

In the rare earth orthoferrite represented by the above chemical formula, spin rearrangement occurs in which the spontaneous magnetization is oriented in the a-axis direction at low temperature, uniaxial magnetic anisotropy appears, and when it is made into a thin film, striped magnetic domains can be obtained. When A has a mixed composition with Sm, this spin rearrangement temperature can be changed, and the optimum one for magnetic flux observation can be selected. Also, adding a small amount of Co in order to change the spin rearrangement temperature does not hinder the effect of the present invention.

(3) Chemical formula: BFe ₁₂ O ₁₉ or BFe _12-x Al _x O ₁₉ Here, one or more selected from B: Pb, Ba and Sr. The main composition is magnetoplumbite represented by x ≦ 6. What to do.

The magnetoplumbite represented by the above chemical formula is a cubic crystal, and the easy axis of magnetization is in the c-axis direction. Therefore, when made into a thin film, the c-axis becomes perpendicular to the film surface and a striped magnetic domain can be obtained. You can B is selected from the combination of Pb, Ba and Sr, and Al
The amount of spontaneous magnetization can be changed by adding. However, if the amount of Fe becomes too small due to the addition of Al, the effect is lost, so the substitution amount x is set within the range of x ≦ 6.

(4) Chemical formula: XZ Amorphous rare earth-transition element represented by one or more selected from X: Y and rare earth elements, and one or more selected from Z: Fe, Co and Ni Main alloy composition.

When an alloy thin film mainly composed of the amorphous rare earth-transition element alloy represented by the above chemical formula is produced by a sputtering method, a vapor deposition method, etc., it has an amorphous structure with an arbitrary composition ratio and has a magnetization perpendicular to the film surface. become. Film thickness is 500
If the thickness is less than about Å, the Faraday effect of transmitted light can be used, but if it is thick, the magnetic Kerr effect of the same magneto-optical effect is used to observe the magnetic domain pattern. In addition, in order to enhance functions other than magnetism such as corrosion resistance, the alloy composition of Ti, A
The addition of elements such as l, Cr, Bi and Be does not hinder the effect of the present invention.

(5) At least one selected from MnBi, MnCnBi, MnGaGe, and MnAlGe.

Among the above compositions, MnBi has a hexagonal NiAs type structure and has a very large uniaxial magnetic anisotropy in the c-axis direction. Therefore, when making a magnetic film, the c-axis becomes perpendicular to the film surface,
The object of the present invention can be achieved. Also MnBi to Cu
Similarly, MnCuBi, MnGaGe, MnAlGe, etc. to which is added can also be used.

In the present invention, in order to bring the magnetic thin film into close contact with the surface of the superconductor, a thin film obtained by applying a magnetic thin film having a striped domain structure in which the direction of spontaneous magnetization is perpendicular to the film surface on at least one surface of the transparent substrate. From the viewpoint of simplicity, the method of preparing a member and pressing this thin film member on the polished surface of the superconductor with a pressure of about 10 ^-3 to 10 g / mm ² with the magnetic thin film as the lower surface is the most preferable, but of course vapor deposition The magnetic thin film may be directly formed on the surface of the superconductor by the method or ion sputtering.

When the thin film member is brought into close contact with the surface of the superconductor by the pressing as described above, it is desirable that the surface of the superconductor has a center line average roughness Ra of about 1.5 μm or less.

Further, in order to coat the surface of the transparent substrate with the magnetic thin film, it goes without saying that vapor deposition or ion sputtering can be used, and a thin plate (single crystal thin plate) having each of the above-mentioned compositions is formed on the substrate surface. It can also be achieved by sticking. Especially when using a single crystal thin plate, its thickness should be 30-50 μm.
The substrate may be omitted as a degree.

Furthermore, the magnetic thin film does not necessarily have to be a single layer film,
A multilayer film or a composite film may be used as long as it has perpendicular magnetization as a whole and has a striped magnetic domain structure. Any substrate can be used as long as it has a light-transmitting property, and gadolinium gallium garnet (GGG) is particularly suitable among garnets.

