JPS5828104A - High critical magnetic field superconductive material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a critical magnetic field superconducting material Kli to exhibit an excellent superconducting flux trapping effect.

Conventionally, Wb, Ta, Ti crystals (D single crystal, or IHA) were used.

Superconducting materials made of alloys such as Hg-In and Pb-B1 are known. However, the superconducting critical magnetic field of these conventional superconducting materials is not so high, and the development of superconducting materials that can allow lossless current to flow up to even higher magnetic fields is being studied. For example, Nb, Hg-
By dispersing or precipitating ferromagnetic particles such as iron, cobalt, and gadolinium in a superconducting material such as In, a heterogeneous structure is introduced, and superconducting magnetic flux is captured at the precipitate grain boundaries. ), attempts have been made to obtain superconducting materials with high superconducting critical magnetic fields.

However, Amami has yet to achieve a sufficient trapping effect. This is presumed to be because the ferromagnetic material exists in the superconductor in the form of fine particles, so it does not function effectively in capturing the superconducting magnetic flux extending in a straight line.

With this in mind, the inventors of the present invention have conducted intensive studies to provide a superconducting material that efficiently captures superconducting magnetic flux □ and has a high critical magnetic field. In order to complete the present invention, he realized that the desired purpose was achieved by laminating K to a specific thickness K, and completed the present invention.
It has arrived.

That is, the gist of the present invention resides in a high critical magnetic field superconducting material in which a ferromagnetic material is laminated to a thickness greater than the magnetic flux penetration depth of the superconductor on a superconductor having a thickness greater than the coherence length. .

To further explain the present invention, various known superconductors can be used as the superconductor used in the present invention.

Preferably, the Landau-Battari parameter (K+
K-λ/8 (λ: magnetic flux penetration depth, ξ: coherence length) is large, preferably FiK 〉/0, which is originally a high critical magnetic field-generating conductive material and is difficult to alloy with ferromagnetic material. The hermitage is used. in particular,
For example, Wb; alloys such as NbTi; Wb, 8n,
V, Ga.

Examples include Mt+ and Gθ intermetallic compounds.

In the present invention, the superconductor must have a thickness that is at least larger than the coherence length of the superconductor used. The coherence length of most superconductors is generally smaller than /θ−′α, so it is usually greater than or equal to 10−”6.
Preferably, it is selected from the range of /θ'''4 to /l''qll. If the thickness of the superconductor is less than its coherence length, the superconducting properties will be diminished, which is not preferable.

Further, in the present invention, when using a crystal of the Ml) type, it is preferable to introduce crystal lattice defects or inhomogeneous interfaces in a certain direction into the superconductor in advance. This is to trap superconducting magnetic flux more effectively. Examples of methods for introducing such crystal lattice defects or inhomogeneous interfaces include methods such as cold working and forming a wire into a composite structure.

The ferromagnetic material used in the present invention includes we.

Examples include alloys between transition metals such as Co, lii, Or, Mn, and oxides thereof. Such a ferromagnetic material can be coated directly onto the superconductor with its particles, preferably 10O
Particles or thin films of OA to 10μ may be coated or vapor-deposited.Furthermore, these may be laminated in multiple layers and subjected to composite (plywood) processing by wire drawing, roll arcing, etc.

In the present invention, the ferromagnetic material must be laminated on the superconductor to a thickness greater than the magnetic flux penetration depth of the superconductor. If the thickness of the KIN layer is smaller than the thickness of the KIN layer, superconducting magnetic flux can be efficiently captured. Usually %10-
"C11r or more, preferably 10-" to 10-"tM
The layers may be laminated to a thickness within the range of .

Furthermore, since the magnetic flux trapping energy in the ferromagnetic material is proportional to the magnetic susceptibility (χ)K, the ferromagnetic material used in the present invention is preferably a material with a large value of 2 up to a high magnetic field. Even better%/
A material having magnetization that does not saturate (unsaturated magnetization) up to a magnetic field of O'Oe or higher is suitable.

The ferromagnetic material is preferably laminated so as to be parallel to a plane including the direction of crystal lattice defects of the superconductor. By laminating ferromagnetic materials in a specific direction and to a specific thickness, the superconducting magnetic flux is captured by the ferromagnetic material, preventing the magnetic flux from entering the superconductor. It is. In addition, the magnetic flux trapping force of a ferromagnetic material is weakened by the demagnetizing field created by the ferromagnetic material itself, so it is preferable to arrange the ferromagnetic material so that the demagnetizing field coefficient is extremely small.・The thickness of the ferromagnetic material is , it is preferable that the size is greater than or equal to the coherence length of the superconductor material because the magnetic flux trapping force is large.

In the present invention, the magnetic flux capture effect by the ferromagnetic material is
Alternate JIK stacking of superconductors and ferromagnetic materials.

