JP2645450B2 - Faraday effect material and magnetic field sensor - Google Patents

Description

The present invention relates to a material having a Faraday effect, a magnetic field sensor for detecting a current or a magnetic field flowing in a transmission line or a distribution line, a magnetic field sensor for flaw detection, and a power amount. The present invention relates to a magnetic field sensor using a Faraday effect material such as a magnetic field sensor for measurement.

[Prior art] When a magnetic field is applied from the outside to a magneto-optical material having good light transmission, such as lead glass, ZnSe crystal, or BSO crystal, and light is transmitted in the same direction as the magnetic field, the magneto-optical material is passing through the magneto-optical material due to the Faraday effect It is known that the polarization plane of light rotates. The rotation angle θ (min) of the plane of polarization is given by the following equation.

θ = VHl where V is the Verdet constant (min / Oe · cm), H is the strength of the magnetic field (Oe), and l is the length (cm) of the Faraday rotator.

A magnetic field can be measured using this magnetic rotation phenomenon. FIG. 7 shows a basic configuration of a magnetic field sensor using the Faraday effect. In FIG. 7, the incident light 9 passes through the optical fiber 1 and the rod lens 2, passes through the cuboid polarizer 3, becomes a linearly polarized wave, and then similarly enters the Faraday rotator 4 having a cuboid shape. Then, the plane of polarization is rotated by the angle θ under the influence of the magnetic field 5 and emerges from the Faraday rotation element 4. The rotation angle θ of the polarization plane at this time is replaced by the light intensity by the rectangular parallelepiped analyzer 6 placed on the output side of the Faraday rotation element 4. Then, this light passes through the rod lens 7 and the optical fiber 8 to become emitted light 10, and can be measured by detecting the intensity of the emitted light with a photodiode.

In the magnetic field sensor shown in FIG.
Optical crystals such as lead glass, ZnSe crystal, and BSO crystal (Bi ₁₂ SiO ₂₀ ) are used, and their sensitivity is represented by the Verdet constant V. At a wavelength of 850 nm, the following values are obtained.

Lead glass 0.01 min / Oe · cm BSO crystal 0.10 min / Oe.cm ZnSe crystal 0.15 min / Oe · cm [Problems to be Solved by the Invention] However, all of the above-mentioned conventional optical crystals have small Verdet constant values. Therefore, the sensitivity was low. In order to obtain practical sensitivity, it is necessary to obtain a constant rotation angle θ. However, as is apparent from the above equation θ = VHl, when the Verdet constant value is low, the length l of the Faraday rotation element
Needs to be set to a length of, for example, about 5 to 30 mm. For this reason, when the conventional Faraday effect material is used, there has been a problem that the size of the sensor increases and it becomes difficult to measure the magnetic field in a narrow place.

An object of the present invention is to provide a Faraday effect material exhibiting a large Verdet constant value and to provide a magnetic field sensor which can be downsized by using the Faraday effect material.

[Means for Solving the Problems and Their Effects] In order to solve the above problems, the present inventor has conducted various studies on a Faraday effect material having a larger Verde number than before, and as a result, obtained a CdMnS-based alloy. Further, they have found that a Faraday effect material having a large Verdet constant can be obtained by forming a ZnS alloy, and have accomplished the present invention.

That is, the Faraday effect material of the present invention is CdS-M
It is characterized by using an nS-ZnS-based alloy as a main component.

Further, the Faraday effect material of the present invention is preferably in the following composition range. That is, as shown in the attached ternary phase diagram of FIG. 1, Cd _0.5 Mn _0.35 Zn _0.15 S (CdS 50%, MnS 35%, ZnS 15%) Cd _0.55 Mn _0.35 Zn _0.1 S (CdS 55%, MnS 35%, ZnS10 _{%) Cd 0.65 Mn 0.3 Zn 0.05} S (CdS65%, MnS30%, ZnS5%) Cd 0.85 Mn 0.1 Zn 0.05 S (CdS85%, MnS10%, ZnS5%) Cd 0.85 Mn 0.05 Zn 0.1 S (CdS85%, MnS5%, (ZnS 10%) Cd _0.8 Mn _0.05 Zn _0.15 S It is preferable to have as a main component a composition within a range (including a boundary line) surrounded by (Sd 80%, MnS 5%, ZnS 15%).

In the present invention, any Faraday effect material containing a CdS-MnS-ZnS-based alloy as a main component may be used.
A trace amount of an element such as Se may be contained.

Further, the magnetic field sensor of the present invention has the above-mentioned Faraday effect material, that is, a Faraday rotation element whose main component is a CdS-MnS-ZnS-based alloy, and has a rotation angle of the freezing polarization plane passing through the Faraday rotation element. The magnetic field is detected from the magnitude.

Also, the magnetic field sensor preferably has the same composition as described above within the range (including the boundary line) shown in the attached FIG.
It has a Faraday rotator made of a Faraday effect material containing a CdS-MnS-ZnS-based alloy as a main component.

The Faraday effect material of the present invention has a large Verdet constant, and particularly those having a composition within the range shown in FIG. 1 have a Verdet constant of 2.0 min / Oe · cm or more. Therefore, lead glass, a conventional Faraday effect material,
Compared to a BSO crystal, a ZnSe crystal, or the like, it has a large Verdet constant of 10 times to several tens times or more. Therefore, in the magnetic field sensor using the Faraday effect material of the present invention, the length 1 of the Faraday rotation element can be reduced to 1/10 to 1 / tens of the length of the related art. For this reason, the magnetic field sensor of the present invention can be miniaturized and can measure a magnetic field even in a narrow place.