The thickness of the magnetic thin film is preferably about 0.1 to 50 μm, and in the case of a thin plate, about 5 to 50 μm.

Next, a magnetic internal property detecting apparatus for a superconductor suitable for carrying out the method of the present invention will be described with reference to the drawings.

The preferred device is shown schematically in FIG. 1a. In the figure, reference numeral 1 is a specimen of a superconducting material, 2 is a thin film member that is in close contact with the surface of the sample, and at least the lower surface of the thin film member 2 has perpendicular magnetization and is a magnetic thin film having a striped domain structure. 3 are covered. Reference numeral 4 is a sample holder for mounting and holding a sample, 5 is a thermometer that can be composed of a resistance thermometer, 6 is a magnetic measuring device that can be composed of a Hall element, and 7 is each of these members. It is a cryostat to store. In addition, 8 is a viewing window provided in the cryostat 7,
Reference numeral 9 is a magnetic field applying device which can be composed of an electromagnet, and 10 is an objective lens of a polarized metal microscope.

Reference numeral 11 is a gripping member that holds the thin film member 2 at least vertically, and this gripping member 11 is shown in FIGS.
As shown in d and d, when the sample is loaded and placed, the thin film member 2 is made to stand by above the loading position or in the retracted position in the lateral direction, and the sample is loaded and placed in the predetermined position. After that, the thin film member 2 is lowered from above to bring it into close contact with the sample surface.

In this case, the dead weight of the thin film member 2 can be used as it is.

In order to bring the thin film member 2 into close contact with the sample surface, in addition to the method of moving the thin film member 2 as described above, the thin film member 2 is fixed above the sample mounting position, and the thin film member 2 is fixed to the fixed thin film member 2. On the other hand, there is also a method of raising the sample.

(Operation) The following experiment was conducted using the apparatus as described above.

First, the melting method {M.Murakami et al., Jpn.J.Appl.Phys.28
(1989) 1189}, YB is an oxide high temperature superconductor.
A ₂ Cu ₃ O _x was prepared and cut into a 0.4 × 1 × 1 (mm ³ ) shape to obtain a measurement sample 1. Then, the surface was finished to be smooth by polishing. The superconducting critical temperature of this sample was 92 K as measured by magnetization.

As shown in FIG. 1A, this sample 1 was placed on a predetermined position of a sample holder 4 made of copper, and the thin film member 2 was brought into close contact with the surface on which the magnetic thin film 3 was formed facing down. . The magnetic thin film 3 used was an iron garnet (BiGd) with a thickness of 4 μm.
YbFe ₅ O ₁₂ ) magnetic thin film deposited on a gadolinium gallium garnet (GGG) substrate by liquid phase epitaxy.

After that, insert into the cryostat 7 shown in the figure,
The sample 1 and the magnetic thin film 2 were cooled using low temperature helium gas.

The temperature monitor and temperature control were performed by a thermometer 5 and a heater (not shown) embedded in the sample holder 4.
The magnetic field was applied by the electromagnet 9 arranged under the cryostat 7, and the magnitude of the magnetic field applied to the sample 1 was measured by the Hall element 6 attached to the sample holder 4. There is a glass peep window 8 on the top of the cryostat 7.
Through this, the sample 1 and the magnetic thin film 3 were observed with a polarizing metallographic microscope.

After cooling from the state of no magnetic field and maintaining the temperature at 77K,
While irradiating the magnetic thin film with polarized light, the magnetic field was changed and the magnetic domain pattern of the magnetic thin film was observed.

2A, 2B and 2C show the superconducting sample photographed in this way and the magnetic domain pattern appearing on the magnetic thin film thereon.