(If used as a multilayer or multilinear composite structure)
Effective 0 For example, if a multilayered superconducting material in which superconductors and ferromagnetic materials are arranged in alternating concentric circles is used in a current cable, it will remain stable even when a large current is applied. It becomes possible to maintain a lossless energized state.

This is because the annular magnetic field lines caused by the current flowing through the cable have a greater energy gain when trapped in a ferromagnetic body than in a diamagnetic superconductor, so the magnetic flux trapped in a ferromagnetic body has a strong electromagnetic force. This is because, due to the interaction between the current and the magnetic flux, the cable resists the force acting on the magnetic flux towards the center of the cable and is captured by the ferromagnetic material, making it difficult to move.

In addition, when a superconducting material with a multi-wire composite structure laminated in a direction parallel to the coil axis is used in a solenoid, the high magnetic flux inside the solenoid loop is suppressed from moving across the coil. Therefore, it is possible to maintain a high magnetic field in a lossless 11LfIL state.

As detailed above, the superconducting material #'i of the present invention obtained as described above has an extremely high superconducting critical a-field because it effectively captures superconducting magnetic flux. Therefore, it is extremely useful for superconducting power transmission cables, superconducting magnet solenoids, etc.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Purified Wb single crystal (coherence length 3×/θ-6e
In) K tensile processing? ) A dislocation line is introduced in the [/, a/] direction, and the thickness θ, j Jr
A disk-shaped sample with a width of 11 mm and a diameter of 2 M11 was cut out. When an external magnetic field of approximately 1030θ was applied perpendicular to the sample surface and the magnetic flux direction was observed using magnetic polarization observation, it was found that [/-2
1] Extremely anisotropic intrusion was observed in the direction Kh with a finger-like distribution. This [/, 2/
] Thickness 4 in the K (///) direction so as to cross the direction at right angles.
A superconducting material was obtained by closely depositing a mu-metal band of tjfim, width θ, and 3 μm on the surface of a disk-shaped sample.

When we observed the superconducting magnetic flux penetration density distribution into Ntt (by magnetic polarization observation method) while applying an increasing magnetic field to the obtained superconducting material at an absolute temperature of 7, we found that the magnetic field increased to #-i up to I00υθ. No intrusion of superconducting magnetic flux into the close contact portion of the U-metal band was observed. In YOOOe, there was a clear level difference in the magnetic flux density between the close contact part and the non-close contact part of the 2,z and mu metal bands, which were allowed to penetrate.

From this, we calculated the superconducting magnetic flux trapping force of the mu-metal band using the following formula:

/cd -<- was there. 'fp: Magnetic flux trapping force B (X): @Flux density H: External magnetic field strength Example / [In place, mu metal band J) K
A superconducting material was produced in the same manner except that a polyethylene terephthalate film having FetOs particles on the surface was used, and the density distribution of superconducting magnetic flux penetrating into Nb was observed. As a result, no superconducting magnetic flux was observed to penetrate into the film-adhesive area when the applied force was 0,000 m2.

Procedural amendment (spontaneous) 1939///Monday Haruki Shimada, Commissioner of the Japan Patent Office 1 Indication of case 1939 Patent application No. 1.27/3
Name of the invention No. g 2 High critical magnetic field superconducting material 3 Person making the amendment Applicant (!9t) Mitsubishi Chemical Industries, Ltd. Approximately 4 agents 〒1
00 (1 other person) Subject of 5 amendments Contents of 6 amendments in column ``Detailed description of the invention'' of the specification (1) From the bottom line of the main page of the specification to the same page/line [rare earth metals such as transition marillam] "alloys between them or their compounds, etc."

(2) On page ♂, line r of the specification, the words ``magnetic flux direction'' are corrected to ``1 magnetic flux density distribution''.

(3) On the second line of the specification page, the phrase ``between the close contact area and the non-contact area'' should be corrected to ``j before and after the close contact area.''

that's all

Claims (1)

[Claims] (1) 1 on a superconductor with a thickness greater than the coherence length.
A high critical magnetic field superconducting material according to item S, item 1 of the high critical magnetic field superconducting material, which is formed by laminating ferromagnetic materials to a thickness greater than the magnetic flux penetration depth of the superconductor. (3) The ferromagnetic material is 70″l′ to IQ″″151
The high critical magnetic field superconducting material according to claim 7, which is laminated to a thickness of 1. (4) Claim 1I in which the superconductor has crystal lattice defects or non-uniform outer regions introduced in a certain direction.
High critical magnetic field superconducting material described in IJ. (5) The high critical magnetic field superconducting material according to claim 7, wherein the ferromagnetic material has magnetization that does not saturate up to a magnetic field of IO'Oe or higher.