JPH04238320A - Faraday effect material and magnetic field sensor - Google Patents

Abstract

PURPOSE:To miniaturize the magnetic field sensor by using a specific Faraday effect material which exhibits a large Verdet's constant value. CONSTITUTION:The Faraday effect material essentially consisting of an HgS- MnS-ZnS alloy is prepd. Namely, ZnS is alloyed to an HgMnS alloy, by which the Faraday effect material having >=2.0min/Oe.cm Verdet's constant value is obtd. Then, the Verdet's constant tens to several tens times larger Verdet's constant than lead glass, BSO crystal, etc., which are the conventional Faraday effect materials is obtd. and, therefore, the magnetic field sensor formed by using this Faraday effect material can reduce the length of the Faraday rotating element to 1/10 to 1/several 10 the length of the conventional elements. The magnetic field sensor is, therefore, miniaturized and the magnetic field measurement is possible even in a narrow place.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to materials having a Faraday effect and magnetic field sensors for detecting currents and magnetic fields flowing in power transmission lines and distribution lines, or for use in Faraday effects such as magnetic field sensors for flaw detection and magnetic field sensors for measuring electric energy. The present invention relates to a magnetic field sensor using an effect material.

0002

[Prior Art] A magnetic field is applied externally to a magneto-optical material with good optical transparency such as lead glass, ZnSe crystal, BSO crystal, etc.
It is known that when light is transmitted in the same direction as a magnetic field, the plane of polarization of the light rotates while passing through a magneto-optical material due to the Faraday effect. The rotation angle θ (min) of the plane of polarization is θ=
It is given by VHl. Here, V is the Verdet constant (min
/Oe·cm), H indicates the strength of the magnetic field (Oe), and l indicates the length (cm) of the Faraday rotation element.

[0003] This magnetic optical rotation phenomenon can be used to measure magnetic fields. FIG. 7 is a conceptual diagram of a magnetic field sensor using the Faraday effect. In FIG. 7, incident light 9 passes through an optical fiber 1 and a rod lens 2, and then passes through a rectangular parallelepiped polarizer 3 to become linearly polarized light. The linearly polarized incident light is similarly passed through a rectangular parallelepiped Faraday rotation element 4.
Here, the plane of polarization is rotated by an angle θ due to the influence of the magnetic field 5 and exits from the Faraday rotation element 4. The rotation angle θ of the plane of polarization at this time is replaced by the intensity of light by a 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 and becomes the output light 10. The intensity of this emitted light can be measured by detecting it with a photodiode.

In the magnetic field sensor shown in FIG. 7, the Faraday rotation element 4 is made of lead glass, ZnSe crystal, BSO crystal (
Optical crystals such as Bi12SiO20) are used,
Their sensitivity is expressed by the Verdet constant V, which at a wavelength of 850 nm has the following value: For lead glass, 0.01 mi
n/Oe・cm, 0.10 min/O for BSO crystal
e・cm, for ZnSe crystal, 0.15 min/Oe・
cm.

[0005]

[Problems to be Solved by the Invention] However, all of the above-mentioned conventional optical crystals have a small Verdet constant value, and therefore have low sensitivity. In order to obtain practical sensitivity, it is necessary to obtain a constant rotation angle θ, but the above formula θ = VHl
As is clear from the above, when the Verdet constant value is low, it is necessary to set the length l of the Faraday rotation element to, for example, about 5 to 30 mm. For this reason, when a conventional Faraday effect material is used, the sensor becomes large and a problem arises in that it becomes difficult to measure a magnetic field in a narrow place.

An object of the present invention is to provide a Faraday effect material that exhibits a large Verdet constant value, and to provide a magnetic field sensor that can be miniaturized by using the Faraday effect material.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have conducted various studies on Faraday effect materials having a larger Verdet constant than conventional ones, and have found that Hg
It was discovered that a Faraday effect material with a large Verdet constant value can be obtained by alloying ZnS with a MnS-based alloy, leading to the present invention. That is,
The Faraday effect material of the present invention is HgS-MnS-ZnS
It is characterized by having a base alloy as its main component.