The magnetic domain pattern is a labyrinthine so-called striped magnetic domain, in which the spontaneous magnetization of the magnetic thin film faces the direction perpendicular to the film surface, and the spontaneous magnetization in two adjacent magnetic domains faces the opposite directions. Because there is. This is because the direction of easy magnetization is perpendicular to the film surface, and the action of magnetic anisotropy energy that tends to set the magnetization perpendicular to the plane is larger than the action of the demagnetizing field that tends to direct the magnetization in the plane. It depends. When a magnetic field is applied to a magnetic thin film having such a magnetic domain structure in a direction perpendicular to the film surface, magnetic domains having spontaneous magnetization in the same direction as the magnetic field expand, while magnetic domains having spontaneous magnetization in the opposite direction narrow.

In Fig. 2a (when a magnetic field of 340 Oe is applied), the magnetic domain width (bright part) corresponding to the applied magnetic field expands in the parts other than the superconductor, but the magnetic flux does not enter inside the superconductor, The domain width remains narrow. However, the magnetic flux enters the edge portion of the sample and the portion where the magnetic flux pinning force is relatively weak, and the magnetic domain width is expanded. As the applied magnetic field increases, the second
Figure b (when applying a magnetic field of 470 Oe) and Figure c (680
As shown in (when a magnetic field of Oe is applied), it can be seen that the magnetic flux enters the inside of the superconductor.

Note that FIG. 2d shows an applied magnetic field of 300 Oe from the state of FIG. 2c.
It shows the magnetic domain pattern when it is reduced to
It is clearly shown that a fine magnetic domain structure is not visible inside the superconductor, and there is a portion where the applied magnetic flux is trapped.

Therefore, in order to detect the magnetic properties inside the superconductor, as described above, the superconducting material is cooled to a temperature indicating superconductivity and then a magnetic field is applied. The same detection can be carried out by the procedure of cooling to temperature and then reducing or removing the applied magnetic field.

Further, according to the method of the present invention, the magnetic flux density distribution inside the superconductor can be accurately calculated from the magnetic domain width of the striped magnetic domain appearing in the magnetic thin film as described below.

Fig. 3 shows iron garnet (BiGdYbFe) as a magnetic thin film.
₅ shows the relationship between the applied magnetic field and the domain width at 85 K when using a ₅ O ₁₂ ) magnetic thin film.

As is clear from the figure, the magnetic domain width increases as the applied magnetic field increases.

Therefore, by utilizing this relationship, on the contrary, the strength of the magnetic field and hence the magnetic flux density inside the superconductor can be obtained from the magnetic domain width.

That is, an experiment was conducted using the above iron garnet film as the magnetic thin film, and when the magnetic domain pattern shown in FIG. 4a was obtained when the external magnetic field was 340 Oe, the relational curve shown in FIG. 3 was used. Thus, the magnetic flux density contour map shown in FIG. 4b can be immediately obtained.

As described above, according to the present invention, the magnetic flux density distribution inside the superconductor can be accurately measured.

Since the relationship between the applied magnetic field and the magnetic domain width as shown in FIG. 3 is unique to the material of the magnetic thin film, if the above relationship is obtained for each material, the measurement of the magnetic domain width will be performed. Therefore, the magnetic flux density distribution inside the superconductor can be immediately obtained.

In this respect, when using europium chalcogenide as in the past, since the magnetic flux change was estimated from the strength of the contrast of the magnetic domain itself rather than the width of the magnetic domain, it was not possible to immediately grasp the magnetic flux gradient from visual observation. .

(Example) Example 1 An oxide high temperature superconductor YBa ₂ Cu ₃ Ox produced by a melting method.
Was cut into a 0.4 × 1 × 1.5 (mm ³ ) shape, and the surface was polished to 0.5 μm with Ra to obtain a sample.

Then, this sample was loaded and placed in the apparatus shown in FIG. 1 and held at 85K, and the magnetic internal properties were investigated. As a thin film member, one surface of a gadolinium gallium garnet substrate was coated with Bi by liquid phase epitaxy.
GdYbFe ₅ O ₁₂ having a thickness of 4 μm was used.