Example A crystal having a composition indicated by ○ in the ternary phase diagram of FIG. 2 was produced by the Bridgman method. CdS, a high-purity raw material,
MnS and ZnS were blended in a graphite boat so as to have respective predetermined composition ratios, placed in a thick quartz reaction tube, and sealed in a vacuum. The quartz reaction tube was placed in a horizontal electric furnace, and the raw material was heated and melted, and then held for about 24 hours. Thereafter, the quartz reaction tube was moved to the low-temperature portion at a very low speed to crystallize from one end. The obtained crystal has a width of 40 mm and a length of 25
The thickness was 0 mm and the depth was 15 mm. A wafer sample having a thickness of 2 mm was cut out from the center in the longitudinal direction of the crystal, and both sides were polished and mirror-finished to obtain a sample having a thickness of 1 mm. As a result of analysis, the structure of the obtained crystal was a single phase of a wurtzite crystal. For each sample, the Verdet constant was measured at room temperature. The measurement wavelength was measured with light of 730, 780, 850 and 1300 nm. FIG. 3 is a ternary phase diagram showing the Verdet constant of the example at a measurement wavelength of 730 nm. The measurement results for the crystals of each composition ratio are shown at the upper right of the points indicating the respective composition ratios. The unit is min / Oe · cm.

Similarly, FIGS. 4, 5 and 6 show the measurement results at the measurement wavelengths of 780 nm, 850 nm and 1300 nm, respectively. As is clear from the measurement results shown in FIGS. 3 to 7, the value of the Verdet constant changes depending on the measurement wavelength, but largely depends on the amounts of Mn, Zn, Cd and S.

The slope region shown in FIG. 1 shows a composition range in which the measured Verdet constant shown in FIGS. 3 to 6 is 2.0 min / Oe · cm or more, which is an unprecedented large value. Note that this composition range is
A part corresponding to a boundary line is also included.

Thus, the Faraday effect material according to the invention,
Since this Faraday effect element is used as a crystal constituting the Faraday rotator due to having a high Verdet constant, sufficient sensitivity can be obtained without setting the length l of the crystal to be long, and a magnetic field can be obtained even in a narrow place. A magnetic field sensor capable of measurement can be provided. In the case where a conventionally used ZnSe crystal or BSO crystal is used for a Faraday rotator, for example, if a length of 5 to 30 mm is required, the present invention
When a CdS-MnS-ZnS-based alloy is used as a main component, the length of the crystal of the Faraday rotator can be reduced to about 0.06 mm to 2.3 mm, and the magnetic field sensor can be downsized.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention in which 2.0 min / O.
FIG. 3 is a ternary phase diagram showing a composition range showing a Verdet constant of e · cm or more. FIG. 2 is a ternary phase diagram showing the composition measured in the example of the present invention. FIG. 3 is a ternary phase diagram showing the Verdet constant of the example at a measurement wavelength of 730 nm. FIG. 4 is a ternary phase diagram showing the Verdet constant of the example at a measurement wavelength of 780 nm. FIG. 5 is a ternary phase diagram showing the Verdet constant of the example at the measurement wavelength of 850 nm. FIG. 6 is a ternary phase diagram showing the Verdet constant of the example at a measurement wavelength of 1300 nm. FIG. 7 is a conceptual diagram of the configuration of a magnetic field sensor. In FIG. 7, 1 is an optical fiber, 2 is a rod lens,
Reference numeral 3 denotes a polarizer, 4 denotes a Faraday rotator, 5 denotes a magnetic field, 6 denotes an analyzer, 7 denotes a rod lens, 8 denotes an optical fiber, 9 denotes incident light, and 10 denotes outgoing light.

Claims (4)

(57) [Claims] 1. A Faraday effect material comprising a CdS-MnS-ZnS-based alloy as a main component. 2. The CdS—MnS—ZnS alloy according to claim 1
As shown in the ternary phase diagram, Cd _0.5 Mn _0.35 Zn _0.15 S (CdS 50%, MnS 35%, ZnS 15%) Cd _0.55 Mn _0.35 Zn _0.1 S (CdS 55%, MnS 35%, ZnS 10%) Cd _0.65 Mn _0.3 Zn _0.05 S (65% CdS, 30% MnS, 5% ZnS) Cd _0.85 Mn _0.1 Zn _0.05 S (85% CdS, 10% MnS, 5% ZnS) Cd _0.85 Mn _0.05 Zn _0.1 S (85% CdS, 5% MnS, 10% ZnS) Cd _0.8 Mn The Faraday effect material according to claim 1, having a composition within a range (including a boundary line) surrounded by _0.05 Zn _0.15 S (80% CdS, 5% MnS, 15% ZnS). 3. A magnetic field sensor for detecting a magnetic field based on a rotation angle of a plane of polarization of light passing through a Faraday rotator, wherein the Faraday rotator is formed mainly of a CdS-MnS-ZnS-based alloy. A magnetic field sensor comprising: 4. The CdS-MnS-ZnS-based alloy according to claim 1
As shown in the ternary phase diagram, Cd _0.5 Mn _0.35 Zn _0.15 S (CdS 50%, MnS 35%, ZnS 15%) Cd _0.55 Mn _0.35 Zn _0.1 S (CdS 55%, MnS 35%, ZnS 10%) Cd _0.65 Mn _0.3 Zn _0.05 S (65% CdS, 30% MnS, 5% ZnS) Cd _0.85 Mn _0.1 Zn _0.05 S (85% CdS, 10% MnS, 5% ZnS) Cd _0.85 Mn _0.05 Zn _0.1 S (85% CdS, 5% MnS, 10% ZnS) Cd _0.8 Mn 4. The magnetic field sensor according to claim 3, having a composition within a range (including a boundary line) surrounded by _0.05 Zn _0.15 S (80% CdS, 5% MnS, 15% ZnS).