Furthermore, the Faraday effect material of the present invention is
It is preferable that the composition falls within the following composition range. That is, Hg0.06Mn0.13Zn0.81S (H
gS6atomic%, MnS13atomic%, Z
nS81atomic%), Hg0.06Mn0.09
Zn0.85S (HgS6atomic%, MnS9a
atomic%, ZnS85atomic%), Hg0.
1Mn0.06Zn0.84S (HgS10 atoms
c%, MnS6atomic%, ZnS84atomic
c%), Hg0.25Mn0.06Zn0.69S (H
gS25atomic%, MnS6atomic%, Z
nS69atomic%), Hg0.3Mn0.09Z
n0.61S (HgS30atomic%, MnS9a
atomic%, ZnS61 atomic%), Hg0.
3Mn0.13Zn0.57S (HgS30atomi
c%, MnS13atomic%, ZnS57atom
It is preferable to have a composition as a main component within the range (including the boundary line) surrounded by (ic%).

In the Faraday effect material of the present invention,
Any Faraday effect material containing an HgS-MnS-ZnS alloy as a main component may be used, and for example, a trace amount of Te or Se elements may be included.

Further, the magnetic field sensor of the present invention has a Faraday rotation element mainly composed of the above-mentioned Faraday effect material, that is, an HgS-MnS-ZnS alloy, and rotates the plane of polarization of light passing through the Faraday rotation element. The magnetic field is detected from the size of the corner.

[0011] Furthermore, the magnetic field sensor of the present invention preferably includes:
It has a Faraday rotation element made of a Faraday effect material whose main component is an HgS-MnS-ZnS alloy having the same composition as above within the range shown in FIG. 1 (including the boundary line).

The Faraday effect material of the present invention has a large Verdet constant, especially those within the range shown in FIG.
．． It has a Verdet constant of 0 min/Oe·cm or more. Therefore, lead glass, which is a conventional Faraday effect material,
This means that it has a large Verdet constant that is 10 to several tens of times or more compared to BSO crystals, ZnSe crystals, and the like. Therefore, in the magnetic field sensor using the Faraday effect material of the present invention, the length l of the Faraday rotation element can be reduced to 1/10 to 1/10 of the conventional length. Therefore, the magnetic field sensor of the present invention can be miniaturized, and magnetic field measurement can be performed even in a narrow place.

[0013]

EXAMPLE Crystals of an HgS-MnS-ZnS alloy having the composition indicated by ● in the ternary phase diagram of FIG. 2 were prepared by the Bridgman method. High purity raw materials HgS and MnS
and ZnS were blended in a graphite boat so that each had a predetermined composition ratio. This graphite boat was placed in a thick-walled quartz reaction tube and sealed under vacuum. After placing this quartz reaction tube in a horizontal electric furnace and heating and melting the raw materials,
It was kept in that state for about 24 hours. Thereafter, by moving the quartz reaction tube to a low temperature section at a slow speed, the molten raw material was crystallized from one end. The obtained crystal had a width of 40 mm, a length of 250 mm, and a depth of 15 mm. When the cut surface was observed, the crystal was polycrystalline. A wafer sample with a thickness of 2 mm was cut from the center in the longitudinal direction of the crystal, and both sides were polished to give a mirror finish to obtain a sample with a thickness of 1 mm. As a result of analysis, the structure of the obtained crystal was found to be a single phase of wurtzite type crystal.

The Verdet constant was measured for each sample at room temperature. Methods for measuring the Verdet constant include the orthogonal polarizer method, the Faraday cell method, the rotating analyzer method, and the circular polarization modulation method. Here, the measurement was performed using the circular polarization modulation method. The measurement is 730
, 780, 850 and 1300 nm wavelengths. FIG. 3 is a ternary phase diagram showing the Verdet constant value of the example at a measurement wavelength of 730 nm. The measurement results of the Verdet constant for crystals of each composition ratio are shown on the upper right of the point indicating each composition ratio. Unit is min/Oe・cm
It is.

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

The shaded area shown in FIG. 1 indicates a composition range in which the measured values of the Verdet constant shown in FIGS. 3 to 6 show an unprecedentedly large value of 2.0 min/Oe·cm or more. Note that this composition range also includes a portion corresponding to the boundary line.