Observation of the magnetic domain pattern while applying a magnetic field, Fig. 2
As shown in a, b, and c, as the magnetic field increased, the magnetic domain width expanded in the thin film other than the sample, the sample end, and the part where the magnetic flux pinning force was relatively weak. It was confirmed that the magnetic field was eliminated inside the superconductor and the domain width did not change.

Example 2 High temperature oxide superconductor YBa ₂ Cu ₃ Ox produced by the melting method
Is cut into a 0.4 × 1 × 1.5 (mm ³ ) shape, and the surface is Ra
It was ground to 0.4 μm and used as a sample.

Then, this sample was charged and placed in the apparatus shown in FIG. 1 above as in Example 1, and the magnetic internal properties were investigated while applying a magnetic field while maintaining the temperature at 77K. As the thin film member, BiYFe ₄ A10 ₁₂ was formed on one surface of the gadolinium gallium garnet substrate by a liquid phase epitaxy method to a thickness of 3
What was formed to a thickness of μm was used.

Also in this case, as in Example 1, the magnetic domain width was widened in the part other than the sample, the sample end, and the part where the magnetic flux pinning force was relatively weak as the magnetic field increased, but the magnetic field was eliminated inside the superconductor. There was no change in the magnetic domain width.

Example 3 Oxide high temperature superconductor YBa ₂ Cu ₃ Ox produced by melting method
Is cut into a 0.4 × 1 × 1.5 (mm ³ ) shape, and the surface is Ra
It was ground to 0.9 μm and used as a sample.

Then, after placing this sample in the apparatus shown in FIG. 1 and mounting it, a thin film member having a YFe ₅ O ₁₂ magnetic thin film having a thickness of 5 μm on one side of a gadolinium gallium garnet substrate was placed on the bottom. The sample was brought into close contact with the polished surface.

Then, after cooling while applying a magnetic field of 500 Oe and maintaining at 50 K, the magnetic domain pattern at that time was observed while reducing the magnetic field.

As a result, the magnetic flux trapped in the sample appeared as the magnetic field decreased, and finally the magnetic domain pattern as shown in FIG. 2d was observed.

Example 4 Oxide high temperature superconductor YBa ₂ Cu ₃ Ox produced by melting method
Is cut into a 0.4 × 1 × 1.5 (mm ³ ) shape, and the surface is Ra
It was ground to 0.6 μm and used as a sample.

Next, this sample was loaded and placed in the apparatus shown in FIG. 1 above and held at 40K, and the magnetic internal properties were investigated while applying a magnetic field. As the thin film member, an Eu _0.7 Sm _0.3 FeO ₃ single crystal thin plate having a thickness of 40 μm was used.

Also in this case, as in Example 1, the magnetic domain width was widened in the part other than the sample, the sample end, and the part where the magnetic flux pinning force was relatively weak as the magnetic field increased, but the magnetic field was eliminated inside the superconductor. No change was observed in the magnetic domain width.

Example 5 Oxide high temperature superconductor YBa ₂ Cu ₃ Ox produced by melting method
Is cut into a 0.4 × 1 × 1.5 (mm ³ ) shape, and the surface is Ra
The sample was polished to 1.0 μm and used as a sample.

Next, this sample was loaded and placed in the apparatus shown in FIG. 1 above and held at 40K, and the magnetic internal properties were investigated while applying a magnetic field. As the thin film member, a BaFe ₁₀ Al ₂ O ₁₉ single crystal thin plate having a thickness of 30 μm was used.

Also in this case, as in Example 1, the magnetic domain width was widened in the part other than the sample, the sample end, and the part where the magnetic flux pinning force was relatively weak as the magnetic field increased, but the magnetic field was eliminated inside the superconductor. No change was observed in the magnetic domain width.

Although the preferred embodiment has been specifically described above,
It is needless to say that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) Thus, according to the method of the present invention, it is possible to easily and easily grasp the magnetic properties inside the superconductor, and therefore, it is possible to achieve great effects in the development and manufacturing of materials and products using the superconductor. .

Further, since the device of the present invention can be incorporated in a line as an on-line inspection device in the manufacturing process, not only the efficiency can be remarkably improved in the actual operation, but also the cost can be remarkably reduced.

[Brief description of drawings]

FIG. 1a is a schematic view of a preferred device according to the present invention, FIG.
c and d are both detailed diagrams of the main parts, and FIGS. 2 a, b, c and d are diagrams showing changes in the magnetic domain pattern appearing in the magnetic thin film due to the change of the applied magnetic field, respectively. Is a graph showing the relationship between the applied magnetic field at 85 K and the magnetic domain width (bright part) when an iron garnet (BiGdYbFe ₅ O ₁₂ ) magnetic thin film was used, and FIG. 4 a is a magnetic domain pattern on the magnetic thin film. FIG. 5B is a contour diagram of magnetic flux density derived from this magnetic domain pattern, and FIG. 5 is an explanatory diagram of a magnetic property observing procedure inside the superconductor according to the conventional method. DESCRIPTION OF SYMBOLS 1 ... Superconducting material sample, 2 ... Thin film member 3 ... Magnetic thin film, 4 ... Sample holder 5 ... Thermometer, 6 ... Magnetic measuring instrument 7 ... Cryostat, 8 ... Peep window 9 ... Magnetic field applying device, 10 ... Objective lens 11 ... Grip Member a ... Polarizer, b ... Analyzer c ... Disc-shaped sample, d ... Composite film e ... Liquid helium, f ... Magnetic field g ... Part where magnetic flux passes h ... Part where magnetic flux does not pass

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Goto 1-14-3 Shinonome, Koto-ku, Tokyo Inside the Superconducting Engineering Laboratory, Foundation Superintendent Industrial Technology Research Center (72) Masaji Yoshida Shinonome, Koto-ku, Tokyo 1-14-3 Foundation Superhuman Industrial Technology Research Center Superconductivity Engineering Laboratory (72) Inventor Naoki Koshizuka 1-14-3 Shinonome, Koto-ku Tokyo Metropolitan Superconductivity Engineering Research Center Superconductivity Engineering Laboratory (72) Inventor Masato Murakami, 1-14-3, Shinonome, Koto-ku, Tokyo Inside the Institute of Superconductivity Engineering, Research Center for International Superconductivity Technology (56) References JP 47-28967 (JP, A) JP Sho 53-50777 (JP, A) JP-A-61-286763 (JP, A) JP-A-62-102103 (JP, A) Kai 58-139082 (JP, A) JP 59-218971 (JP, A) JP 62-150185 (JP, A) JP 62-188982 (JP, A) JP 40-19674 (JP JP, B1) "Magnetic handbook" pp. 1200-1201 Asakura Shoten, June 30, 1975

Claims (2)

[Claims] 1. A magnetic thin film having a striped magnetic domain structure in which the direction of spontaneous magnetization is perpendicular to the film surface in the low temperature region is brought into close contact with the surface of the superconductor, and a magnetic field is applied to the superconductor while polarizing from above. The magnetic properties inside the superconductor can be detected by determining the magnetic flux density distribution from the change in the magnetic domain width corresponding to the magnetic flux distribution inside the superconductor that appears in the magnetic thin film due to the magneto-optical effect associated with this polarized light irradiation. A method for detecting magnetic internal properties of a superconductor characterized by: 2. A magnetic conductor internal property detecting device for a superconductor, comprising: a superconducting material sample cooling means; a magnetic field applying means for the sample; and a sample observing means having at least a polarized light irradiation function. A magnetic thin film having a striped magnetic domain structure in which the direction of spontaneous magnetization is perpendicular to the film surface at least in the lower surface in the low temperature region, and the domain width of the striped magnetic domain changes corresponding to the magnetic flux distribution inside the sample. , And a thin film member that is in close contact with the mounted sample surface is installed so that it can move at least vertically, and the magnetic properties inside the superconductor are detected by obtaining the magnetic flux density distribution from the change in the magnetic domain width. A magnetic internal property detecting device for a superconductor characterized by the above.