As described above, since the Faraday effect material according to the present invention has a high Verdet constant, when the Faraday effect material of the present invention is used as a crystal body constituting a Faraday rotation element, the length l of the crystal body is set to be long. It is possible to obtain a magnetic field sensor that can obtain sufficient sensitivity even without using the magnetic field sensor, and can measure magnetic fields even in a narrow place. Traditionally used Z
When an nSe crystal or a BSO crystal is used in a Faraday rotation element, the length of the crystal body needs to be, for example, 5 to 30 mm.In the case of a crystal mainly composed of the HgS-MnS-ZnS alloy of the present invention, As a result of being able to shorten the length of the crystal of the Faraday rotation element to about 0.06 to 2.3 mm, the magnetic field sensor can be downsized.

[Brief explanation of the drawing]

FIG. 1: In an example of the present invention, 2.0 min at room temperature
H indicating a composition range exhibiting a Verdet constant of /Oe・cm or more
FIG. 3 is a ternary phase diagram of a gS-MnS-ZnS alloy.

FIG. 2 is a ternary phase diagram of a HgS-MnS-ZnS alloy showing a composition whose Verdet constant was measured in an example of the present invention.

[Fig. 3] In the embodiment of the present invention, the measurement wavelength is 730 nm.
FIG. 2 is a ternary phase diagram of a HgS-MnS-ZnS alloy showing the Verdet constant value in FIG.

[Figure 4] In the example of the present invention, the measurement wavelength is 780 nm.
FIG. 2 is a ternary phase diagram of a HgS-MnS-ZnS alloy showing the Verdet constant value in FIG.

[Fig. 5] In the example of the present invention, the measurement wavelength is 850 nm.
FIG. 2 is a ternary phase diagram of a HgS-MnS-ZnS alloy showing the Verdet constant value in FIG.

[Fig. 6] In the embodiment of the present invention, the measurement wavelength is 1300n.
HgS-MnS-ZnS showing the Verdet constant value at m
FIG. 3 is a ternary system phase diagram of the system alloy.

FIG. 7 is a conceptual diagram of the configuration of a magnetic field sensor.

[Explanation of symbols]

1 Optical fiber 2 Rod lens 3 Polarizer 4 Faraday rotation element 5 Magnetic field 6 Analyzer 7 Rod lens 8 Optical fiber 9 Incident light 10 Output light

Claims (4)

[Claims] 1. A Faraday effect material comprising a HgS-MnS-ZnS alloy as a main component. 2. The HgS-MnS-ZnS alloy is composed of Hg0.06Mn0.13Zn0.81S (HgS6a
tomic%, MnS13atomic%, ZnS81
atomic%), Hg0.06Mn0.09Zn0.
85S (HgS6atomic%, MnS9atomic%
c%, ZnS85atomic%), Hg0.1Mn0
．． 06Zn0.84S (HgS10atomic%, M
nS6atomic%, ZnS84atomic%),
Hg0.25Mn0.06Zn0.69S (HgS25
atomic%, MnS6atomic%, ZnS69
atomic%), Hg0.3Mn0.09Zn0.6
1S (HgS30atomic%, MnS9atomic%
c%, ZnS61atomic%), Hg0.3Mn0
．． 13Zn0.57S (HgS30atomic%, M
nS13atomic%, ZnS57atomic%)
The Faraday effect material according to claim 1, having a composition within the range (including the boundary line) surrounded by . 3. A magnetic sensor that detects a magnetic field based on the rotation angle of a polarization plane of light passing through a Faraday rotator, wherein the Faraday rotator is made of HgS-MnS-Z.
A magnetic field sensor characterized by being formed mainly of an nS-based alloy. 4. As shown in the ternary phase diagram of FIG. 1, the HgS-MnS-ZnS alloy contains Hg0.06M
n0.13Zn0.81S (HgS6atomic%,
MnS13 atomic%, ZnS81 atomic%
), Hg0.06Mn0.09Zn0.85S (HgS
6atomic%, MnS9atomic%, ZnS8
5atomic%), Hg0.1Mn0.06Zn0.
84S (HgS10atomic%, MnS6atom
ic%, ZnS84atomic%), Hg0.25M
n0.06Zn0.69S (HgS25atomic%
, MnS6atomic%, ZnS69atomic%
), Hg0.3Mn0.09Zn0.61S (HgS3
0atomic%, MnS9atomic%, ZnS6
1atomic%), Hg0.3Mn0.13Zn0.
57S (HgS30atomic%, MnS13ato
5. The magnetic field sensor according to claim 3, wherein the magnetic field sensor has a composition within a range (including the boundary line) surrounded by (including the boundary line).